112 M.J. Ward et al. 0 193.5 0 100 200 300 400 30.5 31 31.5 32 32.5 33 194 194.5 195 0.8 1 1.2 1.4 1.6 50 100 150 200 Time of experiment [s] (a) (b) Time [s] Amplitude value at: 83 kHz over time Angular Position [deg] Amplitude Velocity [Hz] 250 300 350 0 30 32 34 36 50 100 150 200 Time of experiment [s] Determining Radial Position Spectrogram Amplitude 250 300 350 Fig. 11.10 Probing frequency amplitude with time-synced angular velocity data (a) and a magnified view with time synced angular position data (b) (a) (b) Fig. 11.11 Binned statistical data for radial (a) and angular position (b) Angular position was determined by matching peak amplitudes in the probing line frequency data with specific times and their associated angular positions. The primary peak amplitude appeared where expected, but there was also an unexpected secondary peak around 245ı. Further investigation revealed this secondary peak to be a small extra motion in the damage mechanism due to mechanical limitations in the construction of the damage. This extra signal in a simple test piece emphasizes the need for an accurate constitutive model of the test article. The test described above was repeated 10 times to gain some statistical information about the method with the results complied in Fig. 11.11.
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