Study On Fiber Laser Acoustic Emission System For Concrete Damage Location

The concrete material is the important part of the transportation infrastructure,plays an important role in engineering construction.Recently,because the collapse of large concrete structures often results in loss of life and property,it is particularly important to conduct health monitoring.Damage location is an important index of structural health monitoring.Accurate location of damage can provide important information for maintenance.Optical fiber acoustic emission sensor technology as a new means of structural damage location,with easy networking,anti electromagnetic interference and real-time dynamic detection of weak signal and other advantages,is widely used in the field of traffic structure health monitoring.An intensity type fiber laser acoustic emission system based on distributed feedback fiber laser is designed and applied to the acoustic emission source location of traffic engineering infrastructure concrete structures.The main research work and achievements are as follows:Firstly,this thesis reviews and summarizes the present research situation and expectation of AE technology and acoustic emission detection and localization technology of concrete structures at home and abroad.The acoustic emission mechanism,propagation characteristics of acoustic emission wave in solid and its signal characteristics are introduced.Secondly,this thesis designs an acoustic emission sensor based on the strength properties of DFB fiber laser.The design goal,fabrication technology and packaging technology are described.In order to detect acoustic emission signal in concrete environment,the design and encapsulation of fiber laser acoustic emission sensor are solved.Thirdly,a data acquisition subsystem is designed and built.The experiment analyzes the minimum resolution optical power of the acquisition system.The acoustic emission signal processing method and location algorithm are introduced,and the wavelet packet energy feature extraction program is compiled.The design and construction of fiber laser acoustic emission system are completed.At last,the acoustic emission sensors were tested and the two-dimensional acoustic emission sources of concrete structure with different sizes were located based on the fiber laser acoustic emission system.The acoustic emission response of bare laser and patch type DFB fiber laser acoustic emission sensor has been compared and analyzed by laboratory test.The sensitivity of the patch type DFB fiber laser acoustic emission sensor is calibrated,and the sensitivity error is small.The continuous and abrupt acoustic emission signal was detected by DFB fiber laser acoustic emission sensor.Using the acoustic emission source location system based on genetic algorithm,the damage plane localization experiments of concrete structures with different sizes were carried out.The acoustic emission source localization method of DFB fiber laser sensor had been tested and verified,and the acoustic emission source reached a high precision location.