A mechanical test is conducted on three different materials. In this experiment, a constant tensile stress is applied instantly to a specimen. The first material, a rubber, deforms rapidly during the application of the stress, with the extent of deformation becoming progressively less until it reaches an equilibrium gage length. The second, a thermosetting material, reacts to the applied stress by deforming almost instantaneously to an equilibrium extension. The third, a thermoplastic material, initially deforms to substantial extension in response to the stress and then deforms further with the extension varying linearly with time.
(a) Describe the behavior of each material with an appropriate combination of springs and dashpots.
(b) Describe the behavior of each material following the removal of the tensile stress.