The Effects of Crack Ellipticity on the Mode I SIFs of a Simulated Eroded Pressurized Cylinder

The three dimensional stress intensity factors (3D SIFs) of a pressurized cylinder can be greatly affected by many factors. While an autofrettage process may introduce favorable residual stresses on the bore of the cylinder, other factors such as erosions and cracks, once introduced, may greatly reduce the effectiveness of the autofrettage. In this study, a closer look was given to problems with different crack configurations. Effort was expended to evaluate how the ellipticity of cracks affects the overall fatigue life of a simulated eroded pressurized cylinder in comparison with circular crack only configurations. Numerical analysis was performed using ANSYS, a standard commercially available finite element package. The residual stress due to any autofrettage process was simulated using the equivalent thermal loading. In-depth discussion was given to results when cracks of different ellipticity interact with other parameters including the depth of crack and the geometrical configurations of erosion. Specific cases considered include: crack ellipticity a/c=0.5, 1 and 1.5; relative crack depth a/t=0.01-0.2; relative erosion depth d/t=0.05; erosion relative finite length Le/L=0.12-1; erosion ellipticity d/h=0.3-2. Relevant non-erosion results are used for the sake of comparison.