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Manufacturing Methods and Material Selection
ENM 214
Dr. Tolga Yasa
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.
Introduction
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
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
Introduction Polymeric Materials Polyethylene
thermoplastic Melamine - Thermoset
Rubber - Elastomer
Dacron - Fiber
Nylon 6 6 - Fiber
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 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
Contents
Introduction
Material Properties
Physical Properties
Mechanical 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.)
Material Properties
The material is defined my
Chemical compositions
Method of manufacturing
Definition of material
Material Properties Definition of material
Material Properties Definition of material
Material Properties Definition of material
Method of manufacturing
Material Properties Definition of material
Method of manufacturing
Material Properties Definition of material
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
Material Properties Physical Properties
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 Physical Properties
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
Material Properties Mechanical Properties
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
Material Properties Mechanical Properties
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
Material Properties Mechanical Properties
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)
Material Properties Testing
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
Material Properties Testing
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
Material Properties Testing
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. )
Material Properties Testing
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
Material Properties Mechanical Properties
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
Material Properties Mechanical Properties
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
Material Properties Mechanical Properties
Tensile Properties
Engineering stress = s = F /Ao
Engineering strain = = (Lf – Lo)/Lo = d/Lo
Material Properties Mechanical Properties
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
Material Properties Mechanical Properties
Tensile Properties
Plastic deformation occurs non-linearly
Material Properties Mechanical Properties
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”
Material Properties Mechanical Properties
Tensile Properties
Material Properties Mechanical Properties
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
Material Properties Mechanical Properties
Tensile Properties
Material Properties Mechanical Properties
Tensile Properties
Stress-strain curve for polyamide (nylon) thermoplastic
Material Properties Mechanical Properties
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.
Material Properties Tensile Testing
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
Material Properties Tensile Testing
Before the test Begining of plastic deformation End of the test
Material Properties Tensile Testing
Material Properties Tensile Testing
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.
Material Properties Tensile Testing
Microstructure investigation of failure surface
https://www.youtube.com/watch?v=D8U4G5kcpcM
Tensile Test Example
Material Properties Mechanical Properties
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.
Material Properties Mechanical Properties
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.
Material Properties Mechanical Properties
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.
Material Properties Mechanical Properties
Creep Behavior
Effect of Temperature & Stress
Material Properties Mechanical Properties
Creep Behavior
Creep is different at different loads and temperatures.
A summary of creep data is provided by
Material Properties Mechanical Properties
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
Material Properties Mechanical Properties
Creep Behavior
t : time to failure
T : Temperature
C : Material constant
Q is assumed to a function of stress only
Material Properties Mechanical Properties
Creep Behavior
Material Properties Mechanical Properties
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.
Material Properties Mechanical Properties
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.
Material Properties Creep Testing
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
Material Properties Creep Testing
Test Apparatus
Material Properties Creep Testing
1000 h ~ 42 days
Material Properties Mechanical Properties
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
Material Properties Mechanical Properties
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.
Material Properties Mechanical Properties
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
1045 steelendurance limit
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
Material Properties Mechanical Properties
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.
Material Properties Mechanical Properties
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
Material Properties Fatigue Testing
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
Material Properties Fatigue Testing
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
Material Properties Fatigue Testing
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
Material Properties Fatigue Testing
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 !!
Material Properties Fatigue Testing
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
Material Properties Fatigue Testing
Video about Fatigue
https://www.youtube.com/watch?v=LhUclxBUV_E
Material Properties Mechanical Properties
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.
Material Properties Mechanical Properties
Hardness
Sweden
British
US
Material Properties Mechanical Properties
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.
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
Mechanical Properties
Material Selection
Material Selection
Material Selection
http://www.aksteel.com/pdf/markets_products/stainless/austenitic/304_304l_data_sheet.
A info sheet example of Steel 304L
Ref for the notes : http://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
Pre-Selection of Materials Intuitive Approach
Material Selection
Properties Involved in Pre-Selection of Material Types
(Systematic 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
Discriminating Materials Selection
Material Selection
Discriminating Materials 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
Discriminating Materials Selection
Material Selection
Discriminating Materials Selection
To find the maximum and minimum requirements Ei and Ei
the function specification is transferred to property values.
Material Selection
Discriminating Materials 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
Discriminating Materials Selection
Material Selection
Discriminating Materials Selection
Material Selection
Discriminating Materials Selection Example
Material Selection