The Influence on Modal Parameters of Thin Cylindrical Shell under Bolt Looseness Boundary
Table 6
The disadvantages of different vibration excitation devices for modal test of TCS under under bolt looseness boundary.
Excitation device
Modal parameters of TCS
Disadvantage
Natural frequency
Mode shape
Damping ratio
Hammer
√
√
×
Pulse excitation level can not be precisely controlled and the excitation force varies for each measurement, and double hit can often lead to test errors.
Electromagnetic exciter
×
×
×
The related force sensor will bring added mass and stiffness to TCS, which will severely affect test results of damping and natural frequency.
Piezoelectric ceramic exciter
√
√
×
The excitation energy of piezoelectric ceramic exciter is often insufficient for TCS, which will result in poor response signal with low level of signal noise ratio.
Vibration shaker
√
√
√
Excitation frequencies are not that high, which are often limited to 1 Hz~3000 Hz, and the test procedures are often complicated.
