This paper on "Simulation and Optimisation of Radial Extrusion of Components by Virtual Prototyping" was presented at the NAFEMS World Congress on Design, Simulation & Optimisation: Reliability & Applicability of Computational Methods - 9-11 April 1997, Stuttgart, Germany.

Summary

A major disadvantage of traditional cold forging is the inability to forge slender geometries such as tubes as they tend to collapse under axial forces. In consequence hollow parts are most often forged from solid in processes implying some form of backward or forward extrusion, leaving a central web which is punched out later. A significant form of material waste and a source of component inaccuracy is hereby introduced. A finite element model was used to exploit some evidence, given by early investigations, of the possibility of achieving sufficiently large plastic deformation of tubes, to enable the production of certain engineering components, by extrusion into a die-cavity. By introducing some possible preforming stages the simulation made it possible to establish the basis for the development of a technology for the near net-shape manufacture of a larger range of hollow part geometries with large savings in material. The finite element model uses a rigid plastic formulation having as main variables velocities and pressure. Incompressibility of plastic deformations is effectively solved by resorting to mixed methods or penalty methods. The interaction of the tools and workpiece are modelled by interface elements. The model also includes an adaptive mesh refinement technique based on an error estimation of the energy norm.