A theoretical model for predicting sidewall wrinkling in chain-die forming of channels with variable widths. (November 2022) - Liu, Yang
Abstract: As a kind of progressive sheet metal forming process, chain-die forming is suitable to form thin-walled high-strength channels. However, sidewall wrinkling is one of typical shape defects on the chain-die formed parts and hard to be predicted accurately. In this paper, the mechanism of sidewall wrinkling during the chain-die forming process is investigated numerically and experimentally. Considering the twist of transitional surface which is a characteristic feature of chain-die forming, a new theoretical model for predicting sidewall wrinkling is established by combining the energy method with finite element simulation. A typical channel with variable widths is designed as a benchmark case and the chain-die forming experiment is carried out to verify the accuracy of the proposed model. Moreover, based on the proposed model and response surface methodology, the influence of radial stress on sidewall wrinkling is analyzed and wrinkling limit diagrams in terms of geometrical parameters are established. The results show that the fold angle has the greatest influence on the sidewall wrinkling. Finally, a two-pass chain-die forming scheme is proposed and implemented to suppress the sidewall wrinkling on the channel. The present work provides a wrinkling prediction tool for the process design of thin-walled channels in the chain-die forming. Highlights: A new wrinkling prediction model for progressive forming is established. Twisted transitional surface reduces the anti-wrinkle ability of sidewall. Image recognition method is used to identify onset of sidewall wrinkling. Effects of geometric parameters and stress state on sidewall wrinkling are studied.