The Role of Ice Indentation in the Friction Produced Between the Blade and Ice during Ice Skating

Abstract

Ice skating is an astonishing feat of grace, strength, precision, and speed that has made its way into popular recreation, online media, and international competitions. However, while the remarkable slipperiness of ice is well-known and the creation of a shallow rut where the skater skates can be easily observed, the mechanisms behind these two phenomena remain unclear and debated. The extraordinarily low friction coefficient of ice was first attributed to a meltwater layer forming from pressure melting, but this was later largely disproven and replaced with a frictional melting theory. Later studies revealed nano-scale quasi-liquid layers acting as a lubricant, and more recent research has factored in the role of ejected ice particles in forming an ice-rich slurry at the blade-ice interface. The latter theory invites discussion of ice indentation processes to explain how brittle failure occurs and how crushing impacts friction. High-pressure zones enable pressure melting, microcracking, and spalling; crushing depends on ice hardness which varies with temperature and plowing velocity; and the plowing force contributes about half of the experienced frictional force and changes with blade geometry. Ice indentation can be a complex process with many factors, but it is instrumental in the generation of a lubricating slurry and, thus, in the low friction experienced by skaters.