Experimental Study of Interaction between Frozen Ice and Elastic Plates

To investigate the influences of structural elasticity on ice-structure interaction process, model tests on interaction of frozen ice and elastic plates was conducted in a low temperature laboratory. Plate elasticity is modeled in the tests through varying the plate thickness. By indentating the elastic flat plate onto frozen ice specimen, the load time history and ice failure modes under different test conditions were recorded. The experimental results show that the interaction process is basically classified by two typical phases, that is, loose contact phase and tight contact phase. The loose contact phase results from uneven contact surface between the plate and ice specimen top. Simple data statistics show that the maximum loose contact displacements are concentrated within the range of 0-1.5mm. During the second tight contact phase some of the time histories of loads and displacements are normal single-stage curves, but some are saw-tooth shaped, exhibiting multi-stage failure modes with occurrence probability about 43.3%. From the tests it is established that stiffer plates (thicker plate) are likely to produce single-stage failure of ice, while more flexible plates (thinner plates) are more likely to result in multi-stage failures of ice. Through comparing video clips, we are able to correlate multi-stage failures with outward ice flaking. Observations show that flaking is concentrated in the 450 direction, thus resulting from shearing failure. This is a local failure mode. As the plate is pressed onto ice specimen further, a new flaking failure may occur. This may happen twice or even more times until finally the whole ice specimen fails. Experimental results show that the slope of load-displacement curve is nearly a constant for the multi-stage failure, indicating the stiffness of the ice-elastic plate coupling system remains unchanged during the tight contact phase. These experimental results may help the designer of an ice-going ship to have a better understanding of the complicated interaction mechanics between ice and ship structure, although the structure under consideration in this paper is simplified to a plate.