| The objective of this investigation is to evaluate the effect of residual stresses that arise during welding processes, on localized fracture behavior. The primary fracture parameters of interest are the Stress Intensity Factors (SIFs) associated with cracks that develop around the welded area. The simulation of the welding process is accomplished through the finite element code SYSWELD RTM and the computation of fracture behavior uses a finite element user-defined enriched crack tip element code, FRAC3D, developed at Lehigh University. In this study, quadratic 3D finite element models which are generated in HYPERMESHRTM, are first introduced into SYSWELD RTM to perform the thermo-mechanical transient analysis needed to predict the welding residual stresses, global stresses, stain and displacement. Residual stresses form the welding simulation and the original quadratic 3D finite element HYPERMESHRTM model are combined, modified and transferred into the ANSYS/FRAC3D code to obtain the final Stress Intensity Factor (SIF) for 3D cracks, and the stresses, strains and displacements in the cracked configuration. In order to verify the accuracy of the welding simulation residual stress, different mesh densities were examined in detail. In addition, different welding model meshes were applied to test the sensitivity of the SIF results to different meshes and geometries. Finally, refined weld/crack models with a progression of crack shapes that follow the contours of the highest stresses around the weld zone were generated to simulate the behavior of a crack emerging from a weld defect The effect that different welding parameters have on the fracture parameters represent an important result from this study. |
