Research On Acoustic Emission Sensing And Monitoring System Based On Fiber Grating

Acoustic emission(AE)is a transient high frequency stress wave which emits under external force or internal injury.Acoustic emission is extremely effective means of non-destructive testing.Now,the measuring of AE signal mainly uses the PZT sensors.However,its application has been limited because of its large scale,narrow bandwidth,susceptible to electromagnetic interference and difficult to make large capacity network.AE sensors based on fiber Bragg grating(FBG)technology has high sensitivity,easy networking and its research value is very important.This paper has detailed studied the basic principles,technical methods,development situation of AE detection and has deeply researched FBG acoustic emission sensing principle and has carried out theoretical analysis and experimental testing comparing to the measuring methods of FBG edge AE and has concluded that this "edge method" is not suitable for AE signal detection which requires high sensitivity.This paper introduces AE signal measurement method with a high sensitive optical fiber grating FP(Fabry-Perot)interference structure and has theoretically analysis optical fiber grating FP acoustic emission sensor for different lengths of optical fiber grating,cavity lengths of FP,modulation depths of refractive index,edge visibility and directs center wavelength of gratings and cavity length of FP interferometer.This paper has designed the package of fiber grating FP acoustic emission sensor,the detection circuit of fiber grating AE signal,AE signal test platform and systematically carried out the test of AE signal with broken pencil,PZT,mechanical shock under different frequencies and amplitudes.We have effectively proved that optical fiber grating AE senor based on FP interference structure has higher sensitivity and better response than optical fiber gratings edge AE sensor.This paper also analyzes injury event determination with the characteristic of Fiber grating FP interference structure AE sensing signal and promotes the study of automatic signal processing algorithm.With accurate numerical simulation,this paper fixed the parameters of FP interference structure,designed sensor package and made integrated high-frequency dynamic optical signal detection circuit.This paper contributes to realize AE sensor networking and the miniaturization of signal monitoring system and promotes practical application of high sensitive optical fiber grating FP structure AE sensor.