Numerical simulation of welding

Aim of project:To analyse and model the transient thermal field from arc welding (SMAW, V-shaped buttweld in 15mm plate) and to some extend the mechanical response due to the thermal field. - To implement this model in a general purpose finite element program such as ABAQUS.The simulation is limited to 2D and as regards the thermal model we assume plain cross section when comparing with experiments and analytical solutions.Stresses and deformations based on the thermal model is mainly described qualitatively in relation to the mechanical model in ABAQUS. As regards the mechanical model, plain stress is also taken into account.Work carried out:With few means it is possible to define a thermal model which describes the thermal field from the welding process in reasonable agreement with reality. Identical results are found with ABAQUS and Rosenthal’s analytical solution of the governing heat transfer equation under same conditions. It is relative easy tointroduce boundary conditions such as convection and radiation where not surprisingly the radiation has the greatest influence especially from the high temperature regions in the weld pool and the heat affected zone.Due to the large temperature gradients which occur during welding, temperature dependent material proporties should be used as well as latent heat may be assumed to be of importence when considering the plastic behaviour/response of the material and thus the stresses. These thermal proporties are easily modelled with ABAQUS and if so, good predictions of the thermal field are obtained. This has been verified with experiments. The significance of the right fitting of the model to the topical welding process must be emphasized. With a mechanical model in ABAQUS based on a thermal model as described, distributions of both transient and residual tensile and compression stresses are obtained for both plain strain and especially plain stress calculations. These distributions agree with what was qualitatively expected.It has not been possible to define a generel thermal model, which can be used in generel for numerical analyses of any welding process. Various circumstances are process dependent and require not only knowledge of the process in practice butalso a thorough experience with the numerical modelling of the problem.