Preforming strategies in correcting the spring-back from the U-shape bending

Abstract

Bending accuracy is difficult to predict in multiple profile-rolling because of the complexity in the distribution of the residual stress. The adjustment of the individual rolls is usually time-consuming. Therefore, coining and embossing processes can be implemented as the preforming measures to correct the spring-back or spring-forward defect. In this work, U-shape bending preformed with coining and embossing was investigated for the validity of the correction of the bending accuracy. Both hot-dip galvanized steel SGC 340 and aluminium alloy AA 6016 plates, with a thickness of 1 mm, were tested. Preforming with coining or embossing was conducted on the inner or the outer corner of the plates. Both the FE simulation and experiment were carried out. The result shows that preforming with coining on the inner or outer corners can increase the amount of spring-back. Preforming with embossing on the inner corner can also increase the amount of spring-back. However, the amount of spring-back reduces or even spring-forward occurs in preforming with embossing on the outer corner. Attributed to the distribution of residual stress is discrete after U-shape bending, a steady trend of the correction for spring-back was not observed.