Damage progress of structural steel under cyclic loading using an elastoplastic damage model

Damage in metals is generally regarded as the progressive or sudden deterioration of a material before the beginning of the failure of the material due to loadings. In this paper, an entropy-based damage evolution function is introduced to describe the damage progress of structural steel. Under the condition of cyclic loading, the material tends to deteriorate gradually but at an increasing rate until the abovementioned failure begins. This concept of cumulative damage is suitable for predicting the damage of a material or component involving a range of failure mechanisms such as the growth of microcracks and microcavities. The proposed two surface damage model is developed by combining an existing two surface plasticity model and a damage parameter based on damage mechanics. The two surface plasticity model for a material that has bounding and loading surfaces is based on a yield theory that follows both an isotropic hardening rule and a kinematic hardening rule. This damage model is implemented as a user subroutine in ABAQUS. A simple shear problem and an example of steel under cyclic loading are analyzed to understand the inelastic behavior and the damage progress of structural steel under cyclic loading. In this study, a two surface plasticity damage model is used for simulating the damage progress of structural steel. Further, the numerical results of the two surface damage model are compared with the results of the two surface plasticity model. Parameters used for the simulation in the case of the two surface plasticity damage model are optimized using a numerical algorithm. The results of the damage progress simulation in the case of the two surface damage model show a good interpretation of the damage progress in structural steel.