Multistep stress-relaxation study of a single crystal of n-eicosane (C20H42) in torsion

Multistep stress-relaxation experiments in torsion have been done on a single crystal of the long-chain hydrocarbon compound n-eicosane. It was found that at very small strains the behavior approaches that of a linear viscoelastic material, whereas at larger strains the behavior becomes increasingly nonlinear and time dependent. In the region where the stress-strain behavior becomes nonlinear, it is shown that the second-step response, in an experiment in which the magnitude of the second step is one half that of the first step, can be described very well using a recent constitutive equation proposed by Zapas.