Finite element based evaluation of stress intensity factors for interactive semi-elliptic surface cracks

A finite thickness plate with two coplanar self-same shallow and deep semi-elliptical surface cracks subjected to remote tensile surface traction is considered for fracture analysis. Based on three-dimensional (3D) finite element solutions, stress intensity factors (SIFs) are evaluated along the entire crack front using a force method. The line spring model has also been used to evaluate crack depth point SIFs using shell finite element analysis. A wide range of geometric dimensions and crack configurations viz. crack shape aspect ratio (0.3 less than or equal to a/c less than or equal to 1.2), crack depth ratio (1.25 less than or equal to t/a less than or equal to 6), relative crack location (0.33 less than or equal to 2c/d less than or equal to 0.9) and normalized location on the crack front (0 less than or equal to 2phi/pi less than or equal to 2) are considered for numerical estimation of crack interaction factors. SIFs evaluated at the depth point using the force method from the 3D finite element results are compared with SIFs evaluated using the line spring model. Finally, using finite element results, an empirical relation is proposed for the evaluation of crack interaction factors. For the ranges considered, the proposed empirical relation predicts crack interaction factors at critical locations within +/-2% of the 3D finite element solutions. (C) 2003 Elsevier Ltd. All rights reserved.