Some studies on Sheet Metal Forming

Abstract

Surface finish of tools or blanks exerts profound effects on the forming of sheet metals. Effects of surface finish of aluminum , copper and brass were examined in pure deep drawing (flat bottom swift cupping test), combined drawing and stretch forming test (hemispherical punch drawing test) and pure stretch forming test (Olsen test).Effects of variation of sheet thickness were also studied in each case. It was observed in almost all cases that for pure deep drawing. The improvement was quite marked for aluminium & copper and less so for brass. Increase in blank thickness adversely affected the advantages of increased surface roughness. In case of pure biaxial stretching, on the other hand, increase in surface roughness resulted in lowered cup depth values in all cases. Contrary to pure drawing , however, the effect was more pronounced in the case of brass than in case of pure drawing, with the exception that the effect was more pronounced in case of greater blank thickness. The results have been discussed in terms of frictional forces and fundamental modes of deformation involved in the three cases.