XFEM-based Study Of The Effect Of Residual Stress On Crack Expansion In T-welded Joints

For results subjected to cyclic loading,fatigue damage is very common,especially for welded structures,due to the rapid heating and cooling of the metal during the welding process leading to uneven expansion and contraction,a phenomenon that leads to the generation of residual stresses that exacerbate fatigue damage.Fatigue testing is the most intuitive way to study the fatigue damage of welded structures,but fatigue testing is generally expensive and time-consuming,while numerical simulation is increasingly recognized by scholars due to its repeatability,low cost and visualization of the internal structure.In the past,when studying fatigue performance,the method based on the stress-life curve(S-N method)was commonly used,but this method only considers the stage before crack eruption,ignoring the existence of the initial crack,and cannot describe the stage of crack expansion,which is a fatal flaw for studying the fatigue life of welded structures.Because the presence of initial cracks is very common for welded structures,the stage of crack expansion cannot be ignored for fatigue studies of welded structures.In order to overcome this problem,this thesis adopts a crack extension study method based on fracture mechanics and extended finite element method.This thesis will focus on the analysis of the residual stress field on the impact of crack expansion in T-welded joints based on previous research,the main work is as follows.The use of general finite element software ABAQUS butt welding simulation,and the use of different heat source models,comparative analysis of their simulated temperature field,select the appropriate heat source to prepare for the next step of fracture analysis.T-welded joints for welding simulation,the use of sequential coupling method has simulated the temperature field and residual stresses of T-welded joints,and the relevant tests to verify the comparison,found that there is a high residual tensile stress around the weld,and the residual stress is "several" distribution.The residual stresses obtained as the initial stress field into the T-welded joint crack expansion analysis,compared with the law of crack expansion with or without the influence of residual stresses,found that the residual stresses will have a greater impact on the direction and rate of crack expansion.