A mechanical model of creep of polycrystalline ice

Abstract

The paper presents a two dimensional mechanical model for the deformation and creep of polycrystalline ice that takes into account the elastic and plastic deformations of each crystal.The model applies to many cases of creep so that the different types of creep curves have been defined during the transitory, permanent and accelerated phases and the corresponding creep laws have been derived. The mechanics of cracking are not analyzed in this paper.The expression for the plastic deformation in this model is based on the principle of multiplication of mobile dislocations and Glen's law for permanent creep. The corresponding mathematical expression for creep without cracking, called α creep, is shown to represent, at the lower limit, the flow of glaciers and is shown to verify a large variety of measured creep curves either in monocrystals or in polycrystalline ice.The elastic deformations in this model bring to light the important role played by delayed elasticity, which is shown by experimental data but has never been elucidated previously.