Vertical and inclined edge-indentation of freshwater ice sheets

Abstract

A series of indentation experiments was performed with vertical and downward-breaking inclined indentors in columnar S2 freshwater ice in the ice tank of the Institute for Marine Dynamics. Indentor width ( D), indentor angle (α), indentor velocity ( V) and ice sheet thickness ( h) were varied for a total of 94 tests. Indentor loads, accelerations, displacement, and carriage speed were measured. Significant vibrations were induced in the structure by crushing failure of the ice when the indentor was vertical. Crushing frequency varied proportionately with velocity at low velocities. At higher velocities the response became locked at the natural frequency of thestructure. For the inclined indentation tests, mixed failure modes of crushing and flexural failure were observed. The failure mode underwent a transition from bending to crushing as velocity increased, ice thickness increased, and indentor angle decreased. The horizontal forces exerted on the inclined indentors increased dramatically as the indentor approached vertical.