STRESS INTENSITY FACTORS AND INFLUENCE FUNCTIONS FOR CIRCUMFERENTIAL SURFACE CRACKS IN PIPES

This paper presents the stress intensity factors for a large range of quasi semi-elliptic circumferential cracks in pipes of finite lengths. The cracks are positioned in a plane perpendicular to the pipe centerline and open out into the inside skin. The loads applied were constant tensile loads, overall bending loads and 1st, 2nd and 3rd degree bending loads in the pipe thickness. The crack depth/width ratio (a/c) varies from 0.48 to 0.06, the depth/pipe thickness ratio (a/t) varies from 0.42 to 0.8, the pipe inside radius/thickness ratio (Ri/t) varies from 4.5 to 19.5, the majority of results being given for Ri/t = 9.5. The stress intensity factors were calculated using solid three-dimensional finite elements. The models used approximately 3600 degrees of freedom and quadratic elements. The stress intensity factors were evaluated by a virtual extension method.