doi: 10.3850/S201042862015001179

Laser-Emat Ultrasonic Tofd Signal Enhancement for Defect Measurement

Cuixiang Pei, Dongci Yi and Zhenmao Chen State Key Laboratory for Strength and Vibration of Mechanical Structures,
Shanxi Engineering Research Center of NDT and Structural Integrity Evaluation,
Xi'an Jiaotong University, Xi'an, 710049, China pei.cx@mail.xjtu.edu.cn

ABSTRACT

In this work, a laser-EMAT ultrasonic measurement of cracks in specimens is implemented with the time-of-flight diffraction (TOFD) method. In order to improve the performance of the measurement, a signal processing method based on the combination of the Fourier transform and modified wavelet transform is applied to enhance the defect signal with removing the surface waves and noises, and suppressing the strong reflection wave due to the specimen geometry with a new thresholding algorithm. With using the proposed signal processing method, the defect signals can be recognized very obviously in the B-scan images.

Keywords: Laser ultrasound, EMAT, Time-of-flight diffraction, Wavelet transform.

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