material selection lecture
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BMFB 3323Materials SelectionSEM II 2010/2011
BMFB 3323 SEM II 2014/2015 Lecture 2 THE DESIGN PROCESS THEB!SIC
Lecture 2
Materials Selection:THE DESIGN PROCESS & THE BASIC
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• Materials Attributes:
e.g. Mechanical, thermal, electrical, !tical an" chemical
!r!ertie#, c#t an" a$aila%ilit&, !rce##ing characteri#tic# an" theen$irnmental cn#e'uence# ( it# u#e.
e.g. )en#it&, #trength, , re#i#tance t crr#in.
• Process Attributes :
e.g. *he material# it can han"le, the #ha!e it can ma+e, their #ie,!reci#in an" the ecnmic %atch #ie -the num%er ( unit# that it an
ma+e m#t ecnmicall&.
REF"ECTION#
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To develop a strategy for selecting materials and
process that is design-led.
Using translation, screening, ranking and documentation
as a tool in selection strategy
"E!RNING O$TCOMES
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• “)e#ign i# the !rce## ( tran#lating a ne i"ea r a mar+e" nee"
int "etaile" in(rmatin (rm hich a !r"uct can %e ma"e -M.F.
#h%&
• Engineering "e#ign i# the !rce## ( "e$i#ing a #&#tem,
cm!nent, r !rce## t meet "e#ire" nee"#.
• *he "e#ign !rce## cn#i#t# ( #e$eral #te!#, each ha# certain
characteri#tic# an" certain ta#+# t %e !er(rme":
ecgni#ing a nee" -!r%lem
)e(ining the !r%lem
E#ta%li#hing #!eci(icatin#
athering in(rmatin
INTROD$CTION
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THE DESIGN PROCESS
A systematic problem solving strategy, with criteria and
constraints, used to develop many possible solutions to
solve a problem or satisfy human needs and to narrowdown the possible solutions to one final choice
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TPES O! DESIGN
• New idea working principle !fromscratch"Original design
• #mprovements of e$isting product• e.g% &ars, consumer products !mobile
phones, cameras etc'"
Adaptive/Development
Design
• &hange in scale or dimensions withoutchanging the function
• e.g% desktop (& to laptop computerVariant Design
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THE DESIGN !LO" CHART
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THE DESIGN F"O% CH!RT
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MATERIALS DATA IN THE DESIGNPROCESS
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MATERIALS DATA IN THE DESIGNPROCESS
The design process may notseem as logical ) linear as it is.
The design process is completeonly when a compatible pathfrom “need* to “specification*can be identified.
The key + /#0##T1.
&2s3 &oncepts
2s3 mbodiments of &2s
42s3 4etailed reali5ations of 2s
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Metals
Ceramics
MATERIALSComposites
Polymers
lat ! S"eetS#APES
Prismatic
$%D
Casting
Mo&lding
PROCESSESPo'der Met"ods
Mac"ining
At each stage of thedesign, decisions needto be made aboutwhat to make it out of(Materials),and how to make it(Processes and
S"apes)
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*) Concept&al
4esign proceed by developing concepts to
perform the function
At this stage, all options are open
The designer considers alternatives concepts
and ways
THE DESIGN PROCESS
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+) Em,odiment
Take the promising concepts and seeks to analy5e their
operation at an appro$imate level.
#nvolves selecting materials, si5ing components,
e$amining the implications for performance and cost.
The embodiment stage ends with a feasible layout
Then passed to the detailed design stage
THE DESIGN PROCESS
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$) Detail
6pecifications for each component are drawn up.
7ptimi5ation methods are applied to ma$imi5e
performance.
inal choice of material and process are made
THE DESIGN PROCESS
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• #teration, looping back to e$plorealternatives, is an essential part of thedesign process.
• Think of each of the many possible
choices that could be made as an arrayof blobs in design space as suggested inthe fig.
• Then the design process becomes one ofcreating paths, linking compatible blobs,until a connection is made from the top!88market need22" to the bottom!88product specification22".
• 7nce a path is found, it is alwayspossible to make it look linear andlogical process.
• Thus a key part of design, and ofselecting materials for it, is flexibility, the ability to explore alternatives
quickly.
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DESIGN TOO"S !ND M!TERI!"SD!T!
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!#NCTION$ MATERIAL$SHAPE$ AND PROCESS
unction dictates the choice of bothmaterial and shape.
(rocess is influenced by the material3 byits formability, machinability, weldability,heat-treatability, and so on.
(rocess obviously interacts with shape9the process determines the shape, thesi5e, the precision and the cost.
The interactions are two-way3:.6pecification of shape restricts the choice
of material and process
;.6pecification of process limits thematerials you can use and the shapes they
can take
Functin, material, #ha!e an"
!rce## interact.
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E%a'le o( )esi*n 'rocess+,,Nee) - Conce't - E.o)ient
ConceptsNeed
Embodiments
Direct pull Levered pull Spring assisted pull Geared pull
"e$ice i#
re'uire" t all
acce## t ine in
a cr+e" %ttle
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Detail
E.o)ient -Detail
Embodiment
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S&mmary
The key part of design and of selecting materials is
fle$ibility, the ability to e$plore alternatives <uickly
=eeping the big picture as well as the details in focus.
THE DESIGN PROCESS
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CASE ST#D :/, Coolin* 'o0er electronic
>icrochips, particularly those for power electronics,get hot. #f they get too hot, they cease to function.
?hat is the need@
A scheme for removing heat frompower microchips.
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6tep :34evise concepts to meet the need.
To remove heatfrom power
microchips
CASE ST#D :/, Coolin* 'o0er electronic
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To remove heatfrom powermicrochips
&:3 &onduction
&;3 &onvection
&3 vaporation
&B3 Cadiation
Concept
CASE ST#D :/, Coolin* 'o0er electronic
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6tep ;36ketch an embodiment of all of them.
To remove heatfrom power
microchips
&:3 &onduction
&;3 &onvection
&3 vaporation
&B3 Cadiation
CASE ST#D :/, Coolin* 'o0er electronic
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To removeheat from
powermicrochips
&:3&onduction
>assive, with sufficient heat capacity to absorbheat over work cycle
&ompact, re<uiring back-up by coupling toconvection, evaporation or radiation
&;3&onvection
ree convection not re<uiring fan or pump
orced convection with fan or pump
&3vaporation
Unconfined, such as a continuous spray ofvolatile fluid
&onfined, utilising heat-pipe technology
&B3Cadiation
Cadiation to ambient, using high emissivitycoatings
Cadiation to cooled surface, from high emissivity
surface to highly absorbent surface
Concept Embodiment
CASE ST#D :/, Coolin* 'o0er electronic
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ist three things that you are very clearof.
ist three things that you feel ha5y about.
ist three things that you need further
clarification.
THE DESIGN PROCESS
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BMFB 3323Materials SelectionSEM II 2010/2011
BMFB 3323 SEM II 2014/2015 Lecture 3 THE B!SIC
Lecture 1
Materials Selection:THE BASIC
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6election involves seeking the best matchbetween the property-profiles of the materialsand that re<uired by the design.
The selection task involves3
a" #dentifying the desired attribute profile and then
b" &omparing it with those of real engineering
materials to find the best match.
THE B!SICS OF M!TERI!"SSE"ECTION
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THE B!SICS OF M!TERI!"SSE"ECTION
M!TERI!"S SE"ECTION
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All Materials
Translate Design re-&irements
Screen &sing constraints
Ran. &sing o,ective
See. s&pporting in0ormation
inal MaterialC"oice
M!TERI!"S SE"ECTIONSTR!TEG&
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The selection strategy
• ?hat does component do@unction
• ?hat non-negotiable conditions must be
met@• #s an essential condition that must be met,
usually e$pressed as a limit on a material orprocess attribute.
&onstraints
• ?hat is to be ma$imi5ed or minimi5ed@• #s a <uantity for which an e$treme value !a
ma$imum or minimum" is sought, fre<uentlycost, mass or volume.
7bDective
• ?hat parameters of the problem is thedesigner free to change.ree Eariable
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1) Translation
• Converting the design requirements into a prescription for
selecting a material and a process to shape it.
• Any engineering component has one or more functions,
subject to constraints, have one or more objectives
1'
Translation
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• Certain parameters can be adjusted in order to optimize the
objective free variables).
• !unction, constraints, objectives and free variables Table 1)
define the boundary conditions for selecting a material.
• The first step in relating design requirements to material properties is a clear statement of function, constraints,
objectives and free variables.
1'
Translation
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Table 1: Function, constraints, objectives
and free variablesFunction What does component do? to support a load, to contain a pressure, to
transmit heat, and so forth. This must beachieved
n#traint# hat nn6negtia%lecn"itin# mu#t %e met7
that certain dimensions are fixed, that thecomponent must carry the design loads without
failure, that it insulates or conducts, that it can
function in a certain range of temperature andin a given environment, and many more.
8%9ecti$e hat i# t %e maimie" rminimie"7
to make it as cheap as possible, perhaps, or aslight, or as safe, or perhaps some combinationof these.
Free;aria%le hat !arameter# ( the!r%lem i# the "e#igner (ree tchange
parameters can be adjusted in order to optimizethe objective – the designer is free to varydimensions that are not constrained by designrequirements and, most importantly, free tochoose the material for the component.
THE SELECTION STRATEGY
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THE SELECTION STRATEGY
&onstraints
#s an essential
condition thatmust be met,usually e$pressedas a limit on amaterial orprocess attribute.
7bDective
#s a <uantity forwhich an e$tremevalue !a ma$imumor minimum" issought, fre<uently
cost, mass orvolume.
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THE SELECTION STRATEGY
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Assume that you were an &7 for &apAyam &ompany, how do you select thebest candidate to be your secretary@
Assume that you wanna buy a netbook,how would you decide which brand to gofor@
Disc(ss in)airs#
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6trategy for materialselection involves fourmain steps3
:" Translating;" 6creening
" Canking
B" 4ocumentation
THE B!SICS OF M!TERI!"SSE"ECTION
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6trategy :3 Translating
Translating design re<uirement into function, constraints, objectives & free
variables.
unction@ &onstraints@
7bDective@ ree
variables@
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unction
&onstraint
7bDective
reeEariable
6trategy :3 Translating
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&ase 6tudies3 7ffice scissors
A material is re<uired to manufacture officescissors. (aper is an abrasive material, and scissorssometimes encounter hard obstacles like staples.ist function and constraints% set the obDective to“minimi5e cost* and the free variables to “choice of
material*.
Elements inDesignRe-&irement
E1planation
unction
&onstraints
7bDective
ree variables
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A material is re<uired to manufacture office scissors.(aper is an abrasive material, and scissors sometimesencounter hard obstacles like staples. ist functionand constraints% set the obDective to “minimi5e cost*and the free variables to “choice of material*.
Elements inDesignRe-&irement
E1planation
unction 6cissors
&onstraintsF Gigh hardnessF Ade<uate toughness3 =:c H :I> (a.m J
F Kood wear resistanceF Able to be forged
7bDective >inimi5e cost
ree variables &hoice of material
&ase 6tudies3 7ffice scissors
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A material is re<uired for a heat e$changer toe$tract heat from geo-thermally heated, saline,water at :;Lo& !and thus under pressure". istfunction and constraints% set the obDective to“minimi5e cost* and the free variables to “choice ofmaterial*.
Elements in DesignRe-&irement
E1planation
unction
&onstraints
7bDective
ree variables
&ase 6tudies3 Geat $changer
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6trategy ;3 6creening
Unbiased selection + consider all materialsto be candidates
liminate candidates that cannot do theDob at all because their attributes lies
outside the limits (refer to constraints)
&onstraints@
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6trategy 3 Canking
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6trategy 3 Canking
#dentifying the candidates that remain ) orderingthose that can do the Dob best
>aterial inde$3
a" The property or property group thatma$imi5es performance for a given design
b" (rovide criteria of e$cellence that allowranking of materials by their ability toperform well in the given application
c" >aterial indices are generally e$pressed so
that a ma$imum value is sought
&onstraints setproperty limits.
7bDectives definematerial indices,for which we seek
e$treme values.
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6trategy 3 Canking
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6trategy 3 Canking
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&onventional method + employ selectionmatri$
$ample3 6haft
2ey re-&irements3
L GC& hardnessGigh impact strengthA minimum fatigue
strengthGigh stiffnessow cost
Selection candidates3
(rehard B:BL steel&ase hardened :L;L
steel
:M-B (G stainless steelTitanium A:BE
L:-T aluminum&LLL yellow brass
6trategy 3 Canking
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6trategy 3 Canking
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Candidate materials
(art structurere<uirements
0rass &LLLAluminumL:-T
TitaniumTiA:BE
6tainless steel:M-B (G
&arbon steel:L;L
(rehardenedsteel B:BL O
LGC&
L GC& minimum I :L :L P :L
L ksi endurance
limitB.B ;. :L Q. B.B :L
&harpy Eeeimpact H:I ft lb
P M :L :L :L :L
Gigh elasticmodulusR!/ factor"
:P!$"
:L!.$"
:P!$"
;M!Q$"
L!:L$"
L!:L$"
Custproof P P :L :L
>aterial costSlb
Q L.I I :L Q
Treatmentmachining costs S
:L :L :L I I I
?ill last I years :L :L :L :L :L :L
Score Q.B IQ. MP.I P. PL.B PM
<10 i# %e#t
6trategy 3 Canking
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4ocumentationCanking6creeningTranslating
?hy @
=el!# narr the #hrt6li#t t a (inal chice 4iffers greatly from the structured property data )e#cri!ti$e / gra!hical / !ictrial > ca#e #tu"ie# ( !re$iu#
u#e# ( the material, "etail# ( it# crr#in %eha$iur in
!articular en$irnment#, in(rmatin ( a$aila%ilit&/!ricing,e!erience ( it# en$irnmental im!act#.
6ource3 handbooks, suppliers2 data sheets, &4-based datasources, www.
6trategy B3 4ocumentation
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6trategy B3 4ocumentation
The selection strategy3 &ars
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Requirements
expressed as
Constraints and
Objectives
Data:
Perormance
!conom"
What car? ratin#
Final selection
Comparison en#ine
$creenin#
Ran%in#
Documentation
Ma%e and Model
Dimensions
&umber o doors
Fuel t"pe
Po'er Fuel consumption
CO( ratin# ))
Mid si*e amil" saloon
+ doors
(,, - horse po'er
Least cost of ownership
Deliver" time
$ervice requenc"
&earest dealer
Warrant"
The selection strategy3 &ars
The selection strategy3 >aterials
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Desi#n requirements:
expressed as
Constraints and
Objectives
Data:
Material attributes
Process attributes
Documentation
Final selection
Comparison en#ine $creenin# Ran%in#
Documentation
Densit"
Price
Modulus
$tren#th
Durabilit"Process compatibilit"
More)).
Able to be molded
Water and /0 resistant
$ti enou#h
$tron# enou#h
As light as possible
As cheap as possible
The selection strategy3 >aterials
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Understanding &heck
?hy do we need to do screening ) ranking@
?hat is the difference between screening ) ranking@
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The 0asics of >aterial 6election
ist three things that you are very clear of.
ist three things that you feel ha5y about.
ist three things that you need further clarification.
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Tutorial:Translation: constraints an)
o.ecti3es:. A material is re<uired for the windings of an electric
air-furnace capable of temperatures up to :LLLo&.Think out what attributes a material must have if it isto be made into windings and function properly in afurnace. ist the function and the constraints% set theobDective to “minimi5e cost* and the free variables to“choice of material*.
;.A material is re<uired for a heat e$changer to e$tractheat from geo-thermally heated, saline, water at:;Lo& !and thus under pressure". ist function andconstraints% set the obDective to “minimi5e cost* andthe free variables to “choice of material*.
Ans0er:
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Ans0er:Translation: constraints an)
o.ecti3es
Ans0er
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Ans0er:Translation: constraints an)
o.ecti3es
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4o we achieve our obDective for today2s lesson@
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Why are all these steps necessary?
Without screening and ranking- the candidate-poo is
enor!ous and the "ou!e o# docu!entation
o"er$he!ing%
Screening-ranking steps ha"e identi&ed a s!anu!'er o# potentia candidates( So that detaied
docu!entation can 'e sought #or these #e$ aone(
!aking the task "ia'e%
)ocu!entation heps narro$ the short-ist to a &na
choice( ao$ing a de&niti"e !atch to 'e !ade
'et$een design re*uire!ents and !ateria
attri'utes%
S$MM!R&