Experimental Study on Punch Radius and Grain Size Effects in V-Bending Process

This article investigated the effect of process parameters, including grain size, punch radius and punch speed, on springback in micro V-bending. The effect of yield strength, directly affected by grain size, on the springback was also investigated. A series experiment of micro V-bending were carried out for pure iron sheets, including three grain sizes, four punch radii and three punch speed. In addition to evaluate the grain size effect (refer to yield strength), this study focused on springback control at appropriate punch radius and punch speed. In the case of grain size d=17.23 mu m, the optimal condition of zero springback is near R/t=1.25, and in the case of d=23.41 mu m, the optimal condition of zero springback is near R/t=1.75. Springback decreases as punch speed increases under smaller grain size. High punch speed has the advantage of springback reduction in smaller grain size. However, low punch speed can reduce spring forward in larger grain size. The grain size, punch radius and punch speed play an important role in springback reduction.