Viscoelasticity is the property of materials that exhibit both
viscous and
elastic characteristics when undergoing
deformation. Viscous materials, like honey, resist
shear flow and
strain linearly with time when a
stress is applied. Elastic materials strain when stretched and quickly return to their original state once the stress is removed. Viscoelastic materials have elements of both of these properties and, as such, exhibit time-dependent strain. Whereas elasticity is usually the result of bond stretching along crystallographic planes in an ordered solid, viscosity is the result of the diffusion of atoms or molecules inside an
amorphous material.