Abstract
This paper is concerned with the modelling of forming processes of conventional alloys using the Finite Element (FE) method. The particular forming process under investigation is forward bar extrusion (FBE). The Eulerian description of FE flow formulation coupled with boundary friction was employed. With a simply numerical approach proposed to combine the friction effects with flow analysis, two subroutines of user element (UEL) written in FORTRAN are implemented into the FE commercial code ABAQUS. One is invented in order to define an axisymmetric Eulerian flow element, and another is formulated to incorporate the boundary friction.
As realised that extrusion is an attractive processing route applied by automobile manufacturers for fabricating materials, especially light weight and high strength alloys, into bars of different shapes in order to use as feedstock for further processes or for producing products such as drive shaft tubes. Consequently, the main objective of this research project is to develop a systematic approach of simulating the extrusion of Ti-6Al-4V under cold condition (at room temperature) so that sound product quality can be designed from the material composition to the forming process. As a result, a wide scope is opened to the optimisation of the product. For a given combination of conical die angle (2 á = 90 °) and logarithmic strain for cross-sectional area ( A å = 0.7), it was found that with the introduction of interfacial friction in the modelling the likelihood of a typical defect such as central bursting has been occurred along the centre axis of the extrudate. But, the predictions obtained from the present FE modelling revealed that the friction did not alter the surface tearing/cracking on the extrudate. However, the predicted results agreed well qualitatively with experimental observations, thus verifying the predictive capability of such the FE model.