Stress-intensity factors for a wide range of nearly semi-elliptical surface cracks in pipes and rods are presented. The surface cracks were oriented on a plane normal to the axis of pipes or rods. The configurations were subjected to either remote tension or bending loads. For pipes, the ratio of crack depth to crack length (a/c) ranged from 0.6 to 1, the ratio of crack depth to wall thickness (a/t) ranged from 0.2 to 0.8, and the ratio of internal radius to wall thickness (R/t) ranged from 1 to 10. For rods, the ratio of crack depth to crack length also ranged from 0.6 to 1, and the ratio of crack depth to rod diameter (a/D) ranged from 0.05 to 0.35. These particular crack configurations were chosen to cover the range of crack shapes (a/c) that have been observed in experiments conducted on pipes and rods under tension and bending fatigue loads. The stress-intensity factors were calculated by a three-dimensional finite-element method. The finite-element models employed singularity elements along the crack front and linear-strain elements elsewhere. The models had about 6500 degrees of freedom. The stress-intensity factors were evaluated using a nodal-force method.
The present results were compared with other analytical and experimental results for some of the crack configurations. The results generally agreed within 10%.
These results should be useful in predicting crack growth rates and fracture strengths, designing structural components, and establishing inspection intervals for pipes and rods.