Tensile strain is the ratio of the elongation of the rod to the initial length of the bar.Whenever a stress (no matter how small) is applied to a metal a proportional dimensional change or distortion must take place such a proportional dimensional change (intensity or degree of the distortion) is called strain and is measured as the total elongation per unit length of material due to some applied stress.
Strain may take two forms elastic strain and plastic deformationStrain can be expressed as
ε = ΔL / L
where
Note If we apply tensile force we have tensile strain
Elastic strain is a transitory dimensional change that exists only when the initiating stress is applied and disappears immediately upon removal of the stress.it is also called elastic deformation.
Plastic strain is a dimensional change that does not disappear when the initiating stress is removed.it is usually accompanied by some elastic strain. The state of stress just before the plastic strain begins to appear is known as the proportional limit or elastic limit .
When we apply a force on a body it will undergo deformation and its length will increase or decrease. Length increases when the force is tensile and decreases when the force applied is compressive.
The ratio of Change in dimension to the original dimension is called strain.
Strain( ε) = Change in dimension/original dimension
There are two types of strains.
1. Normal strain (Tensile, compressive and volumetric)
2. Shear strain
Normal strain: It can be divided into three types.
a. Tensile strain: When we apply a tensile force on a body its length increases. The ratio of increase in length to the original length.
Tensile strain = εt = L – L0 / L
Where L = Original length
L0 = new length
b. Compressive strain: When we apply a compressive force on a body its length decreases. The ratio of decrease in length to the original length is called compressive strain.
ompressive strain = εc = L – L0 / L
Where L = Original length
L0 = new length
c. Volumetric strain: When we apply a force on all sides of a body its volume will decrease. The ratio of change in volume to the original volume is called volumetric strain.
Volumetric strain = εv = V – V0 / V
Where V = Original volume
V0 = new volume
Shear Strain: When we apply a tangential force on a body there is an angular displacement (θ), which measures the shear strain.
Shear strain = tan θ