Low-cycle fatigue life prediction of circumferentially notched component in terms of elastic-plastic fracture mechanics.

Abstract

The elastic-plastic stress analysis was made by the finite element method. The surface crack growth rate, da/dN, was analyzed in terms of the elastic-plastic fracture mechanics parameters of the J-integral range, ΔJ and the strain intensity factor range, ΔKε, which were estimated in association with the stress and strain gradients produced in the cross section of the notched specimen. The low-cycle fatigue life for the crack propagation, Nc, was calculated by combining the cyclic stress-strain curve and the crack growth law expressed by the da/dN vs. ΔJ and da/dN vs. ΔKε relations. The calculation based on the fracture mechanics parameters determined from the stress-strain response at the notch root leads to a shorter life in the more sharply notched specimen under the lower stress condition. Meanwhile, the fracture mechanics parameters associated with the stress and strain gradients in the cross section of the notched specimen give a good estimation of the life prediction.