Stress and Strain (Engineering Science)
Stress is the internal resistance which the body offers against a load or an external force.
There various types of stresses classified as follows :
- Simple or direct stress – this includes tension, compression and shear.
- Indirect stress – this includes bending and torsion.
- Combined stress – a combination of direct and indirect stress.
It is usually called direct stress because it develops under direct loading conditions. There are 3 types of simple stress:
- Tensile stress
- Compressive stress
- Shearing stress
The formula for calculating stress is:
Whereby Stress is in Newton per square metre (N/m2) or Pascals (Pa) if Force is in N and Area is in m2.
The strain (e) is a measure of the deformation of a material under stress. There are three main types of strain:
- Tensile Strain
- Compressive Strain
- Shear Strain
Tensile Strain and Compressive Strain
Calculations for shear strain are beyond the scope of this post, however, tensile strain and compressive strain are calculated as follows:
Both extension and original length must be in the same units. This makes strain is a ratio, which means it has no units. However, strain is sometimes expressed as a percentage by multiplying it by 100. For example, a strain of 0.15 is equivalent to 15%.