2020 Volume 61 Issue 710 Pages 69-74
Further weight reduction is required for the automotive body from the viewpoint of global environment protection. Therefore, steel sheets for automotive body parts are becoming increasingly thin and strong. Generally, as the tensile strength of a steel sheet becomes higher, formability deteriorates owing to reduced ductility and deformation localization during forming. Then, we worked on developing a forming technology utilizing deformation dispersion for forming high-strength parts with either a flange-down or flange-up formed portion at the longitudinal edge. As a result, proposed forming method, which enables deformation dispersion, improved the formability, wrinkle resistance in case of flange-down forming and fracture resistance in case of flange-up forming. In addition, the proposed methods make it possible to compensate for decreases in strain dispersion characteristics of high-tensile-strength steel sheets by means of deformation dispersion. As a result, the proposed methods compensate for decreases in flange-down and flange-up formability each due to deteriorations of material properties in high-tensile-strength steel sheets.
