Author(s): Don Spencer; Brian Hill

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Abstract: An icebreaking ship passing through an ice field uses its forward momentum to force its bow up onto the ice sheet where its weight can fail the ice in flexure. Clearly, the process involves deformation of the ice and the energy expended by the vessel is proportional to the force times the distance travelled. Scale models of these ships are tested in ice basins to provide the designers with engineering data on the expected performance of the prototype. For the results to be accurate it is necessary for the model ice to correctly simulate all the significant processes involved. Enkvist (1972) was one of the first to show that it was not sufficient to consider the failure force alone but the work done by the force. From an elastic theory he demonstrated that the energy expended during icebreaking was proportional to a, 2fE, where a, is the flexural strength and E is the elastic modulus. Sea ice have Eta, ratios in the range of 2000 to 8000. Enkvist suggested that the model ice, in use then, had much too Iowa modulus of elastiCity which resulted in excessive energy being transferred to the ice sheet, yielding unrealistically high resistance. Based on this premise, ice basins around the world strove to improve the properties of their model ice, in particular the elastic properties.

DOI:

Year: 1994