Fully Plastic J-Integrals for Through-Wall Axial Cracks in Pipes

The purpose of this paper is to present results for fully plastic J-integrals for through-wall axial cracks in pressurized pipes. Results are presented for power law hardening material for crack lengths ranging from zero to semi-infinite. The small crack results are based on previously available information for through cracks in infinite sheets. The semi-infinite results are obtained in closed form and are based on the differences in stored strain energy of an uncracked pipe and a pipe with a slit running its full length. Finite element computations are used to provide results for two intermediate crack lengths, which then allowed the interpolation between the small and semi-infinite results. The finite element calculations used three-dimensional elements with a singular element that appropriately modeled the crack tip. The results should be of use in the analysis of critical crack length in pipes pressurized to levels where plasticity should be considered, and in the analysis of creep/fatigue crack growth in high-temperature piping.