Analysis of springback in cylindrical bending of bi-directional trapezoidal sandwich panels

Abstract

Integral bending is an efficient and economical method to manufacture curved sandwich panels, and its forming characteristics and springback prediction are a major concern. The equivalent elastic constants of bi-directional trapezoidal sandwich were deduced by the semi-analytic approach with finite element, then the deformation characteristics of face sheets and core and the change of the stress neutral layer in the bending forming were analyzed. On this basis, the theoretical calculation model of plane strain bending springback of sandwich panels was established and applied to predict the stress and springback, then compared with the numerical simulation and experimental results of multi-point bending. The results indicate that springback of sandwich panels is small; it is easy to control the forming precision. the theoretical predicted cross section tangential stress and springback are overestimated, the stress relative deviation of the top face sheet is less than 2.9% and the bottom face sheet is less than 6.5%, the error of vertical center cross section line between is within 1.0mm, all kinds of deviations are in a minor range,so the accuracy of the analytical model is verified.

Keywords

• bi-directional trapezoidal sandwich panel
• bending forming
• elastic constants equivalent
• springback