DISLOCATION MECHANISMS OF PLASTIC DEFORMATION OF ICE

A. Fukuda , T. Hondoh , A. Higashi

Characters and properties of dislocations in ice are thoroughly reviewed on the basis of the knowledge hitherto obtained by the X-ray topographic method as well as recently found dynamical behavior. Extremely low energy of the faults on the basal plane found by the method leads us to conclude that al1 of the dislocations in ice should be extended as wide as several tens to one hundred nano-meter, depending upon their Burgers vectors, on the basal plane. The motion of dislocations, therefore, is severely restricted on the basal plane. The strong anisotropy of plastic deformation of ice single crystal is interpreted in terms of this restriction ; i.e., the primary slip caused by glide motion of the (1/3)<11[MATH]0> dislocations on (0001) is a unique easy slip system in ice because glide planes of the other dislocations do not coincide with their extended plane or the basal plane. It is also shown that the secondary slip system <11[MATH]0>/{10[MATH]0} is due to glide motion of the constricted (1/3)<11[MATH]0> dislocations on the-prismatic planes {10[MATH]0}. Since only very short segments can glide on {10[MATH]0} owing to the tendency of the dislocations to lie on (0001), this slip system is far less easier than the primary one in spite of larger velocities of the segments than the basal glide. In addition to the above two slip systems, which are not responsible for the tensile or compressive deformation along the c-axis, climb mechanism of [0001] or (1/3)<11[MATH]3> dislocations on the basal plane is proposed as the third deformation system in ice. By this mechanism, the ice crystal deforms under uniaxial loading parallel to c-axis at a low rate limited by diffusion process but much faster than by Nabarro-Herring diffusional mechanism.

Domaines: Articles anciens

A. Fukuda, T. Hondoh, A. Higashi. DISLOCATION MECHANISMS OF PLASTIC DEFORMATION OF ICE. Journal de Physique Colloques, 1987, 48 (C1), pp.C1-163-C1-173. ⟨10.1051/jphyscol:1987124⟩. ⟨jpa-00226269⟩