In this paper, a new mesh generating procedure for tubular Yjoints with through-thickness or surface cracks is proposed. The advantage of this procedure is that it can generate cracks of any length at any location along the intersection between the weld toe and the chord member. This makes it possible to study the fatigue and crack growth behaviour of cracked tubular Y-joints subjected to a combination of axial, in-plane and out-of-plane Ioadings. Three typical T-joint mesh models containing semi-elliptical surface cracks at the crown, saddle and between crown and saddle respectively are generated using this new modelling approach. The contact problems at the crack surfaces are also considered in these models. The finite element analysis results of these models are used to evaluate the stress intensity factors (SIFs) of the cracks. The convergence of the SIFs results demonstrates that these models are reliable.
The finite element (FE) method has been used widely to analyze different types of welded tubular joints because of its advantages. In recent years, more and more researchers are using the FE method to get detailed analysis of the fracture and crack growth behaviors to predict the remaining life of a cracked joint. Three-dimensional (3D) quadratic solid elements were adopted recently to model full cracked tubular joints because the best results can be obtained when comparing the results from models with different types of elements (Herion, et al., 1996). There are some commercial programs such as PATRAN (1998), MENTAT II (1993), PRETUBE (1991) available for creating FE models for tubular joints. However, it is not simple to generate good quality meshes for most cracked joints because of the complex geometry of intersections between members and the difficulty in modeling welds and cracks (Cao, et al., 1998).