A new model for describing a stable cyclic stress-strain relationship under non-proportional loading based on activation state of slip systems

摘要

This paper proposes a new simple model for cyclic incremental plasticity based on activation states of slip systems describing stable cyclic stress-strain relationships under non-proportional loading. In the model, the magnitude and the direction of incremental plastic strain are estimated by (1 +alpha f Np) and Q, respectively. Here, alpha is the constant related to the dependence of material on additional hardening and /NP the intensity factor expressing the severity of non-proportional loading. Q is the second-order tensor describing the activation states of slip systems in polycrystalline metals and is given by the calculation using a virtual specimen. The model was examined by application to the prediction of the stable cyclic stress-strain relationship in extensive non-proportional low cycle fatigue tests for type 304 stainless steel and 6061 aluminium alloy. The simulated results showed that the model gave a satisfactory prediction of the stable cyclic stress-strain relationship under complex non-proportional multiaxial loadings for the two materials.