Fiber Bragg Grating Acoustic Emission Sensing System Design Based On LabVIEW

Fiber Bragg grating acoustic emission sensing system is promising in the structural health monitoring field. The paper researches on the fiber Bragg grating acoustic emission sensing system, including the analysis of the sensing mechanism between fiber Bragg grating and acoustic emission wave, the design of fiber Bragg grating acoustic emission sensors, the feature parameters extraction of acoustic emission signal and the design of acoustic emission system software in PC. The research content is divided into the following four aspects:1. Research theoretically on the acting mechanism between fiber Bragg grating and acoustic emission wave. The reflection spectrum characteristics of fiber Bragg grating are numerically calculated based on the coupling theory and the propagation matrix method. When the ratios between grating gauge length and the acoustic emission wavelength are different, the modulation effects from acoustic emission wave on fiber Bragg grating are researched, including the shape of reflection spectra, the central wavelength, the peak refractive index and the sidelope suppression ratio.2. Research experimentally on the fiber Bragg grating acoustic emission sensors with high sensing features after the theoretical research in the first chapter. Sensing characteristics are researched using different packaging materials and structures. The fiber Bragg grating acoustic emission sensors without the effects from the strain field generated by the distortions of the detected structure are designed. The sensing system is established based on3-dB bandwidth method. The detection sensitivity of the designed sensors are measured using the standard signal. The method of improving the signal noise ratio is researched to optimize the system.3. Features extraction and analysis of the acoustic emission signal detected by fiber Bragg grating. The methods, including parameter waveform analysis, the parameter correlation coefficient judge and the fatigue damage estimation through the Bayesian Statistics, are studied to extract and analyze the feature. The application of the main parameters in acoustic emission signal proceeding is analyzed. The method of reducing the noise is discussed for better features extraction of the acoustic emission signal.4. Software in PC of fiber Bragg grating acoustic emission system is designed based on Lab VIEW. The structure of software in PC and the programming process are analyzed. The important VI sub model and DLL functions are introduced. Finally, the software in PC is programmed with the functions of hardware parameter setup, high-speed sampling of acoustic emission signal, multi-channel synchronization analysis and proceeding, data saving, features and waveforms display.