Simulation of bridge die extrusion using the finite element method

Abstract

This communication reviews previous work on the extrusion of hollow shapes and uses a three-dimensional (FEM) solution to predict load-required, temperature of the extrudate and material¯ow during the process. A comparison with experiments is made to assess the relative importance of some extrusion parameters in the extrusion process and to ensure that the numerical discretisation yields a realistic simulation of the process. The usefulness and limitations of FEM when modelling complex shapes is also discussed. Methods to assess the dif® culty of extrusion of hollow extrusions in general are presented. The paper also illustrates the essentials of numerical analysis to assist the reader in the comprehension of the thermomechanical events occurring during extrusion through bridge dies. Results are presented for velocity distribution in the extrusion chamber, iso-temperature contours and pressure/ displacement traces. These are compared with experiments conducted using a 5 MN press. It is shown that the ® nite element program predicts the pressure requirement: the pressure/displacement trace showing a double peak which is discussed in some detail. The ® nite element program appears to predict all the major characteristics of the¯ow observed macroscopically. MST/5236Mr Flitta (i¯itta@bournemouth.ac.uk) and Professor Sheppard (tsheppar@bournemouth.ac.uk) are at Bournemouth University,

Investigation of metal flow in bridge die extrusion of Alloy 6063 and subsequent effect on surface quality and weld seam integrity

“…Later, Flitta and Sheppard 23 achieved more realistic result of the metal flow on this plane using Forge3; another early version of Forge2009. In this study, a finer grid plane is possible using the three-dimensional model to represent the material movement.…”

Material flow during the extrusion of simple and complex cross-sections using FEM

“…It should be noted that the pressuredisplacement curves have not been represented in this paper because the trends observed are similar to that of round cross-section. 3,4,[10][11][12]22 This increase in load with the increase in section complexity can be attributed to several interrelated reasons in which the complexity of extrusion increases the resistance to deformation. The increase in load is required to overcome the increase in frictional resistance and complexity flow associated with the increase in the contact area in the die land regions.…”

“…3,4,[11][12][13][14][15] In addition to the plastic deformation of the work piece, Forge2 software is capable of coupling the temperature calculation of both the work piece and the die(s), and of incorporating the elastic deformation of the die(s). The automatic remeshing technique enables the simulation of very complex parts.…”

“…They range from the most commonly used technique such as the gridded billet, [6][7][8] introducing pins of an aluminium alloy into the as-cast billet and then grinding and etching the surface after the end of the extrusion, 5,9,10 to marking grids within the initial billet. 3,4,11 However, the gridded billet technique relies on planar flow, and is not suitable to study material flow for complex cross-sections. The pins or volume element technique is more successful than the gridded billet technique.…”

“…The occurrences of material flow during the extrusion process have been the focus of much interest in aluminium alloys in general [3][4][5][6][7][8] but has been most often limited to rod extrusions. The influence of section geometry on the deformation zone is difficult to establish, unlike axisymmetric rod extrusion where the circumferential strain is essentially zero, the introduction of a third dimensional strain requires more careful interpretation.…”