Commercially pure lead was extruded through a sharp-edged circular orifice by an indirect or inverted extrusion process. Metal flow directions and plastic strains were determined during a small stepwise deformation process from distorted, originally square, grid-line network scribed on a meridian plane. It was found that the metal flow directions do not coincide with instantaneous grid-line directions nor with the streamline directions in frictionless or potential fluid flow. It was further found that the metal located in the corner, formed by cylinder wall and die face, was in a state of plastic deformation. This observation is contrary to previously reported investigations and shows that the surface quality of the finished extrusion is dependent on the surface quality of the billet from which the extrusion was pressed. A strain analysis was made from which principal stress directions in the plastic metal were calculated.

This content is only available via PDF.
You do not currently have access to this content.