Application of Aigtek power amplifier in multi-source excitation research of mechanical plate structure damage
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Experiment Name: Study on the response characteristics of fiber Bragg grating under multi-source excitation
Purpose:
The distributed strain signal measured by FBG reveals the strain sensing characteristics of FBG under multi-source excitation.
Experimental equipment: signal generator, ATA-2041 power amplifier , tunable laser light source, oscilloscope, photodetector
Experimental content:
The focus is on studying the influence of the frequency, phase, amplitude, position and other factors of the two excitation source signals on the FBG response characteristics, providing a parameter basis for subsequent damage location.
Experimental process:
This scheme mainly studies the excitation parameter characteristics of isotropic plates. The research object is 6061 aluminum alloy thin plate with a size of 400mmx400mmxlmm.
Build a multi-source excitation detection system:
The detection system scheme of multi-source excitation-fiber Bragg grating sensing based on isotropic plate structure is shown in the figure, which mainly includes the excitation part and the FBG demodulation part. The excitation part includes a signal generator and a high-voltage amplifier (ATA-2041), and the FBG demodulation part mainly includes a broadband coupler, an adjustable laser light source, a photodetector, and an oscilloscope. The signal of channel 1 of the signal generator is directly applied to the piezoelectric sheet, and the signal of channel 2 is applied to the piezoelectric sheet after the signal amplifier. Using the inverse piezoelectric effect, a strain wave is generated in the plate structure, and the response is received by the FBG sensor. After demodulation, it is converted into an electrical signal by the photodetector and displayed on the oscilloscope.
Experimental results:
(1) Excitation size parameters
Comparison of the excitation effects of piezoelectric sheets A and B with excitation size diameters of 20mm and 10mm respectively: When piezoelectric sheets A and B act alone, the response curve on #1FBG is obtained. As shown in the figure, from 0-33kHz, the output response under the action of piezoelectric sheet A is much greater than the output response under the action of piezoelectric sheet B. In the range above 33kHz-100kHz, except for individual frequency points that may have sudden changes due to environmental factors, the overall change law remains basically unchanged. It can be seen that when the thickness of the component and the excitation amplitude parameters are the same, the larger the diameter, the larger the response amplitude. Therefore, to obtain a larger response amplitude, a larger diameter size can be appropriately selected. However, if the diameter is too large, the influence of the size cannot be ignored during the analysis process.
Incentive effects at different sizes
(2) Excitation angle parameters
Comparison of the excitation effects of piezoelectric sheets A and D with excitation angles of 0 and 10 degrees respectively: When piezoelectric sheets A and D act alone, the response curve on #1FBG is shown in the figure. The response obtained when A is excited in the axial direction is mostly better than that when D is excited in the 10-degree direction. The difference is that some frequency bands have large deviations; some frequency bands have small deviations. It can be seen that the excitation angle has a certain influence on the FBG detection signal.
#1FBG response curves at different excitation angles
Under the same excitation conditions, the FBG sensing response effects at different positions are compared. As shown in the figure, since the excitation A is along the axis direction of #1FBG, the black curve in Figure a represents the larger response under the action of excitation A. Similarly, since the excitation C is along the axis direction of #2FBG, the red curve in Figure b represents the larger response under the action of excitation C. It can be seen that no matter #1FBG or #2FBG, the response effect is better when it is facing the detection position of the excitation element.
FBG response curves at different positions
In summary, it can be seen that the relative position of the excitation and FBG has a certain influence on the detection results. When arranging the excitation elements, it is best to place them on the FBG sensing axis as much as possible, and the detection effect is good. However, in distributed detection, it is impossible to take into account the positions of multiple FBGs and excitation elements at the same time. Therefore, in order to reduce the impact of the angle factor, the frequency band with a smaller angle factor deviation can be selected as the excitation frequency.
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