Pass design and redundant strains in forward tube extrusion

The reduction or, ideally, elimination of redundant shears in metal forming operations leads, in general terms, to an improvement in the quality of the product combined with an increased rate of yield and, in more extreme cases, to the possibility of using less expensive materials than those necessarily employed in conventional forming passes. Since the geometry of the pass determines the incidence, pattern and level of redundant deformation, the problem of rational die design becomes all important. The present investigation is concerned with establishing the relationship between the profile of the extrusion die and the development of the redundant shears, and points the way towards rationalisation of tooling in the process of tube extrusion.