Elastic Relaxation Time The time delay in restoring the original configuration after removal of deforming force is called elastic relaxation time.
For quartz and phosphor bronze this time is negligible. Elastic After Effect
The temporary delay in regaining the original configuration by the elastic body after the removal of deforming force, is called elastic after effect.
Elastic Fatigue
The property of an elastic body by virtue of which its behaviour becomes less elastic under the action of repeated alternating deforming force is called elastic fatigue.
Ductile Materials
The materials which show large plastic range beyond elastic limit are called ductile materials, e. g., copper, silver, iron, aluminum, etc.
Ductile materials are used for making springs and sheets. Brittle Materials
The materials which show very small plastic range beyond elastic limit are called brittle materials, e. g., glass, cast iron, etc.
Elastomers
The materials for which strain produced is much larger than the stress applied, with in the limit of elasticity are called elastomers, e. g., rubber, the elastic tissue of aorta, the large vessel carrying blood from heart. etc.
Elastomers have no plastic range. Elastic Potential Energy in a Stretched Wire
The work done in stretching a wire is stored in form of potential energy of the wire.