Question

As we have learned in this unit, Hooke's law cannot perfectly predict the relationship between stress and strain of materials. Can you provide your opinion why the materials behave like this on the elastic limit?

Answer 1

Materials behave in a plastic manner beyond their elastic limit due to irreversible deformation and the variety of microscopic mechanisms responsible for plasticity.

Step-by-step explanation:

Hooke's law states that the stress applied to a material is directly proportional to the strain produced, as long as the stress does not exceed the elastic limit. However, on reaching the elastic limit, materials exhibit plastic behavior, where they deform irreversibly and do not return to their original shape. This occurs because the microscopic mechanisms responsible for plasticity in materials vary based on their composition. For rubber-like materials, stress increases as strain increases, making them more difficult to stretch until they reach a fracture point. Ductile materials, such as metals, show a gradual decrease in stress as strain increases, making them easier to deform until they reach their breaking point.