Research On Multi-source Excitation&FBG Sensing Technology Andapplications Of Mechanical Damage Detection

The traditional ultrasonic nondestructive testing which is based on the lineartheory and used to evaluate material properties and material damage, is not sensitiveto the micro-damage.However,the theoretical analysis and experimental results showthat the structure in the micro-damage will have certain structural nonlinear.So thestudy on multi-source excitation&FBG detection technology which is based on thetheory of nonlinear ultrasound has important implications.This paper is dedicated tothe research of multi-source excitation&FBG detection technology of the aluminumalloy plate and the detailed content shows as follows.(1) The static and dynamic characteristics analysis of piezoelectric actuator.Thenumerical results of the static and dynamic characteristics analysis by COMSOLshow that the relation between the output displacement and the input voltage is linearand the piezoelectric actuator has good dynamic response characteristics.(2) The study of the aluminum plate structure response under the singleexcitation.It gives the curve of the input frequency (1-100kHz and50-2000Hz) andthe structural response amplitude,and proposes that the received signal’s amplitude ofFBG has direct relationship with the input voltage of piezoelectric actuator based onthe single excitation&FBG detection system.Furthermore,when the axial of FBGcoincides with the axis of the ultrasonic sound field,the received signal’s amplitude ofFBG should be the strongest.(3) Crack identification of the multi-source excitation&FBG detectiontechnology.It is proved that the multi-source excitation&FBG detection technologyused to artificial micro-crack detection in aluminum plate is feasible throughexperiment research.In addition,It was concluded that when the structure is intact, themodulation of the received signal will not appear and the amplitude of the dominantfrequency component and the voltage of the input signal have positive correlation.Onthe contrary,When the structural have damage cracks,the modulation signal willproduce new frequency components.(4) Study on the impact of excitation signal parameters of the multi-sourceexcitation&FBG detection technology.Experimental results show that when the voltage of low-frequency vibration excitation increases, the tendency of the side-lobeamplitude and the modulation factor X increase monotonously,the high-frequencycomponent amplitude is almost the same but the low-frequency component amplitudeincreases linearly.At the same time,when the voltage of high-frequency vibrationexcitation increases, the tendency of the side-lobe amplitude increases monotonously,the modulation factor X changes randomly,the high-frequency component amplitudeincreases linearly but the low-frequency component amplitude is almost thesame.Therefore,the frequency of multi-source excitation should be selected thefrequency point which can cause the response amplitude of the structure larger.Andthe voltage of multi-source excitation should be strong as far as possible.(5) Research on the impact of FBG layout position of the multi-source excitation&FBG detection technology.Experimental studies have shown that when the axial ofFBG coincides with the axis of the ultrasonic sound field,the modulation effect ismore conducive to be improved.