Low cycle fatigue life estimation for ductile metals using a nonlinear continuum damage mechanics model

Continuum damage mechanics is an effective approach to model ductile failure. The same concepts can be extended to the low cycle fatigue damage process, where plasticity is still the key mechanism for crack initiation. In addition, in low cycle fatigue a relevant part of life is spent by the material to initiate a macroscopic crack that leads to complete failure. In this paper, the nonlinear damage model, initially proposed by Bonora, N. (1997) A non-linear CDM model for ductile fracture Engineering Fracture Mechanics (in press), is extended to the case of cyclic loading. Three possible formulations are proposed and discussed that take into account in different ways the accumulation of damage, plastic strain and the material cyclic properties change. Fully coupled life model was used to predict low cycle fatigue life in Al 2024 T3 alloy and HY80 low carbon steel. Comparison with a large fatigue experimental data set is also presented. (C) 1998 Elsevier Science Ltd.