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
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
Nanomaterials, shape-memory alloys, superconductors, …

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. Ni & Ni alloys 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.

15. Cu & Cu Alloys 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)

16. Al & Al alloys 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.

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

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

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

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. Measures how much the material can be stretched before fracture
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
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
Application: Drop forging
Testing for Impact Strength

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