Mechanisms and Theory of Indentation of Ice Plates

Abstract

This study gives the results and interpretation of tests made in a cold room on ice plates held vertically in a press and indented at various speeds with a rectangular indentor. These plates, 81 cm square, were held and frozen solid to a steel frame to represent semi-infinite ice sheets. The tests were carried out at — 10°C with indentation speeds varying from 6 × 10 -5 cm/s to 3 cm/s.It was found that the nominal pressure of indentation varies as a function of loading rates in a manner similar to that of the strength of S2 ice in uniaxial compression. The pressure increases rapidly with loading rates up to its maximum value at a strain-rate of 5 × 10-4 S-1. From there on, the pressure decreases. In the ductile range and up to the point of maximum pressure, a theoretical model was proposed where the theory of Hill (1950) of indentation of an ideal plastic body can be applied to predict an indentation pressure close to three times that of the uniaxial crushing strength.The tests did not show any so-called “ratio effect” caused by the ratio of the indentor width to the plane thickness. This effect could be explained by the influence of the geometry of the indentor on the strain-rate.

A Critical Review of Constitutive Models Applied to Ice-Crushing Simulations

“…Shi et al [51] observed that while the constitutive model accurately captures the compressive creep behaviour under low to moderate strain rates, it potentially overestimates ice strength during iceberg-ship collisions, which involve considerably higher strain rates compared to creep tests. According to Shi et al [51], this overestimation arises because the model does not accommodate the transition from ductile to brittle behaviour, resulting in a continuous exponential growth in stress with strain rate, even past the transition point, after which, based on empirical evidence, the ice strength should plateau or slightly decrease and then increase, with a noticeably lower rate [9,[52][53][54].…”

Experimental Investigation of Ice Loads on Structures during Quasi-Static Compression Tests

“…A widely accepted classical empirical formula was proposed by Korzhavin [1], who conducted extensive research on the characteristics of river ice loads based on measurements of dynamic and static pressures in Siberia. Similarly, Croasdale, Michel, Frederking, and other researchers employed similar on-site or experimental measurement methods [2][3][4], with variations in the types of ice studied, such as lake ice and freshwater ice. Currently, several classification societies and standard organizations, including Bureau Veritas (BV) [5] and the International Organization for Standardization (ISO) [6] recommend using empirically based methods for assessing ice loads.…”