Physical and numerical modelling of ram extrusion of paste materials: conical die entry case

A ram extrusion process with a conical die entry is analysed using a physically based analysis and a numerical modelling procedure involving the finite element method. The aim of the study is to test the applicability of the elastoviscoplastic constitutive model combined with an established boundary condition criterion for describing this forming operation. "Plasticine", a commercial modelling clay which exhibits an elasto-viscoplastic flow response, is used to study the nature of the material deformation. For the numerical modelling, an elasto-viscoplastic finite element program has been implemented. Satisfactory agreement, between experiment and simulation, is obtained for the force-time data and the material displacement fields which indicates that the bulk and interfacial constitutive relationships adopted, along with the associated numerical parameters, are an appropriate description of the flow behaviour of the system. The evolution of the deformation, within the material during the extrusion process, is interpreted. The study indicates that the procedures described may ultimately provide a numerical rheometric tool from which the effects of various process boundary conditions, on the evolution of paste material deformation, can be examined and quantified for the ram extrusion process with conical die entries. (C) 2000 Elsevier Science B.V. All rights reserved.