Development of a finite element analysis program for roller leveling and application for removing blanking bow defects of thin steel sheet

For the analysis of roller leveling process and application for controlling blanking bow defects in a thin steel sheet, a finite element analysis program modeling large deformation of shell has been developed. This program for elastic-plastic large deformation analysis of sheet includes spring-back analysis as well as contact treatment between sheet and rolls of roller leveler. This is verified by the simple leveling experiment with 5 rolls at laboratory. The residual curvatures of strip predicted by finite element analysis are within 20 % error range of the experiment. An optimum entrance intermesh condition, that is able to remove the blanking bow or deviation of curvature of a sheet, are found by finite element analysis for initially curved three strips by applying virtually divided strip model. The curvature difference of strips after leveling is decreased as increasing the entrance intermesh of roller leveler, and the optimum intermesh value is affected by the roll diameter and arrangement. The predicted optimum intermesh values are consistent with the experimental results. The residual stress distributions after leveling is predicted numerically by the curvature of strip obtained from the finite element analysis. It is found that the change in the residual stress distributions due to leveling is also markedly affected by the intermesh condition.