164527.fig.0018a
(a) PZT 2 sensor signal before Bolt 5 loosening
164527.fig.0018b
(b) PZT 2 sensor signal after Bolt 5 loosening
164527.fig.0018c
(c) PZT 4 sensor signal before Bolt 9 loosening
164527.fig.0018d
(d) PZT 4 sensor signal after Bolt 9 loosening
Figure 18: PZT sensor signal change before and after bolt loosening bolts.