Stress intensity factor influence coefficients for internal surface cracks in thick-walled cylinders

Using the boundary integral equation method for three-dimensional elastostatics, stress intensity factor influence coefficients for a wide range of internal semi-elliptical surface cracks in cylinders with radius ratios 2·0 and 2·5 are obtained. Only one crack shape is considered, namely, a semi-ellipse with ellipse aspect ratio 0·8, but the crack depths treated range from 20% to 80% of the wall thickness. The influence coefficients obtained correspond to the stress intensity factor, K I , solutions for the cracks subjected to four different stress distributions—uniform, linear, quadratic and cubic pressure variations—on the crack faces. They can be superposed to obtain K I solutions for other stress distributions, such as those caused by internal pressure, thermal gradients and autofrettage. Numerical results are presented for all these load situations. In the case of autofrettage, the effects on K I for a wide range of overstrain conditions are considered.