Stress-Intensity Factors for Internal Surface Cracks in Cylindrical Pressure Vessels

Abstract

The purpose of this paper is to present stress-intensity factors for a wide range of semi-elliptical surface cracks on the inside of pressurized cylinders. The ratio of crack depth to crack length ranged from 0.2 to 1; the ratio of crack depth to wall thickness ranged from 0.2 to 0.8; and the ratio of wall thickness to vessel radius was 0.1 to 0.25. The stress-intensity factors were calculated by a three-dimensional finite-element method. The finite-element models employ 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 from a nodal-force method. An equation for the stress-intensity factors was obtained from the results of the present analysis. The equation applies over a wide range of configuration parameters and was within about 5 percent of the present results. A comparison was also made between the present results and other analyses of internal surface cracks in cylinders. The results from a boundary-integral equation method were in good agreement (± 2 percent) and those from another finite-element method were in fair agreement (± 8 percent) with the present results.