Elastic Region | Plastic Region | Yield Point | Plastic Strain | Strain Hardening | Necking

Elastic Region:

The region of the stress-strain curve in which the material returns to the undeformed state when applied forces are removed is called the elastic region.
Plastic Region:

The region in which the material deforms permanently is called the plastic region.

Yield Point:

The point demarcating the elastic from the plastic region is called the yield point. The stress at yield point is called the yield stress.

Plastic Strain:

The permanent strain when stresses are zero is called the plastic strain.

The off-set yield stress is a stress that would produce a plastic strain corresponding to the specified off-set strain.

A material that can undergo large plastic deformation before fracture is called a ductile material.

A material that exhibits little or no plastic deformation at failure is called a brittle material.

Hardness is the resistance to indentation.

The raising of the yield point with increasing strain is called strain hardening.

Necking Phenomenon:

The sudden decrease in the area of cross-section after ultimate stress is called necking.