対向カップ型試験片を用いた自動車用高張力鋼板スポット溶接部の疲労特性評価

概要

論文の詳細を見る
Double-cup (DC) specimens of spot welded joint are newly produced for high strength steel sheets (HSS), and fatigue tests are conducted under three kinds of loading directions (shear, tension and mixed mode) for steel sheets with tensile strength ranging from 270MPa (mild steel) to 980MPa. The fatigue strength is degraded as the load component in the tensile direction increases. The HSSes show higher fatigue strength than the mild steel under the shear loading, whereas the fatigue strength of the JIS tensile-shear (TS) specimen is almost equal regardless of the steel grade. The deformation behavior and the stress state are investigated for the DC and TS specimens by finite element analysis. In the TS specimen, the spot weld rotates and it is subjected to the mixed mode loading. Moreover, the tensile stress of the HSS is higher than that of the mild steel under the identical load because the smaller plastic deformation takes place in the HSS. In the DC specimen, on the other hand, rotation of the spot weld is smaller due to deformation restraint around the spot weld and the stress state is close to pure shear, which may lead to the fair evaluation of the effects of the steel grade.
2009-05-25