Strain and temperature dependence of crack populations in columnar-grain ice

It has been shown that the development of grain-boundary and transgranular crack populations in transverse isotropic columnar-grain ice by a uniaxial compressive stress is a random process. The lognormal distribution function was found to be a good descriptor of the strain dependence of the crack density and of the crack length. It is shown, in the present paper, that the populations are induced in the first 10?2 strain and within the time range for the anelastic strain. These time and strain limits, and the strain-rate, stress, temperature, and grain-size dependence of the characteristics of the crack populations, indicate a two-stage process involving the development of precursors and the formation of cracks. The increasing probability for the formation of grain-boundary cracks with increasing strain rate is consistent with a time-dependent growth of voids and an increase in the associated stress intensity factors. The increasing probability for the formation of transgranular cracks with decreasing stain rate is consistent with an increasing density of dislocations and grain distortion due to shear.Peer reviewed: YesNRC publication: Ye