A new springback calculation method for double-curved medium thick plates based on the curvature of discrete points

Springback is an inevitable phenomenon in plate forming. Compared with single-curved plates, the springback prediction of double-curved plates is more difficult due to the mutual influence of bidirectional curvature. This work proposes a new springback calculation method for double-curved medium thick plates based on the curvature of discrete points. Considering the transverse load and friction, the new method discretizes the double-curved plates into strips and calculates the plastic bending moments at discrete points of a single strip under different axial forces. Then it obtains the springback ratios at discrete points by considering the bidirectional coupling effect between strips. A series of sail-shaped and saddle-shaped medium thick plates with different curvature radii and thicknesses are finite element (FE) numerically simulated. Experiments are also carried out to validate the new method. By comparing the theoretical, numerical, and experimental results, it can be concluded that the calculation method proposed in this work can predict the springback quickly and provide rapid guidance for practical stamping. In this work, springback ratio and springback displacement are used to characterize the springback, which both show the springback of sail-shaped plates with the same curvature radius and thickness is greater than that of saddle-shaped plates. The varying curvature radius affects springback similarly in sail-shaped and saddle-shaped plates, but varying thickness does not.