SIMPLE STRESS AND STRAIN

 Simple Stresses and Strains

1. Concept of stress and strain

The internal resistance set up per unit cross sectional area called as stress, or intensity of stress or unit stress.

It is denoted by sigma

Sigma = R/A

In the equilibrium condition, the internal resistance R is equal to external load P

L.e. R=P

 Sigma = R/A = PA

Where o = Stress I

P = Load acting on the body

A= Cross sectional area of the body

Mathematically, stress may be defined as the force per unit

area S.I. Unit Is N/m2

1Pa = 1N/m

Mathematically, stress may be defined as the force per un

area S.I. Unit is N

1Pa = 1N

1.1.1. Normal stress

The stresses which are act normal to the plane on which the forces act are called as normal stress or direct stres

There are two type

1. Tensile stress

2. Compressive stress

1.1.2. Strain

Strain is simply a measure of deformation produced in a member due to the loads acting on it. It is defined as the ratio of change in dimension to the original dimension of the members

Strain = Change in dimension / Original dimensions

S.I. unit - No unit

There are the three types of strain :

1. Linear strain

2. Lateral strain

3. Volumetric Strain

Stress - Strain Curve

In engineering and material science, a stress-strain curve for a material gives the relationship between stress and strain. It is obtained by gradually applying load to a test coupons and measuring the deformation from which the stress and strain can be determined These curves reveal many of the properties of a material, such as the Youngs modulus, the yield strength and the ultimate tensile strength.