Statistical characteristics for the strain-dependent density and the spatial position for deformation-induced cracks in columnar-grain ice

Abstract

Observations on the spatial distribution and on the strain dependence of the crack density are given for cracks formed during compressive, unidirectional, constantstrain-rate deform~tion of column~r-grain ice. Sp~fim~~s, in th~~~1in-size c;ange of a~out 2 9 mm, were stramed at the nom mal rates of 10 . ,10 and 10 . s at 10 C. The aXIsof hexagonal crystallographic symmetry of each specimen grain tended to be in the plane perpendicular to the long direction of the grains and to have a random orientation in that plane. For stress applied perpendicular to the long direction of the grains, the deformation was practically two-dimensional. It was found that the log-normal distribution function provided a good approximation to the strain dependence of the crack density. Statistical characteristics of the distribution had a maximum in the same range of strain rate as found for the strength of columnar-grain ice. Analysis of tbe spatial distribution of the cracks indicated some deviation from randomness for specimens of grain-size less than 5 mm and total strain less than 50 x 10-4 . The observations provide further evidence that crack formation under the experimental conditions is a random process.