864 B
Viscous materials, like water, resist both shear flow and strain linearly with time when a stress is applied. Elastic materials strain when stretched and immediately return to their original state once the stress is removed.
A viscoelastic material has the following properties:
Hysteresis is seen in the stress–strain curve stress relaxation occurs: step constant strain causes decreasing stress creep occurs: step constant stress causes increasing strain its stiffness depends on the strain rate
A viscoelastic substance dissipates energy when a load is applied, then removed.
In most of the analyses, extensional/compressional strains of the viscoelastic layer are not taken into account since the damping comes mostly from the shear strain.
Nota Bene
The properties of a viscoelastic layer change with the frequency of excitation .