| Résumé | Using indentation experiments on freshwater ice as a starting point, numerical models for ice damage, clearing and flexure have been developed together with a mechanical model of ice-induced vibration. Indentation speeds were such as to cover a range of ice behaviour, from essentially pure crushing to situations where both flexural failure and crushing took place. Modelling of the damage process was used to estimate the thickness and equivalent viscosity of the crushed layer under various circumstances, and also to demonstrate the change in pressure distributions at different stages in the loading cycle. Crushing is complicated by the presence of spalling as well as distributed damage. Analysis of these effects and associated local high pressure zones is important for determining when crushing failure occurs. With regard to flexural failure, important issues that are dealt with are the influence of local crushing, the effect of speed and the hydrodynamic effect on the distance at which circumferential cracks are formed. The distance to primary flexural cracks was predicted successfully using analytical plate bending solutions and an equivalent beam model was calibrated. Hydrodynamic effects did not account for observed secondary cracks at shorter distances. A simple mechanical model was developed to integrate the above behaviour with regard to crushing and flexure. The model includes the structural and far field ice responses, and was successful in simulating peak forces and the frequency of dynamic loading cycles in a variety of ice and loading conditions. |
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