Measurement of viscoelastic characteristics of materials represents observation
involving transient regimes of deformation (see Chapter 2). When one of its characteris
tics (kinematic or dynamic) is kept constant, the time dependence of other characteristics
can be measured.
Thus measurement of viscoelastic characteristics is usually carried out in the following
regimes:
• a constant stress is imposed and variations of strain with time are measured, i.e.,
creep is studied at various stresses
• a constant strain is imposed and variations of stress with time are measured, i.e.,
a relaxation of stress at various deformations is studied.