Scattered echo of surface defect in the far field of Rayleigh wave generated by laser

WANG Wei; ZHONG Zheng; PAN Yongdong

doi:10.7510/jgjs.issn.1001-3806.2015.02.003

In order to detect the surface defect quantitatively with laser ultrasonic technique, the interaction between the laser-generated surface wave and the open rectangular defect was simulated by means of the finite element method. After comparing the displacement signals at the same receiver generated in the near-field and far-field laser irradiation, it was found that reflected waves could be separated the from the mode-converted waves sufficiently when the laser was located in the far field of the defect, which may be helpful to analyze the complicated process of the interaction between the incident wave and the defect. Then, the wave interaction with either the front or the back of the defect was studied in detail, and Huygens principle was further employed to interpret the possible interaction features among the reflected signals. Finally, the influences of depth and width of the defect on the scattered echo were also studied. The results show that the arrival time difference of the scattered echo is linearly related to the depth and width of the defect. This research may provide the theoretical basis to quantify the defect.

Scattered echo of surface defect in the far field of Rayleigh wave generated by laser

Corresponding author: ZHONG Zheng, zhongk@tongji.edu.cn;

1. School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092, China

Received Date: 2014-05-16

Accepted Date: 2014-07-17

Available Online: 2015-03-25

Abstract: In order to detect the surface defect quantitatively with laser ultrasonic technique, the interaction between the laser-generated surface wave and the open rectangular defect was simulated by means of the finite element method. After comparing the displacement signals at the same receiver generated in the near-field and far-field laser irradiation, it was found that reflected waves could be separated the from the mode-converted waves sufficiently when the laser was located in the far field of the defect, which may be helpful to analyze the complicated process of the interaction between the incident wave and the defect. Then, the wave interaction with either the front or the back of the defect was studied in detail, and Huygens principle was further employed to interpret the possible interaction features among the reflected signals. Finally, the influences of depth and width of the defect on the scattered echo were also studied. The results show that the arrival time difference of the scattered echo is linearly related to the depth and width of the defect. This research may provide the theoretical basis to quantify the defect.

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Reference (15)

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Scattered echo of surface defect in the far field of Rayleigh wave generated by laser

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