Author(s): B. L. Parsons

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Abstract: Recent experiments have demonstrated that slow stable subcritical crack growth is possible in sea ice warmer than -15°C, but not below this temperature. The implication of this behaviour on risk analysis is explored. In cold sea ice, theory predicts that under a constant applied stress, the probability of failure from crack growth to critical crack length increases with time. This is in contrast with experimental evidence - at a constant applied stress, the probability of ice failure decreases with time. In warm sea ice, however, where slow crack growth is possible, it may be that the probability of failure does increase with time. This depends on the relative magnitudes of the creep power exponent and the Weibull modulus. An expression is developed for time to failure that includes the creep power exponent, the Weibull modulus, the fracture toughness, initial and threshold (for stable crack growth) strength, and the specified level of risk. It is the change with temperature, and damage, of n, the creep power exponent that is the controlling parameter. The competition between the creep crack growth rate and the applied stress rate determines if and when the crack becomes critical. Limits may be put on the value of n that determines when the theoretical prediction of increasing probability of failure with time becomes valid.

DOI:

Year: 1992