Question

if external deforming force crosses the elastic limit, what happens to the elastic potential energy of the wire?

Answer 1

When a deforming force is applied to the material, work done against the internal restoring forces get stored in the material in the form of potential energy. This energy is called elastic potential energy. When the deforming force crosses the elastic limit, the material get permanently deformed. The material is no longer storing its elastic energy as no restoring force act between the particles of material after the elastic limit. Hence, elastic potential energy becomes zero if external deforming force crosses the elastic limit.