Deformation of Rectangular Billets Between Dies with Unparallel Grooves

Abstract

Deformation of rectangular billets between grooved dies takes place in an extrusion forging mode in which the billet material is simultaneously forced into the die cavity and expand laterally. This process is similar to the initial stages of the closed-die forging. The understanding of the material flow patterns and the prediction of the forming load in such deformation process is important both for the die design and the product quality control.

The deformation of rectangular billets between parallel grooves has been previously investigated by the authors. By assuming the existence of three distinct deformation modes, an analytical solution was presented using an upper bound approach, which can successfully predict the forging load as well as the deformed profiles. It was found that the deformation patterns in such process depends not only on the relative widths of die grooves, but also on the relative geometry of the die and the billet.

In this paper, experimental and analytical investigations have been performed on the deformation of rectangular billets between dies with unparallel grooves. Three combinations of dies with different angles of unparallelness were used to deform the lead billets and the theoretical results have been obtained by choosing an “average groove width” and dealing the problem as one involving dies with parallel grooves.