Research And Application Of Magnetostrictive Guided Wave Non-destructive Testing

Nondestructive testing(NDT)technique based on magnetostrictive effect can inspect not only over long distance from a single position but also achieve the rapid detection of the unreachable area.As a mew type of non-destructive testing technology,magnetostrictive guided wave has broad application prospects,especially the status monitoring of structures(such as pipes,buried components,wire ropes,etc.)In this paper,the principle,the implementation and the engineering application of the technology are investigated through the experiment.Combined with the background and significance of the magnetostrictive wave guide,the research status of the technology is summarized.Magnetostrictive guided wave NDE is studied from different aspects,such as mainly in guided wave testing instruments,testing method and application design,development of sensors and signal processing technology.Based on the magnetostrictive effect and inverse effect,the excitation,detection and dissemination of guided wave are elaborated creatively.Especially for non-contact longitudinal guided wave,the sensor based on magnetostrictive effect is designed for the next research.The experimental platform is developed,concluding incentive system,sensors and detection part.The excitation source,the power amplification circuit and preamplifier units are designed.Excitation signal source is analyzed from the pulse signal selection,in particular the number of excitation pulses and the frequency of the detection resolution.The frequency of the detection signal is verified from the experiment.The magnetic source and coil structure are designed for the subsequent research.Because of the dispersion,multi-mode and attenuation,the echo signals are difficult to be analyzed so that different analytical methods are description such as in time,frequency(FFT)and time-frequency(STFT).For the real-time requirement,hardware and software filter are discussed for the signal processing.The system is carried out to test the seamless steel pipe using the L(0,1)modal.Through observing the defect detection results about different geometries,they show that the longitudinal guided wave can detect circumferential defects with higher sensitivity.Then,the detect location and loss rate of the cross-sectional area are analyzed by the test results.In short,the experiment can be verified the relevant principle correctly in previous section.