A New Model for Describing Stable Cyclic Stress-strain Relationship Under Nonproportional Loading Based on Activation States 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 relationship under nonproportional loading. In this model, the magnitude and the direction of incremental plastic strain are estimated by (1+αf_(NP)) and Q, respectively. Here, α is the constant related to the material dependence of additional hardening and f_(NP) the nonproportional factor expressing the severity of nonproportional loading. Q is a second-order tensor describing the activation states of slip systems in poly crystalline metals and is given by the calculation using a virtual specimen. The model was examined the applicability to the estimation of the stable cyclic stress-strain relationship in extensive nonproportional low cycle fatigue tests for Type 304 stainless steel and 6061 aluminum alloy. The simulated results showed that the model gave a satisfactory estimation of the stable cyclic stress-strain relationship under the complex nonproportional multiaxial loadings for different materials.