A Review of the Processes that Control Snow Friction

Authors: Samuel C. Colbeck; COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH

Abstract:

There is a long history of interest in snow friction, but it is still necessary to speculate about the details of the processes. Roughness elements and contact areas must be characterized before the basic processes can be well understood. These parameters change with movement over snow and, in fresh snow, probably change along the length of the slider. Friction results from a mixture of processes: dry, lubricated, and possibly capillary. Dry rubbing occurs at low speeds, loads, and/or temperatures and is characterized by solid-to-solid interactions requiring solid deformation. With small quantities of meltwater present, elastohydrodynamics must be used to account for processes at partially separated surfaces and, when too much water is present, the contact area increases and there may be capillary attachments. Static charging probably occurs and may attract dirt that, even in the size range of micrometers, could complicate the processes. Slider thermal conductivity and even color are very important. Heat is generated by friction and solar radiation absorbtion but some is conducted away by the slider and ice particles. The remaining heat is available to generate meltwater, which acts as a lubricant. Polyethylene bases offer many advantages including low ice adhesion, high hydrophobicity, high hardness and elasticity, good machinability, and good absorption of waxes. While sliders must be designed for use over a narrow range of snow and weather conditions, polyethylene bases can be structured and waxed to broaden that range. The important processes operate, not at the air temperature, but at the ski base temperature, which is highly dependent on such things as snow surface temperature, load, and speed. Friction, Rubbing, Snow physics, Plastics, Skis, Wax, Polyethylene, Sliding, Polymers, Snow.

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APPROVED FOR PUBLIC RELEASE