Comparison between rubber–ice and sand–ice friction and the effect of loose snow contamination

The application of sand particles is a common method to improve the friction of aircraft tires on snow or ice covered runways. Hence, an understanding of the prevailing rubber–ice and sand–ice friction mechanisms is of practical interest. Rubber–ice and sand–ice friction measurements were made with a British Pendulum Tester at temperatures between −22 and 0 °C and the effect of loose snow contamination on top of the ice was investigated. The results (the response of the instrument) were expressed in a sliding length averaged friction coefficient μBP. Close to the melting point the friction of rubber on ice was low and increased with decreasing ice temperature. Below −5 °C, reasonably high friction levels (0.2<μBP<0.5) were obtained between rubber and ice, but the friction level dropped drastically by the presence of a very thin layer of snow. The sand–ice friction level was less dependent on ice temperature and clearly not as much affected by the presence of snow, compared to rubber–ice friction. The micromechanisms involved in rubber–ice and sand–ice frictions were investigated by the application of etching and replicating technique (ERT) developed for the examinations of the dynamics of dislocations in ice during deformation.