Friction-reducing contact area expansion in upsetting

The most obvious problem in static and dynamic upsetting is dealing with th e effects of friction. In upsetting with friction, the final contact area c an be divided into two parts: the expanded original contact area and the im migrated contact area. In this paper, upsetting of aluminium alloy AA 6082, low-carbon steel W.No.1.0303 and stainless steel W.No.1.4301 with three ki nds of machined end surface lubricated by five different lubricants is carr ied out. Finite element analyses applying five different friction models ar e performed to estimate the contact areas and metal flows. Contact area con figurations and two parameters, namely the friction area ratio and immigrat ed contact area ratio, are suggested. The influences of reduction, lubricat ion and temperature on the contact areas are experimentally and theoretical ly investigated. It is found that reducing the contact area expansion is a basic characteristic of friction in upsetting by both experiments and finit e element method simulations.