EXPERIMENTAL STUDY ON NON-PROPORTIONALLY MULTIAXIAL TIME-DEPENDENT CYCLIC DEFORMATIONS OF SS304 STAINLESS STEEL AT HIGH TEMPERATURE

The time-dependent strain cyclic characteristics and ratcheting behavior of SS304 stainless steel were studied by experiments under non-proportionally multiaxial cyclic loading and at 973 K. The effects of loading path, straining/stressing rate and holding-time at peak/valley of each cycle on cyclic softening/hardening behavior and ratcheting were discussed. It is shown from experimental results that the cyclic softening/hardening behavior and ratcheting of the material are characterized by apparent time-dependence, i.e., the cyclic deformation behaviors depend not only greatly on loading rate, but also apparently on holding-time, besides, the ratcheting behavior of the material also presents a great dependence on loading path at high temperature. Some results obtained are helpful to construct a time-dependent constitutive model of ratcheting.