The effect of notch depth on the fracture toughness of freshwater ice

Abstract

Fracture toughness tests have been performed on polycrystalline freshwater ice of two grain sizes (3.4 and 7.3 mm) at loading rates of 10 kPa/m s −1 and a temperature of − 10° C. The sample geometry used was the circumferentially notched cylinder, and notch depths were varied from 2.54 to 17.8 mm (2.8 to 19.6% of the sample diameter). For notch depths greater than 5.1 mm no variation of toughness with notch depth was found for either the large or the small grained samples. For notch depths of 2.54 mm none of the samples broke at the notch. The results indicate that notches greater than 5.1 mm in depth are sufficiently deep to allow fully polycrystalline behavior in this size and geometry of sample, for the range of grain sizes studied. This confirms that the variation of toughness with grain size noted by Nixon and Schulson (1986a) is not an artefact of the sample geometry, and thus lends support to their model of microcrack toughening in freshwater ice (Nixon and Schulson, 1987).