NONLINEAR VISCOELASTICITY DETERMINED FROM QUASI-STATIC AND DYNAMIC TESTS

The dependence of mechanical properties on the excitation amplitude sh ows the presence of nonlinear effects. Several experimental devices, h owever, are not sensitive enough to detect the amplitude dependence, o r measure the mechanical response on assuming ab initio a linear visco elastic behavior. This paper gives an alternative procedure to determi ne the existence of nonlinear processes, based on the frequency or tim e dependence of the dynamic or quasistatic moduli and compliances. The methodology is applied to stress relaxation curves of AlMg5Si and pol y(vinylchloride). Furthermore, some experimental problems involved in the study of nonlinear mechanical behavior of materials are discussed. [S0163-1829(98)00617-1].