Test And Analrsis Of Acoustic Singnals Under The Cyclic Loading

As a new motion Nondestructive Testing(NDT) technique, acoustic emissiontechnology detects the signal from active defect itself of the test piece, it is possible toachieve real-time monitoring of the defect, and it can determine the severity of the defectand the remaining life of the device. As a non-contact ultrasonic testing technique in thedetection of metallic materials, Electromagnetic ultrasonic transducer (EMAT) technologyhave been widely used, and especially achieved very good results in the surface crackdetection.First of all, based on the study of generate principle of EMAE and Ultrasonicsignal,taking signal characteristics into consideration, this paper designs the weak acousticemission signal loading Ultrasonic signal experiments to detect the loading conditions, andthe signals make Fourier transform and wavelet transform.We can clearly see two signals ofdifferent frequencies in the frequency domain and We extract and display the featuresegment signal after wavelet transform, so that two different frequency signal is separated.Secondly, based on mastering the signal of wavelet transform.This paper designvibration fatigue in the metal plate and loading ultrasonic signal experiment to capture faintcrackle of acoustic emission signals. After thresholding and FFT transform, the applicationof acoustic nonlinear detection theory, We can separate equipment of nonlinear effects andharmonic acoustic signals, and ultimately determine generating acoustic emissionsignals.This way provide a method for the prevention of early fatigue damage in metalplate.At last, based on the electromagnetic ultrasonic nondestructive testing, This paperdesign electromagnetic ultrasonic experiments in the metal plates with or without defectsand in the metal plates of different defect. We determine whether the defects in the metalplate,in time-domain analysis and frequency-domain analysis,and initially identified defecttypes and sizes. The research has laid a good foundation for the non-destructive testingdefect detection and quantitative determination of defect in large metal plate...