Which term describes the permanent deformation of a material when stress exceeds its yield point?

The term that describes the permanent deformation of a material when the stress exceeds its yield point is plastic deformation. When a material is subjected to stress, it initially responds elastically, meaning it returns to its original shape upon the removal of the stress. However, once the stress surpasses a specific threshold known as the yield point, the material enters the plastic deformation phase. In this phase, the material undergoes changes in its internal structure that result in permanent changes to its shape or dimensions.

This phenomenon is critical in understanding how materials behave under different loading conditions. Structural engineers and materials scientists pay close attention to the yield point and the transition from elastic to plastic behavior, as it influences the design and reliability of components in various applications.