Nature of friction in extrusion process and its effect on material flow

Abstract

This investigation focuses on simulation of the extrusion process and in particular the effect of the initial billet temperature on friction and its consequences on material flow. The simulation is compared with data obtained from an experimental extrusion press. All the simulations are performed with the implicit finite element codes FORGE2 and FORGE3. The effect of the initial billettemperature on the deformation zone pattern and its consequent effect onfriction using bothnumerical simulationandexperimentalworkare presented.A comparison withexperimentsis made to assess the relative importance ofsome extrusion parameters in the extrusion process and to ensure that the numerical discretisation provided a true simulation of the process. A specific functional relationship to directly measure interfacial friction under conditions approaching those encountered in the quasi-static deformation process is described. The results revealed that the friction factor increases with increase in initial billet temperature and varies from 0.65 at 300 ° C to a 0.91 at 450 ° C after reaching the peak pressure. The dead metal zone is observed to vary in form and has a greater volume at high temperatures. The increase in friction results in an increase of initial extrusion load. The finite element program appears to predict all the major characteristics of the flow observed macroscopically.