Question

Which of the following deformations is/are irreversible?
A) Elastic deformation
B) Plastic deformation
C) Fracture
D) All of the above

Answer 1

Just remember, the concept of deformation i.e. its types and how it occurs. Remember, irreversible deformation is the deformation in which the material transforms itself into the original form, after the removal of external force.

Complete step by step answer: let us first discuss all the terms used in the question.
DEFORMATION: Deformation is defined as the change in the size or shape of an object.

ELASTIC DEFORMATION: Elastic deformation is defined as the temporary change in the size or shape of an object when the external stress is applied to it.

PLASTIC DEFORMATION: Plastic deformation is defined as the permanent change in the size or shape of an object when an external force is applied.

FRACTURE: Fracture of the material is defined as the breakage of a material into two pieces when an external field is applied.

Now, deformation will be irreversible, if it stays even after the removal of the applied field or in the case of permanent deformation. Here, plastic deformation and fracture undergo permanent deformation which means that deformation will be irreversible in both cases.

Therefore, option (B) and (C) are the correct option.

Additional Information:
In elastic deformation, atoms of the material are temporarily displaced from their original lattice. In this deformation, the stress-strain curve is linear. It can be characterized by the property of elasticity, therefore, Hooke’s law of elasticity is applicable in this deformation.
In plastic deformation, atoms of the material are permanently displaced from their original position. In this deformation, the stress-strain curve is non-linear. It can be characterized by the property of elasticity.

Note: In elastic deformation, with the application of external force, the material will firstly undergo elasticity and then regain its original shape. On the other hand, in plastic deformation, the material will firstly undergo elastic deformation and then undergo plastic deformation.