Driving on ice is a rather delicate exercise due to the poor adherence of tire on ice. In this context of road safety improvement under severe climatic conditions, it becomes necessary to precisely study and investigate the sliding contact between rubber and ice and to identify the key mechanisms governing the tribological behavior of the rubber-ice contact.<br/>A multi-scale strategy was chosen in this work, from the scale of apparent surface area to the scale of groups of asperity contacts, in order to understand the effect of adhesion and of thermal heating of the contact on the rubber/ice friction.The KORI tribometer, developed in LTDS, was used to perform ice/rubber friction experiments over four decades of sliding velocities, under an initial loading of 10N. The contact was simultaneously visualized and measured by means of a camera with a resolution of 5x5 mm<sup>2</sup>. A cooling system was designed in order to maintain the contact zone at a negative temperature, down to -20°C, for several hours, independently of the external temperature and humidity conditions. In parallel, an ice-manufacturing unit was designed to produce a repeatable transparent vertically grown ice disc. Rubber/ice friction experiments were performed Each measurement was repeated three times for each sliding velocity. The friction behavior was analyzed at the macro and micro scales for temperatures ranging from -15°C to -2.5°C on rubbers with various mechanical properties and glass transition temperature. Thanks to the visualization of the real contact area, it was possible to measure the interfacial shear strength of rubber/ice contact.<br/>The rubber-ice friction as a function of the sliding velocity formed a bell-shaped curve classically observed for rubber friction. The higher the temperature, the lower the friction coefficient. In the ’high velocity’ range, the thermal effects cannot be neglected. The modeling of the mean contact temperature, Tc, suggested the initiation of melting on the ice surface at 0.1 m/s regardless of the environmental temperature, T. This phenomenon controlled the transition of friction regime. The values (Tc − T)/(Tm − T), where Tm is melting point of ice calculated for each temperature collapsed onto a master curve. The existence of this master-curve implies that the interfacial shear stress within the contact can be analytically predicted as function of the sliding velocity, temperature and viscoelastic properties of the rubber.

Ice-rubber friction mechanisms

2019 Fall National Meeting

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