Mechanical Engineering Notes | EduRev

Mechanical Engineering : Mechanical Engineering Notes | EduRev

 Page 1


IIT, Bombay 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Module 
2 
Selection of Materials and 
Shapes 
 
 
Page 2


IIT, Bombay 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Module 
2 
Selection of Materials and 
Shapes 
 
 
IIT, Bombay 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Lecture 
1 
Physical and Mechanical Properties of 
Engineering Materials 
Page 3


IIT, Bombay 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Module 
2 
Selection of Materials and 
Shapes 
 
 
IIT, Bombay 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Lecture 
1 
Physical and Mechanical Properties of 
Engineering Materials 
IIT, Bombay 
 
Instructional objectives 
At the of this lecture, the student should be able to appreciate 
(a) general classification of engineering materials, and 
(b) physical and mechanical properties of engineering materials  
 
Engineering Materials 
Materials play an important role in the construction and manufacturing of various parts and 
components. An appropriate selection of a material for a given application adds to economy, 
working and life of the final part and component.  
 
Classification of Engineering Materials 
Engineering materials can be broadly classified as metals such as iron, copper, aluminum and 
their alloys, and non-metals such as ceramics (e.g. alumina and silica carbide), polymers (e.g. 
polyvinyle chloride or PVC), natural materials (e.g. wood, cotton, flax, etc.), composites (e.g. 
carbon fibre reinforced polymer or CFRP, glass fibre reinforced polymer or GFRP, metal matrix 
composites or MMC, Concrete, Ceramic matrix composites, Engineering wood such as plywood, 
oriented strand board, wood plastic composite etc.) and foams. 
 
Properties of Engineering Materials 
Material property is the identity of material, which describes its state (physical, chemical) and 
behavior under different conditions. The material properties can be broadly categorized as 
physical, chemical, mechanical and thermal.  
The physical properties define the physical state of material and are independent of its chemical 
nature. The physical properties of engineering materials include appearance, texture, mass, 
density, Melting point, boiling point, viscosity, etc. The chemical properties describe the 
reactivity of a material and are always mentioned in terms of the rate at which the material 
changes its chemical identity, e.g. corrosion rate, oxidation rate, etc. The mechanical properties 
describe the resistance against deformation, in particular, under static and dynamic mechanical 
Page 4


IIT, Bombay 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Module 
2 
Selection of Materials and 
Shapes 
 
 
IIT, Bombay 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Lecture 
1 
Physical and Mechanical Properties of 
Engineering Materials 
IIT, Bombay 
 
Instructional objectives 
At the of this lecture, the student should be able to appreciate 
(a) general classification of engineering materials, and 
(b) physical and mechanical properties of engineering materials  
 
Engineering Materials 
Materials play an important role in the construction and manufacturing of various parts and 
components. An appropriate selection of a material for a given application adds to economy, 
working and life of the final part and component.  
 
Classification of Engineering Materials 
Engineering materials can be broadly classified as metals such as iron, copper, aluminum and 
their alloys, and non-metals such as ceramics (e.g. alumina and silica carbide), polymers (e.g. 
polyvinyle chloride or PVC), natural materials (e.g. wood, cotton, flax, etc.), composites (e.g. 
carbon fibre reinforced polymer or CFRP, glass fibre reinforced polymer or GFRP, metal matrix 
composites or MMC, Concrete, Ceramic matrix composites, Engineering wood such as plywood, 
oriented strand board, wood plastic composite etc.) and foams. 
 
Properties of Engineering Materials 
Material property is the identity of material, which describes its state (physical, chemical) and 
behavior under different conditions. The material properties can be broadly categorized as 
physical, chemical, mechanical and thermal.  
The physical properties define the physical state of material and are independent of its chemical 
nature. The physical properties of engineering materials include appearance, texture, mass, 
density, Melting point, boiling point, viscosity, etc. The chemical properties describe the 
reactivity of a material and are always mentioned in terms of the rate at which the material 
changes its chemical identity, e.g. corrosion rate, oxidation rate, etc. The mechanical properties 
describe the resistance against deformation, in particular, under static and dynamic mechanical 
IIT, Bombay 
 
loading condition. The mechanical properties include elastic modulus, Poisson’s ratio, yield 
strength and ultimate tensile strength, hardness and toughness, etc. The thermal properties 
describe material behavior under thermal loading and include thermal conductivity, specific heat, 
thermal diffusivity, coefficient of thermal expansion, etc. For a given application or service, an 
engineering material is selected based on a set of appropriate material properties, often referred 
to as attributes, that would be requisite to sustain various expected loads. Figure 2.1.1 depicts a 
schematic representation of material family, which is utilized in selection of materials for a target 
application. 
 
 
 
 
 
 
 
 
 
 
 
Figure 2.1.1 Organized classification of materials and properties [1] 
 
Physical Properties 
Physical properties describe the state of material, which is observable or measurable. Color, 
texture, density, melting point, boiling point, etc. are some of the commonly known physical 
properties. 
• Color: Represents reflective properties of substance 
• Density: Amount of mass contained by unit volume of material. The higher the density 
the heavier is the substance. (SI unit: kg/m
3
) 
Page 5


IIT, Bombay 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Module 
2 
Selection of Materials and 
Shapes 
 
 
IIT, Bombay 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Lecture 
1 
Physical and Mechanical Properties of 
Engineering Materials 
IIT, Bombay 
 
Instructional objectives 
At the of this lecture, the student should be able to appreciate 
(a) general classification of engineering materials, and 
(b) physical and mechanical properties of engineering materials  
 
Engineering Materials 
Materials play an important role in the construction and manufacturing of various parts and 
components. An appropriate selection of a material for a given application adds to economy, 
working and life of the final part and component.  
 
Classification of Engineering Materials 
Engineering materials can be broadly classified as metals such as iron, copper, aluminum and 
their alloys, and non-metals such as ceramics (e.g. alumina and silica carbide), polymers (e.g. 
polyvinyle chloride or PVC), natural materials (e.g. wood, cotton, flax, etc.), composites (e.g. 
carbon fibre reinforced polymer or CFRP, glass fibre reinforced polymer or GFRP, metal matrix 
composites or MMC, Concrete, Ceramic matrix composites, Engineering wood such as plywood, 
oriented strand board, wood plastic composite etc.) and foams. 
 
Properties of Engineering Materials 
Material property is the identity of material, which describes its state (physical, chemical) and 
behavior under different conditions. The material properties can be broadly categorized as 
physical, chemical, mechanical and thermal.  
The physical properties define the physical state of material and are independent of its chemical 
nature. The physical properties of engineering materials include appearance, texture, mass, 
density, Melting point, boiling point, viscosity, etc. The chemical properties describe the 
reactivity of a material and are always mentioned in terms of the rate at which the material 
changes its chemical identity, e.g. corrosion rate, oxidation rate, etc. The mechanical properties 
describe the resistance against deformation, in particular, under static and dynamic mechanical 
IIT, Bombay 
 
loading condition. The mechanical properties include elastic modulus, Poisson’s ratio, yield 
strength and ultimate tensile strength, hardness and toughness, etc. The thermal properties 
describe material behavior under thermal loading and include thermal conductivity, specific heat, 
thermal diffusivity, coefficient of thermal expansion, etc. For a given application or service, an 
engineering material is selected based on a set of appropriate material properties, often referred 
to as attributes, that would be requisite to sustain various expected loads. Figure 2.1.1 depicts a 
schematic representation of material family, which is utilized in selection of materials for a target 
application. 
 
 
 
 
 
 
 
 
 
 
 
Figure 2.1.1 Organized classification of materials and properties [1] 
 
Physical Properties 
Physical properties describe the state of material, which is observable or measurable. Color, 
texture, density, melting point, boiling point, etc. are some of the commonly known physical 
properties. 
• Color: Represents reflective properties of substance 
• Density: Amount of mass contained by unit volume of material. The higher the density 
the heavier is the substance. (SI unit: kg/m
3
) 
IIT, Bombay 
 
• Melting point: Melting point is the temperature at which material changes its state from 
solid to liquid. (SI units: K)  
• Boiling point: Boiling point is the temperature at which material changes its state from 
liquid to gaseous. (SI units: K) 
Chemical Properties 
Chemical properties are the measure of reactivity of a material in the presence of another 
substance or environment which imposes change in the material composition. These properties 
are always mentioned in term of the rate of change in its composition. Corrosion rate, oxidation 
rate, etc. are some of the chemical properties of material. 
• Corrosion rate: Corrosion rate is measured in terms of corrosion penetration for given 
period of time at specific surrounding condition. Corrosion rate is given by length of 
penetration per unit time. (Units: mm/year) 
• Oxidation rate: Oxidation rate is measured in terms of amount of material consumed 
forming oxide or amount of oxide scale formed for given period of time at specific 
surrounding temperature. Oxidation rate is given by amount of mass of material lost or 
thickness of scale formed during oxidation per unit time. (Units: gms/min or µm/min). 
Mechanical Properties 
Mechanical properties describe the behavior of material in terms of deformation and resistance to 
deformation under specific mechanical loading condition. These properties are significant as they 
describe the load bearing capacity of structure. Elastic modulus, strength, hardness, toughness, 
ductility, malleability are some of the common mechanical properties of engineering materials. 
Every material shows a unique behavior when it is subjected to loading. Figure 2.1.2 shows a 
typical stress-strain curve of C-steel under uniaxial tensile loading. Point ‘A’ indicates the 
proportional limit. Stress strain behavior is linear only up to this point. Point ‘B’ represents the 
point at which the material starts yielding. Between point A and B, the stress strain behavior is 
not linear, though it is in elastic region. Point ‘C’ is referred to the upper yield point. The 
material behavior after point ‘D’ is highly nonlinear in nature. Point ‘E’ is the maximum stress 
that the material can withstand and the point ‘F’ schematically indicates the point of rupture. 
 
 
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