What is the term for the amount of deformation that occurs when a material is stressed beyond the proportional limit?

The term that describes the amount of deformation that occurs when a material is stressed beyond the proportional limit is known as strain. Strain refers to the degree to which a material deforms in response to an applied stress, and it can be classified into various types. When the material is subjected to stress exceeding its proportional limit, it no longer returns to its original shape once the stress is removed. This deformation that persists after the removal of stress is what is observed when materials experience plastic deformation.

In this context, while other terms may describe aspects of permanent deformation, strain encompasses the total deformation experienced by the material. Therefore, understanding strain helps engineers predict how materials will behave under different loading conditions, making it a fundamental concept in material science and engineering.