Under cyclic loading, the plastic zone becomes complicated during unloading. The energy-absorbing cyclic plastic zone is a stimulant for crack growth and can be a criterion for determining the damage around the fatigue crack tip. Presenting analytical models for determining the shape and size of the plastic zone often makes restrictive assumptions such as elastic-perfectly plastic response. In this research, the effects of non-linear kinematic hardening behavior of pure copper on the cyclic plastic reaction of the crack tip in different conditions were investigated. Chaboche nonlinear material model was used to determine the hardening parameters. According to the numerical results, the cyclic plastic zone around the crack tip was constant in the same load range but load ratio had a slight effect on this zone. Moreover, presence of the kinematic hardening in the cyclic loading caused reverse plastic zone to be predicted smaller than analytical model. According to the results, for materials such as pure copper with kinematic hardening behavior, the cyclic plastic zone increases with increase in the crack length. Therefore, the cyclic plastic zone, as well as other parameters in the fracture mechanics can be a proper criterion for fatigue crack growth studies.
