Investigating Dry Ski–Snow Friction: Mechanisms and Temperature Dependence
The gliding of skis on snow involves multiple coexisting mechanisms, including dry friction, lubrication by frictional meltwater, and capillary suction, complicating the isolation of individual contributions. This study focuses exclusively on dry friction, employing a linear tribometer with a flat slider at -8 °C under conditions where no frictional meltwater was previously observed. To eliminate the influence of the quasi-liquid layer (QLL), experiments were also conducted below -30 °C using dry ice, ensuring dry friction as the sole active mechanism. Additionally, frictional behavior representative of cross-country skiing was investigated. Results show that the friction coefficient decreased with increasing speed at temperatures below -30 °C, but increased with speed at -8 °C. Increasing pressure reduced the friction coefficient at both temperatures. Comparison with theoretical models indicates that the primary friction mechanism is the tearing out of grains below -30 °C, and the shearing off of grain tips (abrasion) at -8 °C. The findings demonstrate that friction under all investigated conditions can be explained by these mechanisms, along with mechanical and thermal effects and granular lubrication, without invoking the QLL. While the QLL is often considered crucial for ice friction, its role in snow friction appears far less significant.