This document provides an overview of basic concepts in strength of materials, including: 1) It defines stress as the forces of resistance per unit area offered by a body against deformation, and strain as the rate of change of dimension of a body due to external forces. 2) It describes the different types of stress (normal, shear) and strain (tensile, compressive, volumetric, shear). 3) It explains elasticity as the ability of a material to return to its original shape after external forces are removed, and introduces Hooke's law which states that stress is proportional to strain within the elastic limit. 4) It defines modulus of elasticity (Young's modulus) as the ratio

1. few basic concepts of
Strength of materials
Power point presentation
By
k. Anand Babu

2. Contents
Stress ………………………………………………….2
Strain ………………………………………………….3
Types of stress ……………………………………………….....4-11
Elasticity and elastic limit ………………………………………………….11
Hooke’s law ….………………………………………………12
Young’s modulus ………………………………………………….12
Shear modulus …………………………………………………13
Factory safety ………………………………………………...13

3. Introduction
when an external forces act on body, the body tends to undergo some deformation due to
cohesion between the molecules ,the body resist deformation .this resistances by which
material of body opposes the deformation is known as ‘strength of material’
Here the downward arrows are forces acts on body
Hence the upward arrows are forces opposes the
External forces from body body
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4. stress
The forces of resistances per unit area offered by a
body against deformation is known as ‘stress’
Here the small circle in a rectangular section .
the circle is the forces acting per unit area on rectangular section
Is called stress
the mathematical written as
Stress=forces applied unit area area
Units of Stress is Newton –meter square
Here the forces unit is newton and area unit is meter square
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5. Strain
When a body is subjected to some external forces ,their is some change
of dimension of the body
The rate of change of dimension of the body to the original dimension
Is known as ‘strain’
Strain = change in length original length
Units of strain is no units
Here the units of length is meter
So meter/meter gets cancel
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6. Types of stress and strain
Types of stress and strain they are
Stress;
Stress may classified into two types they are
Normal stress and
Shear stress
Normal stress is divided into two types
Tensile stress
Compressive stress
Strain
Strain is classified into four types they are
Tensile strain
Compressive strain
Volumetric strain
Shear strain
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7. Normal stress
Normal stress Is stress which acts in a direction perpendicular to the area it is represented by
Sigma
Tensile stress: the stress induced in a body when subjected to two equal and opposite pull
As shown in fig as a result of which there is an increase in length is known as ‘tensile stress ‘
Tensile stress = resisting force /area
Tensile stress
Its units is newton /meter square
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8. Compressive stress
Tensile stress: the stress induced in a body when subjected to two equal and opposite pushes
As shown in fig as a result of which there is an decrease in length of body is known as ‘compressive stress’
Compressive stress = resisting force / area
Its units is newton /meter square
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9. Shear stress
The stress induced in a body ,when subjected to two equal and opposite forces which are acting tangentially
Across the resting section as shown in fig as a result of which the body tends to shear off across the section
Is known as ‘shear stress’
Its units is newton /meter square
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10. Types of Strain
Tensile strain
If there is increase in length of body due to external load (or)external forces then the ratio of increase of
Length to the original length of body is known as ‘tensile strain’
It has no units
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11. Compressive strain
If there is some decrease in length of the body then the ratio of decrease of length of the body to
The original length of body is known as ‘compressive strain’
It has no units
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12. Volumetric strain
The ratio of change of volume of the body to the original volume of body is known as ‘volumetric strain’
It has no units
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13. Shear strain
Then produced by shear is known as shear strain
Elasticity
By virtue o which certain material returns back to their original position
After the removal of the external forces is ‘elasticity’
EXTERNAL FORCES
ACTING ON MATERIAL
AFTER REMOVING
FORCES
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It has no units

14. ELASTICITY LIMIT
Then body will regains its previous shape and size only when the deformation caused by the
External forces is with in a certain limit while removing the external load .the deformation completely
Disappears on body
Hooke’s law
Hooke’s law, states that when a material load with in elastic limit the stress is directly proportional to
The strain produced by the stress . This means the ratio of the stress to the corresponding strain is
A constant with in the elastic limit this constant is known as ‘modulus of elasticity’ (or)
‘modulus of rigidity’(or) ‘elastic moduli’
Its units is newton /meter square
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15. Modulus of elasticity (or) young’s modulus
The ratio of tensile stress (or) compressive stress to corresponding strain is a constant
This ratio is known as ‘young’s modulus’ it is denoted by ‘E’
Its units is newton /meter square
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16. Modulus of rigidity (or) shear modulus
The ratio of the shear stress to the corresponding shear strain with in the
elastic limit is known as ‘modulus of rigidity’ (or) ‘shear modulus’
It is denoted by C ,G or N
Factor of safety
It is define as the ratio of ultimate stress to the working stress(or) permissible stress
(or) design load is known as ‘factor of safety’
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