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Importance of Plastic Deformation in Regelation of Ice

Published online by Cambridge University Press:  30 January 2017

K. Tusima and
S. Tozuka
K. Tusima
Affiliation:
Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan 060
S. Tozuka
Affiliation:
Institute of Low Temperature Science, Hokkaido University, Sapporo, Japan 060
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Abstract

It is well known that regelation may occur by pressure-melting in front of a wire and refreezing at the rear. The velocity of the wire has been observed to have values ranging from 10–5 to 10–1 mm/s. However, there have always been large discrepancies between experiments and any theory based on this mechanism, and, when moving at a comparable velocity, hard balls slid on an ice surface leave grooves made by plastic deformation. So, we conducted experiments to test whether regelation phenomena might be explained by plastic deformation of ice around the wire.

Information

Type
Research Article
Information
Journal of Glaciology , Volume 23 , Issue 89 , 1979, pp. 422 - 423
Copyright
Copyright © International Glaciological Society 1979

  • (1) Two single crystals of ice were vertically connected to a rigid base and a loop of copper was hung over the top of the ice with a weight attached. The velocity in the lower ice block which had its basal plane horizontal was 20% faster than that in the upper ice block where the basal plane was vertical, this result strongly suggests plastic deformation as the mechanism of regelation.

  • (2) An elliptical wire which had its long axis vertical moved five times more rapidly than one with its long axis horizontal, and when the long axis is inclined, the wire was deflected along the direction of the long axis.

  • (3) Under the same conditions of wire diameter and load, the velocity only showed a difference of a factor or two in spite of changes in thermal conductivity of the wire by more than a thousand times. These small differences of velocity when compared to thermal conductivity may be explained by the surface roughness, flexibility of the wire, and other physical properties of the interface.

  • (4) A thin wire moved faster than a thick wire even if the same pressure was applied. Under constant load, the velocity decreased as R–n where R is the radius of the wire and n takes a value between 1.3 and 2.

    These four effects suggest strongly that plastic deformation is responsible as they cannot be understood by the classical theory of regelation. However other observations show that we cannot completely give up the classical theory.

  • (5) Many cracks occurred in the ice in front of the wire and then filled by melt water, and melt water moved upwards around the wire in places. If dyes were dropped on the top surface of ice, coloured water diffused to the rear of the wire. These observations give fine evidence of the existence of melt water.

  • (6) Different weights were hung on each end of the wire and the weight difference at which the wire started to slide horizontally was determined. Friction coefficients of c. 0.001 for nylon and 0.01 for copper were obtained. The coefficient for silk string, however, was extremely high so that the string could not move even though string showed regelative movement as compared to nylon.

It may be concluded that part of the regelation occurred by plastic deformation although the classical theory cannot be completely abandoned as a mechanism of regelation.