Determination of friction factor by ring compression test for Al-5Zn-1Mg using graphite and MoS2 lubricants

Abstract

There are two types of friction viz, sliding friction and sticking friction. Both of them can be quantified by either friction coefficient (μ) or friction factor (m), but, friction factor is advantageous. Friction coefficient, μ, decreases inversely with interface pressure and can lead to misinterpretation of frictional forces. On the other hand, friction factor, m, is independent of normal stress at the interface. Moreover, it can easily be measured and also leads to a mathematical simplification of analysis of forces for metal working processes. In the present study an attempt has been made to study the friction factor, m, of Al-5Zn-1Mg alloy by Ring compression test in a 40 T Universal testing machine with graphite and MoS2 as lubricants. The test was carried out at temperatures from 303-673K. The reduction in height and change in internal diameter were measured and using a calibration chart, the friction factor was estimated.
It was noticed that friction factor, m was considerably low for graphite lubricant between temperatures 303 and 673K. It can be concluded that graphite is a better lubricant compared to MoS2 for Al-5Zn-1Mg between temperatures 303 and 673K from the aspect of lower frictional force. Lower frictional forces implies less wear and tear of tooling, hence, increased tool life.

Keywords: Friction factor, sticking,sliding, aluminium, zinc, magnesium