Endochronic Theory of Cyclic Plasticity With Applications

Integral constitutive equations of the endochronic type with only two easily determined material constants are shown to predict with computational ease the stress (plastic strain) response of normalized mild steel and Grade 60 steel to a variety of general strain (stress) histories, without a need for special unloading-reloading or memory rules. These equations are derived from the endochronic theory of plasticity of isotropic materials with an intrinsic time scale defined in the plastic strain space. Close agreement between theoretical predictions and experiments is obtained in the case of normalized mild steel in a variety of uniaxial, constant, strain-amplitude histories, variable strain-amplitude histories, and cyclic relaxation. Similar results are shown in the case of Grade 60 steel subjected to a random uniaxial strain history.