Cyclic constitutive relation in nonproportional plastic-creep loading
Nozaki Mineo; Sakane Masao; Ohnami Masateru
Abstract:The cyclic nonproportional plastic-creep constitutive relation was studied by experiments and analysis, in order to estimate the stress response of Type 304 stainless steel which shows a significant additional hardening and fatigue life reduction by nonproportional loading. Mises' equivalent strain controlled push -pull/reversed torsion plastic-creep loading tests were carried out at 923 K in air using two proportional and three nonproportional strain paths. Every strain path had the same Mises' equivalent strain wave form but the combination of normal and shear strains was different. A simplified incremental inelastic analysis was made for five different proportional and nonproportional loadings. In the analysis, Mises yield criterion with the Prager kinematic hardening rule was used and the total strain was assumed to be a linear combination of elastic, plastic and creep strains. The simplified analysis predicted well the actual stress response obtained in the experiments. Key Words:nonproportional loading, constitutive relation, inelastic analysis, multiaxial stress, high temperature, additional hardening