A Mechanics Approach to the Creep Rupture Strength of Notched Bodies under Longitudinal Shear

Abstract

This paper deals with a mechanical analysis of the notch creep rupture behavior under the longitudinal or mode III shear stress condition. The crack initiation, propagation and rupture lives (nondimensional) of prismatic bodies with double-edged hyperbolic notches were predicted using the results of stress and strain analysis of these bodies under the steady-state creep condition, as combined with a fracture criterion, in which a crack was assumed to grow by a characteristic distance, ρs, when the strain at the distance, ρs, ahead of the crack reached a critical value.The effects of several geometrical and material parameters on the crack initiation life of the notched prismatic bodies and also on the rupture life and the crack propagation rate of a deep-cracked prismatic body were predicted. It was found that “notch-weakening” in creep rupture strength prevails under the longitudinal shear stress condition, and that the crack propagation rate changes approximately linearly in a log-log diagram against the net section stress or the elastic stress intensity factor of the prismatic body. The physical interpretation and the extension of the fracture criterion used were discussed.The prediction was extended to the tensile or mode I notch creep rupture behavior, using an analogue between the modes I and III, which is empirically accepted in fracture mechanics. Qualitative agreement was observed between the predicted values and the experimental mode I results available in the literature.