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Skiing sports have experienced a significant boost in the 1990s when the classical ski geometry was replaced by a deep side cut ski, the carving ski. The geometrical and mechanical characteristics of modern carving skis are adjusted to typical turn radii, such that the skis cut through the snow surface with minimized skidding. As a ski passes over the snow surface in a carved turn the inclined skis penetrate the snow surface until the contact area suffices to allow snow of a given resistive strength to support the load exerted by the ski. In this study we measured the mean resistance pressure the snow exerts to an inclined plate penetrating the snow surface as a function of penetration depth. The tests were carried out on several groomed ski pistes of different snow types. We found that the mean penetration resistance pressure for homogeneous snow increased linearly with the penetration depth. Hence, the snow resistance of different snow types can be characterized by the slope A and the offset pressure B of this linear function. For groomed, homogeneous snow pistes values of the coefficient A lie typically between 5 and 40 MPa m − 1 , values of the coefficient B lie typically between 0 and 400 kPa. Moreover, the slope A increases with increasing edging angle, but if the edging angle surpasses a threshold angle found between 30° and 45° the mean snow resistance pressure falls due to frequent shear fractures, by which the snow is pressed out of the indent. The overall trend in snow resistance curves can still be approximated by a linear function, but the slope A falls to values in between 2 and 20 MPa m − 1 . The offset pressure B strongly depends on surface characteristics of the snow, which often deviate from the subjacent snow due to exposure to the sun's radiation or to skier's traffic. If the snow surface is considerably softer than lower snow layers, then the offset pressure B of the overall snow resistance function may even be negative. This study provides the so far missing experimental data for models of the ski–snow interaction in carved turns. |
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