Effect of Different Clamping Modes on Dimples of Sheet Metal Parts in Multi-Point Stretch Forming

Abstract

Dimples are a typical defect in multi-point stretch forming (MPSF) of sheet metal. Comparison on the numerical simulation of the spherical parts in MPSF with traditional and flexible clamping modes were done, the effects of transition zone length and elastic cushion on the dimples of the spherical parts were studied. The results show that thickness strain of the forming parts using traditional clamping mode is greater than that using flexible clamping mode under the same forming conditions, so the dimpling depth of the former is relatively deeper than that of the latter. With the increasing transition zone length, dimpling gradually becomes shallow. Dimples of the parts are reduced and forming quality of the parts is improved using flexible clamping mode compared with traditional clamping mode under the same transition zone length. The technique of elastic cushion is a method to restrain dimples, and no-dimpling limits of the parts was obtained, the dimples defect can be eliminated using the relatively thinner elastic cushion with flexible clamping mode than that with traditional clamping mode, so the shape error of the parts can be decreased.