The permanent set in stress strain relation refers to the amount of deformation or elongation of a material that remains even after the applied stress or force has been removed. It is a measure of the material's ability to return to its original shape after being subjected to stress.
Permanent set is calculated by measuring the total deformation or elongation of a material after the applied stress has been removed. This can be done by using a strain gauge or by visually measuring the change in length of the material. The permanent set is then expressed as a percentage of the original length of the material.
The permanent set of a material can be affected by various factors such as the type and amount of stress applied, the temperature, and the duration of the stress. Additionally, the material's composition and microstructure can also play a role in determining its permanent set.
The calculation of permanent set is important in understanding the behavior and properties of a material under stress. It can help engineers and scientists determine the suitability of a material for a specific application and make necessary adjustments to prevent excessive permanent deformation.
The permanent set of a material can be reduced by using materials with higher strength and stiffness, avoiding high stress or strain rates, and controlling the temperature and duration of the stress. Additionally, proper design and maintenance can also help reduce the permanent set of a material.