Stress-intensity-factor equations for compact specimen subjected to concentrated forces

A Green’s function (GF) for the standard compact C(T) specimen was developed that can be applied over a wide range in crack-configuration parameters and for any arbitrary residual-stress distribution along a symmetry-plane crack path from the front face to the back face. Finite-element and boundary-element analyses were conducted to obtain stress-intensity factors over a wide range in crack-length-to-width ratios (a/w) and in concentrated force locations along the crack surface. These results were compared with previous boundary-collocation results from the literature and were used to develop an improved GF equation. As a validation of the newly developed wide-range equation, stress-intensity factors were calculated on a C(T) specimen subjected to a stress distribution induced by the standard pin loading without a crack-starter notch or crack and were compared with well-known results from the literature. The accuracy of the GF equation is within about ±1.3% of the numerical analyses over a wide range in a/w ratios from 0.2 to 0.9.