title: Influence of the lift-off effect on the cut-off frequency of the EMAT-generated Rayleigh wave signal.
abstract: 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.
authors.affiliation: School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074, China. pxyi@hust.edu.cn.
authors.forename: Pengxing
authors.initials: P
authors.lastname: Yi
authors.affiliation: School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074, China. zhangkang@hust.edu.cn.
authors.forename: Kang
authors.initials: K
authors.lastname: Zhang
authors.affiliation: School of Mechanical Science & Engineering, Huazhong University of Science & Technology, Wuhan 430074, China. liyh20@163.com.
authors.forename: Yahui
authors.initials: Y
authors.lastname: Li
authors.affiliation: School of Life Science & Technology, Huazhong University of Science & Technology, Wuhan 430074, China. zxmboshi@hust.edu.cn.
authors.forename: Xuming
authors.initials: X
authors.lastname: Zhang