ATF Additive Effects on Hot Spot Formation in Wet Clutches

Wet clutch interfaces that operate in high-energy environments experience significant frictional heating. Under such conditions, thermoelastic or thermoplastic instabilities may lead to a transition from evenly distributed surface contacts to unevenly distributed regions that manifest themselves as hot spots on the separator plate. The critical power at which these instabilities occur depend on the thermal conductivity, thermal expansion, and stiffness of the components. Modeling has shown that for wet clutch interfaces the stiffness of the friction material has a dominant influence on the critical power. We have found that the lubricant additive package also plays a significant role in the onset of hot spots. In this paper, we report the influence of antiwear systems on the occurrence of hot spots.