Understanding the process limits of folding-shearing

Globally, 44 % of sheet metal used in the production of passenger vehicles is scrapped. To reduce this scrap, folding-shearing has been proposed previously. In this process, a blank is first folded to collect excess material in a region of incompatibility. Folded sheet is then sheared in-plane to achieve the target geometry. In a preliminary study, folding-shearing was used to create a U-channel part in a compression testing machine and a process operating window was defined by considering failure limits of springback, thinning and thickening. For the first time, this study develops analytical models, validated with numerical models and physical trials to define process limits and generate an understanding of the underlying mechanics of the process limits. These analytical models can be used as a basis to develop a process operating window instantly and are shown to be within 25 % of the process limits found using numerical models and physical trials. Results show that springback, thinning and thickening limits are strongly influenced by the part radius, height, fold geometry, and material properties.