Effect of pressure and temperature variations on FEM prediction of deformation during extrusion

Abstract

The extrusion process is complex, involving interaction between the process variables and the material's high temperature properties and is typically conducted at relatively high temperatures because the lower flow stress of the material permits larger section reductions to be achieved. This lowers the power requirements and processing times. Temperature is, perhaps, the most important parameter in extrusion. The flow stress is reduced if the temperature is increased and deformation is, therefore, easier, but at the same time, the maximum extrusion speed is reduced because localised temperatures must be well below any incipient melting temperature. The present investigation focuses on the evolution of the temperature in the billet from upsetting and until the end of the extrusion cycle is reached. The extrusion pressure and the temperature rise are predicted and the pressure-displacement trace and the events which take place in the deformed material during the extrusion process are also simulated. The simulation is compared with data obtained from an experimental extrusion press. All simulations are performed with the implicit finite element code FORGE2. A comparison with experiments is made to validate the predicted temperatures readings from FORGE2 to ensure that the numerical discretisation provides a true simulation of the process. It was found that the extrusion parameters (friction, heat transfer, etc.) are significantly influenced by the temperature gradients produced in the billet during transfer to the container, and after upsetting in the container. These parameters are thus clearly extremely sensitive input data when attempting to simulate the extrusion process.

Temperature and Die Angular Effect on Tensile Strength, Hardness, Extrusion Load and Flow Stress in Aluminum 6063 Processed by Equal Channel Angular Extrusion Method

“…It substantially decreases to 4.8 MN and 4.5 MN, respectively, at 425 °C and 500 °C. The fl ow stress falls with high temperature thus, processing time decreases [27][28] and this can be used as the justifi cation for the considerable reduction in load.…”

A high-temperature deformation model based on dislocation movement for wrought aluminium alloys

“…The area annihilated by the movement of high-angle boundaries can be written as dS(u, 1)dV with the volume of dV swept by the mobile boundaries. The relative fraction of low-angle boundaries with misorientation angles between u + du and u + du + du can be given by the equation (10).…”

“…[5][6][7] The main focus of modelling and simulation nowadays for the high-temperature deformation of wrought aluminium alloys may be summarised as follows: (1) characterising the workability and optimising size parameters of parts by reproducing a thermomechanical process using the finite element method that cannot well present microstructure evolution. [8][9][10][11] Only some finite element software on thermomechanical processing can present grain size evolution through models embedded therein constructed based on experience instead of physical significance. (2) Response on atomic and molecular scale to the thermomechanical processing of wrought aluminium alloys.…”

Introduction to Modelling the Correlation Between Grain Sizes of Feed Material and the Structure and Efficiency of the Process of Co-Rotating Twin-Screw Extrusion of Non-Flammable Composites with a Pla Matrix

“…The greatest advantage of the twin-screw extruders over the single-screw extruders is the possibility of using interlocking kneading segments, as well as mixing screws, thanks to which the mixing takes place both on the edge (screwbarrel) and on the above-mentioned elements inducing the shear forces [3,4]. The combination of these two features allows for better dispersion of the filler in the polymer matrix, but a limitation of the process is the fact that the shear forces cause an increase in temperature due to friction [5,6]. It is difficult to describe this process mathematically because there are many variables here that are specific both for the polymers themselves and even for polymer-filler systems [7][8][9][10].…”