STRESS INTENSITY FACTORS FOR LONG AXIAL SURFACE CRACKS AT THE OUTER WALL OF A PIPE LOADED BY STRESS GRADIENTS.

By means of the finite element method, crack opening displacements were calculated for long axial surface cracks at the outer wall of a pipe. The wall thickness to inner radius ratio of the pipe was 1 to 10. Weight functions were evaluated by means of the finite element results. Using these weight functions it is possible to calculate stress intensity factors for arbitrary radially varying stress distributions. In this paper stress intensity factors were evaluated for a constant hoop stress loading as well as for stress distributions with a linear and a quadratic dependence on the radius.