The non-uniform heat input during the welding process leads to problematic permanent deformations of welded parts. The control of these welding distortions is, with the absence of the knowledge of the fundamental mechanisms responsible for these deformations, an extremely time and cost consuming iterative “trial-and-error” optimization process. The visualization of the involved physical phenomena, like temperature and distortions, .is an indispensable tool to clearly identify these mechanisms in order to adapt the welding parameters and clamping conditions target-oriented. Both experimental and virtual methods exist to obtain these physical data, however the possibilities to visualize them with experimental methods are laborious, expensive and limited in their application. Welding Simulation using finite element analysis (FEA) offers many benefits and has a great potential to reduce the experimental effort. Nevertheless, the industrial application of welding Simulation is not yet established widely because of reservations regarding the computation costs and the resulting accuracy for instance. In this paper, the results of a case study for a welding Simulation with an industrial background are presented. A welded assembly from the automotive industry has been investigated with numerical and experimental methods. A comparison between both methods demonstrates the Potentials of welding Simulation in terms of visualization. Furthermore, the numerical results reveal the possibilities of current resources. regarding calculation time and result accuracy of an industrial applied welding Simulation.
Analytical and numerical methods are used to estimate the temperature field due to the heat effects of welding. Numerical techniques are more adapted for industrial complex applications where analytical solutions do not exist yet. However, computational time is much lower with analytical models and a combination of both methods is investigated. Therefore, the two approaches are introduced and confronted in this paper. The finite-element software Ansys has been used for numerical simulations and Scilab for analytical simulations. In order to get a similar result quality, both methods have to be analysed and compared with respect to boundary conditions. These configurations are presented in this paper. Before starting any analysis, the analytical and numerical models have to be comparable. For the numerical simulation, every in- or output is given in discrete form and, for the analytical simulation, in continuous form. Thus, an analysis of the energy input distribution in both models is compulsory to ensure that the same amount of energy is applied. After this first study, a comparison of the analytical and numerical temperature field simulation is done from a fix point source in an infinite volume in steady state to a moving point source in a finite dimension in a transient state. A good agreement between the analytical and the numerical simulation results is found. However, some techniques, like a consideration of an image heat source for the analytical model or the selection of boundary conditions for the numerical model, need to be taken into consideration when the degree of complexity of the study (finite dimension or cooling time) increases. The limit of the comparison is reached when the geometry becomes too complex and when the effect of variable thermal properties with temperature cannot be neglected.
Fusion welding is widely used in the automotive industry to join metal structures. It is well-known that distortions and residual stresses occur during and after the welding process. Many procedures exist to decrease these negative heat effects of welding, but are often coupled with highly cost intensive experiments. The implementation of a welding Simulation tool to reduce this very expensive experimental procedures is therefore of high interest. Despite the fact that the automotive industry is a key sector for Simulation procedures, welding Simulation Software is nevertheless not yet widely implemented. This is mainly due to the complexity of the Simulation tools requiring expert users and the resulting high time to Solution.
In this study, a new fast thermo-mechanical Simulation of a complex and large laser beam welded automotive sheet metal assembly with several non linear welds is simulated. Assumptions and simplifications of the complex physical welding phenomenon, which are made to keep the computational cost and the complexity of the Simulation in an industrial frame, are discussed. The calibration time of the phenomenological heat source model has been optimized with a very fast analytical thermal model and the resulting simulated temperature fields match perfectly with the measured ones. Additionally, the user experience and the time-to-solution are kept within a reasonable time frame for arr industrial environment. All Simulation results are validated with experimental results.