Influence of the Lift-Off Effect on the Cut-Off Frequency of the EMAT-Generated Rayleigh Wave Signal

Sensors

Pengxing Yi¹  Kang Zhang¹  Yahui Li¹ 

[1] School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074, China; E-Mails:

关键词: EMAT;    cut-off frequency;    rayleigh wave;    lift-off;   

DOI  :  10.3390/s141019687

来源: mdpi

【 摘 要 】

The electromagnetic acoustic transducer (EMAT), a non-contact NDT tool with large lift-off, is becoming an attractive method for detecting the cracks in the metal parts. However, the lift-off of the transducer has a direct effect on the feature that is used to characterize the defects. A detailed investigation on the relationship between the feature and the lift-off of the EMAT is crucial in the detection process. This paper investigates the lift-off effect on the feature, cut-off frequency of EMAT in the Rayleigh wave. The study can be divided into two parts. Firstly, with a multi-field coupling environment, 2-D electromagnetic and wave generation EMAT models are built to simulate the interaction of the Rayleigh wave with the surface crack. Then, the lift-off effect on the cut-off frequency is investigated through simulation and experiment. Compared to the previous studies, it is found that lift-off would cause a negative result when the lift-off varies in the testing process. Besides, the calibration obtained from the tests at a random lift-off value can be used in other tests with any different lift off value provided that the lift-off is kept as a constant during the detection process.

【 授权许可】

CC BY   
© 2014 by the authors; licensee MDPI, Basel, Switzerland.