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B Konh T Sorensen A Trimble Z Song 1 of XXME 481 ndash Fall 2018
Material Selection
Senior Design ME481
Fall 2017Dr Bardia Konh
Fall 2018Dr A Trimble
B Konh T Sorensen A Trimble 2 of XXME 481 ndash Fall 2018
Materials Selection in Design
This Lecture
- Importance of material selection in design
- Exploring materials using materials property charts
- Materials selection process
- Selecting materials materials indices
- Case studies
Material selection is critical part of almost all engineering designs
So many factors to consider
strength stiffness durability corrosion cost formability etc
Design ishellip
ldquohellipthe process of translating a new idea or a market need into detailed
information from which a product can be manufacturedrdquo
M F Ashby ldquoMaterials Selection in Mechanical Designrdquo
B Konh T Sorensen A Trimble 3 of XXME 481 ndash Fall 2017
Materials Selection in Design
B Konh T Sorensen A Trimble 4 of XXME 481 ndash Fall 2017
Materials selection is a key step for a successful design
A large number of materials to select from
Recently there has been more emphasis on the role of materials
Discovery of new and advanced materials
The Role of Materials Selection in Design
Function
Mechanical
Properties Failure
ModeManufacturability
CostEnvironmental
Considerations
Advanced new materials can introduce
new products with more efficiencies
lower manufacturing costs
Exhibit desired behavior
An ability to select materials that best meet requirements of a design
Access to information and tools for comparison and selection
B Konh T Sorensen A Trimble 5 of XXME 481 ndash Fall 2017
Need for a new product and new materials
Development of a new materials
httphleelabhomewixsitecommysiteresearch2
httphleelabhomewixsitecommysite
bull Soft active materials
bull Biologically inspired design principles
Soft robotics
Dr Howon Lee
Rutgers University
Soft multi-material actuators
Dr Conor Walsh
Harvard University
httpsbiodesignseasharvardedusoft-robotics
bull Large bending motions
B Konh T Sorensen A Trimble 6 of XXME 481 ndash Fall 2017
Evolution of materials
[ASHBY99] - Materials Selection In Mechanical Design
httpwwwutcfr~hagegebeUVMQ12CORRECTIONS_TD5BASHBY995D20-
20Materials20Selection20In20Mechanical20Design202Edpdf
B Konh T Sorensen A Trimble 7 of XXME 481 ndash Fall 2017
Material Properties
Physical
ndash Density
ndash Melting point
ndash Vapor pressure
ndash Viscosity
ndash Porosity
ndash Permeability
ndash Reflectivity
ndash Transparency
ndash Optical properties
ndash Dimensional stability
Chemical
ndash Corrosion
ndash Oxidation
ndash Thermal stability
ndash Biological stability
ndash Stress Corrosion
ndash hellip
Electrical
ndash Conductivity
ndash Dielectric constant
ndash Coersive force
ndash Hysteresis
Thermal
ndash Conductivity
ndash Specific Heat
ndash Thermal expansion
ndash Emissivity
Mechanical
ndash Hardness
ndash Elastic constants
ndash Yield strength
ndash Ultimate strength
ndash Fatigue
ndash Fracture Toughness
ndash Creep
ndash Damping
ndash Wear resistance
ndash Spalling
ndash Ballistic performance
ndash helliphellip
B Konh T Sorensen A Trimble 8 of XXME 481 ndash Fall 2017
httpwwwmatwebcom
What do we expect from a design
The products should perform their functions effectively safely at acceptable costrdquo
Test Test data
Data
capture
Statistical
analysis
Allowables
Mechanical Properties
Bulk Modulus 41 - 46 GPa
Compressive Strength 55 - 60 MPa
Ductility 006 - 007
Elastic Limit 40 - 45 MPa
Endurance Limit 24 - 27 MPa
Fracture Toughness 23 - 26 MPam12
Hardness 100 - 140 MPa
Loss Coefficient 0009- 0026
Modulus of Rupture 50 - 55 MPa
Poissons Ratio 038 - 042
Shear Modulus 085 - 095 GPa
Tensile Strength 45 - 48 MPa
Youngs Modulus 25 - 28 GPa
Successful
applications
$
Economic analysis
and business caseSelection of
material and process
Potential
applications
Characterization Selection and implementation
DATA INFORMATION KNOWLEDGE
B Konh T Sorensen A Trimble 9 of XXME 481 ndash Fall 2017
Materials Data - Organization
bull Properties for a particular material is called the ldquomaterial attributesrdquo
bull Includes both structured and non-structured information
bull We need to find the best match between the design requirements and the
materials attributes
B Konh T Sorensen A Trimble 10 of XXME 481 ndash Fall 2017
Material stiffness
httpwwwgrantadesigncomdownloadpdfteaching_resource_books2-Materials-Charts-2010pdf
B Konh T Sorensen A Trimble 11 of XXME 481 ndash Fall 2017
Metals
Metal Examples of application
Ferrous Metals Carbon Steels Utensils construction automotive transmission
towers hellip
Stainless Steels Off shore drilling rigs naval construction
chemical transport food preparation medical
instruments
Cast Irons Cylinders pistons motor blocks construction
wear resistant materials
Light Alloys Aluminum Alloys Aerospace construction transport packaging
electrical conductors
Magnesium Alloys Aerospace automotive sporting equipment
Titanium Alloys Aerospace chemical industry
Copper Alloys Copper Electrical conductors
Bronze Heat exchangers chemical industry maritime
industry
Brass Pressure vessels fittings
Nickel Alloys Aerospace currency
B Konh T Sorensen A Trimble 12 of XXME 481 ndash Fall 2017
Interactions
Material
ProcessShape
Functionality
Materials Selection Methodology
Ashby Methodology
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 13 of XXME 481 ndash Fall 2017
Material selection
[ASHBY99] - Materials Selection In Mechanical Design
B Konh T Sorensen A Trimble 14 of XXME 481 ndash Fall 2017
First Step Translation
ldquoExpress design requirements as constraints and objectivesrdquo
Using design requirements analyze four items
1 Function What does the component do
2 Objective What essential conditions must be met
3 Constraints What is to be maximized or minimized
4 Free variables Which design variables are free
ndash Which can be modified
ndash Which are desirable
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 2 of XXME 481 ndash Fall 2018
Materials Selection in Design
This Lecture
- Importance of material selection in design
- Exploring materials using materials property charts
- Materials selection process
- Selecting materials materials indices
- Case studies
Material selection is critical part of almost all engineering designs
So many factors to consider
strength stiffness durability corrosion cost formability etc
Design ishellip
ldquohellipthe process of translating a new idea or a market need into detailed
information from which a product can be manufacturedrdquo
M F Ashby ldquoMaterials Selection in Mechanical Designrdquo
B Konh T Sorensen A Trimble 3 of XXME 481 ndash Fall 2017
Materials Selection in Design
B Konh T Sorensen A Trimble 4 of XXME 481 ndash Fall 2017
Materials selection is a key step for a successful design
A large number of materials to select from
Recently there has been more emphasis on the role of materials
Discovery of new and advanced materials
The Role of Materials Selection in Design
Function
Mechanical
Properties Failure
ModeManufacturability
CostEnvironmental
Considerations
Advanced new materials can introduce
new products with more efficiencies
lower manufacturing costs
Exhibit desired behavior
An ability to select materials that best meet requirements of a design
Access to information and tools for comparison and selection
B Konh T Sorensen A Trimble 5 of XXME 481 ndash Fall 2017
Need for a new product and new materials
Development of a new materials
httphleelabhomewixsitecommysiteresearch2
httphleelabhomewixsitecommysite
bull Soft active materials
bull Biologically inspired design principles
Soft robotics
Dr Howon Lee
Rutgers University
Soft multi-material actuators
Dr Conor Walsh
Harvard University
httpsbiodesignseasharvardedusoft-robotics
bull Large bending motions
B Konh T Sorensen A Trimble 6 of XXME 481 ndash Fall 2017
Evolution of materials
[ASHBY99] - Materials Selection In Mechanical Design
httpwwwutcfr~hagegebeUVMQ12CORRECTIONS_TD5BASHBY995D20-
20Materials20Selection20In20Mechanical20Design202Edpdf
B Konh T Sorensen A Trimble 7 of XXME 481 ndash Fall 2017
Material Properties
Physical
ndash Density
ndash Melting point
ndash Vapor pressure
ndash Viscosity
ndash Porosity
ndash Permeability
ndash Reflectivity
ndash Transparency
ndash Optical properties
ndash Dimensional stability
Chemical
ndash Corrosion
ndash Oxidation
ndash Thermal stability
ndash Biological stability
ndash Stress Corrosion
ndash hellip
Electrical
ndash Conductivity
ndash Dielectric constant
ndash Coersive force
ndash Hysteresis
Thermal
ndash Conductivity
ndash Specific Heat
ndash Thermal expansion
ndash Emissivity
Mechanical
ndash Hardness
ndash Elastic constants
ndash Yield strength
ndash Ultimate strength
ndash Fatigue
ndash Fracture Toughness
ndash Creep
ndash Damping
ndash Wear resistance
ndash Spalling
ndash Ballistic performance
ndash helliphellip
B Konh T Sorensen A Trimble 8 of XXME 481 ndash Fall 2017
httpwwwmatwebcom
What do we expect from a design
The products should perform their functions effectively safely at acceptable costrdquo
Test Test data
Data
capture
Statistical
analysis
Allowables
Mechanical Properties
Bulk Modulus 41 - 46 GPa
Compressive Strength 55 - 60 MPa
Ductility 006 - 007
Elastic Limit 40 - 45 MPa
Endurance Limit 24 - 27 MPa
Fracture Toughness 23 - 26 MPam12
Hardness 100 - 140 MPa
Loss Coefficient 0009- 0026
Modulus of Rupture 50 - 55 MPa
Poissons Ratio 038 - 042
Shear Modulus 085 - 095 GPa
Tensile Strength 45 - 48 MPa
Youngs Modulus 25 - 28 GPa
Successful
applications
$
Economic analysis
and business caseSelection of
material and process
Potential
applications
Characterization Selection and implementation
DATA INFORMATION KNOWLEDGE
B Konh T Sorensen A Trimble 9 of XXME 481 ndash Fall 2017
Materials Data - Organization
bull Properties for a particular material is called the ldquomaterial attributesrdquo
bull Includes both structured and non-structured information
bull We need to find the best match between the design requirements and the
materials attributes
B Konh T Sorensen A Trimble 10 of XXME 481 ndash Fall 2017
Material stiffness
httpwwwgrantadesigncomdownloadpdfteaching_resource_books2-Materials-Charts-2010pdf
B Konh T Sorensen A Trimble 11 of XXME 481 ndash Fall 2017
Metals
Metal Examples of application
Ferrous Metals Carbon Steels Utensils construction automotive transmission
towers hellip
Stainless Steels Off shore drilling rigs naval construction
chemical transport food preparation medical
instruments
Cast Irons Cylinders pistons motor blocks construction
wear resistant materials
Light Alloys Aluminum Alloys Aerospace construction transport packaging
electrical conductors
Magnesium Alloys Aerospace automotive sporting equipment
Titanium Alloys Aerospace chemical industry
Copper Alloys Copper Electrical conductors
Bronze Heat exchangers chemical industry maritime
industry
Brass Pressure vessels fittings
Nickel Alloys Aerospace currency
B Konh T Sorensen A Trimble 12 of XXME 481 ndash Fall 2017
Interactions
Material
ProcessShape
Functionality
Materials Selection Methodology
Ashby Methodology
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 13 of XXME 481 ndash Fall 2017
Material selection
[ASHBY99] - Materials Selection In Mechanical Design
B Konh T Sorensen A Trimble 14 of XXME 481 ndash Fall 2017
First Step Translation
ldquoExpress design requirements as constraints and objectivesrdquo
Using design requirements analyze four items
1 Function What does the component do
2 Objective What essential conditions must be met
3 Constraints What is to be maximized or minimized
4 Free variables Which design variables are free
ndash Which can be modified
ndash Which are desirable
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 3 of XXME 481 ndash Fall 2017
Materials Selection in Design
B Konh T Sorensen A Trimble 4 of XXME 481 ndash Fall 2017
Materials selection is a key step for a successful design
A large number of materials to select from
Recently there has been more emphasis on the role of materials
Discovery of new and advanced materials
The Role of Materials Selection in Design
Function
Mechanical
Properties Failure
ModeManufacturability
CostEnvironmental
Considerations
Advanced new materials can introduce
new products with more efficiencies
lower manufacturing costs
Exhibit desired behavior
An ability to select materials that best meet requirements of a design
Access to information and tools for comparison and selection
B Konh T Sorensen A Trimble 5 of XXME 481 ndash Fall 2017
Need for a new product and new materials
Development of a new materials
httphleelabhomewixsitecommysiteresearch2
httphleelabhomewixsitecommysite
bull Soft active materials
bull Biologically inspired design principles
Soft robotics
Dr Howon Lee
Rutgers University
Soft multi-material actuators
Dr Conor Walsh
Harvard University
httpsbiodesignseasharvardedusoft-robotics
bull Large bending motions
B Konh T Sorensen A Trimble 6 of XXME 481 ndash Fall 2017
Evolution of materials
[ASHBY99] - Materials Selection In Mechanical Design
httpwwwutcfr~hagegebeUVMQ12CORRECTIONS_TD5BASHBY995D20-
20Materials20Selection20In20Mechanical20Design202Edpdf
B Konh T Sorensen A Trimble 7 of XXME 481 ndash Fall 2017
Material Properties
Physical
ndash Density
ndash Melting point
ndash Vapor pressure
ndash Viscosity
ndash Porosity
ndash Permeability
ndash Reflectivity
ndash Transparency
ndash Optical properties
ndash Dimensional stability
Chemical
ndash Corrosion
ndash Oxidation
ndash Thermal stability
ndash Biological stability
ndash Stress Corrosion
ndash hellip
Electrical
ndash Conductivity
ndash Dielectric constant
ndash Coersive force
ndash Hysteresis
Thermal
ndash Conductivity
ndash Specific Heat
ndash Thermal expansion
ndash Emissivity
Mechanical
ndash Hardness
ndash Elastic constants
ndash Yield strength
ndash Ultimate strength
ndash Fatigue
ndash Fracture Toughness
ndash Creep
ndash Damping
ndash Wear resistance
ndash Spalling
ndash Ballistic performance
ndash helliphellip
B Konh T Sorensen A Trimble 8 of XXME 481 ndash Fall 2017
httpwwwmatwebcom
What do we expect from a design
The products should perform their functions effectively safely at acceptable costrdquo
Test Test data
Data
capture
Statistical
analysis
Allowables
Mechanical Properties
Bulk Modulus 41 - 46 GPa
Compressive Strength 55 - 60 MPa
Ductility 006 - 007
Elastic Limit 40 - 45 MPa
Endurance Limit 24 - 27 MPa
Fracture Toughness 23 - 26 MPam12
Hardness 100 - 140 MPa
Loss Coefficient 0009- 0026
Modulus of Rupture 50 - 55 MPa
Poissons Ratio 038 - 042
Shear Modulus 085 - 095 GPa
Tensile Strength 45 - 48 MPa
Youngs Modulus 25 - 28 GPa
Successful
applications
$
Economic analysis
and business caseSelection of
material and process
Potential
applications
Characterization Selection and implementation
DATA INFORMATION KNOWLEDGE
B Konh T Sorensen A Trimble 9 of XXME 481 ndash Fall 2017
Materials Data - Organization
bull Properties for a particular material is called the ldquomaterial attributesrdquo
bull Includes both structured and non-structured information
bull We need to find the best match between the design requirements and the
materials attributes
B Konh T Sorensen A Trimble 10 of XXME 481 ndash Fall 2017
Material stiffness
httpwwwgrantadesigncomdownloadpdfteaching_resource_books2-Materials-Charts-2010pdf
B Konh T Sorensen A Trimble 11 of XXME 481 ndash Fall 2017
Metals
Metal Examples of application
Ferrous Metals Carbon Steels Utensils construction automotive transmission
towers hellip
Stainless Steels Off shore drilling rigs naval construction
chemical transport food preparation medical
instruments
Cast Irons Cylinders pistons motor blocks construction
wear resistant materials
Light Alloys Aluminum Alloys Aerospace construction transport packaging
electrical conductors
Magnesium Alloys Aerospace automotive sporting equipment
Titanium Alloys Aerospace chemical industry
Copper Alloys Copper Electrical conductors
Bronze Heat exchangers chemical industry maritime
industry
Brass Pressure vessels fittings
Nickel Alloys Aerospace currency
B Konh T Sorensen A Trimble 12 of XXME 481 ndash Fall 2017
Interactions
Material
ProcessShape
Functionality
Materials Selection Methodology
Ashby Methodology
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 13 of XXME 481 ndash Fall 2017
Material selection
[ASHBY99] - Materials Selection In Mechanical Design
B Konh T Sorensen A Trimble 14 of XXME 481 ndash Fall 2017
First Step Translation
ldquoExpress design requirements as constraints and objectivesrdquo
Using design requirements analyze four items
1 Function What does the component do
2 Objective What essential conditions must be met
3 Constraints What is to be maximized or minimized
4 Free variables Which design variables are free
ndash Which can be modified
ndash Which are desirable
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 4 of XXME 481 ndash Fall 2017
Materials selection is a key step for a successful design
A large number of materials to select from
Recently there has been more emphasis on the role of materials
Discovery of new and advanced materials
The Role of Materials Selection in Design
Function
Mechanical
Properties Failure
ModeManufacturability
CostEnvironmental
Considerations
Advanced new materials can introduce
new products with more efficiencies
lower manufacturing costs
Exhibit desired behavior
An ability to select materials that best meet requirements of a design
Access to information and tools for comparison and selection
B Konh T Sorensen A Trimble 5 of XXME 481 ndash Fall 2017
Need for a new product and new materials
Development of a new materials
httphleelabhomewixsitecommysiteresearch2
httphleelabhomewixsitecommysite
bull Soft active materials
bull Biologically inspired design principles
Soft robotics
Dr Howon Lee
Rutgers University
Soft multi-material actuators
Dr Conor Walsh
Harvard University
httpsbiodesignseasharvardedusoft-robotics
bull Large bending motions
B Konh T Sorensen A Trimble 6 of XXME 481 ndash Fall 2017
Evolution of materials
[ASHBY99] - Materials Selection In Mechanical Design
httpwwwutcfr~hagegebeUVMQ12CORRECTIONS_TD5BASHBY995D20-
20Materials20Selection20In20Mechanical20Design202Edpdf
B Konh T Sorensen A Trimble 7 of XXME 481 ndash Fall 2017
Material Properties
Physical
ndash Density
ndash Melting point
ndash Vapor pressure
ndash Viscosity
ndash Porosity
ndash Permeability
ndash Reflectivity
ndash Transparency
ndash Optical properties
ndash Dimensional stability
Chemical
ndash Corrosion
ndash Oxidation
ndash Thermal stability
ndash Biological stability
ndash Stress Corrosion
ndash hellip
Electrical
ndash Conductivity
ndash Dielectric constant
ndash Coersive force
ndash Hysteresis
Thermal
ndash Conductivity
ndash Specific Heat
ndash Thermal expansion
ndash Emissivity
Mechanical
ndash Hardness
ndash Elastic constants
ndash Yield strength
ndash Ultimate strength
ndash Fatigue
ndash Fracture Toughness
ndash Creep
ndash Damping
ndash Wear resistance
ndash Spalling
ndash Ballistic performance
ndash helliphellip
B Konh T Sorensen A Trimble 8 of XXME 481 ndash Fall 2017
httpwwwmatwebcom
What do we expect from a design
The products should perform their functions effectively safely at acceptable costrdquo
Test Test data
Data
capture
Statistical
analysis
Allowables
Mechanical Properties
Bulk Modulus 41 - 46 GPa
Compressive Strength 55 - 60 MPa
Ductility 006 - 007
Elastic Limit 40 - 45 MPa
Endurance Limit 24 - 27 MPa
Fracture Toughness 23 - 26 MPam12
Hardness 100 - 140 MPa
Loss Coefficient 0009- 0026
Modulus of Rupture 50 - 55 MPa
Poissons Ratio 038 - 042
Shear Modulus 085 - 095 GPa
Tensile Strength 45 - 48 MPa
Youngs Modulus 25 - 28 GPa
Successful
applications
$
Economic analysis
and business caseSelection of
material and process
Potential
applications
Characterization Selection and implementation
DATA INFORMATION KNOWLEDGE
B Konh T Sorensen A Trimble 9 of XXME 481 ndash Fall 2017
Materials Data - Organization
bull Properties for a particular material is called the ldquomaterial attributesrdquo
bull Includes both structured and non-structured information
bull We need to find the best match between the design requirements and the
materials attributes
B Konh T Sorensen A Trimble 10 of XXME 481 ndash Fall 2017
Material stiffness
httpwwwgrantadesigncomdownloadpdfteaching_resource_books2-Materials-Charts-2010pdf
B Konh T Sorensen A Trimble 11 of XXME 481 ndash Fall 2017
Metals
Metal Examples of application
Ferrous Metals Carbon Steels Utensils construction automotive transmission
towers hellip
Stainless Steels Off shore drilling rigs naval construction
chemical transport food preparation medical
instruments
Cast Irons Cylinders pistons motor blocks construction
wear resistant materials
Light Alloys Aluminum Alloys Aerospace construction transport packaging
electrical conductors
Magnesium Alloys Aerospace automotive sporting equipment
Titanium Alloys Aerospace chemical industry
Copper Alloys Copper Electrical conductors
Bronze Heat exchangers chemical industry maritime
industry
Brass Pressure vessels fittings
Nickel Alloys Aerospace currency
B Konh T Sorensen A Trimble 12 of XXME 481 ndash Fall 2017
Interactions
Material
ProcessShape
Functionality
Materials Selection Methodology
Ashby Methodology
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 13 of XXME 481 ndash Fall 2017
Material selection
[ASHBY99] - Materials Selection In Mechanical Design
B Konh T Sorensen A Trimble 14 of XXME 481 ndash Fall 2017
First Step Translation
ldquoExpress design requirements as constraints and objectivesrdquo
Using design requirements analyze four items
1 Function What does the component do
2 Objective What essential conditions must be met
3 Constraints What is to be maximized or minimized
4 Free variables Which design variables are free
ndash Which can be modified
ndash Which are desirable
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 5 of XXME 481 ndash Fall 2017
Need for a new product and new materials
Development of a new materials
httphleelabhomewixsitecommysiteresearch2
httphleelabhomewixsitecommysite
bull Soft active materials
bull Biologically inspired design principles
Soft robotics
Dr Howon Lee
Rutgers University
Soft multi-material actuators
Dr Conor Walsh
Harvard University
httpsbiodesignseasharvardedusoft-robotics
bull Large bending motions
B Konh T Sorensen A Trimble 6 of XXME 481 ndash Fall 2017
Evolution of materials
[ASHBY99] - Materials Selection In Mechanical Design
httpwwwutcfr~hagegebeUVMQ12CORRECTIONS_TD5BASHBY995D20-
20Materials20Selection20In20Mechanical20Design202Edpdf
B Konh T Sorensen A Trimble 7 of XXME 481 ndash Fall 2017
Material Properties
Physical
ndash Density
ndash Melting point
ndash Vapor pressure
ndash Viscosity
ndash Porosity
ndash Permeability
ndash Reflectivity
ndash Transparency
ndash Optical properties
ndash Dimensional stability
Chemical
ndash Corrosion
ndash Oxidation
ndash Thermal stability
ndash Biological stability
ndash Stress Corrosion
ndash hellip
Electrical
ndash Conductivity
ndash Dielectric constant
ndash Coersive force
ndash Hysteresis
Thermal
ndash Conductivity
ndash Specific Heat
ndash Thermal expansion
ndash Emissivity
Mechanical
ndash Hardness
ndash Elastic constants
ndash Yield strength
ndash Ultimate strength
ndash Fatigue
ndash Fracture Toughness
ndash Creep
ndash Damping
ndash Wear resistance
ndash Spalling
ndash Ballistic performance
ndash helliphellip
B Konh T Sorensen A Trimble 8 of XXME 481 ndash Fall 2017
httpwwwmatwebcom
What do we expect from a design
The products should perform their functions effectively safely at acceptable costrdquo
Test Test data
Data
capture
Statistical
analysis
Allowables
Mechanical Properties
Bulk Modulus 41 - 46 GPa
Compressive Strength 55 - 60 MPa
Ductility 006 - 007
Elastic Limit 40 - 45 MPa
Endurance Limit 24 - 27 MPa
Fracture Toughness 23 - 26 MPam12
Hardness 100 - 140 MPa
Loss Coefficient 0009- 0026
Modulus of Rupture 50 - 55 MPa
Poissons Ratio 038 - 042
Shear Modulus 085 - 095 GPa
Tensile Strength 45 - 48 MPa
Youngs Modulus 25 - 28 GPa
Successful
applications
$
Economic analysis
and business caseSelection of
material and process
Potential
applications
Characterization Selection and implementation
DATA INFORMATION KNOWLEDGE
B Konh T Sorensen A Trimble 9 of XXME 481 ndash Fall 2017
Materials Data - Organization
bull Properties for a particular material is called the ldquomaterial attributesrdquo
bull Includes both structured and non-structured information
bull We need to find the best match between the design requirements and the
materials attributes
B Konh T Sorensen A Trimble 10 of XXME 481 ndash Fall 2017
Material stiffness
httpwwwgrantadesigncomdownloadpdfteaching_resource_books2-Materials-Charts-2010pdf
B Konh T Sorensen A Trimble 11 of XXME 481 ndash Fall 2017
Metals
Metal Examples of application
Ferrous Metals Carbon Steels Utensils construction automotive transmission
towers hellip
Stainless Steels Off shore drilling rigs naval construction
chemical transport food preparation medical
instruments
Cast Irons Cylinders pistons motor blocks construction
wear resistant materials
Light Alloys Aluminum Alloys Aerospace construction transport packaging
electrical conductors
Magnesium Alloys Aerospace automotive sporting equipment
Titanium Alloys Aerospace chemical industry
Copper Alloys Copper Electrical conductors
Bronze Heat exchangers chemical industry maritime
industry
Brass Pressure vessels fittings
Nickel Alloys Aerospace currency
B Konh T Sorensen A Trimble 12 of XXME 481 ndash Fall 2017
Interactions
Material
ProcessShape
Functionality
Materials Selection Methodology
Ashby Methodology
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 13 of XXME 481 ndash Fall 2017
Material selection
[ASHBY99] - Materials Selection In Mechanical Design
B Konh T Sorensen A Trimble 14 of XXME 481 ndash Fall 2017
First Step Translation
ldquoExpress design requirements as constraints and objectivesrdquo
Using design requirements analyze four items
1 Function What does the component do
2 Objective What essential conditions must be met
3 Constraints What is to be maximized or minimized
4 Free variables Which design variables are free
ndash Which can be modified
ndash Which are desirable
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 6 of XXME 481 ndash Fall 2017
Evolution of materials
[ASHBY99] - Materials Selection In Mechanical Design
httpwwwutcfr~hagegebeUVMQ12CORRECTIONS_TD5BASHBY995D20-
20Materials20Selection20In20Mechanical20Design202Edpdf
B Konh T Sorensen A Trimble 7 of XXME 481 ndash Fall 2017
Material Properties
Physical
ndash Density
ndash Melting point
ndash Vapor pressure
ndash Viscosity
ndash Porosity
ndash Permeability
ndash Reflectivity
ndash Transparency
ndash Optical properties
ndash Dimensional stability
Chemical
ndash Corrosion
ndash Oxidation
ndash Thermal stability
ndash Biological stability
ndash Stress Corrosion
ndash hellip
Electrical
ndash Conductivity
ndash Dielectric constant
ndash Coersive force
ndash Hysteresis
Thermal
ndash Conductivity
ndash Specific Heat
ndash Thermal expansion
ndash Emissivity
Mechanical
ndash Hardness
ndash Elastic constants
ndash Yield strength
ndash Ultimate strength
ndash Fatigue
ndash Fracture Toughness
ndash Creep
ndash Damping
ndash Wear resistance
ndash Spalling
ndash Ballistic performance
ndash helliphellip
B Konh T Sorensen A Trimble 8 of XXME 481 ndash Fall 2017
httpwwwmatwebcom
What do we expect from a design
The products should perform their functions effectively safely at acceptable costrdquo
Test Test data
Data
capture
Statistical
analysis
Allowables
Mechanical Properties
Bulk Modulus 41 - 46 GPa
Compressive Strength 55 - 60 MPa
Ductility 006 - 007
Elastic Limit 40 - 45 MPa
Endurance Limit 24 - 27 MPa
Fracture Toughness 23 - 26 MPam12
Hardness 100 - 140 MPa
Loss Coefficient 0009- 0026
Modulus of Rupture 50 - 55 MPa
Poissons Ratio 038 - 042
Shear Modulus 085 - 095 GPa
Tensile Strength 45 - 48 MPa
Youngs Modulus 25 - 28 GPa
Successful
applications
$
Economic analysis
and business caseSelection of
material and process
Potential
applications
Characterization Selection and implementation
DATA INFORMATION KNOWLEDGE
B Konh T Sorensen A Trimble 9 of XXME 481 ndash Fall 2017
Materials Data - Organization
bull Properties for a particular material is called the ldquomaterial attributesrdquo
bull Includes both structured and non-structured information
bull We need to find the best match between the design requirements and the
materials attributes
B Konh T Sorensen A Trimble 10 of XXME 481 ndash Fall 2017
Material stiffness
httpwwwgrantadesigncomdownloadpdfteaching_resource_books2-Materials-Charts-2010pdf
B Konh T Sorensen A Trimble 11 of XXME 481 ndash Fall 2017
Metals
Metal Examples of application
Ferrous Metals Carbon Steels Utensils construction automotive transmission
towers hellip
Stainless Steels Off shore drilling rigs naval construction
chemical transport food preparation medical
instruments
Cast Irons Cylinders pistons motor blocks construction
wear resistant materials
Light Alloys Aluminum Alloys Aerospace construction transport packaging
electrical conductors
Magnesium Alloys Aerospace automotive sporting equipment
Titanium Alloys Aerospace chemical industry
Copper Alloys Copper Electrical conductors
Bronze Heat exchangers chemical industry maritime
industry
Brass Pressure vessels fittings
Nickel Alloys Aerospace currency
B Konh T Sorensen A Trimble 12 of XXME 481 ndash Fall 2017
Interactions
Material
ProcessShape
Functionality
Materials Selection Methodology
Ashby Methodology
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 13 of XXME 481 ndash Fall 2017
Material selection
[ASHBY99] - Materials Selection In Mechanical Design
B Konh T Sorensen A Trimble 14 of XXME 481 ndash Fall 2017
First Step Translation
ldquoExpress design requirements as constraints and objectivesrdquo
Using design requirements analyze four items
1 Function What does the component do
2 Objective What essential conditions must be met
3 Constraints What is to be maximized or minimized
4 Free variables Which design variables are free
ndash Which can be modified
ndash Which are desirable
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 7 of XXME 481 ndash Fall 2017
Material Properties
Physical
ndash Density
ndash Melting point
ndash Vapor pressure
ndash Viscosity
ndash Porosity
ndash Permeability
ndash Reflectivity
ndash Transparency
ndash Optical properties
ndash Dimensional stability
Chemical
ndash Corrosion
ndash Oxidation
ndash Thermal stability
ndash Biological stability
ndash Stress Corrosion
ndash hellip
Electrical
ndash Conductivity
ndash Dielectric constant
ndash Coersive force
ndash Hysteresis
Thermal
ndash Conductivity
ndash Specific Heat
ndash Thermal expansion
ndash Emissivity
Mechanical
ndash Hardness
ndash Elastic constants
ndash Yield strength
ndash Ultimate strength
ndash Fatigue
ndash Fracture Toughness
ndash Creep
ndash Damping
ndash Wear resistance
ndash Spalling
ndash Ballistic performance
ndash helliphellip
B Konh T Sorensen A Trimble 8 of XXME 481 ndash Fall 2017
httpwwwmatwebcom
What do we expect from a design
The products should perform their functions effectively safely at acceptable costrdquo
Test Test data
Data
capture
Statistical
analysis
Allowables
Mechanical Properties
Bulk Modulus 41 - 46 GPa
Compressive Strength 55 - 60 MPa
Ductility 006 - 007
Elastic Limit 40 - 45 MPa
Endurance Limit 24 - 27 MPa
Fracture Toughness 23 - 26 MPam12
Hardness 100 - 140 MPa
Loss Coefficient 0009- 0026
Modulus of Rupture 50 - 55 MPa
Poissons Ratio 038 - 042
Shear Modulus 085 - 095 GPa
Tensile Strength 45 - 48 MPa
Youngs Modulus 25 - 28 GPa
Successful
applications
$
Economic analysis
and business caseSelection of
material and process
Potential
applications
Characterization Selection and implementation
DATA INFORMATION KNOWLEDGE
B Konh T Sorensen A Trimble 9 of XXME 481 ndash Fall 2017
Materials Data - Organization
bull Properties for a particular material is called the ldquomaterial attributesrdquo
bull Includes both structured and non-structured information
bull We need to find the best match between the design requirements and the
materials attributes
B Konh T Sorensen A Trimble 10 of XXME 481 ndash Fall 2017
Material stiffness
httpwwwgrantadesigncomdownloadpdfteaching_resource_books2-Materials-Charts-2010pdf
B Konh T Sorensen A Trimble 11 of XXME 481 ndash Fall 2017
Metals
Metal Examples of application
Ferrous Metals Carbon Steels Utensils construction automotive transmission
towers hellip
Stainless Steels Off shore drilling rigs naval construction
chemical transport food preparation medical
instruments
Cast Irons Cylinders pistons motor blocks construction
wear resistant materials
Light Alloys Aluminum Alloys Aerospace construction transport packaging
electrical conductors
Magnesium Alloys Aerospace automotive sporting equipment
Titanium Alloys Aerospace chemical industry
Copper Alloys Copper Electrical conductors
Bronze Heat exchangers chemical industry maritime
industry
Brass Pressure vessels fittings
Nickel Alloys Aerospace currency
B Konh T Sorensen A Trimble 12 of XXME 481 ndash Fall 2017
Interactions
Material
ProcessShape
Functionality
Materials Selection Methodology
Ashby Methodology
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 13 of XXME 481 ndash Fall 2017
Material selection
[ASHBY99] - Materials Selection In Mechanical Design
B Konh T Sorensen A Trimble 14 of XXME 481 ndash Fall 2017
First Step Translation
ldquoExpress design requirements as constraints and objectivesrdquo
Using design requirements analyze four items
1 Function What does the component do
2 Objective What essential conditions must be met
3 Constraints What is to be maximized or minimized
4 Free variables Which design variables are free
ndash Which can be modified
ndash Which are desirable
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 8 of XXME 481 ndash Fall 2017
httpwwwmatwebcom
What do we expect from a design
The products should perform their functions effectively safely at acceptable costrdquo
Test Test data
Data
capture
Statistical
analysis
Allowables
Mechanical Properties
Bulk Modulus 41 - 46 GPa
Compressive Strength 55 - 60 MPa
Ductility 006 - 007
Elastic Limit 40 - 45 MPa
Endurance Limit 24 - 27 MPa
Fracture Toughness 23 - 26 MPam12
Hardness 100 - 140 MPa
Loss Coefficient 0009- 0026
Modulus of Rupture 50 - 55 MPa
Poissons Ratio 038 - 042
Shear Modulus 085 - 095 GPa
Tensile Strength 45 - 48 MPa
Youngs Modulus 25 - 28 GPa
Successful
applications
$
Economic analysis
and business caseSelection of
material and process
Potential
applications
Characterization Selection and implementation
DATA INFORMATION KNOWLEDGE
B Konh T Sorensen A Trimble 9 of XXME 481 ndash Fall 2017
Materials Data - Organization
bull Properties for a particular material is called the ldquomaterial attributesrdquo
bull Includes both structured and non-structured information
bull We need to find the best match between the design requirements and the
materials attributes
B Konh T Sorensen A Trimble 10 of XXME 481 ndash Fall 2017
Material stiffness
httpwwwgrantadesigncomdownloadpdfteaching_resource_books2-Materials-Charts-2010pdf
B Konh T Sorensen A Trimble 11 of XXME 481 ndash Fall 2017
Metals
Metal Examples of application
Ferrous Metals Carbon Steels Utensils construction automotive transmission
towers hellip
Stainless Steels Off shore drilling rigs naval construction
chemical transport food preparation medical
instruments
Cast Irons Cylinders pistons motor blocks construction
wear resistant materials
Light Alloys Aluminum Alloys Aerospace construction transport packaging
electrical conductors
Magnesium Alloys Aerospace automotive sporting equipment
Titanium Alloys Aerospace chemical industry
Copper Alloys Copper Electrical conductors
Bronze Heat exchangers chemical industry maritime
industry
Brass Pressure vessels fittings
Nickel Alloys Aerospace currency
B Konh T Sorensen A Trimble 12 of XXME 481 ndash Fall 2017
Interactions
Material
ProcessShape
Functionality
Materials Selection Methodology
Ashby Methodology
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 13 of XXME 481 ndash Fall 2017
Material selection
[ASHBY99] - Materials Selection In Mechanical Design
B Konh T Sorensen A Trimble 14 of XXME 481 ndash Fall 2017
First Step Translation
ldquoExpress design requirements as constraints and objectivesrdquo
Using design requirements analyze four items
1 Function What does the component do
2 Objective What essential conditions must be met
3 Constraints What is to be maximized or minimized
4 Free variables Which design variables are free
ndash Which can be modified
ndash Which are desirable
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 9 of XXME 481 ndash Fall 2017
Materials Data - Organization
bull Properties for a particular material is called the ldquomaterial attributesrdquo
bull Includes both structured and non-structured information
bull We need to find the best match between the design requirements and the
materials attributes
B Konh T Sorensen A Trimble 10 of XXME 481 ndash Fall 2017
Material stiffness
httpwwwgrantadesigncomdownloadpdfteaching_resource_books2-Materials-Charts-2010pdf
B Konh T Sorensen A Trimble 11 of XXME 481 ndash Fall 2017
Metals
Metal Examples of application
Ferrous Metals Carbon Steels Utensils construction automotive transmission
towers hellip
Stainless Steels Off shore drilling rigs naval construction
chemical transport food preparation medical
instruments
Cast Irons Cylinders pistons motor blocks construction
wear resistant materials
Light Alloys Aluminum Alloys Aerospace construction transport packaging
electrical conductors
Magnesium Alloys Aerospace automotive sporting equipment
Titanium Alloys Aerospace chemical industry
Copper Alloys Copper Electrical conductors
Bronze Heat exchangers chemical industry maritime
industry
Brass Pressure vessels fittings
Nickel Alloys Aerospace currency
B Konh T Sorensen A Trimble 12 of XXME 481 ndash Fall 2017
Interactions
Material
ProcessShape
Functionality
Materials Selection Methodology
Ashby Methodology
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 13 of XXME 481 ndash Fall 2017
Material selection
[ASHBY99] - Materials Selection In Mechanical Design
B Konh T Sorensen A Trimble 14 of XXME 481 ndash Fall 2017
First Step Translation
ldquoExpress design requirements as constraints and objectivesrdquo
Using design requirements analyze four items
1 Function What does the component do
2 Objective What essential conditions must be met
3 Constraints What is to be maximized or minimized
4 Free variables Which design variables are free
ndash Which can be modified
ndash Which are desirable
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 10 of XXME 481 ndash Fall 2017
Material stiffness
httpwwwgrantadesigncomdownloadpdfteaching_resource_books2-Materials-Charts-2010pdf
B Konh T Sorensen A Trimble 11 of XXME 481 ndash Fall 2017
Metals
Metal Examples of application
Ferrous Metals Carbon Steels Utensils construction automotive transmission
towers hellip
Stainless Steels Off shore drilling rigs naval construction
chemical transport food preparation medical
instruments
Cast Irons Cylinders pistons motor blocks construction
wear resistant materials
Light Alloys Aluminum Alloys Aerospace construction transport packaging
electrical conductors
Magnesium Alloys Aerospace automotive sporting equipment
Titanium Alloys Aerospace chemical industry
Copper Alloys Copper Electrical conductors
Bronze Heat exchangers chemical industry maritime
industry
Brass Pressure vessels fittings
Nickel Alloys Aerospace currency
B Konh T Sorensen A Trimble 12 of XXME 481 ndash Fall 2017
Interactions
Material
ProcessShape
Functionality
Materials Selection Methodology
Ashby Methodology
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 13 of XXME 481 ndash Fall 2017
Material selection
[ASHBY99] - Materials Selection In Mechanical Design
B Konh T Sorensen A Trimble 14 of XXME 481 ndash Fall 2017
First Step Translation
ldquoExpress design requirements as constraints and objectivesrdquo
Using design requirements analyze four items
1 Function What does the component do
2 Objective What essential conditions must be met
3 Constraints What is to be maximized or minimized
4 Free variables Which design variables are free
ndash Which can be modified
ndash Which are desirable
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 11 of XXME 481 ndash Fall 2017
Metals
Metal Examples of application
Ferrous Metals Carbon Steels Utensils construction automotive transmission
towers hellip
Stainless Steels Off shore drilling rigs naval construction
chemical transport food preparation medical
instruments
Cast Irons Cylinders pistons motor blocks construction
wear resistant materials
Light Alloys Aluminum Alloys Aerospace construction transport packaging
electrical conductors
Magnesium Alloys Aerospace automotive sporting equipment
Titanium Alloys Aerospace chemical industry
Copper Alloys Copper Electrical conductors
Bronze Heat exchangers chemical industry maritime
industry
Brass Pressure vessels fittings
Nickel Alloys Aerospace currency
B Konh T Sorensen A Trimble 12 of XXME 481 ndash Fall 2017
Interactions
Material
ProcessShape
Functionality
Materials Selection Methodology
Ashby Methodology
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 13 of XXME 481 ndash Fall 2017
Material selection
[ASHBY99] - Materials Selection In Mechanical Design
B Konh T Sorensen A Trimble 14 of XXME 481 ndash Fall 2017
First Step Translation
ldquoExpress design requirements as constraints and objectivesrdquo
Using design requirements analyze four items
1 Function What does the component do
2 Objective What essential conditions must be met
3 Constraints What is to be maximized or minimized
4 Free variables Which design variables are free
ndash Which can be modified
ndash Which are desirable
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 12 of XXME 481 ndash Fall 2017
Interactions
Material
ProcessShape
Functionality
Materials Selection Methodology
Ashby Methodology
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 13 of XXME 481 ndash Fall 2017
Material selection
[ASHBY99] - Materials Selection In Mechanical Design
B Konh T Sorensen A Trimble 14 of XXME 481 ndash Fall 2017
First Step Translation
ldquoExpress design requirements as constraints and objectivesrdquo
Using design requirements analyze four items
1 Function What does the component do
2 Objective What essential conditions must be met
3 Constraints What is to be maximized or minimized
4 Free variables Which design variables are free
ndash Which can be modified
ndash Which are desirable
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 13 of XXME 481 ndash Fall 2017
Material selection
[ASHBY99] - Materials Selection In Mechanical Design
B Konh T Sorensen A Trimble 14 of XXME 481 ndash Fall 2017
First Step Translation
ldquoExpress design requirements as constraints and objectivesrdquo
Using design requirements analyze four items
1 Function What does the component do
2 Objective What essential conditions must be met
3 Constraints What is to be maximized or minimized
4 Free variables Which design variables are free
ndash Which can be modified
ndash Which are desirable
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 14 of XXME 481 ndash Fall 2017
First Step Translation
ldquoExpress design requirements as constraints and objectivesrdquo
Using design requirements analyze four items
1 Function What does the component do
2 Objective What essential conditions must be met
3 Constraints What is to be maximized or minimized
4 Free variables Which design variables are free
ndash Which can be modified
ndash Which are desirable
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 15 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Function
Support a tension load
Objective
Minimize mass
Constraints
Length specified
Carry load F wo failure
Free variables
Cross-section area
Material
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 16 of XXME 481 ndash Fall 2017
Example Materials for a Light Strong Tie
Objective
Constraints
Rearrange to eliminate free variable
Minimizing weight by minimizing
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 17 of XXME 481 ndash Fall 2017
Second Step Screening
Eliminate materials that cannot do the job
Need effective way of evaluating large range of material classes and
properties
Metals Steels Cast irons Al-alloys Cu-
alloys Ti-alloys
Ceramics Alumina Si-carbide Si-nitride
Ziconia
Hybrids Composites Sandwiches Lattices
Segmented
Polymers PE PP PC PS PET PVC
PA (Nylon) Polyester Epoxy
Glasses Soda glass Borosilicate Silica
glass Glass ceramic
Elastomers Isoprene Butyl rubber
Natural rubber Silicones EVA
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 18 of XXME 481 ndash Fall 2017
Comparing Material Properties
Material Bar Charts
Good for elementary selection
(eg find materials with large modulus)
Material Property Charts
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 19 of XXME 481 ndash Fall 2017
Screening Example
Function
Heat Sink
Constraints
1 Max service temp gt 200 C
2 Electrical insulator
R gt 1020 μohm cm
3 Thermal conductor
T-conduct λ gt 100 Wm K
4 Not heavy
Density lt 3 Mgm3
Free Variables
Materials and Processes
Heat Sink for Power Electronics
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 20 of XXME 481 ndash Fall 2017
Heat Sink Screening Bar Chart
200 ordmC
λ gt 100 WmK
R gt 1020 micro ohm cm
temp gt 200 C
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 21 of XXME 481 ndash Fall 2017
Third Step Ranking
ldquoFind the materials that do the job bestrdquo
- What if multiple materials are selected after screening
- Which one is best
- What if there are multiple material parameters for evaluation
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 22 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Function
Transmit electricity
Objective
Minimize electrical Resistance
Constraints
Length L and section A are specified
Must not fail under wind or ice-load
Required tensile strength gt 80 MPa
Free variables
Material choice
gtgt Screen on strength rank on resistivity
Electrical resistivity
Overhead Transmission Cable
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 23 of XXME 481 ndash Fall 2017
Single Property Ranking Example
Screening on strength eliminates polymers some ceramics
Ranking on resistivity selects Al and Cu alloys
Overhead Transmission Cable
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 24 of XXME 481 ndash Fall 2017
Advanced Ranking The Material Index
Use this method
1 Identify function constraints objective and free variables
List simple constraints for screening
2 Write down equation for objective -- the ldquoperformance equationrdquo
If objective involves a free variable (other than the material)
Identify the constraint that limits it
Use this to eliminate the free variable in performance equation
3 Read off the combination of material properties that maximizes
performance -- the material index
4 Use this for ranking
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 25 of XXME 481 ndash Fall 2017
Optimized Selection
Example
Tension Load
strength limited
- Maximize M = σρ
- In log space
log σ = log ρ + log M
- This is a set of lines
with slope=1
- Materials above line are candidates
Using Material Indices amp Property Charts Strength
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 26 of XXME 481 ndash Fall 2017
Material Indices amp Property Charts
Example
Stiff beam
- Maximize M = Ε12ρ
- In log space
log E = 2 (log ρ + log M)
- This is a set of lines
with slope=2
- Candidates change with objective
Stiffness
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 27 of XXME 481 ndash Fall 2017
Considering Multiple ObjectivesConstraints
With multiple constraints
Solve each individually
Select candidates based on each
Evaluate performance of each
Select performance based on most limiting
May be different for each candidate
With multiple objectives
Requires utility function to map multiple metrics to common performance
measures
Design performance is determined by the combination of
Shape Materials Process
Underlying principles of selection are unchanged
- BUT do not underestimate impact of shape or the limitation of process
Method for Early Technology Screening
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 28 of XXME 481 ndash Fall 2017
Ashby Method for Early Material Selection
Four basic steps
1 Translation express design requirements as constraints amp objectives
2 Screening eliminate materials that cannot do the job
3 Ranking find the materials that do the job best
4 Supporting information explore pedigrees of top-ranked candidates
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 29 of XXME 481 ndash Fall 2017
Other Materials Selection Charts
bull Modulus-Relative Cost bull Facture Toughness-Density
bull Strength-Relative Cost bull Conductivity-Diffusivity
Modulus-Strength bull Expansion-Conductivity
bull Specific Modulus-Specific
Strength
bull Fracture Toughness-
Modulus
bull Fracture Toughness-
Strength
bull Expansion-Modulus
bull Strength-Expansion
bull Strength Temperature
bull Wear Rate-Hardness
bull Environmental Attack Chart
bull Loss Coefficient-Modulus
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 30 of XXME 481 ndash Fall 2017
Summary
bull Material affects design based on
- Geometric specifics
- Loading requirements
- Design constraints
- Performance objective
bull Effects can be assessed analytically
bull Keep candidate set large as long as is feasible
bull Materials charts give quick overview software can be used to more
accurately find options
bull Remember strategic considerations can alter best choice
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 31 of XXME 481 ndash Fall 2017
Function Objective Constraint
What does
component do
What is to be maximized
or minimized
What specific requirements
must be met
Any engineering
component has
one or more
functions (to
support a load to
contain a pressure
to transmit heat
etc)
The designer has an
objective (to make it
as cheap as possible
or as light as possible
or as safe as possible
or some combination
of these)
The objective must be
achieved subject to
constraints (eg the
dimensions are fixed the
component must carry the
given load without failure it
should function in a certain
temperature range etc
Free variables What is the designer free to change
Defining the Design requirements
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 32 of XXME 481 ndash Fall 2017
1 List the constraints (eg no buckling high stiffness) of the
problem and develop an equation for them if possible
2 Develop an equation of the design objective in terms of functional
requirements geometry and materials properties (objective function)
3 Define the unconstrained (free) variables
4 Substitute the free variable from the constraint equation into the
objective function
5 Group the variables into three groups functional requirements (F)
geometry (G) and materials functions (M) to develop the performance
metric (P)
6 Read off the materials index M in order to maximize the
performance metric (P)
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 33 of XXME 481 ndash Fall 2017
Materials Selection Charts
bullThe performance metric of a design is limited by the materials
bullPerformance metric is a function of multiple properties f(multiple
properties)
bullCharts Property 1 versus Property 2 (P1 vs P2)
bullIt can be plotted for classes and subclasses of materials (Classes metals
ceramics polymers composites) (Sub-Classes engineering ceramics
porous ceramics etc)
bullCombinations of properties are important in evaluating usefulness of
materials
bullStrength to Weight Ratio f
bullStiffness to Weight Ratio E
bullThe properties have ranges
bullE(Cu) = few (purity texture etc)
bullStrength of Al2O3 can vary by a factor of 100 due to (porosity grain
size heat treatment etc)
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
B Konh T Sorensen A Trimble 34 of XXME 481 ndash Fall 2017
Materials Indices
Materials indices are specific functions derived from design
equations that involve only materials properties that can be used in
conjunction with materials selection charts
bulleg strong light tie rod in tensionndashminimize ρσy
bulleg stiff light beam in bending ndashminimize ρE12
bulleg stiff light panel in bending -minimize ρE13
Derivation of MIrsquos
top related