The Basic Rules on the Fracture in Sheet Metal Drawing

Abstract

This paper gives an account of the effects of drawing conditions on the drawability, using soft, half-hard and hard aluminium sheets of 0.4 mm in nomimal thickness. The drawing conditions examined included punch profile and lubricants over punch head. In order to clarify the mechanism of the fracture to govern the drawability, the fracture forces (i.e. the supportable drawing tension of metal sheet over punch head) were compared with the drawing forces throughout the drawing process and the strain and stress distributions of metal sheets over punch head were examined experimentally. As the result, three basic rules to control the fracture of metal sheets during the drawing process have been established. According to these basic rules, the effects of the drawing conditions on the limiting drawing ratio could be systematically understood.