Experimental investigation and prediction of the maximum edge longitudinal membrane strain and springback of Chain-die-formed AHSS U-channels using response surface methodology

Chain-die forming is a promising manufacturing technology that is emerging as an alternative to roll forming and stamping in fabricating advanced high-strength steel (AHSS) products. The maximum edge longitudinal membrane strain (MELMS) and the springback are regarded as the crucial indicators for evaluating the quality of fabricated AHSS products. As Chain-die forming is a newly developed sheet metal fabricating method, the evaluations and predictions of the effects of the independent product parameters on MELMS and springback are of high interest. This paper selects three important quantitative product parameters (tensile strength, flange height, and thickness) to investigate experimentally the effects of different product parameters on the quality of Chain-die-formed U-profile AHSS products. Experimental verification on a new group of experimental samples using the established mathematical expressions is also performed successfully. This study shows that response surface methodology with Box-Behnken design can be efficiently applied for evaluating and predicting the MELMS and springback of Chain-die-formed AHSS products. It is found that the most influential parameter which determines the severity of the MELMS is the linear effect of flange height. This study also indicates that the springback is largely determined by the linear effect of tensile strength. The findings are expected to help designers and researchers to identify the formability range and predict the quality of Chain-die-formed AHSS products in advance of the quality control and fabrication stages.