What characterizes elastic deformation?

Elastic deformation is characterized by a temporary change in shape or volume of a material under applied stress, which is fully reversible once the stress is removed. This means that when a force is applied, the material stretches or compresses, but when that force is taken away, it returns to its original shape and size. This behavior is typical of materials like rubber or springs, which can withstand considerable deformation without incurring permanent changes.

In contrast, gradual changes in the material's properties over time relate more to phenomena like plastic or creep deformation, which occur under sustained stress and lead to permanent changes. Similarly, a permanent alteration of a material's structure indicates plastic deformation where the material does not return to its original form after the stress is removed. A change in stress direction does not inherently describe a deformation type but rather indicates a variant in the application of forces, which might influence a material differently depending on its properties. Thus, the defining feature of elastic deformation is its ability to revert to the original form, making it a crucial concept in understanding material behavior under stress.