Experimental modeling of strain-dependent cyclic plasticity for prediction of hysteresis curve

Although attempts have been devoted to consider the strain range effect in the material models, identification of material constants for accurate modeling the material response under cyclic loading within a wide range of strain amplitude is still a challenge. The experiments show that the cyclic stress-strain curves are severely dependent on the strain range for ductile metals. In most of the cyclic material models, only the stabilized cycle is considered to compute the constants of the models. Considering this strategy in the simulation of ductile metals subjected to cyclic loading may lead to erroneous results particularly for the initial cycles of the loading. In this study, strain-controlled tests were conducted to study the cyclic behavior of oxygen-free high thermal conductivity pure copper at different strain ranges. Each cycle of the hysteresis curve was divided into a tensile and a compressive half cycle. The yield stress and the constants of the four-rule Chaboche kinematic hardening model were computed for each half cycle using an automated program developed based on the genetic algorithm optimization. The results indicated that the constants of Chaboche model were dependent on the strain range and the accumulated plastic strain. Therefore, new strain range-dependent relations for isotropic and kinematic hardening conditions were proposed and the constants of the relations were computed. The proposed model could accurately simulate the stress-strain curve of the hysteresis loop from monotonic loading to the stabilized cycle. © 2015 Institution of Mechanical Engineers