• Comparison of Sequentially and Fully Coupled Generalized Plane Strain FE Modelling of Multipass Welding

      Jiang, Wei; Yahiaoui, Kadda; Hall, Frank Richard; Laoui, Tahar (NAFEMS, 2005)
      The residual stress predictions from sequentially and fully coupled thermo-mechanical generalized plane strain models of thick multipass welded plate are shown to be in agreement with each other and experimental data. The research enabled the less computationally resource intensive sequential coupling method to be recommended when simulating this welding process.
    • Finite Element Modelling of Multipass Fusion Welding with Application to Complex Geometries

      Jiang, Wei; Yahiaoui, Kadda (Professional Engineering Publishing, 2007)
      The current paper presents recently completed work in the development of advanced multi-pass weld modelling procedures, with the ultimate objective of predicting weld residual stress distributions in thick-walled complex geometries. The modelling technique was first developed using simple three-dimensional geometries, for which experimental data was available for validation purposes. All the non-linearities associated with welding, including geometry, material, and boundary non-linearities, as well as heat source movement were taken into account. The element removal/reactivate technique was employed to simulate the deposition of filler material. Combined with a newly developed meshing technique, the model was then applied to predict residual stress distributions for a relatively thick stainless steel piping branch junction. Finally, a parametric study was conducted to assess the effects of various manufacture-related welding parameters on the final residual stress fields. The interpass temperature and cooling rate were found to be the two most sensitive parameters affecting resultant residual stresses. The residual stress profiles can be optimized relatively easily by adjusting these parameters. This research demonstrated that the developed modelling technique has potential in multi-pass welding process optimization and wide industrial applications including weld repairs.(Professional Engineering Publishing)
    • Finite Element Prediction of Residual Stress Distributions in a Multipass Welded Piping Branch Junction

      Jiang, Wei; Yahiaoui, Kadda (ASME (American Society of Mechanical Engineers), 2007)
      Piping branch junctions and nozzle attachments to main pressure vessels are common engineering components used in the power, oil and gas, and shipbuilding industries amongst others. These components are usually fabricated by multipass welding. The latter process is known to induce residual stresses at the fabrication stage, which can have severe adverse effects on the in-service behavior of such critical components. It is thus desirable if the distributions of residual stresses can be predicted well in advance of welding execution. This paper presents a comprehensive study of three dimensional residual stress distributions in a stainless steel tee branch junction during a multipass welding process. A full three dimensional thermomechanical finite element model has been developed for this purpose. A newly developed meshing technique has been used to model the complex intersection areas of the welded junction with all hexahedral elements. Element removal/reactivate technique has been employed to simulate the deposition of filler material. Material, geometry, and boundary nonlinearities associated with welding were all taken into account. The analysis results are presented in the form of stress distributions circumferentially along the weld line on both run and branch pipes as well as at the run and branch cross sections. In general, this computational model is capable of predicting three dimensional through-thickness welding residual stress, which can be valuable for structural integrity assessments of complex welded geometries. (ASME)
    • Finite Element Simulation of Multipass Welding: Full Three-Dimensional Versus Generalized Plane Strain or Axisymmetric Models

      Jiang, Wei; Yahiaoui, Kadda; Laoui, Tahar (Professional Engineering Publishing, 2005)
      A full three-dimensional (3D) thermo-mechanical finite element (FE) model has been developed to simulate the step-by-step multipass welding process. Non-linearities associated with welding, such as a moving heat source, material deposition, temperature-dependent material properties, latent heat, and large deformations, were taken into account. The model was applied to multipass butt-welded mild steel plate and girth butt-welded stainless steel pipe for validation. The simulation results were compared with independently obtained experimental data and numerical predictions from two-dimensional (2D) generalized plane strain and axisymmetric models. Good agreements between the 3D predictions and experimental data have been obtained. The computational model has the potential to be applied to multipass welded complex geometries for residual stress prediction. (Professional Engineering Publishing)