Abstract
AbstractThe mechanics underlying ice–skate friction remain uncertain despite over a century of study. In the 1930s, the theory of self-lubrication from frictional heat supplanted an earlier hypothesis that pressure melting governed skate friction. More recently, researchers have suggested that a layer of abraded wear particles or the presence of quasi-liquid molecular layers on the surface of ice could account for its slipperiness. Here, we assess the dominant hypotheses proposed to govern ice–skate friction and describe experiments conducted in an indoor skating rink aimed to provide observations to test these hypotheses. Our results indicate that the brittle failure of ice under rapid compression plays a strong role. Our observations did not confirm the presence of full-contact water films and are more consistent with the presence of lubricating ice-rich slurries at discontinuous high-pressure zones (HPZs). The presence of ice-rich slurries supporting skates through HPZs merges pressure-melting, abrasion and lubricating films as a unified hypothesis for why skates are so slippery across broad ranges of speeds, temperatures and normal loads. We suggest tribometer experiments to overcome the difficulties of investigating these processes during actual skating trials.
Highlights
You are slippery on skates from the moment you touch the ice
Our review of these models and our skating-trial observations indicate that the underlying mechanics may not be correct
The mechanics responsible for the low friction of skates on ice remains uncertain despite research interest for over a century
Summary
You are slippery on skates from the moment you touch the ice. Why should this be true? Given that two solid materials are in contact, researchers have long sought to explain low ice–skate friction based on unique properties of ice. Reynolds (1899) described a ‘eureka’ moment wherein he postulated that a thin water film formed by pressure melting could account for the slipperiness of ice. Canale and others (2019) conducted micro-scale rheology measurements on ice–slider interfaces and found that the interfacial film displayed viscoelastic behavior, with viscosity much higher than that of water They suggested that abrasive wear could produce a slurry consisting of liquid and sub-micrometer debris to yield the observed behavior and called for an overhaul of prevailing theories of ice friction. Gagnon (2016) crushed ice against millimeter-scale rough surfaces with concurrent sliding motion and measured remarkably low friction He suggested that the formation and extrusion of ice-rich slurries controlled the friction mechanics and that these processes could explain the friction of skate blades on ice. Observations and numerical simulations of nano-scale quasi-liquid layers (QLLs) on ice surfaces provide some evidence that the increased mobility of molecules in these thin layers accounts for low friction of smooth sliders on ice (Weber and others, 2018; Liefferink and others, 2021). None of these recent hypotheses have been formulated into models to predict ice–skate friction, but they postulate quite different contact mechanics from self-lubrication
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