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

辊压成型是冷轧型材的一种连续制造工艺，在汽车和家具行业中有着独特的用途。与不连续的弯曲方法(如模具弯曲)不同，板材是在三维成形过程中成形的。除了横截面的弯曲外，还会发生与工艺有关的额外变形，从而导致型材缺陷。尤其是不对称型材经常受到扭转和多维弯曲的影响，目前，在工艺设计过程中使用有限元模拟是检测型材缺陷的唯一途径。由于计算时间较长，有限元模拟的应用受到了限制。此外，工艺参数与型材缺陷之间的相互作用还不完全清楚，因此工艺设计主要是经验性的，所产生的型材缺陷必须在耗时的校正过程中得到补偿。非对称帽子轮廓最适合，因为它可以表示具有多个折弯区的复杂轮廓几何图形。在该项目中，工艺设计将从两个方面进行改进。一方面，建立了不需要有限元模拟的非对称HAT型材扭转预测的解析模型，作为数值优化的初始值。另一方面，对非对称帽形辊弯成形进行了数值模拟和实验研究，以表征和分析与工艺相关的附加变形、所产生的型材缺陷以及工艺参数对辊弯成形过程的影响。在此基础上，可以推导出有效的对策，并进行数值研究。在此基础上，采用优化算法结合有限元模拟对最有效的对策进行了优化。因此，关于轮廓内应变的平衡状态，优化了反措施的参数。通过加深对复杂型材轮廓缺陷产生的认识，制定有效的对策，并在设计初期建立扭矩预测分析模型，实现了工艺设计的精确化和高效化，大大缩短了修正工序，提高了生产效率。

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.