Abstract
Y. Sawaragi and H. Tokumaru advanced a phenomenological theory of visco-plasto-elasticity derived from a mechanical model composed of three kinds of elements---spring, dashpot and slider (Coulomb's frictional mechanism) ---to explain non-linear visco-elasticity. Here we discuss the applicability of this theory for non-linear relaxation. The necessary condition for applying the theory to relaxation is:
∂/∂ε0 [-∂Er(ε0t)/∂ 1n t]>0
where
Er(ε0t) : Relaxation modulus at time t in the strain ε0
The relaxation behavior of polyethylene (reported in previous paper) did not satisfy this condition and, accordingly, could not be represented by Sawaragi and Tokumaru's equation.
