Investigation of the J-integral Range under Biaxial Stresses Using Numerical Simulations of Fatigue Crack Growth

Abstract

In previous papers, the authors discussed the J-integral range, ΔJ, evaluated by the path integral and by Dowling's simple estimation formula and showed that ΔJ was a good parameter for characterizing the crack tip stress and strain field under uniaxial and elastic-plastic conditions. In this paper, finite element simulations of fatigue crack growth in a plate under biaxial stresses are conducted in order to clarify whether ΔJ is also applicable under biaxial conditions. It is found that ΔJ-values evaluated by the path integral are almost path-independent irrespective of the depth of crack and ratio of transverse and longitudinal applied stresses. Furthermore, the examination of the relationship between ΔJ and the crack-tip-opening displacemint leads to the conclusion that ΔJ evaluated on the basis of crack opening level is the most appropriate parameter for representing the mechanical state near the crack tip under biaxial loading. ΔJ evaluated by the simple estimating formula is found to agree well with ΔJ evaluated by the path integral.