Achieving pure shear deformation with curved beaks in folding-shearing

The deep drawing process in the automotive industry generates up to 45% of material waste. To address this issue, the folding-shearing process was developed as a drop-in solution, enabling the formation of parts in pure shear with minimal thickness variation. This process involves folding a blank while collecting the excess material in a region called the ‘beak’, which is subsequently sheared in-plane using a single set of tools in one forming direction. In previous work, the beak has had flat faces, which can lead to workpiece thickening and tool wear. This paper investigates the extent to which the beak geometry can be modified to minimise the thickening, focussing on a curved beak geometry. Numerical simulations, validated using physical trials, demonstrate that introducing a negative gaussian curvature in the deformation zone reduces the maximum thickening by 65%. An analytical model is developed to predict thickness in folding-shearing, achieving 12.5% accuracy compared to physical trials. Ultimately, a design map is proposed to instantly identify the optimal beak design parameters, without the need for extensive numerical or physical validations while ensuring a minimal thickness change.