Environmental Engineering Reference
In-Depth Information
Fig. 9.26 Strain versus time
curve of the blade
Fig. 9.27 Strain versus force
curve of the blade
9.4.2.2 Results of PZT Transformer
The eight PZT sensors were attached to a data acquisition system and recorded to a
laptop computer. The data were filtered and analyzed with MATLAB software,
employing an FIR-based high pass filter of 60 Hz to reduce noise. By establishing
a threshold of 4 mV, acoustic emission events whose RMS amplitude exceeded
this value could be logged for further analysis. Data from each event were also
collected, including arrival time, event duration, rise time, and peak value. The
counts of the number of events that occurred according to each sensor versus time
in the static loading tests are displayed in Fig.
9.28
.
In the first loading test, sensors 1 and 7 registered no emissions and in both
loading tests sensor 5 most frequently detected emissions. Sensor 5 was also the
closest sensor to the point of failure on the surface of the blade. Between the first
