Servo-Hydraulic Pin Loading Device (HPLD) for in Situ Ice Testing

Abstract

A hydraulic test instrument has been designed and fabricated to perform fracture experiments on edge-cracked pin-loaded floating square plates of ice. Because ice has large grains relative to metals, large specimen sizes are necessary. To preserve the natural temperature and salinity distributions in the ice sheet, the fracture tests must be performed in situ. the servohydraulic in situ pin loading device described in this paper uses a two-actuator feedback-control configuration to accurately impart a load while actively controlling the moment about the estimated neutral axis of the ice sheet to be zero. This system can be used to perform tests in both load and displacement control and can perform low load level, high frequency tests not previously possible with a pneumatic flatjack system. Stable crack growth was observed under displacement control.