The most obvious problem in static and dynamic upsetting is dealing with the effects of friction. In upsetting with friction, the final contact area can be divided into two parts: the expanded original contact area and the immigrated 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 kinds of machined end surface lubricated by five different lubricants is carried out. Finite element analyses applying five different friction models are performed to estimate the contact areas and metal flows. Contact area configurations and two parameters, namely the friction area ratio and immigrated contact area ratio, are suggested. The influences of reduction, lubrication and temperature on the contact areas are experimentally and theoretically investigated. It is found that reducing the contact area expansion is a basic characteristic of friction in upsetting by both experiments and finite element method simulations.
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