Ice-on-metal and metal-on-metal: low temperature adhesion and friction
Diego MARCHETTO
(Università di Modena e Reggio Emilia, Rete Alta Tecnologia della Regione Emilia-Romagna)
ABSTRACT
The study of friction between metals and ice is as struggling as important in a wide-range of fields, from ice sports to motorized traffic. Friction of ice is indeed related to the existence of a liquid layer of water between the slider and the ice itself. The liquid layer originates from the melting of the ice surface causing a continuous evolution of the frozen surface.
To further complicate the analysis of friction of ice is the changing impact of the surface morphology of the slider at different lubrication regimes on ice.
In boundary lubrication the frictional behavior is ruled by asperities contact between the surfaces (and a greater roughness of the slider increases interlock contacts and the shear stresses), because the liquid layer height is smaller than the roughness of the surfaces involved. In mixed lubrication regime the liquid-like layer starts to support the load of the slider, but the contact between the surface asperities is still present. In full lubrication regime (or hydrodynamic regime) the thickness of the liquid-like layer is greater than the roughness of the surfaces: the load is fully supported by hydrodynamic lift, and there is no more contact between surface asperities.
This work examines the transition between different friction regimes and the role of the surface of the slider in terms of roughness, topography and wettability. Tribological tests through different friction regimes were performed varying separately temperature and sliding velocity in a stainless steel-ice contact. Finally, the dependence of friction from surface morphology is studied by inducing different degrees of roughness on stainless-steel surfaces.
Metal on metal tribological tests were also conducted at T lower than 0°C in order to study the influence of humidity and temperature on friction and wear of these surfaces.