Utilizing 2-D and 3-D simulations in assisting tooling design in Chain-die forming threshold product

摘要

With the increasing demand of reducing the body weight of automobiles, the utilization of advanced high strength steel has increased dramatically in recent years. However, high residual stress and redundant strain caused by the traditional cold roll forming process is still an outstanding problem. Under such circumstances, the Chain-die forming method is developed as a novel sheet metal forming approach which combines roll forming and stamping processes. A Chain-die former employs discrete die blocks which run on a chain track with significant virtual roll radius, simulating a roll forming process. Meanwhile, individual pairs of die blocks deform the sheet metal gradually acting as a stamping process. Through the enlargement of virtual roll radius, the peak longitudinal strain developed during the forming process is dramatically decreased (contained in the elastic region), leading to significantly reduced residual stress and almost no redundant deformation. Due to low longitudinal strain, the cross-sections of the product can be considered as a plane strain state throughout the entire forming process, allowing utilization of 2-D plane strain simulations to represent for 3-D simulations. In this paper, using 2-D FE stamping simulations and 3-D FE Chain-die forming simulations in assisting die design for a Chain-die formed threshold product using AHSS material is discussed. The results show 2-D stamping simulations are able to predict the average forming angles of 3-D simulation results with high accuracy and much higher efficiency. In the initial tooling design process, 2-D stamping models should be employed to design the tooling geometry in order to compensate the springback effect, followed by 3-D Chain-die forming models validating the 2-D design and providing additional information such as variation of the flange angle along the longitudinal direction and the longitudinal bow condition. The findings can be applied in industrial practice which can significantly accelerate the tooling design process for the Chain-die forming method.