Stress and springback adjustment in pressing forming of 316L stainless steel sheet using rigid-elastic compound die

Thin-walled components with large size and complex curved surface are extensively used in a multiplicity of fields. Due to their complex profile and the demand for high dimensional accuracy, traditional rigid die stamping processes are challenging for forming these components. To solve this problem, a pressing forming process using a rigid-elastic compound die is proposed in this investigation, in which polyurethane elastomer was used to replace part of the rigid dies. This approach allows for nearly uniform loading on the sheet blank, enhancing its filling capacity toward the die and reduce its springback. The deformation behavior of 316 L stainless steel sheet was investigated during the pressing process on a single-curvature die. On this basis, the effect of the rigid-elastic compound die was analyzed on the springback behavior of the sheet after pressing. It is shown that the elastic die can apply a nearly uniform contact pressure on the sheet blank. This can improve the deformation uniformity of components and reduce the springback. In rigid die pressing with a 10 kN load, the maximum contact pressure on the sheet is 16.6 MPa, while it is 7.4 MPa in the rigid-elastic compound dies pressing. In the rigid-elastic compound die pressing with a 20 kN load, the profile height of specimen has exhibited springback by an average of 25% compared to the designed value, which decreases by 43% compared to that of the rigid die pressing. Furthermore, using local elastic compensation pads pressing, the specimen profile deviation can be controlled within 0.4 mm.