Abstract
Different guided wave mode has different sensitivity to the defects of rail head, rail web and rail base in the detection of rail defects using ultrasonic guided wave. A novel guided wave mode selection and excitation method is proposed, which is effective for detection and positioning of the three parts of rail defects. Firstly, the mode shape data in a CHN60 rail is obtained at the frequency of 35 kHz based on SAFE method. The guided wave modes are selected, combining the strain energy distribution diagrams with the phase velocity dispersion curves of modes, which are sensitive to the defects of the rail head, rail web and rail base. Then, the optimal excitation direction and excitation node of the modes are calculated with the mode shape matrix. Phase control and time delay technology are employed to achieve the expected modes enhancement and interferential modes suppression. Finally, ANSYS is used to excite the specific modes and detect defects in different rail parts to validate the proposed methods. The results show that the expected modes are well acquired. The selected specific modes are sensitive to the defects of different positions and the positioning error is small enough for the maintenance staff to accept.
Highlights
It is of great significance to discover the internal defects of rails in time for maintaining and ensuring the safety of trains
The mode shape data in the CHN60 rail is obtained at the frequency proposed based on ultrasonic guided waves
The modes with good non-dispersion characteristics, which are respectively sensitive to the defects of the rail head, rail web and rail base, are selected combining the strain energy distribution diagrams with group velocity dispersion are respectively sensitive to the defects of the rail head, rail web and rail base, are selected combining the strain energy distribution diagrams with group velocity dispersion curves
Summary
It is of great significance to discover the internal defects of rails in time for maintaining and ensuring the safety of trains. In the research of rail defect detection based on guided waves, some scholars selected the suitable modes for rail defect detection by a mode classification method. In the frequency range of 60~200 kHz, the transverse and vertical vibration modes with smooth dispersion curves of rail base are more suitable for defect detection than the longitudinal vibration modes [11]. A rail base defect of 20 mm in length was successfully detected by exciting the vertical modes. The signal was mode with energy concentrated on the rail head to detect excited according to the experimental method. In mode and mode can be selected to detect rail head defects, mode for rail web Figure 4c, it can be seen that the strain energy of mode 3 is focused on the rail web.
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