2016 Volume 57 Issue 660 Pages 28-33
The numerical analyses and experiments of press-forming were carried out in order to clarify the mutual effects of the punch shoulder radius Rp, flange height H and mechanical properties on flange-up formability for the flange in the longitudinal edge. The results showed that the formability is strongly mutually affected by not only Rp and H but also the r value and plastic tangent modulus normalized by yield stress H’/YP. When Rp is small and H is high, the r value and H’/YP also significantly affect the formability. As a result, the formability of high-tensile-strength steels, whose r value and H’/YP are relatively small, is inferior to that of mild steel. Moreover, it was clarified that when Rp is small and H is high, the bending radius of sheets around the base of the flange becomes smaller than Rp during forming, which causes strain concentration in the flange edge. Therefore, it is suggested that the bending radius of sheets during forming should be controlled to be larger than Rp to obtain good formability.