| Résumé | The CCGS Terry Fox field trials produced impacts with growlers, bergy bits and a small iceberg over a range of velocities. Ice mass ranged from 30 t to 22,000 t and velocity from 0.1 m/s to 6.6 m/s. Results have been analysed looking at the effect of speed and ice mass on the measured impact force. There was considerable scatter in the results until the rate of the rise time of the measured impact force was taken into consideration. A trend of increasing impact force with loading rate was observed. To further examine this aspect of rate effect on impact forces, medium scale field indentation tests were also studied, since they were done to simulate full scale impact loading. The tests were done at a number of locations in the Arctic on iceberg ice and multi-year ice, and also showed a rate effect. For the CCGS Terry Fox the maximum force related to the loading rate with the following expression where F is force in MN and is loading rate in MN/s. The expression is supported by data up to a maximum force of 6 MN. Higher forces at comparable loading rates were achieved in the field indentation tests due to higher loading system capacity and better ice-indentor contact. |
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