Numerical investigation about the effect of increasing the number of forming passes on the quality of AHSS roll formed products

Over recent years, roll forming has gained an increasing interest for the manufacture of structural components made of Advanced High Strength Steel (AHSS) sheets. It is an incremental forming technique where the material is bent into the desired shape by feeding it through a number of roll forming stands. Springback is a major concern in forming of AHSS, and springback is lower in roll forming when compared to that in single step and multi-step bending. Some experimental studies suggest that this is may be due to the incremental nature of the roll forming process. In this study the effect of forming passes/steps on springback is numerically analyzed for DP 780 by means of FEA – Abaqus standard. The cyclic hardening characteristics of DP780 were determined by the pure bending test. The hardening model generated from bend data set was imported into Abaqus. The effect forming pattern on the springback was analyzed by forming a V-section shaped profile (15 mm forming radius). The numerical results show that there is a reduction in springback with increasing number of forming passes in the roll forming process, and that this may be the result of straining experienced by the sheet during the multi-step roll forming. This study seems to provide a greater insight into understanding the nature of springback with the forming passes and process design.