Creep behaviour of ice single crystals loaded in torsion explained by dislocation cross-slip

Abstract

Torsion creep experiments are carried out in order to understand the physics of ice plasticity. A dislocation spreading mechanism based on double cross-slip of basal dislocations is proposed to explain the strong plastic anisotropy and the power law relationship between stress and strain rates. The scenario is tested using three-dimensional dislocation dynamics simulations. Numerical investigations give a stress exponent n = 2.3 in agreement with experimental measurements. This dislocation spreading mechanism sheds a new light on the interpretation of former experimental observations.

Keywords:

• dislocation dynamics
• creep
• ice
• cross-slip

Acknowledgements

Fruitful discussions with Dr D. Rodney are gratefully acknowledged. This work was performed under the auspices of the French Centre National de la Recherche Scientifique.