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On the grain-size dependence of secondary creep

Published online by Cambridge University Press:  20 January 2017

Stephen J. Jones  and
Hemming A. M. Chew
Stephen J. Jones
Affiliation:
Fisheries and Environment Canada, National Hydrology Research Institute, Inland Waters Directorate, Snow and Ice Division, 562 Booth Street, Ottawa, Ontario KIA 0E7, Canada
Hemming A. M. Chew
Affiliation:
Fisheries and Environment Canada, National Hydrology Research Institute, Inland Waters Directorate, Snow and Ice Division, 562 Booth Street, Ottawa, Ontario KIA 0E7, Canada
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Abstract

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Information

Type
Correspondence
Information
Journal of Glaciology , Volume 27 , Issue 97 , 1981 , pp. 517 - 518
Copyright
Copyright © International Glaciological Society 1981

The Editor,

Journal of Glaciology

Sir,

In their recent paper Reference Duval and Le GacDuval and Le Gac (1980) show that the permanent creep-rate of polycrystalline ice does not increase with grain-size. We wish to agree with their conclusion by presenting data we have collected at higher strain-rates (5.5 × 10−4 s−1), on laboratory-grown, randomly oriented, polycrystalline ice tested at a constant strain-rate in compression. Figure 1 shows the maximum yield stress reached as a function of grain-size, for the, albeit narrow, range of grain-sizes from 0.8 to 1.8 mm diameter. No significant effect of grain-size is seen. We are extending the results to smaller grain-sizes, but are having difficulty in obtaining small-grain ice which is also air free. We cannot go to much larger grain-sizes because our sample diameter is fixed at 20 mm and our results (Fig. 2) show that the sample diameter should be approximately 12 times the grain diameter for the maximum yield stress to be independent of grain-size. For this reason Duval and Le Gac should be cautious in interpreting their results from samples greater than 7 mm diameter when their sample size is 80 mm. The same comment applies to Reference BakerBaker’s (1978) original work.

Fig. 1.

The maximum yield stress plotted against grain-size, for laboratory-grown polycrystalline ice tested at −10.5°C strain-rate 5.5 × 10−4 s−1, sample diameter 20 mm, sample length 60 mm.

Fig. 2.

The maximum yield stress plotted against the ratio of sample size to grain-size. The grain-size was kept constant at 1.0 mm and the sample diameter was varied. Below a ratio of 12 the yield stress depends on this ratio.

References

Baker, R. W. 1978. The influence of ice-crystal size on creep. Journal of Glaciology, Vol. 21, No. 85, p. 485–500.Google Scholar
Duval, P., and Le Gac, H. 1980. Docs the permanent creep-rate of polycrystalline ice increase with crystal size? Journal of Glaciology, Vol. 25, No. 91, p. 151–57.Google Scholar
Figure 0

Fig. 1. The maximum yield stress plotted against grain-size, for laboratory-grown polycrystalline ice tested at −10.5°C strain-rate 5.5 × 10−4 s−1, sample diameter 20 mm, sample length 60 mm.

Figure 1

Fig. 2. The maximum yield stress plotted against the ratio of sample size to grain-size. The grain-size was kept constant at 1.0 mm and the sample diameter was varied. Below a ratio of 12 the yield stress depends on this ratio.