Numerical simulation on chain-die forming U-channel made of ultra-high strength steel

Ultra-High Strength Steel (UHSS) is an ideal steel material to fulfil a high demand for weight reduction in automotive vehicles while maintaining safety. However, such a material is hard to form with desired profiles using traditional sheet metal forming processes such as Cold Roll Forming. Therefore, an alternative solution proposed recently was Chain-die Forming (CDF). It combines both roll forming and bending processes. Thereby, its primary advantage is it increases elongated deformation length while providing a super large roll radius beyond traditional roll forming. In literature, attempts on finite element modelling and simulations of the CDF process have been conducted using relatively simple models for conventional metal alloys. However, these simple models are insufficient for designing a typical CDF process for UHSS. This study focuses on simulating the CDF of UHSS to devise an optimal solution for forming a 90° U-Channel with one single pass via developing exact finite element models and constructing a reliable process for it. The obtained numerical results reveal that the CDF could generate less residual stress, low strain and a small spring back for the 90° UHSS Channel. The proposed design analysis procedure could greatly help devise a cost-effective and reliable CDF process for forming UHSS.