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This paper assesses the relative accuracy of a number of techniques that are capable of predicting a wide range of creep properties. The techniques studied in this paper include the 4-Θ, 6-θ, CRISPEN, Omega and CDM methodologies. The parameters of these models were estimated from short-term creep property data on 1CrMoV steel and these estimated models were then used to predict the known longer-term creep properties of this steel. It was found that the CDM approach yielded predicted times to failure that were wholly inadequate. The 6-θ approach was best for predicting long term times to failure. The best minimum creep rate predictions came from using either the 4-Θ, or the CRISPEN or the Omega technique. Finally, times to small strains were best predicted using the 6-θ and CRISPEN techniques. [ABSTRACT FROM AUTHOR]

A series of three-point bend tests using single edge notched testpieces of pure polycrystalline ice have been performed at three different temperatures (-20°C, -30°C and -40°C). The displacement rate was varied from 1 mm/min to 100 mm/min, producing the crack tip strain rates from about 10-3 to 10-1 s-1. The results show that (a) the fracture toughness of pure polycrystalline ice given by the critical stress intensity factor (KIC) is much lower than that measured from the J—integral under identical conditions; (b) from the determination of KIC, the fracture toughness of pure polycrystalline ice decreases with increasing strain rate and there is good power law relationship between them; (c) from the measurement of the J—integral, a different tendency was appeared: when the crack tip strain rate exceeds a critical value of 6 × 10-3 s-1, the fracture toughness is almost constant but when the crack tip strain rate is less than this value, the fracture toughness increases with decreasing crack tip strain rate. Re-examination of the mechanisms of rate-dependent fracture toughness of pure polycrystalline ice shows that the effect of strain rate is related not only to the blunting of crack tips due to plasticity, creep and stress relaxation but also to the nucleation and growth of microcracks in the specimen. [ABSTRACT FROM AUTHOR]