Elasticity, plasticity, and creep

Elasticity : Property of a material, by which it returns to its original dimension during unloading

Partially elastic : During unloading the bar returns partially to its original shape

i. Residual elongation of the bar is called the permanent set  and the strain associated with that is known as residual strain

Plasticity : characteristic of a material by which it undergoes inelastic strains beyond the strain at the elastic limit

Reloading of material

ii. By stretching a material such as steel or aluminum into the inelastic or plastic range, the properties of the material are changed

1. the linearly elastic region is increased,

2. the proportional limit is raised

3. elastic limit is raised

4. ductility is reduced

Creep

i.) When loaded for long periods of time, some materials develop additional strains and are said to creep

ii.) Relaxation

5. a wire that is stretched between two immovable supports so that it has an initial tensile stress

6. With the elapse of time, the stress in the wire gradually diminishes, eventually reaching a constant value, even though the supports at the ends of the wire do not move.