An Energy Criterion for Low-Cycle Fatigue

A criterion for low-cycle fatigue is developed which supposes that the segment of strain hysteresis associated with work-hardening is a measure of damage. On the basis of this “damage” work criterion and assuming a linear work-hardening law, the well-known plastic strain-cyclic life equation, N1/2Δεp = C is derived. The constant C in this equation is evaluated by setting the total damage energy absorbed in N cycles equal to the damage work of a static tensile test. This method of predicting the constant C is in much better agreement with room-temperature strain-cycling data than the previously suggested method of plotting the fracture ductility at 1/4 cycle.