Study of weldment fracture behavior using the J-integral

Residual stresses are formed in a welded plate due to a nonlinear temperature history caused by a thermal load. High tensile residual stress around a weld area is a major factor for cracking problems in a welded plate. Therefore, analysis of welding residual stress and fracture behavior is important for the evaluation of static or fracture strength of a welded structure.; A fracture assessment procedure and modeling techniques were developed for welded plates. Finite element method was used to predict a residual stress distribution and the J-integral values for combined residual stress and external loads. The thermal model includes welding heat input and deposition of weld beads. A lumped model was developed for multipass welding of thick plates.; A crack driving force estimation procedure was developed for a welded plate subjected to combined residual stress and external loads. Finite element formulation was conducted to include the effect of initial plastic strain caused by welding on the J-integral. Residual stress in the welded plate was determined without a crack. Generalized plane strain assumption was used for a residual stress analysis to consider the strain of a cross section in the welding direction. A crack was introduced in the next step, which resulted in the redistribution of the residual stress field. An external load was superimposed on the redistributed residual stress field to evaluate the J-integral for combined loads.