Energy Criterion for Low-Cycle Fatigue on the Basis of Distributed Element Model

Abstract

A criterion for low-cycle fatigue has been developed on the supposition that the stress-strain hysteresis energy is a measure of fatigue damage. The total strain energy to cause fracture was calculated by means of the distributed element model which had been previously proposed by the authors. The result shows clearly that fatigue failure takes place when the strain energy accumulated in the most defective element having the maximum hysteresis loop reaches a certain value. On the basis of this fatigue criterion, the well-known plastic strain-cyclic life equation NΔε_p²=C can be derived. In addition, a procedure has been developed for predicting the fatigue failure of a material subjected to complex stress-strain histories. The agreement between theory and the experiments is found to be satisfactory.