Engineering Material, Material Classification, characteristics of materials like metal, ceramics, organic, composites and semiconductors, Engineering requirements of materials, Properties of Engineering materials, factors affecting mechanical properties, Factors affecting the selection of materials for engineering purposes, Destructive and non-destructive testing, Tensile test, stress-strain diagram, spark test, macro etching, chemical analysis, Izod Impact testing, Charpy Impact testing, Fracture, Ductile Fracture, Brittle fracture, Ductile to brittle transition, creep failure, fatigue failure, radiography testing, dye penetration testing, magnetic particle testing, ultrasonic testing,

1. Engineering
Materials
By: Ratnadeepsinh Jadeja

2. Material
• A material is that out of which anything is or may be made. A material
relates itself to matter.
• Material comprise a wide range of metals and non metals which must be
operated upon to form the finished product.

3. Material Classification
• Most engineering materials may be classified into one of the following
types
(a) Metals – Ferrous and Non-ferrous
(b) Ceramics
(c) Organics
(d) Composites
(e) Semiconductors

4. Metals
• Metals are composed of elements which are readily give up electrons to provide a metallic
bond and electrical conductivity.
• Metals generally possess the following characteristics:
1. Luster
2. Hardness
3. Low specific heat
4. Plastic deformability
5. Good thermal and electrical conductivity
6. Relatively high melting point
7. Strength
8. Ductility
9. Malleability
10. Opaqueity
11. Stiffness
12. Rigidity
13. Formability
14. Machinability
15. Weldability
16. Castability
17. Dimensional stability
Examples of commonly employed metals are: Iron, Aluminum, Copper, Zinc, Magnesium, etc…

5. Ceramic Materials
• Ceramics usually consists of oxides, nitrides, carbides, silicates or borides of various metals.
• Ceramics are any inorganic, non metallic solids (or super cooled liquids) processed or used at high
temperatures.
• Such materials contain both iconic and covalent bonds.
• Ceramics generally possess the following characteristics:
1. Brittleness
2. Rock like appearance
3. Resistance to high temperature
4. Hardness
5. Abrasiveness
6. Insulation (to flow of electric current
7. Corrosion resistance
8. Opaque to light
9. High temperature strength.
Examples of commonly employed ceramic are:
1. Sand
2. Glass
3. Brick
4. Concrete
5. Silicon carbide
6. Boron nitride
7. Abrasives
8. Cement
9. Insulators
10. Tungusten carbide
11. Refractories
12. Plaster.

6. Organic Materials
• They are polymeric materials composed of carbon compounds. Polymers are solid composed of long molecular
chains
• Organic materials generally possess the following characteristics:
1. light weight
2. Combustible
3. Soft
4. Ductile
5. Dimensionally unstable
6. Poor conductors
7. Poor resistance to temperature. Etc…
Examples of commonly employed organic materials are:
1. Rubber
2. Plastic
3. Paper
4. Fuels
5. Wood
6. Lubricants
7. Textiles
8. Paints and finishes
9. Adhesives
10. Explosives
Organic materials find following uses:
1. As electric insulation
2. As fuels
3. As vitamins and medicines
4. For improving appearance
5. For protection against high temp
6. As explosives
7. For protection against corrosion
8. As refrigerants
9. As adhesives
10. As detergent
11. As lubricants

7. Composites
• Composites materials consists of more than one material type. Fiber glass is a familiar example, in
which glass fiber are embedded within a polymeric material. A composite is design to display a
combination of the best characteristics of each of the component materials. Fiberglass acquire
strength of the glass and flexibility from the polymer.
Semiconductors
• Semiconductors have electrical properties that are intermediate between the electrical conductors and
insulators.
• The semiconductors have made possible the advent of integrated circuitry that has totally
revolutionized the electronics and computer industries.

8. Engineering Requirements of materials
The main engineering requirements of materials fall under three categories,
1. Fabrication Requirements
2. Service requirements
3. Economic requirements.

9. Properties of Engineering Materials
Property of a material is a factor that influences qualitatively or quantitatively the response of a given
material to imposed stimuli and constraints, e.g., forces, temperature, etc.
Different material properties are:
1. Mechanical properties
2. Thermal properties
3. Electrical properties
4. Magnetic properties
5. Chemical properties
6. Optical properties
7. Physical properties
8. Technological properties

10. Mechanical Properties
• Mechanical properties include those characteristics of material that describe its behavior under the
action of external forces.
• Mechanical properties can be determine by conducting experimental tests on the material specimen.
• Various mechanical properties are :
1. Elasticity
2. Plasticity
3. Toughness
4. Resilience
5. Tensile strength
6. Yield strength
7. Impact strength
8. Ductility
9. Malleability
10.Brittle ness
11.Hardness
12.Fatigue
13.Creep
14.Wear Resistance

11. Factors affecting mechanical properties
Mechanical properties of materials are affected due to :
1. Alloy contents such as addition of W, Cr, etc., improve hardness and strength.
2. Fine grain size materials exhibit higher strengths and vice versa.
3. Crystal imperfection such as dislocations reduce the strength.
4. Excessive cold working produces strain-hardening and the material may crack.
5. Manufacturing defects such as cracks, blowholes, etc., reduces the strength.

12. Effects of Grain size on Properties of Metals
On the basis of grain size, materials may be classifies as:
1. Course grained materials, (the grain size is large).
2. Fine grained materials, (the grain size is small).
• Fine grained material possess higher strength, toughness, hardness and resistance to
suddenly applied force, better fatigue resistance and impact strength, crack resistance and
provide better finish in deep drawing. This materials preferred for structural applications with
greater yield stresses than course grained materials.
• A course grained material is responsible for surface roughness. It possesses more ductility,
malleability and better machinability, are difficult to polish or plating.
• Course grained steels have grater depth of hardening power as compared to fine grained
ones.
• At elevated temperatures, course grained materials show better creep strength than fine
grained ones.

13. Effects of Heat treatment on properties of metals
• Heat treatment is an operation or combination of operations involving heating and
cooling of a metal/alloy in solid state to obtain desirable properties and conditions.
• Some important heat treatment processes are:
• Annealing
• Normalising
• Hardening
• Tempering
• Martempering
• Austempering etc…

14. Effects of Heat treatment on properties of metals
• One or the other heat treatment processes produces the following effects on the properties
of metals:
1. Hardens and strengthens the metals.
2. Improves machinability.
3. Change or refines grain size.
4. Soften metals for further working as in wire drawing.
5. Improves ductility and toughness.
6. Increase resistance of materials to heat, wear, shock and corrosion.
7. Improves electrical and magnetic properties.
8. Homogenises the metal structure.
9. Relieves internal stresses developed in metals/alloy during cold working, welding, casting,
forging etc..
10. Produces a hard wear resistant surface on a ductile steel piece (as in case of hardening)
11. Improves thermal properties such as conductivity.

15. Thermal Properties
• By thermal property meant the response of a material to the application
of heat.
• Thermal properties such as:
1. Heat capacity
2. Specific heat
3. Thermal expansion
4. Melting point
5. Thermal conductivity
6. Thermal shock resistance
7. Thermal stability

16. Electrical Properties
• Different electrical properties are:
1. Resistivity
2. Conductivity
3. Temperature coefficient of resistance
4. Dielectric strength
5. Thermoelectricity.
6. Electrochemical phenomena
7. Electrophysical effects
8. Electromechanical effects.

17. Magnetic Properties
• Some of the magnetic properties are:
1. Permeability
2. Coercive force
3. Hysteresis
4. Superconductivity.

18. Chemical Properties
• Some of the chemical properties are:
1. Corrosion Resistance
2. Chemical Resistance
3. Acidity or Alkalinity.

19. Optical Properties
• Some of the optical properties are:
1. Refractive index
2. Absorptivity and Absorption coefficient
3. Reflectivity.

20. Physical Properties
• Some of the physical properties are:
1. Dimensions
2. Appearance
3. Colour
4. Density
5. Melting point
6. Porosity
7. Structure etc.

21. Technological Properties
• Some of the technological properties are:
1. Castability
2. Machinability
3. Weldability
4. Solderability
5. Workability/Formability.

22. Factors affecting the selection of materials for
engineering purposes
1. Properties of Materials
2. Performance Requirements
3. Material’s Reliability
4. Safety
5. Physical Attributes
6. Environmental conditions
7. Availability
8. Disposability and Recyclability
9. Economic Factor

23. Destructive Testing

24. What is Destructive Testing?
• Destructive testing is undertaken in order to understand a specimen’s performance or
material behavior, these procedures are carried out to the test specimen’s failure.
Destructive testing procedures can either follow specific standards or can be tailored to
reproduce set service conditions.
• Destructive testing methods are commonly used for materials characterization,
fabrication validation, failure investigation, and can form a key part of engineering critical
assessments

25. Tensile Test• In tension test ends of a test piece are fixed into
grips connected to a straining device and to a load
measuring device. The test involves straining a test
piece by tensile force generally to fracture for the
purpose of determining one or more of the
mechanical properties.
• The straining unit of universal testing machine
consists of main hydraulic cylinder with robust base
inside and piston which moves up and down. The
lower table connected to main piston through a
ball & the ball seat is joined to ensure axial loading.
There is a connection between lower table and
upper head assembly that moves up and down with
main piston. The control panel consists of a power
pack complete with drive motor and an oil tank,
control valves and an autographic recorder. Load
Indicator system consists of a large dial and a
pointer. A dummy pointer is provided to record the
maximum load reached during the test.

26. Tensile Test
• Load is applied by a hydrostatically lubricated ram. Main cylinder
pressure is transmitted to the cylinder of the pendulum
dynamometer system housed in the control panel. The cylinder of
the dynamometer is also of self-lubricating design. The load
transmitted to the cylinder of the dynamometer is transferred
through a lever system to a pendulum. Displacement of the
pendulum actuates the rack and pinion mechanism which
operates the load indicator pointer and the autographic recorder.
The deflection of the pendulum represents the absolute load
applied on the test specimen. Return movement of the pendulum
is effectively damped to absorb energy in the event of sudden
breakage of a specimen.

27. Stress-strain
Diagram

28. Spark Test
• Spark testing is a method of determining the general classification of ferrous materials. It
normally entails taking a piece of metal, usually scrap, and applying it to a grinding wheel
in order to observe the sparks emitted.
• These sparks can be compared to a chart or to sparks from a known test sample to
determine the classification. Spark testing also can be used to sort ferrous materials,
establishing the difference from one another by noting whether the spark is the same or
different.
• Spark testing is used because it is quick, easy, and inexpensive. Moreover, test samples
do not have to be prepared in any way, so, often, a piece of scrap is used. The main
disadvantage to spark testing is its inability to identify a material positively; if positive
identification is required, chemical analysis must be used. The spark comparison method
also damages the material being tested, at least slightly.
• Spark testing most often is used in tool rooms, machine shops, heat treating shops, and
foundries.

29. Macro-etching
• Macro-etching, also known as deep etching, involves etching specimens prepared with a
suitable acid or reagent for macrostructural examination at low magnifications and rating
by a grades series of photographs showing the incidence of certain conditions such as:
cracks, pipe, center voids, center unsoundness, pinholes, porosity, white band, chill
structure, dendritic structure, inclusions, hydrogen flakes, segregation, banding, grain
size, mold slag, and other discontinuities or defects such as laps and seams.

30. Chemical Analysis
• Chemicals analysis determines the composition of the material. The chemical
composition of a metal alloy is the starting point for a right classification of the material
itself. Quantitative chemical analysis is performed to accurately determine the
concentration of elements in the material

31. Izod Impact Testing
• The Izod impact test was named for English engineer Edwin Gilbert Izod, who first
described the test method in 1903. The test apparatus and specimen design are very
similar to Charpy impact, with some notable differences, including the orientation of the
specimen, which is clamped into the apparatus vertically with the notch facing toward
the pendulum. The pendulum then impacts the sample at a specified area above the
notch.
• One of the main differences from Charpy impact is that Izod impact testing can be
performed on either plastic or metallic specimens. Plastic samples are typically a 64 x
12.7 x 3.2 mm bar with a machined V-shaped notch. Metallic samples are typically round
127 x 11.43 mm bar with 1 or 3 machined V-shaped notch(es).
• Common Izod impact test methods include ASTM D256, ASTM E23, and ISO 180.

32. Charpy Impact Testing
• The Charpy impact test was developed by S.B. Russell and Georges Charpy at the turn of the 20th
century. It remains to this day one of the most popular impact testing methods due to the
relative ease of creating samples and obtaining results. The test apparatus consists of a weighted
pendulum, which is dropped from a specified height to contact the specimen. The energy
transferred to the material can be inferred by comparing the difference in the height of the
pendulum before and after the fracture.
• A Charpy test specimen, which is placed horizontally into the machine, is typically a 55 x 10 x
10mm (2.165" x 0.394" x 0.394") bar with a notch machined into one of the faces. This notch,
which can be either V-shaped or U-shaped, is placed facing away from the pendulum and helps
to concentrate the stress and encourage fracture. Testing can be performed at both ambient and
reduced temperatures, sometimes as low as -425F.
• Charpy impact testing is most performed to ASTM E23, ASTM A370, ISO 148, or EN 10045-1.
While the test is most performed on metals, there are also a few standards that exist for plastics
and polymers, including ASTM D6110 and ISO 179.

33. Fracture
• Fracture is the separation of an object or material into two or more pieces under the
action of stress. The fracture of a solid usually occurs due to the development of certain
displacement discontinuity surfaces within the solid.
• If a displacement develops perpendicular to the surface of displacement, it is called a
normal tensile crack or simply a crack.
• If a displacement develops tangentially to the surface of displacement, it is called a shear
crack, slip band, or dislocation.
• Brittle fractures occur with no apparent deformation before fracture; ductile fractures
occur when visible deformation does occur before separation. Fracture strength or
breaking strength is the stress when a specimen fails or fractures. A detailed
understanding of how fracture occurs in materials may be assisted by the study of
fracture mechanics.

34. Ductile Fracture
• Ductile fracture is a type of fracture characterized by extensive deformation of plastic or
"necking." This usually occurs prior to the actual fracture. The term "ductile rupture"
refers to the failure of highly ductile materials. In such cases, materials pull apart instead
of cracking.
• In ductile fracture, there is absorption of massive amounts of energy and slow
propagation before the fracture occurs.

35. Brittle Fracture
• Brittle Fracture is the sudden, very rapid cracking of equipment under stress where the
material exhibited little or no evidence of ductility or plastic degradation before the
fracture occurs. Unlike most other tensile failures, where the material plastically strains
under overload conditions and becomes thinner until the point of rupture, when a piece
of equipment suffers a brittle fracture, there is no thinning or necking down. Rather, this
damage mechanism often causes cracking without warning, sometimes fracturing
equipment into many pieces.
Ductile Fracture Brittle Fracture

36. Ductile to Brittle transition
• At low temperatures, some metals that would be ductile at room temperature become
brittle. This is known as a ductile to brittle transition.

37. Creep Failure
• In materials science, creep is the tendency
of a solid material to move slowly or
deform permanently under the influence of
persistent mechanical stresses. It can occur
as a result of long-term exposure to high
levels of stress that are still below the yield
strength of the material. Creep is more
severe in materials that are subjected to
heat for long periods and generally
increases as they near their melting point.

38. Fatigue Failure
• Fatigue failure is defined as the tendency of a material to fracture by means of
progressive brittle cracking under repeated alternating or cyclic stresses of an intensity
considerably below the normal strength.

39. Non-Destructive Testing

40. What is Non-Destructive Testing?
• Non-destructive testing (NDT) is a wide group of analysis techniques used in science and
technology industry to evaluate the properties of a material, component or system
without causing damage.
• Non-destructive examination (NDE), non-destructive inspection (NDI), and non-
destructive evaluation (NDE) are also commonly used to describe this technology
because NDT does not permanently alter the specimen being inspected, it is a highly
valuable technique that can save both money and time in product evaluation,
troubleshooting, and research.

41. Radiography Testing
• Radiographic Testing is a non-destructive testing method which uses either x-rays or
gamma rays to examine the internal structure of manufactured components identifying
any flaws or defects.
• In Radiography Testing the test-part is placed between the radiation source and receiver.
The material density and thickness differences of the test-part will reduce the
penetrating radiation through interaction processes involving scattering and/or
absorption. The differences in absorption are then recorded.
• There are two different radioactive sources available for industrial use; X-ray and
Gamma-ray. These radiation sources use higher energy level, i.e. shorter wavelength,
versions of the electromagnetic waves. Because of the radioactivity involved in
radiography testing, it is of paramount importance to ensure that the Local Rules is
strictly adhered during operation.

42. Dye Penetration Testing
• Dye penetrant inspection (DP), also called liquid penetrate inspection (LPI) or penetrant
testing (PT), is a widely applied and low-cost inspection method used to check surface
defects in all non-porous materials (metals, plastics, or ceramics). The penetrant may be
applied to all non-ferrous materials and ferrous materials. LPI is used to detect casting,
forging and welding surface defects such as hairline cracks, surface porosity, leaks in new
products, and fatigue cracks on in-service components.
• Inspection steps
• Pre cleaning
• Application of Penetrant
• Excess Penetrant Removal
• Application of Developer
• Inspection
• Post Cleaning

43. Magnetic Particle Testing
• Magnetic particle Inspection (MPI) is a process for detecting surface and shallow
subsurface discontinuities in ferromagnetic materials such as iron, nickel, cobalt, and
some of their alloys.
• The process puts a magnetic field into the part. The piece can be magnetized by direct or
indirect magnetization. Direct magnetization occurs when the electric current is passed
through the test object and a magnetic field is formed in the material.
• Indirect magnetization occurs when no electric current is passed through the test object,
but a magnetic field is applied from an outside source. The magnetic lines of force are
perpendicular to the direction of the electric current, which may be either alternating
current or some form of direct current.

44. Ultrasonic Testing
• Ultrasonic testing is a non-destructive testing techniques based on the propagation of
ultrasonic waves in the object or material tested. In most common UT applications, very
short ultrasonic pulse-waves with center frequencies ranging from 0.1-15 MHz, and
occasionally up to 50 MHz, are transmitted into materials to detect internal flaws or to
characterize materials.
• Ultrasonic testing is often performed on steel and other metals and alloys, though it can
also be used on concrete, wood and composites, albeit with less resolution. It is used in
many industries including steel and aluminum construction, metallurgy, manufacturing,
aerospace, automotive and other transportation sectors.