| Abstract | Data from ice impact tests using a large double-pendulum apparatus have been analyzed and high spatial resolution pressure-pattern images, recorded at rates of 500 images per second, are presented. The freshwater ice samples were grown in the lab and were cone-shaped with a base diameter of 1 m and base angle of 30o. Energy of the impacts was controlled by varying the ‘drop angle’ of the pendulum arms. Patterns of high-pressure zones (HPZ's, consisting of relatively intact ice) that were surrounded by low-pressure zones (LPZ's, i.e. shattered spall debris), due to spallation of ice from the HPZ's, were evident. Most of the tests showed consistent results, where the instantaneous average interface pressure of the contact area was relatively consistent (5–8.5 MPa), and found to be constant or slightly increasing with contact area as tests progressed. Maximum pressures (i.e. associated with HPZ's) were in the 35–52 MPa range and generally increased with contact area as tests progressed. Peak loads during tests were in the 410–630 kN range. LPZ contact areas were generally 2–6 times the size of the HPZ contact areas. In most tests the time-averaged total load was shared roughly equally between HPZ and LPZ contact areas. The peak loads were found to be directly proportional to the maximum HPZ contact areas. The detailed characteristics of the total load time series records were generally reflected in the corresponding HPZ load time series records much more so than in the LPZ load time series records. Average pressures on the HPZ's and LPZ's were remarkably consistent, 21 MPa and 3.7 MPa respectively. For all tests the actual average pressure was roughly constant, or slightly increasing, while the nominal pressure followed a decreasing trend. |
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