Wang Kaican

Rail flaw detection system based on electromagnetic acoustic technique

As a result of the development of higher speeds and heavier loads of rail networks, rail defects have been more serious than ever before. Current piezoelectric ultrasonic detection devices are often inadequate for rail inspection, due to high misjudgement or undetected error rate, and complex structure. This paper introduces a novel rail detection system. The system is based on multi-channel electromagnetic acoustic transducers under the control of DSP. Cumulative average and cross-correlation algorithms are realized by FPGA, exploiting the advantages of FPGA in high calculating speed and designing flexibility. Combining EMATs with FPGA, the system is free of couplant, compact in structure and low use-cost, and can realize an overall detection of rails.

Unidirectional line-focusing shear vertical wave EMATs used for rail base center flaw detection

Electromagnetic acoustic transducer (EMAT) is used for rail base flaw detection. The bidirectional radiation pattern of Shear Vertical wave (SV-wave) EMAT limits the accuracy and efficiency of the transducers. In view of this problem, a method of generating unidirectional focusing SV wave is brought up by a unidirectional line-focusing SV-wave EMAT. A 2D finite element model is built to demonstrate the feasibility of rail base flaw detection. Finally, the unidirectional line-focusing SV-wave EMAT is compared experimentally with other three kinds of SV-wave EMATs. The results show that using the unidirectional SV-wave EMAT can enhance the amplitude of echo signal into around two times of the bidirectional EMAT. Compared with bidirectional SV-wave EMAT and unidirectional SV-wave EMAT, the amplitude of echo signals are increased by 7% and by 10% by line-focusing SV-wave EMAT and unidirectional line-focusing SV wave EMAT, respectively.