Strain-Rate and Grain‒Size Effects in Ice

• Published in: Journal of Glaciology
• Main Author: Cole, David M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1987
• Subjects: Journal of Glaciology
• Online Access: http://dx.doi.org/10.1017/s0022143000008844; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022143000008844

Abstract This paper presents and discusses the results of constant deformation-rate tests on laboratory-prepared polycrystalline ice. Strain-rates ranged from 10 −7 to 10 −1 s −1 , grain–size ranged from 1.5 to 5.8 mm, and the test temperature was −5°C. At strain-rates between 10 −7 and 10 −3 s −1 , the stress-strain-rate relationship followed a power law with an exponent of n = 4.3 calculated without regard to grain-size. However, a reversal in the grain-size effect was observed: below a transition point near 4 × 10 −6 s −1 the peak stress increased with increasing grain-size, while above the transition point the peak stress decreased with increasing grain-size. This latter trend persisted to the highest strain-rates observed. At strain-rates above 10 −3 s −1 the peak stress became independent of strain-rate. The unusual trends exhibited at the lower strain-rates are attributed to the influence of the grain-size on the balance of the operative deformation mechanisms. Dynamic recrystallization appears to intervene in the case of the finer-grained material and serves to lower the peak stress. At comparable strain-rates, however, the large-grained material still experiences internal micro-fracturing, and thin sections reveal extensive deformation in the grain-boundary regions that is quite unlike the appearance of the strain-induced boundary migration characteristic of the fine-grained material.