Author(s): Ekaterina Kim; Erland Ulson
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Keywords: No Keywords
Abstract: Indentation tests provide a simple means to study the behavior of ice under a compressive stress field. Many researchers have conducted small- and medium-scale indentation tests in the laboratory and in the field, to understand the process of ice crushing. The term crushing is generally understood as either ductile (elastic and creep) deformation or brittle failure of ice, and it operates during either the movement of an indenter into ice or vice versa. A time-history plot of the interaction force is often converted to a pressure-area (PA) relationship. Ice PA curves are widely used in design of ships and offshore structures. Despite their usage, and despite many attempts to relate the empirical results to theory, the mechanics underlying PA curves is not clearly understood. The present study is motivated by findings of T. J. O. Sanderson in 1988 who noted that pressure (p) is proportional to contact area (A) as p=CAq (where C and q<0 are constants for the specific ice under examination) and by experimental findings of D. M. Masterson et al. in 1992, who pointed out that that indenter curvature affects the pressures measured. In the present work, indentation of freshwater polycrystalline ice beneath spherical indenters with radii 5 mm – 2300 mm is addressed. Data from earlier small- and medium-scale tests have been reanalyzed. Sanderson’s relation is found to hold for indenters submerged to their diameters. The analysis revealed that the index q<0 is almost independent of the indenter radius, but that C increases with increasing radius. The paper presents an explanation of these experimental findings in terms of the strain softening character of ice and compares ice crushing behavior with that of metals and ceramics.
Year: 2014