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34 SAMC
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T • Annual report 2012
Fig. 31. The multi-degree of freedom structure from the DIIV test campaign, with adjustable masses and stiffness of the
test rig, enabled the researchers to capture a range of natural frequencies to be configured. Vibrations were measured
by the sensors deployed on the lower part of the structure.
Fig. 32. The ice force and response of the structure change with increasing velocity. At certain velocities, the forces are
severely increased. Researchers also observed that the structural response frequencies change. The horizontal red
lines indicate the natural frequencies of the structure, so that any indication of vibrations at those frequencies could be
investigated more thoroughly.
Ice forces identified inversely frommeasured response. The velocity was gradually increased for both tests
Force [N]
Force-diagram
Time [s]
Time [s]
Response –spectra