Dynamics of the Ice-Crushing Process

Abstract

During fast indentation tests on ice sheets at constant rates, crushing is commonly observed at appropriate combinations of speed and aspect ratio. An analysis is made of this mode of failure, using as a basis a recently conducted test on an ice sheet under controlled conditions. The variation of load with time is given special attention, and cyclic variation of load is associated with periodic crushing (pulverization) events, followed by clearing of the crushed ice particles. An analysis of the clearing process is summarized in the paper, treating the crushed ice as a viscous material. A detailed analysis of the energy exchanges during the indentation process is given. Elastic variations of stored energy in the indenter and in the ice sheet are calculated; these are relatively minor. The dissipation of energy during a typical load cycle (3 mm movement during 0.05 s) is about 8 J. The energy required to create surfaces of the crushed ice particles is small (0.006 J), as is the work of crushing based on mechanical testing (0.09 J). It is concluded that the process of viscous extrusion of crushed ice is the main seat of energy dissipation, basically as a frictional process. A relationship for the mean thickness of the crushed ice layer is developed, based on energy-balance considerations.

Snow machining and side slipping in alpine skiing

“…At the lower end of the cutting depth range, the chip was more or less continuous, but at the higher end it was in the form of spray of small ice particles. In the latter case, Lieu and Mote (1984) observed a pronounced tool chatter and fluctuation of the cutting force about its mean value on the level of approximately 10%, as expected for quasiperiodic crashing of ice (Jordaan & Timco, 1988). Later, Tada and Hirano (1999) found a reasonable agreement with the results of Lieu and Mote (1984) in their own experiments in ice machining.…”

“…Moreover, ice and snow are extremely brittle and easily disintegrate into individual grains under sufficiently high strain rate, with very low energy consumption (e.g. Jordaan & Timco, 1988;Schweizer, Michot, & Kirchner, 2004). As a result, instead of a continuous chip, a spray of pulverised snow is formed.…”

Laboratory experiments to study ice-induced vibrations of scaled model structures during their interaction with level ice at different ice velocities

“…10b), hence the superstructure motion contributed insignificantly to the ice crushing. Jordaan and Timco (1988) found two dominating frequencies in the measured force signal when they pushed a flat-faced indenter through S2 ice sheets at an indentation speed of 60 mm s −1 . The major crushing occurred at a frequency of 20 Hz, while a secondary frequency at approximately 50 Hz was attributed to further crushing or clearing events.…”

Energy exchanges during indentation tests in fresh-water ice

“…Similar energy computations have been given by Nakazawa and Sodhi (1990), but these were done only during the period of increasing interaction forces. Jordaan and Timco (1988) estimated the different energy components during the interaction. Because the displacements of the structure and the indentor were not measured independently, they deduced the structure’ s displacement from its stiffness.…”