Some Considerations on Estimation of Energy Release Rates for Circumferentially Cracked Pipes

The estimation of energy release rates under multiple loading conditions is discussed from the viewpoint of variation of the potential energy of the nonlinear elastic cracked body. Applications of this concept to pipes with a circumferential through-wall crack under combined bending and constant tension conditions are reviewed. For a part-through-wall crack, a simple perturbation analysis of a pipe with an internal circumferential surface crack under combined bending and constant tension gives the variation of the energy release rate J along the circumferential surface crack front. The results suggest that the common assumption of uniform crack growth in the radial direction for a circumferential surface crack with a uniform crack depth [5] is not generally valid.