Fundamentals of process design for dimensionally accurate roll forming of asymmetrical profile geometries

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Roll forming is a continuous manufacturing process for cold rolled profiles, which sees use besides others in the automotive and furniture industry. In contrast to discontinuous bending methods, like die bending, the sheet metal is formed in a three-dimensional forming process. Besides the bending of the cross section additional process-related deformations happen which lead to profile defects. Especially asymmetrical profiles are always subjected to torsion and multi-dimensional bowing.Nowadays, the use of Finite-Element-Simulations during the process design is the only way to detect the profile defects. Due to the time intensive calculations the application of FEM-simulations is limited. Furthermore, the interactions between process parameters and profile defects are not fully understood, so the process design is mainly empirical and the resulting profile defects have to be compensated in time-consuming correction processes.The project aims at the prediction, analysis and reduction of the defects after roll forming of an asymmetrical hat profile. The asymmetrical hat profile is suited best, because it can represent complex profile geometries with several bending zones. Within the project the process design will be improved in two ways. On the one side, an analytical model for the prediction of torsion of asymmetrical hat profiles, without the necessity of FEM-simulations, is developed to be used as the initial value for the numerical optimization. On the other side, numerical and experimental investigations of roll forming of asymmetrical hat profiles are conducted to characterize and analyse the process-related additional deformations, the resulting profile defects as well as the influence of process parameters of the roll forming process. Based on the results, effective counter measures can be deduced and numerically investigated. Following the investigation, the counter measure found most effective, is optimized by an optimization algorithm coupled with the FEM-simulations. Thereby, the parameters of the counter measures are optimized with regard to a balanced state of strains within the profile. Finally, the counter measure and the optimization algorithm are validated experimentally.By deepening the understanding of the creation of profile defects of complex profile geometries, the developing of effective counter measures and the development of an analytical model to predict torsion in the early design stage, this project contributes to an more accurate and efficient process design with the aim to significantly shorten correction processes and to increase the production rate.