An investigation on the formation and propagation of shear band in fine-blanking process

摘要

An investigation has been made on the formation and propagation of shear band in fine-blanking process. Examinations by optical microscopy and SEM reveal that the highly elongated narrow subgrains extended in the shear direction within the band, while in the other regions, fine equiaxed cell were observed. Both the presence of white-etching trace and the distribution of surface microhardness in the shear band reveal that fine-blanking process involves large deformation and high temperature. Although strain localization is severe in the shear band, especially in the area adjacent to the edges of the punch and die, no cracking has been observed. It is indicated that high hydrostatic pressure, built up by specially designed fine-blanking fixture, plays a significant role to suppress the generation of fracture zones in the sheared surface. On the basis of present findings, the mechanisms of the formation and propagation of shear band in fine-blanking are discussed.