What term describes the permanent change in shape or size of a material when subjected to stress beyond its limit?

The term that describes a permanent change in shape or size of a material when it is subjected to stress beyond its limit is plastic deformation. In this context, plastic deformation occurs when the applied stress exceeds the yield strength of the material, leading to a change in shape that does not revert to the original form once the stress is removed.

When materials are elastic, they can return to their original shape after the stress is removed, which is what occurs during elastic deformation. This temporary change means that the material has not exceeded its limit. On the other hand, fracture refers to the breaking or separation of a material, which typically occurs after significant deformation and under extreme stress, rather than just a change in shape. Shear deformation involves a change in shape through sliding layers of the material relative to one another but does not specifically imply a permanent change in size or shape unless it becomes plastic in nature.

Thus, plastic deformation accurately captures the scenario of a permanent alteration in shape or size when a material endures stress that surpasses its elastic limit.