material properties

1. Engineering materials &
Properties

2. Engineering Materials
Metals Non - Metals
Ferrous Organic
Non-ferrous Inorganic
Fe & its alloys Ni & Ni alloys
Cu & Cu alloys
Al & Al alloys
Ti & Ti alloys
etc.
Polymer
Rubbers
etc.
Ceramics
Graphite
Glass, etc.
Composites Polymer matrix
Metal matrix
Ceramic matrix

3. Metal
• In chemistry, a metal is defined as an
element with a valence of 1,2 or 3.
• All metals posses metallic properties such
as luster, opacity, malleability, ductility and
electrical conductivity.
• Typical examples of metallic materials are
iron, copper, aluminum, zinc etc., and their
alloys.

4. Ceramics
• A ceramic can be defined as a combination of
one or more metals with a non-metallic element.
• Metal oxides, carbides, nitrides, borides and
silicates are considered as ceramics.
• These are characterized by high hardness,
abrasion resistance, brittleness and chemical
inertness, and are poor conductors of electricity.
• Examples of ceramics include refractories,
glasses, abrasives, and cements.

5. Polymers
• Polymers are organic substances and
derivatives of carbon and hydrogen.
• They are known as plastics
• Most plastics are light in weight and are soft as
compared to metals.
• They posses high corrosion resistance and can
be molded into various shapes by application of
heat and pressure.
• Typical examples of polymers are polyesters,
phenolics, polyethylene, nylon and rubber.

6. Composites
• A composites is a combination of two or more
materials that have properties different from its
constitutes.
• Typical example of composites are wood, clad
metals, fibre glass, reinforced plastics, cemented
carbides, etc.
• Composites as class of engineering materials
provide almost an unlimited potential for high
strength, stiffness, and corrosion resistance over
the ‘pure’ material systems of metals, ceramics
and polymers.

7. Materials
Nanomaterials, shape-memory alloys, superconductors, …
Ferrous metals: carbon-, alloy-, stainless-, tool-and-die steels
Non-ferrous metals: aluminum, magnesium, copper, nickel,
titanium, superalloys, refractory metals,
beryllium, zirconium, low-melting alloys,
gold, silver, platinum, …
Plastics: thermoplastics (acrylic, nylon, polyethylene, ABS,…)
thermosets (epoxies, Polymides, Phenolics, …)
elastomers (rubbers, silicones, polyurethanes, …)
Ceramics, Glasses, Graphite, Diamond, Cubic Boron Nitride
Composites: reinforced plastics, metal-, ceramic matrix composites

8. ASTM Standards
• American Society of Testing and Materials has
standardized specifications for materials.
• ASTM has followed the following series for easy
identifications of their standards. These are:
• ASTM A : Ferrous materials
• ASTM B : Non-Ferrous materials
• ASTM C : Cementitious ceramic, concrete and masonry materils
• ASTM D : Miscellaneous materials (Plastic, FRP, PVC materials)
• ASTM E : Miscellaneous subjects (Testing, heat treatment etc.)
• ASTM F : Materials for specific applications (PTFE lined pipes, etc.)
• ASTM G : Corrosion, deterioration and degradation of materials.
• ASTM ES : Emergency standards
• ASTM P : Proposals
• ASTM PS : Provisional standards.

9. ASTM Standards
• The ASTM standards for metals provide the mechanical properties
of the metals and chemical composition. Specifications for steels
usually provide compositions that refer to either the analysis of the
steels in ladle or in its final form.
• The specifications also provide information concerning the form and
size of the products, size tolerance of products, testing procedures,
inspection, and so on.
• ASTM specifications are identified by a prefix letter, A- indicating
ferrous materials and B- indicating non-ferrous metals etc. this is
followed by a one-two-, or three digit number indicating the exact
specification number which is then followed by a exact grade (if
applicable). At the end a two digit number indicating the year that
the specification was normally adopted.
• A suffix letter ‘T’, when used, indicates that it is a tantative
specification.

10. Iron and Iron alloys
Why iron alloys are so popular?
 Ore availability.
 Manufacturing process.
 Useful properties:
 Allotropy / Polymorphism.
 Alloying.
 Heat treatment. etc.

11. Allotropy
• An element that can exist in two or more
forms is said to be allotropic, the different
forms are called allotropes, and the
existence of these other forms as a
phenomena called allotropy.
• Allotropes exist when there is more than
one way for the atoms of a particular
element to combine with each other to
form molecules or a crystalline array.

12. Polymorphism
• There are often several ways to arrange the
particles of a substance in the solid phase. Such
substances are said to be polymorphic or
polymorphous, the variations are called
polymorphs, and the existence of these other
forms as a phenomena is called polymorphism.
• Polymorphs exist when there is more than one
way for the particles of a particular substance to
arrange themselves into a crystalline array

13. Primary Allotropes of Carbon (The Elementary
Version)
diamond graphite
the hardest substance known
(10 on the mohs scale)
used as an abrasive
among the softest substances
(0.5 on the mohs scale)
used as a lubricant
usually transparent
colorless to red or blue
used in jewelry
always opaque
black (somewhat metallic)
used in pencils (thus the name)
a good electrical insulator
~TΩ·m resistivity
a good electrical conductor
650 nΩ·m resistivity
high thermal conductivity
(higher than any metal)
895 W/m·K
dual thermal conductivity
1950 W/m·K parallel to plane layers
5.7 W/m·K perpendicular to layers

14. High toughness / High strength.
Possessing good oxidation & Corrosion resistance.
Good forming properties, machinability & weldability.
Some alloys useful for Cryogenic services.
Some other have good strength up to 2000° F.
Mainly used as alloys, classified in Five Groups:
 Pure Ni ‘or’ High Ni (> 10 %) alloys.
 Ni – Mo / Ni – Mo – Cu alloys.
 Ni – Mo – Cr – Cu alloys.
 Ni – Cu alloys.
 Ni – Cr / Ni – Cr – Fe alloys.
Ni & Ni alloys

15. Excellent electrical conductivity.
Resistance to atmospheric corrosion.
Alloys classified in following main groups.
Brasses.
Cu – Zn brasses.
Cu – Zn – Pb; Leaded brass.
Cu – Zn – Sn; Tin brass.
Cu – Zn – Al brass.
Bronzes.
Cu – Sn – P; Phosphor bronze.
Cu – Sn – Pb – P; Leaded phosphor bronze.
Cu – Al ; Aluminium bronze.
Cu – Sn – Zn – Si ; Silicon bronze.
Cupro-Nickel / Nickel silver (Cu – Ni alloy)
Cu & Cu Alloys

16. High electrical and thermal conductivity.
Resistance to corrosion.
Hardening by Strain
Hardening by alloying – Age hardening.
Alloy classification as per AAA.
1XXX: Commercial or High purity Al.
2XXX: Al – Cu alloys.
3XXX: Al – Mn alloys.
4XXX: Al – Si alloys.
5XXX: Al – Mg alloys.
6XXX: Al – Mg – Si alloys.
7XXX: Al – Sn alloys.
Al & Al alloys

17. Properties of materials
Mechanical properties of materials
Strength, Toughness, Hardness, Ductility,
Elasticity, Fatigue and Creep
Chemical properties
Oxidation, Corrosion, Flammability, Toxicity, …
Physical properties
Density, Specific heat, Melting and boiling point,
Thermal expansion and conductivity,
Electrical and magnetic properties

18. Strength
• Strength is the ability of a material to resist deformation.
• The strength of a component is usually considered based on the
maximum load that can be borne before failure is apparent.
• If under simple tension the permanent deformation (plastic strain)
that takes place in a component before failure, the load-carrying
capacity, at the instant of final rupture, will probably be less than the
maximum load supported at a lower strain because the load
is being applied over a significantly smaller cross-sectional area.
• Under simple compression, the load at fracture will be the maximum
applicable over a significantly enlarged area compared with the
cross-sectional area under no load.
• This obscurity can be overcome by utilizing a nominal stress figure
for tension and shear.
• This is found by dividing the relevant maximum load by
the original area of cross section of the component.
• Thus, the strength of a material is the maximum nominal stress it
can sustain.
• The nominal stress is referred to in quoting the "strength" of a
material and is always qualified by the type of stress, such as tensile
strength, compressive strength, or shear strength.

19. ULTIMATE TENSILE STRENGTH
The ultimate tensile
strength (UTS) is the
maximum resistance to
fracture.
It is equivalent to the
maximum load that can be
carried by one square inch of
cross-sectional area when the
load is applied as simple
tension.
It is expressed in pounds per
square inch or Kilograms per
square centimeter.

20. YIELD STRENGTH
• The yield strength is defined as the
stress at which a predetermined amount
of permanent deformation occurs.

21. Mechanical properties: Stress analysis
Why do we need stress/strain (not just force, elongation) ?
Tension
Compression
Shear
F1
F2
F3
sx
txy
sy
sz
txz
tzx
tzy
tyx
tyz
Stresses in an infinitesimal element of a beam
Tensile, compressive and shear stresses
stress = s = Force/Area

22. Tensile Test
• A tensile test is a fundamental mechanical test where a
carefully prepared specimen is loaded in a very
controlled manner while measuring the applied load and
the elongation of the specimen over some distance.
• Tensile tests are used to determine:
– the modulus of elasticity,
– elastic limit,
– elongation,
– proportional limit,
– reduction in area,
– tensile strength,
– yield point,
– yield strength and other tensile properties.

23. Failure in Tension, Young’s modulus and Tensile strength
Engineering stress = s = P/Ao
Engineering strain = e = (L – Lo)/Lo = d/Lo

24. Failure in Tension, Young’s modulus and Tensile strength..
Original
Final
Necking
Fracture
Linear elastic

25. Linear-Elastic Region and Elastic
Constants
• As can be seen in the figure, the stress and strain initially increase
with a linear relationship.
• This is the linear-elastic portion of the curve and it indicates that no
plastic deformation has occurred.
• In this region of the curve, when the stress is reduced, the material
will return to its original shape.
• In this linear region, the line obeys the relationship defined as
Hooke's Law where the ratio of stress to strain is a constant.
• The slope of the line in this region where stress is proportional to
strain and is called the modulus of elasticity or Young's
modulus.
• The modulus of elasticity (E) defines the properties of a material as
it undergoes stress, deforms, and then returns to its original shape
after the stress is removed.
• It is a measure of the stiffness of a given material.

26. Failure in Tension, Young’s modulus and Tensile strength…
In the linear elastic range: Hooke’s law: s = E e or, E = s/e
E: Young’s modulus

27. Elastic recovery after plastic deformation

28. Toughness
The ability of a metal to deform plastically and to
absorb energy in the process before fracture is
termed toughness.
Recall that ductility is a measure of how much
something deforms plastically before fracture, but
just because a material is ductile does not make it
tough.
The key to toughness is a good combination of
strength and ductility.
A material with high strength and high ductility will
have more toughness than a material with low
strength and high ductility.
Therefore, one way to measure toughness is by
calculating the area under the stress strain curve
from a tensile test. This value is simply called
“material toughness” and it has units of energy per
volume. Material toughness equates to a slow
absorption of energy by the material.

29. True Stress, True Strain, and Toughness
Engg stress and strain are “gross” measures:
s = F/A => s is the average stress ≠ local stress
e = d/Lo => e is average strain
Final
Necking
Fracture
engg strain d/Lo true strain ln(L/Lo)
true
stress
P/A
engg
stress
P/A
o
fracture
fracture
Toughness = energy used to fracture
= area under true stress-strain curve

30. DUCTILITY
• The ductility of a material is a measure of the
extent to which a material will deform before
fracture.
• The amount of ductility is an important factor
when considering forming operations such as
rolling and extrusion.
• It also provides an indication of how visible
overload damage to a component might become
before the component fractures.
• Ductility is also used a quality control measure to
assess the level of impurities and proper
processing of a material.

31. DUCTILITY
• The conventional measures of ductility are the engineering
strain at fracture (usually called the elongation ) and the
reduction of area at fracture.
• Both of these properties are obtained by fitting the
specimen back together after fracture and measuring the
change in length and cross-sectional area.
• Elongation is the change in axial length divided by the
original length of the specimen or portion of the specimen.
It is expressed as a percentage.
• Because an appreciable fraction of the plastic deformation
will be concentrated in the necked region of the tensile
specimen, the value of elongation will depend on the gage
length over which the measurement is taken. The smaller
the gage length the greater the large localized strain in the
necked region will factor into the calculation. Therefore,
when reporting values of elongation , the gage length
should be given.

32. Ductility
Measures how much the material can be stretched before fracture
Ductility = 100 x (Lf – Lo)/Lo
High ductility: platinum, steel, copper
Good ductility: aluminum
Low ductility (brittle): chalk, glass, graphite
- Walkman headphone wires: Al or Cu?

33. HARDNESS
• Hardness is the property of a material that enables it to resist plastic
deformation, penetration, indentation, and scratching.
• Hardness is important from an engineering standpoint because
resistance to wear by either friction or errosion by steam, oil, and
water generally increases with hardness.
• Hardness tests serve an important need in industry even though
they do not measure a unique quality that can be termed hardness.
• The tests are empirical, based on experiments and observation,
rather than fundamental theory. Its chief value is as an inspection
device, able to detect certain differences in material when they arise
even though these differences may be undefinable.
• For example, two lots of material that have the same hardness may
or may not be alike, but if their hardness is different, the materials
certainly are not alike.
• Several methods have been developed for hardness testing. Those
most often used are Brinell, Rockwell, Vickers, Tukon, Sclerscope,
and the files test. The first four are based on indentation tests and
the fifth on the rebound height of a diamond-tipped metallic
hammer.

34. Hardness resistance to plastic deformation by indentation

35. Fatigue Properties
• Fatigue cracking is one of the primary damage mechanisms of
structural components.
• Fatigue cracking results from cyclic stresses that are below the
ultimate tensile stress, or even the yield stress of the material.
• The name “fatigue” is based on the concept that a material becomes
“tired” and fails at a stress level below the nominal strength of the
material.
• The facts that the original bulk design strengths are not exceeded
and the only warning sign of an impending fracture is an often hard
to see crack, makes fatigue damage especially dangerous.
• The fatigue life of a component can be expressed as the number of
loading cycles required to initiate a fatigue crack and to propagate
the crack to critical size.
• Therefore, it can be said that fatigue failure occurs in three stages –
crack initiation; slow, stable crack growth; and rapid fracture.

36. Fatigue
Fracture/failure of a material subjected cyclic stresses
100
200
300
500
400
S
(amplitude
in
MPa)
104
105
107
109
106
108
1010
2014-T6 Al alloy
No of cycles, N
1045 steel
endurance limit
Modes of fatigue testing
100
200
300
500
400
S
(amplitude
in
MPa)
104
105
107
109
106
108
1010
2014-T6 Al alloy
No of cycles, N
1045 steel
endurance limit
100
200
300
500
400
S
(amplitude
in
MPa)
104
105
107
109
106
108
1010
2014-T6 Al alloy
No of cycles, N
1045 steel
endurance limit
Modes of fatigue testing
S-N curve for compressive loading

37. FATIGUE

38. FATIGUE

39. Factors Affecting Fatigue Life
• In order for fatigue cracks to initiate, three basic
factors are necessary.
– First, the loading pattern must contain minimum and maximum
peak values with large enough variation or fluctuation. The peak
values may be in tension or compression and may change over
time but the reverse loading cycle must be sufficiently great for
fatigue crack initiation.
– Secondly, the peak stress levels must be of sufficiently high
value. If the peak stresses are too low, no crack initiation will
occur.
– Thirdly, the material must experience a sufficiently large number
of cycles of the applied stress.
• The number of cycles required to initiate and
grow a crack is largely dependant on the first to
factors.

40. Factors Affecting Fatigue Life..
• In addition to these three basic factors, there are a host of other
variables, such as:
– stress concentration,
– corrosion,
– temperature,
– overload,
– metallurgical structure, and
– residual stresses which can affect the propensity for fatigue.
• Since fatigue cracks generally initiate at a surface, the surface
condition of the component being loaded will have an effect on its
fatigue life. Surface roughness is important because it is directly
related to the level and number of stress concentrations on the
surface.
• The higher the stress concentration the more likely a crack is to
nucleate. Smooth surfaces increase the time to nucleation. Notches,
scratches, and other stress risers decrease fatigue life. Surface
residual stress will also have a significant effect on fatigue life.
Compressive residual stresses from machining, cold working, heat
treating will oppose a tensile load and thus lower the amplitude of
cyclic loading

41. Failure under impact
Charpy
Izod
pendulum
scale
pointer starting position
sample placed here
Charpy
Izod
Izod
pendulum
scale
pointer starting position
sample placed here
Testing for Impact Strength
Application: Drop forging

42. Residual stresses
Internal stresses remaining in material after it is processed
Causes:
- Forging, drawing, …: removal of external forces
- Casting: varying rate of solidification, thermal contraction
Problem: warping when machined, creep
Releasing residual stresses: annealing

43. Tensile properties
Stress.
Strain.
Elasticity.
Plasticity.
Breaking load.

46. Tensile properties
Young’s modulus.
Yield point.
Ultimate tensile strength.
% Elongation / % RA.
Toughness /
Impact Strength.

47. Creep Properties
High temperature + Constant stress
Slow permanent deformation
Stages in Creep:
• Primary.
• Secondary / steady state.
• Tertiary.