Analysis of springback in air bending process

Abstract

One of the most critical problems in air bending process is springback compensation to satisfy dimensional tolerances. In this research the finite element (FE) method was used to predict stressstrain state and part geometry under load and the amount of compensation. In order to evaluate accuracy of the FE simulation the predictions have been compared to corresponding experimental results. The bending experiments were conducted for different combination of bending angles, punch radii and die widths where three materials: Al 99.5, mild steel DD13 EN and high strength steel S355MC EN have been used. To be able to change tool setups an experimental tool with adjustable geometry has been made and placed in the laboratory tensile test machine. The results obtained showed that the springback can be predicted with satisfying accuracy for Al99.5 and mild steel, but for high strength steel was significantly underestimated. It was found that achieving of parts accuracy for high strength steels requires the FE material model adaptation or use of tool setups with decreased die width where the springback is minimized and less sensitive to variations in material.