Question

Time dependent permanent deformation is called
(A) Plastic deformation
(B) Elastic deformation
(C) Creep
(D) Anelastic deformation

Answer 1

Hint: Investigate the options one after the other for which definition is a match with the one given in question. Elastic deformation is not even a permanent deformation

Complete step by step answer:
To answer the question, let us investigate the options for their definition one after the other.
Plastic deformation – This is the permanent deformation of a body due to a tensile, compressional, torsional stress (or other forms of stresses) is applied on the body causing it to become elongated, shortened, twisted (or other response to various stresses). It is due to an instant applied stress and is hence time independent.
Elastic deformation – similar to the plastic deformation, but different, it is the temporary deformation of a body due to a tensile, compressional, torsional stress (or other forms of stresses) is applied on the body causing it to become elongated, shortened, twisted (or other response to various stresses). It is also due to an instant applied stress and is hence also time independent.
Creep – this is the permanent deformation of a body due to persistent stress. This stress can be tensile, compressional, torsional or other mechanical stress. As mentioned, as creep is due to persistent stress, it is time dependent.
Hence, creep is the correct answer.
This, the correct option is C.

Note:
For understanding, creep which can also be called cold flow, is time dependent in the sense that if a stress is applied on a body which may not cause permanent deformation (if applied briefly) is applied for a long time, it would tend to cause a permanent deformation.