Improvement of Shape Accuracy in Press-Formed Product of High-Strength Steel by Determining Springback Driving Stress

Abstract

Springback is one of the most serious problems in high-strength steel-sheet forming to produce automotive body parts. It is, therefore, important to control and suppress springback in the use of high-strength steels. Against this background, two springback-root-cause analysis methods were developed to identify the areas of stresses at the bottom dead point, which are the most influential in springback. One method uses stresses at the bottom dead point, and the other method uses springback driving stresses, that is, the difference between stresses before and after springback. The two methods were applied to the forming of an actual part. The areas of stresses that have a major impact on springback were identified by the two methods and were almost the same. From the viewpoint of accuracy, however the method of using springback driving stresses was more accurate than that using stresses at the bottom dead point. A countermeasure based on these results was applied to the actual part, enabling the amount of springback to be reduced substantially.

Simple Springback Cause Analysis Using Measured Shapes of Dies and Pressed Part

“…Accordingly, the authors developed a method of springback-root-cause analysis which can identify the area and stresses which mainly cause springback [3]. In the analysis, a press-formed model is divided into some areas, and the influence of each area on springback is evaluated by FEM analysis.…”

Improvement of Shape Accuracy in Press-Formed Parts of High-Strength Steel by Springback-Root-Cause Analysis

“…To identify the factors for the occurrence of springback, the stresses at the bottom dead point in a pressed part is focused on. And a method in which those stresses are correlated with springback deformation has been developed [2,3].…”