Optimum arrangement of rubber layout for stretch bending method to improve the shape accuracy

In bending process of sheet materials, a springback is remarkable due to the residual stress generated inside of the material, which greatly affects the product accuracy. In order to suppress the springback, the rubber-assisted stretch bending method, which bending process is performed with applying a tensile force in the longitudinal direction of a sheet material has been proposed. We propose the optimum arrangement of the two kinds of rubbers for the "rubber-assisted stretch bending method" for the uniform bending with a constant curvature radius. The optimum tensile stress is realized by each frictional force between the individual rubber and specimen. And since the rubber is partially affixed to the dies, the bending deformation is carried out by the metal surface of the die material, improvement of shape accuracy can be expected. The upper and lower dies are divided into three division on the surface, and the two elastic rubbers are placed on each part on the bending surface of the die. The springback was decreased to 17% in comparison with simple bending using ordinary metal dies by the optimum arrangement of rubber layout.