Author(s): I. J. Jordaan; J. Wells; J. Xiao; A. Derradji-Aouat
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Abstract: At very slow loading rates, ice will creep; as the rate is increased, microstructural changes occur and the rate of creep is enhanced as a result. These microstructural changes are referred to as “damage”. As the rate of loading is increased further, the damage becomes localized into a layer adjacent to the indentor. This layer is associated with “high-pressure zones” (hpz’s). A bulb of pressure develops over these zones with values up to 100 MPa at the centre. Processes within the layer vary with distance from the centre; microfracturing and recrystallization occur near the outside with recrystallization and pressure melting (it is supposed) along grain boundaries in the central part. Cyclic loading can result since the cycle of pressure softening and subsequent hardening upon release of the pressure results in a repetitive cycle. An analysis has been performed using the ABAQUS computer program that encapsulates the principal features of the process. Some results of this analysis are given. It is also shown that the mechanics can be scaled geometrically without any basic change. This explains why the hpz’s are found over widely differing scales. Laboratory and field data involving cyclic loading, including Molikpaq and medium scale data, are reviewed and discussed in the context of feedback mechanisms and iceinduced vibration. Finally, data and results from impact tests on other materials, as well as dynamic recrystallization at high speeds are reviewed and discussed in the context of ice compressive failure.
Year: 2008