Residual stress-controlled incremental sheet forming of high-strength sheet metal components

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The incremental sheet metal forming (ISF) process is suitable to economically manufacture components in small batch sizes according to specific requirements. The component properties are particularly determined by the residual stresses in the component. The aim of the research project is to improve the component properties made of high-strength steel through forming-induced residual stresses. The potential of influencing the residual stresses in a specific way through the forming process was proven in the previous funding periods. It was shown that the process parameters of ISF directly influence the deformation mechanisms bending, shearing and normal stress component, which effects the residual stress state. In the second funding period the achievable improvement of the component properties by forming induced residual stresses was analyzed. Process enhancements enable an induction of higher residual stresses or an inversion of compressive to tensile residual stresses. The third funding period focused on the prediction of the component property improvements and the residual stress stability under continuous operation in a corrosive environment. In a transfer project with Faurecia Autositze GmbH these findings are transferred under industrial requirements. For this purpose, the previously analyzed materials are extended to high-strength dual-phase steels and application-oriented geometries for an industrial use. In addition to the component performance under static and cyclic loads, the influence on the geometrical accuracy of the manufactured components is analyzed. A concept with an oscillating tool movement is applied to introduce additional near-to-surface compressive residual stresses close and reduce the process forces. A reduction of process time should be achieved by the simultaneous use of multiple forming tools.