Sliding temperatures of ice skates
Colbeck-SC; Najarian-I; Smith-HB, American-Journal-of-Physics. vol.65, no.6; June 1997; p.488-92
Abstract: The two theories developed to explain the low friction of ice, pressure melting and frictional heating, require opposite temperature shifts at the ice-skate interface. The arguments against pressure melting are strong, but only theoretical. A set of direct temperature measurements shows that frictional heating is the dominant mechanism because temperature behaves in the manner predicted by the theory of frictional heating. Like snow skis, ice skates are warmed by sliding and then cool when the sliding stops. The temperature increases with speed and with thermal insulation. The sliding leaves a warm track on the ice surface behind the skate and the skate sprays warm ejecta.
Pressure melting and ice skating
Colbeck-SC, American-Journal-of-Physics. vol.63, no.10; Oct. 1995; p.888-90
Abstract: Pressure melting cannot be responsible for the low friction of ice. The pressure needed to reach the melting temperature is above the compressive failure stress and, if it did occur, high squeeze losses would result in very thin films. Pure liquid water cannot coexist with ice much below -20 degrees C at any pressure and friction does not increase suddenly in that range. If frictional heating and pressure melting contribute equally, the length of the wetted contact could not exceed 15 mu m at a speed of 5 m/s, which seems much too short. If pressure melting is the dominant process, the water films are less than 0.08 mu m thick because of the high pressures.
Ice friction during speed skating
De-Koning-JJ; De-Groot-G; Van-Ingen-Schenau-GJ, Journal-of-Biomechanics. vol.25, no.6; June 1992; p.565-71
Abstract: During speed skating, the external power output delivered by the athlete is predominantly used to overcome the air and ice frictional forces. Special skates were developed and used to measure the ice frictional forces during actual speed skating. The mean coefficients of friction for the straights and curves were, respectively, 0.0046 and 0.0059. The minimum value of the coefficient of ice friction was measured at an ice surface temperature of about -7 degrees C. It was found that the coefficient of friction increases with increasing speed. In the literature, it is suggested that the relatively low friction in skating results from a thin film of liquid water on the ice surface. Theories about the presence of water between the rubbing surfaces are focused on the formation of water by pressure-melting, melting due to frictional heating and on the 'liquid-like' properties of the ice surface. From the authors' measurements and calculations, it is concluded that the liquid-like surface properties of ice seem to be a reasonable explanation for the low friction during speed skating.
A model for the formation and melting of ice on surface waters
de-Bruin-HAR; Wessels-HRA, Journal-of-Applied-Meteorology. vol.27, no.2; Feb. 1988; p.164-73
Abstract: Ice covers have an important influence on the hydrology of surface waters. The growth of ice layers on stationary waters, such as lakes or canals, depends primarily on meteorological parameters like temperature and humidity of the air, windspeed and radiation balance. A model is described that simulates ice growth and melting utilizing observed or forecast weather data. The model includes situations with a snow cover. Special attention is given to the optimal estimation of the net radiation and to the role of the stability of the near-surface air. Since a major practical application in the Netherlands is the use of frozen waters for recreation skating, the model is extended to include artificial ice tracks.
A geometrical model of speed skating the curves
De-Boer-RW; Ettema-GJC; Van-Gorkum-H; De-Groot-G; Van-Ingen-Schenau-GJ, Journal-of-Biomechanics. vol.21, no.6; 1988; p.445-50
Abstract: The centripetal force in speed skating the curves has to be delivered by the push off force which also does the external work to maintain the speed. Based on the geometry of the speed skating oval and the sideward push off characteristics in speed skating, a mathematical model of the power output in skating the curves was deduced. The power required to follow the curve is dependent on the mean speed in the curve, the work per stroke and the radius of the speed skating oval. Measurements (by means of film and video analysis) during the 5000 m races at the European Championships for ladies (n=16) yielded on the one hand power from the geometrical model and on the other hand power losses due to air- and ice-friction. The difference between power delivered and power lost is used by the skaters to increase their speed. The difference between predicted power and measured power used to increase the kinetic energy of c.g. was only 3% thereby providing strong support for the validity of the model. The analysis suggested that skaters who want to accelerate in the curves should increase their work per stroke. The model can be a useful tool to provide insight into this form of human locomotion and its optimization under competitive conditions.
The kinetic friction of ice
Evans-DCB; Nye-JF; Cheeseman-KJ, Proceedings-of-the-Royal-Society-of-London,-Series-A-(Mathematical-and- Physical-Sciences). vol.347, no.1651; 1976; p.493-512
Abstract: An apparatus based on a pendulum hanging around a revolving drum of ice was developed to measure the kinetic friction between a slider and an ice surface under conditions commonly experienced in ice skating (temperatures from -15 to -1 degrees C and velocities from 0.2 to 10 ms/sup -1/). The results are explained by a quantitative development of the frictional heating theory of Bowden and Hughes (1939): heat produced by friction raises the surface to its melting point and a small amount of water is produced which lubricates the contact area. The frictional heat used in melting is usually small. This makes it possible to calculate the dependence of the coefficient of friction on the thermal conductivity of the slider, the ambient temperature and the velocity of sliding, without considering the detailed mechanism that produces the frictional force.
Subtleties of phenomena involving ice-water equilibria
Loucks-LF, Journal-of-Chemical-Education. vol.63, no.2; Feb. 1986; p.115-16
Abstract: The effect of pressure on the ice-water equilibrium is sometimes cited to explain the source of a water layer that permits the ease of ice skating and to explain the observation that a weight suspended on a wire around a block of ice can cause the wire to cut through the block of ice with the ice refreezing behind the wire. A close examination of the details of the equilibrium reveals that the above conclusions are invalid except for very particular conditions.
The control of speed in elite female speed skaters
Van-Ingen-Schenau-GJ; de-Groot-G; de-Boer-RW, Journal-of-Biomechanics. vol.18, no.2; 1985; p.91-6
Abstract: From ten participants in the World Championships Speed Skating for Ladies 1983 a number of selected mechanical parameters were measured and correlated with speed and external power. The parameters were derived by means of video and film analysis of strokes at the four distances: 500 m, 1500 m, 3000 m and 5000 m. The results show that these speed skaters control the different speeds at different distances mainly by changing their stroke frequency and not by changing the amount of work per stroke. However, at the same distance the relatively small interindividual differences in performance level appeared not to be correlated to differences in stroke frequency but were correlated to differences in push-off mechanics. Better performers gain some potential energy during the gliding phase and show a more horizontally directed push-off in the frontal plane. Maximal knee extension velocity did not show any correlation with performance. The fact that this might be connected to the absence of a plantar flexion during push-off is discussed.
Friction and wear with a fully melting surface
Stiffler-AK, Transactions-of-the-ASME.-Journal-of-Tribology. vol.106, no.3; July 1984; p.416-19
Abstract: A theoretical model for melt lubrication is given which depends on the mass melt rate itself to develop load support between parallel surfaces. Expressions are derived for film thickness and temperature, coefficient of friction, and wear. The theory is applied to projectile rotating bands and ice skating.
Ulf Helmersson, firstname.lastname@example.org