ABSTRACT
Viscoelastic materials are those for which the relationship between stress and strain depends on time. Anelastic solids represent a subset of viscoelastic materials: they have a unique equilibrium configuration and ultimately recover fully after removal of a transient load. Synthetic polymers, wood, and human tissue as well as metals at high temperature display significant viscoelastic effects. Knowledge of the viscoelastic response of a material is based on measurement. Materials used for structural applications of practical interest may exhibit viscoelastic behavior which has a profound influence on the performance of that material. Viscoelasticity is of interest in some branches of materials science, metallurgy, and solid-state physics since it is causally linked to a variety of microphysical processes and can be used as an experimental probe of those processes. Viscoelastic behavior manifests itself in creep, or continued deformation of a material under constant load; and in stress relaxation, or progressive reduction in stress while a material is under constant deformation.
