Mechanisms and Theory of Indentation of Ice Plates

Abstract

AbstractThis 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.