J-integral and limit load analysis of semi-elliptical surface cracks in plates under combined tension and bending

Systematic detailed finite element (FE) analyses are performed for semi-elliptical surface cracks in plates under combined tension and bending. The Newman and Raju stress intensity factor solution is confirmed and non-linear J solutions are generated and expressed as the EPRI type h(1) function for a wide range of geometry factors and ratios of bending to tensile load. Limit load solutions are obtained from the FE J results through the reference stress method. The results show that relationship between J and the limit load depends on a/t, a/c and the load ratio lambda. Here a and c are the depth and half-length of the crack and t is the plate thickness. When both tension and bending are effective (e.g. lambda = 0.5), for a/t less than or equal to 0.5 and a/c = 0.2, J for any position along a crack front can be predicted by the reference stress method using a single limit load value except for the points very close to the plate surface. For all other cases analysed, it can only be approximately estimated by the reference stress method because a limit load value that can satisfy all the FE J solutions along the crack front cannot be found. However, for all the cases, the maximum J along the crack front can be well predicted by the reference stress method when a proper global limit load is used. The FE limit load data can be well predicted by the extended Goodall and Webster solution. (C) 2004 Elsevier Ltd. All rights reserved.