THE STRAIN PATH DEPENDENCE OF MULTIAXIAL CYCLIC HARDENING BEHAVIOR

The small-strain, isotropic deformation theory is used in incremental form to model an additional cyclic hardening for any arbitrary loading path. The theory is of the unified type and does not employ yield or loading/ unloading criteria. The scalar-valued functions involved in t he tensorial constitutive equations as well a growth law for these fun ctions are identified based on idea of the equivalent state. Definitio ns of equivalent stress and equivalent strain have been developed to c orrelate step by step loading programmes taking the history of deforma tion into account. Use is made of the total work increment together wi th an interpolation method for tensor functions to generalize the simp le state to a multiaxial behaviour in the strain space for a given str ain increment. For the demonstration of model capability, the numerica l simulation is undertaken on cyclic nonproportional paths in two-dime nsional axial-shear strain space. The results are verified for stainle ss steel and brass by comparison with the material response experiment ally obtained in the stress space.