A semi-analytic model to predict and compensate springback in the 3D stretch bending process

Abstract

With the increase of using aluminum alloys and high strength steels to replace traditional steels, precise prediction of sheet springback and corresponding compensation methods become more and more important for die design because these material' s higher ratio of yield strength to elastic modulus causes more serious springback problems. In this paper, a semi-analytic springback prediction and compensation model based on in-process measurement is proposed. For springback prediction, measured strain and curvature data from the actual stamping process are incorporated in a semi-analytic model, and then springback is predicted based on the elastic unloading from the residual differential stress during sheet metal forming. In the next stage of die design, a procedure to automatically compensate the tool geometry, including the fundamental mechanics analysis and the reconstruction of the tool surface, is presented. For validation purpose, a case study was carried out for the tool optimization of a double curved panel.