Model-based minimization of distortion when machining post-processing of formed aluminum thick sheets

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Due to more and more complex geometries and the use of new materials, the quality requirements for sheet metal components are increasing, whereby, above all, the control of distortions plays a major role. A currently insufficiently solved problem is the inherent stress-induced distortion of thick sheet metal components in the post-processing processes, due to released residual stresses from upstream production processes. The resulting dimensional deviations are a major problem for the industry, which can only be compensated by a costly and time-consuming further post-processing step like heat-treatment. Using the example of thick sheet metal forming with machining finishing, it should be shown that a dimensionally stable geometry is possible even without costly reworking processes to minimize distortion. Within the scope of this research project, the internal stresses introduced during the forming process are to be simulated first, as well as by suitable measuring methods on the reference component and then taken into account during machining in order to minimize component distortion. In this case, it is first necessary to build up a simulation model, which is suitable for the forming and for the subsequent machining process and reflects the prevailing residual stress state as accurately as possible. Subsequently, the strategy of the post-machining must be adapted to the current residual stress state. Based on numerical and experimental results, the influence of the process parameters, such as forming speed, friction, removal strategy, feed rate or immersion depth on the residual stresses and their distribution in the component is investigated. With the aid oft he received database, the causal relationships are subsequently analyzed and suitable measures for minimizing component distortion are derived. The aim is to adapt the machining post-processing to the prevailing residual stress state and to produce a dimensionally stable component by means of suitable process parameters. In this case, generally valid measures are to be derived on the basis of a reference component. Likewise, the influence of the process parameters of the forming process on the residual stress state is investigated in order to be able to achieve the most suitable residual stress state for the subsequent machining by selecting the parameters. In contrast to the previously applied approaches, which are mostly based on an experience-based approach, the novel approach aims to expand the understanding of the process and thereby systematically produce dimensionally stable machined thick sheet metal components. The research results thus offer an innovative way to increase the efficiency of the production of machined thick sheet steel components.