482
K. Zhang et al.
Fig. 42.6 The distribution of frequency bands energy of AE signals caused by debris cloud impact
W E E =
−
6
j=1
p j log 2 ( p j )
− log 2 (1/6)
(42.6)
The characteristic value changes with the impact velocity is shown in Fig. 42.7.
The entropy value increases with the initial velocity of the projectile. The value
reflects the spectrum characteristics of debris cloud impact signals: the closer the
value is to 0, the more concentrated signals distribution in frequency domain; the
closer the value is to 1, the more uniform signals distribution in frequency domain.
Fig. 42.7 Wavelet packet
energy entropy versus
projectile initial velocity