Study On The Influencing Factors Of The Fiber Optic Acoustic Emission Detection

With today's science and technology continued to deepen, the country's infrastructure construction is in a stage of rapid development. Therefore the reliable non-destructive technology of health assessment and flaw detection for the concrete structure of is of great significance.The application that use of fiber materials to evaluate the integrity of material structure and monitor structural health has been the concern of all researchers. So in this paper besides brief introduction of the acoustic emission (AE) mechanism, the fundamental characteristics of the sound waves propagating in the solid and the interaction between acoustic waves and optical fiber, the focuses is the experimental study of the three factors which are characteristics of the structure, phase and direction of the sensitivity of fiber optic sensor that affect fiber optic sensor for the acoustic emission detection. Firstly, study on the different structures of the fiber optic AE sensor. The characteristics of that is analyzed, the advantages of the different interferometers is combined to structure new fiber optic AE sensor to improve detection sensitivity, and different environment and conditions for the fiber optic acoustic emission sensors are given. Secondly, the phase of fiber optic interferometer is researched. The theoretical basis that using the inverse piezoelectric effect of PZT to change the fiber length further changes its phase is proposed and static phase modulation of the fiber optic interferometer is completed by the experiment, further more the fiber-phase modulation coefficient is modified. That provides an experimental basis for the engineering application of the same type of fiber-phase modulation PZT. Finally, the content of this part is the sensitivity of direction of the fiber optic sensor. the methods of Wavelet analysis is used to multi-scale decomposition, filtering and noise reduction for the AE signal which is detected by the fiber optic sensors, the frequency characteristic of seven different directions' AE signals on the three-dimensional stone is extracted, the corresponding frequency amplitude sizes are analyzed in the same dominant frequency signals, and then the distribution of the sensitivity of direction is given. To lay the foundation for further study the internal AE source location, internal cracks and fracture situation analysis in the concrete.