Comparative study of numerical models of the laser forming process

Even though the laser forming process is not used at a large scale, it has a potential value for small product series. Its advantage is in its capacity to deform a sheet into arbitrary shapes by a contact-free laser irradiation, avoiding the need for costly tools in which materials need to be formed in arbitrary shapes. One of the reasons that the process has not become very popular is by the difficulty to predict and control the process and determine the right processing plan to obtain the shape needed. The simulation of the laser forming process is not easy to carry out, because the nature of the problem is three-dimensional and the process is transient. In addition, the description of the material behavior, which includes thermo-elastoplastic behavior, is complex and results in strongly nonlinear problems. Moreover, the temperature dependent material behavior, including the microstructural evolution of the material is often not known to a sufficient degree of precision, which leads to approximate descriptions. For that reason, in the current study a simple application, bending of a flat plate by irradiation over a straight line, is studied by a range of models with a varying degree of complexity. The models are compared in order to evaluate if a simplified model can be used to obtain adequate numerical results under particular conditions. Simplifications can be the reduction of the moving point heat source to a fixed but transient line heat source over the complete trajectory, or reducing the 3D model to a 2D model. From the analysis, it becomes clear that the effects of all three dimensions and the heat source movement are relevant for the ultimate precision of the simulation results, and to obtain the correct tendencies of the effect of changes of some of the parameters on the process results. Nevertheless, the results also demonstrate that some relevant thermal and stress data can be obtained using simplified models at a considerably lower computational cost. In particular, the thermal data are less affected by model simplifications, whereas the stress and deformation fields are more sensitive to the model approximations. An improved 2D model is proposed and evaluated, which is able to take into account the effect of the moving point heat source, while ignoring the longitudinal dimension. (C) 2015 Laser Institute of America.