manufacturing methods and material...

Manufacturing Methods and Material Selection

ENM 214

Dr. Tolga Yasa

[email protected]

Mechanical Engineering Department

MAK 208

Material Science

Introduction, Properties, Selection

Reference

Materials: “Principles of Material Science and Engineering” by

William F. Smith

Manufacturing Processes: “Introduction to Manufacturing

Processes by John A. Schey

Fundamentals of Modern Manufacturing Materials, Processes,

and Systems by Mikell P. Groover

Contents

Introduction

Material Properties

Physical Properties

Mechanical Properties

Material Selection

Introduction

Materials are used since the begining to produce any kind of

needs.

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Introduction

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Introduction

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Introduction

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Introduction Metals

inorganic

Composed of one or more metallic elements

(iron, copper, aluminum, nickel titanium)

Sometimes contains non-metallic elements

(carbon, nitrogen, oxygen)

Crystalline structure

Good conductors

Strong and ductile

Introduction Metals

Metals: only one type of elements ( copper, aluminum etc.)

Alloys: combination of elements (bronze, steel etc.)

Iron is majority Iron is not majority

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Introduction Polymeric Materials

Organic (Carbon containing) long molecular chains/networks

Generally non-Crystalline (amorphous) structure

Poor conductors

Strength and ductile vary

Low density

Low decomposition temperature

Introduction Polymeric Materials

https://www.youtube.com/watch?v=YduOEGBtNfo

https://www.youtube.com/watch?v=YduOEGBtNfo

Introduction Polymeric Materials Polyethylene

thermoplastic Melamine - Thermoset

Rubber - Elastomer

Dacron - Fiber

Nylon 6 6 - Fiber

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Introduction Ceramics

Inorganic (may contain metallic and non-metallic elements)

Crystalline, non-Crystalline (amorphous) or mixture of both

Low density, High hardness, Brittle

Poor conductors

Resistive to high temperatures and wear

Introduction Ceramics

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Introduction Composites

Mixture of two or more materials

Reinforcing material + binder (physically combained)

Properties are depends on the composited type

Fiberglass (reinforcing) + Polyester/epoxy(binder)

Carbonfiber+ Epoxy

Introduction Commercial Types

Raw Materials

unprocessed materials

crude oil, coal, cotton

Semi-Products

Partially processed, open for further processing

Ingots, bars, sheets, wire, tubes

standardized semi-products

non-standardized semi-products

https://en.wikipedia.org/wiki/File:Lingot_aluminium.jpg

Contents

Introduction

Material Properties

Physical Properties


Material Selection

Material Properties

How do we chose a material ?

Quantitative

Defines the material

Defines its behavior

We need information that defines materials and its behavior

Introduction

They are defined by standardized test methods

Material Properties

Property may depended on the direction

(Isotropic /Anisotropy)

Introduction

Material properties depends on micro-structures

Physical properties (Density, elasticity,

Electrical properties (Dielectric behavior, conductivity etc.)

Optical properties (Color, absorbance, reflectivity etc.)

Thermal properties (boiling temp, heat capacity etc.)

Mech. properties (Creep, fatigue, hardness, strength etc.)

Chemical properties (Oxidation, corrosion, flammability, toxicity etc.)

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Material Properties

The material is defined my

Chemical compositions

Method of manufacturing

Definition of material

Material Properties Definition of material


Method of manufacturing


Specification: A precise statement of a set of requirements, to be

satisfied by a material.

It is desirable that the requirements, together with their limits,

should be expressed numerically in appropriate units.

A standard specification for a material is the result of agreement

between those concerned in a particular field and involves

acceptance for use by participating agencies.

International specifications

Company specifications

INCONEL alloy 718 - bar form

ASTM B637, AMS 5662, AMS 5663, AMS 5664

PWA 1009, PWA 1010, GE B50TF15

Material Properties Physical Properties

They are the properties that reflects the behavior of material

under changing physical conditions like pressure and

temperature.

Micro-structure and chemical composition are unaltered

colour – light wave length

specific heat (cp) – the heat required to raise the temperature of

one gram of a substance by one degree centigrade (J/kg K)

density ()– mass per unit volume (kg/cm 3)

melting point – a temperature at which a solid begins to liquefy


electrical conductivity – a measure of how strongly a material

opposes the flow of electric current (Ω⋅m)

coefficient of thermal expansion (L) – degree of expansion

divided by the change in temperature (m/°C)

Porosity – fraction of the volume of voids over the total volume

Microstructure - The arrangement of phases and defects within

a material. (length scale: nm-cm)

Material Properties Mechanical Properties

Characterize the behavior of material under the effect of a

certain load. The temperature is also a critical parameter for

characterizations.

Elasticity – the property of a material that returns to its original

shape after stress (e.g. external forces) that made it deform or

distort is removed

Plasticity - the deformation of a material undergoing non-

reversible changes of shape in response to applied forces

Ductility – a measure of how much strain a material can take

before rupturing


Brittleness –breaking or shattering of a material when

subjected to stress (when force is applied to it)

Toughness – the ability of a material to absorb energy and

plastically deform without fracturing

Hardness – the property of being rigid and resistant to pressure;

not easily scratched


Tensile properties – measures the force required to pull

something such as rope, wire or a structural beam to the point

where it breaks

Fatique properties – characterize the behaivour of material

under cyclic loads. The amount of time (cycle) needed to break

the material at a given constant cyclic load.

Creep properties – The time required to break the material

under a constant load condition at very high temperatures


Bending Force

Torsion

Material Properties Testing

The testing of materials may be performed for

to supply routine information on the quality of a product

(industrial need)

Collect more information on known materials to develop

new materials (material science)

to obtain accurate measures of fundamental properties

of materials (design engineering)


Industrial need

Purpose:

checking the acceptability of materials with respect to the

specifications,

Generally, the type of the test has been specified.

Standard procedures are used

Material Science

Purpose:

obtain new understanding of known materials,

discover the properties of new materials,

develop meaningful standards of quality or test procedures

Generally, the type of the test has been specified.

Standard procedures are used


Specimen Types:

Full size structures, members, or parts

Design verification

Models of structures, members, or parts

Design verification

Specimens cut from finished parts

To understand the effect of the processing

Specimens of raw or processed materials

To generate material database


Destructive testing is carried out until the specimen’s failure. These tests are generally much easier to carry out, yield more information and are easier to interpret than non-destructive testing

(Tensile test, Creep rupture test etc.)

Non-destructive testing is the type of testing that does not destroy the test object. It is vital when the material in question is still in service.

(X-ray, Ultrasonic Inspection etc. )


There are standarts for each testing methods in order to have a

comparable results from different test center.

Therefore, when a test is needed a standart test procedure

needs to be carried out

You can find standart test specs.

Turkish Standards Institute (TSE)-Turkish Standards (TS) http://www.tse.org.tr/

American Society for Testing and Materials (ASTM)- ASTM Specifications http://www.astm.org

International Standards Organization (ISO)- ISO Standards http://www.iso.org

European Commitee for Standardization (CEN)- European Norms (EN) http://www.cen.eu

http://www.tse.org.tr/http://www.astm.org/http://www.iso.org/http://www.cen.eu/


Tensile Properties

When a piece of metal is subjected to the a uniaxial tensile force

deformation of the metal occurs.

Elastic deformation: the piece turns to its orginal dimensions

after removing the applied force

Plastic deformation: the piece cannot fully recover after

removing the applied force

Engineering stress = s = F /Ao

Engineering strain = = (Lf – Lo)/Lo = d/Lo

d

F


Tensile Properties

Yield point – End of elastic

deformation

Ultimate strength – Maximum stress

that can be applied to a material

Point of rupture – the failure occurs


Tensile Properties

Engineering stress = s = F /Ao

Engineering strain = = (Lf – Lo)/Lo = d/Lo


Tensile Properties

During elastic deformation, the engineering stress-strain

relationship follows the Hooke's Law.

the force F needed to extend or compress a spring by some

distance X is proportional to that distance. That is: F = kX

In material science

F s X k E (Young’s modulus)

sE


Tensile Properties

Plastic deformation occurs non-linearly


Tensile Properties

For brittle material it is difficult to clearify the yield point.

Since it is often difficult to pinpoint the exact stress at which

plastic deformation begins, the yield stress is often taken to be

the stress needed to induce a specified amount of permanent

strain, typically 0.2%. The construction used to find this “offset

yield stress”


Tensile Properties

http://www.shodor.org/~jingersoll/weave/tutorial/img21.png


Tensile Properties

Toughness – total amount of enegry that is absored by the

material

Ductile – how much the material can be stretched before

fracture

modulus of

toughness

High ductility: platinum, steel, copper

Good ductility: aluminum

Low ductility (brittle): chalk, glass, graphite


Tensile Properties


Tensile Properties

Stress-strain curve for polyamide (nylon) thermoplastic


Tensile Properties – Effect of temperature

Material Properties Tensile Testing

The following MATERIAL PROPERTIES can be evaluated /

determined by TENSILE TESTING:

STRENGTH - the greatest stress that the material can

withstand prior to failure.

DUCTILITY - a material property that allows it to undergo

considerable plastic deformation under a load before

failure.

ELASTICITY - a material property that allows it to retain its

original dimensions after removal of a deforming load.

STIFFNESS - a material property that allows a material to

withstand high stress without great strain.


A machine which applies a tensile force (a force applied in

opposite directions) to the specimen, and then measures that

force and also the elongation.

This machine usually uses a hydraulic cylinder to create the

force. The applied force is determined by system pressure,

which can be accurately measured.

Test Sample

Testing

Machine


Before the test Begining of plastic deformation End of the test


The classic cup & cone shape of a fairly

ductile tensile fracture is visible here.

Upon completion of the test, the

sample is reassembled and final

measurements for total elongation and

minimum diameter are made using a

vernier caliper.


Microstructure investigation of failure surface

https://www.youtube.com/watch?v=D8U4G5kcpcM

Tensile Test Example

https://www.youtube.com/watch?v=D8U4G5kcpcM


Creep Behavior

Creep is high temperature progressive deformation at constant

stress.

It is critical if the part is running at elevated temperatures

(furnuce liner, gas turbine blades, etc.)

It is a time- dependent deformation

Occurs at high temperatures

As a result, the material undergoes a time dependent increase in

length

Provides prediction of life expectancy before service. This is

important for example turbine blades.


Creep Behavior

The rate of deformation is called the creep rate.

It is the slope of the line in a Creep Strain vs. Time curve.


Creep Behavior

•Primary Creep: starts at a rapid rate and slows with time.

•Secondary Creep: has a relatively uniform rate.

•Tertiary Creep: has an accelerated creep rate and terminates

when the material breaks or ruptures. It is associated with both

necking and formation of grain boundary voids.


Creep Behavior

Effect of Temperature & Stress


Creep Behavior

Creep is different at different loads and temperatures.

A summary of creep data is provided by


Creep Behavior

t : time to failure

Q : The activation energy for atomic motion

R : Universal gas constant (8.314 J/mole K)

T : Temperature

Q is stress and temperature independent


Creep Behavior

t : time to failure

T : Temperature

C : Material constant

Q is assumed to a function of stress only


Creep Behavior


Creep Behavior

The Sherby-Dorn equation is log t − Q/(RT) = PSD. From Table, Q = 460

At 750ºC, T = 1,023 K and t = 20 hours.

Thus, PSD = log 20 − (460 × 103/8.314 × 1023)

At 650◦C, T = 9230 K, and we obtain log t = PSD + 0.43(Q/RT) so that

t = 6 × 103 hours.

Example :

Calculate the time to rupture at 650ºC and 100MPa stress for a 1%Cr-1% Mo-0.25%V

steel, according to the Larson-Miller and Sherby--Dorn, methods, if this alloy underwent

rupture in 20hrs when tested in tension at the same stress level at a temperature of

750ºC.

The Larson-Miller equation is T (log t+ C) = PLM.

At 750ºC, T = 750 + 273 = 1,023 K and t= 20 hours. Therefore,

PLM = 1023 × (log 20 + 22) ≈ 2.4 × 104

At 650◦C, T = 650 + 273 = 923K, and we have

923 ×(log t + 22) = 2.4 × 104, so that log t = (2.4 × 104/923)− 22

t = 6.7 × 103 hours.


Creep Behavior

Material Properties Creep Testing

A creep test involves a tensile specimen under a constant

load maintained at a constant temperature.

Measurements of strain are then recorded over a period of

time.

Creep generally occurs at elevated temperatures, so it is

common for this type of testing to be performed with an

environmental chamber for precise heating/cooling control.

Smooth, notched, flat specimens or samples of any

combination can be tested.


Typical Test Procedure

The unloaded specimen is first heated to the required T and

the gage length is measured.

The predetermined load is applied quickly without shock

Measurement of the extension are observed at frequent

interval


Test Apparatus


1000 h ~ 42 days


Fatigue Behavior

Fatigue, as understood by materials technologists, is a process

in which damage accumulates due to the repetitive application of

loads that may be well below the yield point.

In one popular view of fatigue in metals, the

fatigue process is thought to begin at an internal

or surface flaw where the stresses are

concentrated, and consists initially of shear flow

along slip planes. Over a number of cycles, this

slip generates intrusions and extrusions that

begin to resemble a crack. A true crack running

inward from an intrusion region may propagate

initially along one of the original slip planes, but

eventually turns to propagate transversely to the

principal normal stress as seen in Figure


Fatigue Behavior

The modern study of fatigue is generally

dated from the work of A. Wöhler, a

technologist in the German railroad system in

the mid-nineteenth century. Wöhler was

concerned by the failure of axles after various

times in service, at loads considerably less

than expected. A railcar axle is essentially a

round beam in four-point bending, which

produces a compressive stress along the top

surface and a tensile stress along the bottom.

After the axle has rotated a half turn, the

bottom becomes the top and vice versa, so

the stresses on a particular region of material

at the surface varies sinusoidally from tension

to compression and back again. This is now

known as fully reversed fatigue loading.


Fatigue Behavior

engineers had developed empirical means of quantifying the fatigue process

and designing against it. Perhaps the most important concept is the S-N

diagram.

100

200

300

500

400S

(a

mplit

ud

e in

MP

a)

104 105 107 109106 108 1010

2014-T6 Al alloy

No of cycles, N

1045 steelendurance limit

Modes of fatigue testing

100

200

300

500

400S

(a

mplit

ud

e in

MP

a)

104 105 107 109106 108 1010

2014-T6 Al alloy

No of cycles, N


100

200

300

500

400S

(a

mplit

ud

e in

MP

a)

104 105 107 109106 108 1010

2014-T6 Al alloy

No of cycles, N


Modes of fatigue testing


Fatigue Behavior

ferrous alloys, the S − N curve flattens out eventually, so that

below a certain endurance limit (se) failure does not occur no

matter how long the loads are cycled.

se

For some other materials

such as aluminum, no

endurance limit exists

and the designer must

arrange for the planned

lifetime of the structure to

be less than the failure

point on the S − N curve.


Fatigue Behavior

Fatigue behavior is affected by specimen geometry, surface

condition, and material characteristics.

Material Properties Fatigue Testing

Fatigue test is very similar to the tensile test but;

Load is adjusted precisely

Both tension and compression forces are applied in a

periodical manner

Statistical variability is troublesome in fatigue testing; it is

necessary to measure the lifetimes of perhaps twenty

specimens at each of ten or so load levels to dene the S − N

curve with statistical condence


The period of force applied is limited by inertia in components

of the testing machine and heating of the specimen.

With a frequency of 10 Hz, it takes 11.6 days to reach 107

cycles

Therefore, it is very expensive to generate a database for S-N

curve


At first glance, the scatter in measured lifetimes seems

enormous, especially given the logarithmic scale of the

abscissa. If the coefficient of variability in conventional tensile

testing is usually only a few percent, why do the fatigue

lifetimes vary over orders of magnitude? It must be

remembered that in tensile testing, we are measuring the

variability in stress at a given number of cycles (one), while in

fatigue we are measuring the variability in cycles at a given

stress. Stated differently, in tensile testing we are generating

vertical scatter bars, but in fatigue they are horizontal. Note

that we must expect more variability in the lifetimes as the

S−N curve becomes flatter, so that materials that are less

prone to fatigue damage require more specimens to provide a

given confidence limit on lifetime.

Confidence Level


Always Sinusoidal Loading ???

Of course, not all actual loading applications involve fully reversed stress

cycling. A more general sort of fatigue testing adds a mean stress (sm) on

which a sinusoidal cycle is superimposed.

Such a cycle can be phrased in several ways, a common one being to state

the alternating stress (salt )and the stress ratio (R = smin/ smax)

For fully reversed loading, R = −1.

A stress cycle of R = 0.1 is often

used in aircraft component testing,

and corresponds to a tension-

tension cycle in which

smin=0.1smax


Goodman Diagram

One of the key limitations to the S-N curve was the inability to

predict life at stress ratios different from those under which the

curve was developed.

It will usually be impractical to determine whole families of

curves for every combination of mean and alternating stress

!!GOODMAN DIAGRAM !!


Goodman Diagram !!!!!!!!

Mean Stress

Altern

ating s

tress

UTS

Alternatively, if the design application dictates a given ratio of e to alt, a line is drawn

from the origin with a slope equal to that ratio. Its intersection with the lifeline then

gives the eective endurance limit for that combination of f and m

Available

Operation Zone

Dangerous

Operation Zone


Video about Fatigue

https://www.youtube.com/watch?v=LhUclxBUV_E

https://www.youtube.com/watch?v=LhUclxBUV_E


Hardness

Resistance to plastic deformation

a strong metal is also a hard metal

It is widely used for the quality control of surface treatments

processes.


Hardness

Sweden

British

US


Hardness

https://www.youtube.com/watch?v=6I2yMEVLclc

Rockwell hardness : https://www.youtube.com/watch?v=G2JGNlIvNC4

Vickers Hardness :

https://www.youtube.com/watch?v=7Z90OZ7C2jI&ebc=ANyPxKr_AYwwL

VNTc7j5p_rMqXr9Bsi_aBW5lVhvgEHXuB0zDVmIj0PXkmhQqKZRIRaNy-

wZU0Qwma6aen2vLfnJBLlnbGvz1A

Brinell Hardness : https://www.youtube.com/watch?v=RJXJpeH78iU

Vickers / Knoop micro hardness

the indentations are small so you need to measure with a microscope

Rockwell / Brinell macro hardness

Among the three hardness tests discussed, the Brinell ball makes the deepest and

widest indentation, so the test averages the hardness over a wider amount of

material, which will more accurately account for multiple grain structures, and any

irregularities in the uniformity of the alloy.

https://www.youtube.com/watch?v=6I2yMEVLclchttps://www.youtube.com/watch?v=G2JGNlIvNC4https://www.youtube.com/watch?v=7Z90OZ7C2jI&ebc=ANyPxKr_AYwwLVNTc7j5p_rMqXr9Bsi_aBW5lVhvgEHXuB0zDVmIj0PXkmhQqKZRIRaNy-wZU0Qwma6aen2vLfnJBLlnbGvz1Ahttps://www.youtube.com/watch?v=RJXJpeH78iU

Material Properties Summary

Knowledge of materials’ properties is required to

Select appropriate material for design requirement

Select appropriate manufacturing process

Optimize processing conditions for economic manufacturing

…

Materials have different physical, chemical, mechanical properties

Contents

Introduction

Material Properties

Physical Properties


Material Selection

Material Selection

Material Selection

http://www.aksteel.com/pdf/markets_products/stainless/austenitic/304_304l_data_sheet.

pdf

A info sheet example of Steel 304L

Ref for the notes : http://core.materials.ac.uk/repository/eaa/talat/1502.pdf

http://www.aksteel.com/pdf/markets_products/stainless/austenitic/304_304l_data_sheet.pdfhttp://core.materials.ac.uk/repository/eaa/talat/1502.pdf

Material Selection

1.First best material

The material is selected among the few materials the design engineer is

familiar with.

2. Same material as for a similar part

a material which works satisfactorily in one application will do in a similar one.

3. Problem solving material selection

A property has given rise to problems. A new material is chosen in the same

group of material with a higher value of the property

4. Searching material selection

The designer takes more or less randomly into account one requirement at the

time

Intuitive Methods in Material Selection

Material Selection

Drawbacks with Intuitive Methods:

- Important requirements have often given rise to failures in operation.

- First solution at hand is taken which is not very likely to be good solution.

- Unconventional solutions are not considered e.g. advanced materials are

not analyzed.

- The solution is typically far from the optimum giving the part poor

competitiveness.

Intuitive Methods in Material Selection

Material Selection

Material Selection Basics

Material Selection

Connection to Design

Material selection is an integral part of the design process.

Material selection is performed for simple parts or components.

Material Selection

General Guidelines for Successful Material Selection

Material Selection

Function Specification

Material Selection

Functional Requirements

Material Selection

Pre-Selection of Materials

Material Selection

Pre-Selection of Materials Intuitive Approach

Material Selection

Properties Involved in Pre-Selection of Material Types

(Systematic Approach)

Material Selection

Example : Casserole

Material Selection

Example : Ladder

GRP: glass fibre reinforced polyester

Material Selection

the purpose of pre-selection is to eliminate unsuitable material types

which do not satisfy requirements on overriding properties.

Material Selection

Discriminating Materials Selection

Material Selection


The weldability must be above a certain lower level in order

that one component can be

joined to another one.

The corrosion resistance must have a minimum value to give a

component a sufficient lifetime in an aggressive environment. A

given material can not be used independently of how good the

other properties are if the corrosion resistance is not adequate.

As a consequence a large amount of data must be

available for many properties for successful selection. The

use of material databases is important in this respect.

Material Selection


Material Selection


To find the maximum and minimum requirements Ei and Ei

the function specification is transferred to property values.

Material Selection


Material Selection

Discriminating Materials Selection Property Values

Use properties

(properties of relevance for the use of materials)

Corrosion resistance

Wear resistance

Manufacturing properties

(properties of relevance for the manufacturing of materials)

Availability Properties

Cost

Material Selection


Material Selection

Discriminating Materials Selection Example

Material Selection

manufacturing methods and material...

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