LAUSR

Abstract The springback phenomenon plays a significant role in precision sheet metal bending. In an early attempt, Gardiner proposed an analytical solution for springback under pure bending with perfect elastoplasticity. Several studies expanded on Gardiner's research to provide improved solutions of springback. However, the fore-mentioned studies did not account for mechanical analysis considering deformation history in their improved solutions. Thus, the present study divides the deformation history of metal material bend-forming into three stages, namely a loading stage, a free unloading stage, and a non-free unloading stage. An elastoplastic analysis was performed by considering deformation history based on uniaxial stress state and plane section assumptions. The study also investigated the springback rule of bilinear kinematic hardening elastoplastic metal materials with uniform rectangular cross-section under pure bending. With respect to common metal materials, the study obtained an improved springback prediction solution in which the hardening component was considered, and its prediction results indicated a degree of agreement with the experimental data that exceeded those of the prediction results obtained by Gardiner's approximate solution when applied to the springback prediction of sheet metals.