A New Surface Wave EMAT with High SNR and the Application for Defect Detection in Thick-walled Pipes

doi:10.3901/JME.2017.04.059

Abstract

Abstract:

A type of surface wave EMATs with different configuration is developed to improve the signal to noise ratio (SNR) of receive signal in pulse-echo mode. The mechanism which improve the receive signal SNR and the influence factors are analyzed. It is the interval between magnet and meander-line coil that decrease the disturbance of the ultrasonic in magnet, and then the receive signal SNR are improved. It is shown that the SNR of receive signal is not only related with the interval between magnet and meander-line coil, but also positively correlated with the EMAT center frequency. The performance of 3 surface wave EMATs is evaluated and it is found that the measured center frequency is consistent with the design value and the directivity is agreed well with theoretical analysis. The 5 defects with different depth on the standard block are tested by the developed surface wave EMATs. The testing result shows that the defect can be detected when the depth reaches about 1/4 wavelength. What’s more, 3 types of defect on a thick-walled pipe such as circumferential rectangular slot, axial rectangular slot and flat-bottom hole are respectively detected by the developed EMATs with center frequency of 1.0 MHz.

Key words: defect detection, signal noise ratio, thick-walled pipes, surface wave EMAT

HE Cunfu, DENG Peng, Lü Yan, JIAO Jingpin, WU Bin. A New Surface Wave EMAT with High SNR and the Application for Defect Detection in Thick-walled Pipes[J]. Journal of Mechanical Engineering, 2017, 53(4): 59-66.

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A New Surface Wave EMAT with High SNR and the Application for Defect Detection in Thick-walled Pipes

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