Low-Cycle Fatigue Damage Model for Ductile Materials

Abstract

In this paper, a uniaxial material model with the ability to describe progressive damage growth, but also to provide a reliable estimation of fatigue life in the low-cycle regime of loading, is presented. The determination of damage in the material is based on two levels of modeling mechanical behavior. The element on the micro level establishes an elastoplastic damage model that depends on the maximum strain. The second level of modeling is defined by the connection of microelements with different values of total energy dissipated at failure. Hysteretic energy dissipated in heat during cyclic loading is determined for each micro element based on the analytical expression provided by a hysteretic operator. Different distributions of values of maximum dissipated energy can thus provide various fatigue damage evolution laws. The analytical expression for hysteretic energy loss for one element and its numerical implementation is enabled by the computational model whose parameters can be defined by monotonic and cyclic loading experimental tests. Validation of the introduced material model can additionally be concluded by constant and variable strain-controlled experiments, as well as with the comparison of constructed failure curves with existing methods for assessment of mean stress effect in fatigue analysis.