Plastic deformation of single crystal ice

Abstract

Single crystal ice was deformed in tension at constant strain rates at temperatures between − 42°C and 0°C. For shear stresses below 100 psi and nominal strains less than 25 per cent (starting with asgrown crystals), basal slip was the primary mechanism of deformation. No preferred crystallographic slip direction or work hardening were observed. The rate of basal glide in the direction of maximum shear stress is given by γ ̇ = (2.25 ± 1.5) × 10 7γτ n(γ) exp(−14.3 ± 1.5 × 10 3 RT ) min −1 , where γ is the resolved shear strain, τ is the resolved shear stress (psi) and n equals 2.5 for low strains and decreases with strain, with an average value of about 2.0 for nominal strains less than 25 per cent. Annealing after deformation has no effect on subsequent deformation behavior of ice. Etch pit evidence indicates the existence and activity of secondary slip systems during deformation. It is proposed that the observed plastic deformation of ice results from glide of dislocations whose velocity is limited by a temperature activated process.