**BASIC CONCEPTS (INTRODUCTION)**

## ELASTICITY AND PLASTICITY

## ELASTIC BEHAVIOUR OF SOLIDS

**STRESS AND STRAIN**

## Stress

## Types of Stress

## Strain

## Types of Strain

**SOLVED EXAMPLES**

## Illustration-01

## Solution

## Illustration-02

## Solution

**HOOKE’S LAW**

## Hooke’s Law

**STRESS-STRAIN CURVE**

## Stress-Strain Curve

## Elastic Limit

## Elastic Hysteresis

## Elastomers

Substances like tissue of aorta, rubber etc. which can be stretched to cause large strains are called elastomers.**ELASTIC MODULUS**

## Elastic Modulus

The modulus of elasticity or coefficient of elasticity of a body is defined as the ratio of the stress to the corresponding strain produced.## Elastic Modulus

## Relation between Y, B, η and σ

**ELASTIC POTENTIAL ENERGY**

## Elastic Potential Energy

**POISSON’S RATIO**

## Poisson’s Ratio

Value of σ lies between 0 and 0.5**APPLICATIONS OF ELASTIC BEHAVIOUR OF MATERIALS**

## Applications

- (1) The bridges are designed in such a way that they do not bend much or break under the load of heavy traffic, force of strongly blowing wind and its own weight. So the beams used in constructions of bridges, as supports are made in shape of I.

(2) The metallic parts of the machinery are never subjected to a stress beyond elastic limit, otherwise they will get permanently deformed.

(3) The thickness of the metallic rope used in the crane in order to lift a given load is decided from the knowledge of elastic limit of the material of the rope and the factor of safety.