Low Cycle Fatigue Based on Unilateral Damage Evolution

This article deals with the modeling of the low cycle fatigue of AISI 316L stainless steel from the viewpoint of continuum damage mechanics. The concept of kinetic law of damage evolution is adapted and three models are presented: one in which the effect of crack closure/opening is excluded and two others where either classical or new continuous microcrack closure/opening effects are taken into account. The problem is described by a system of ordinary differential equations derived for the case of uniaxial stress, then extended to the three-dimensional (3D) state of stress accompanying strain localization by the use of approximate, axisymmetric 3D stress formulas by Davidenkov and Spridonova. The results of numerical simulation for all models are compared and verified in order to achieve the best agreement with the experimental data. Detailed quantitative and qualitative analysis of obtained solutions confirms the necessity and correctness of an application of continuous microcrack closure/opening effect.