Dynamic Detection of Rail Surface Crack Based on ACFM

In view of the rail surface crack, The Alternating Current Field Measurement (ACFM) technology is easy to produce signal distortion at high speed. Based on the ACFM technology, this paper studies the influence of probe scanning speed, crack length and depth on the detection signal. Combined with the optical moving rail device and ACFM detector, a rail dynamic scanning platform is built. The scanning speed of the probe is controlled by changing the moving speed of the rail, and then the influence of the speed on the magnetic response is explored. The detection results show that: with the increase of the speed, the abnormal variables of Bx and Bz signals decrease gradually. When the speed increases to 100 mm/s, defects are missed; under the same length and width, the abnormal variables of Bx and Bz signals increase with the increase of the defect depth. Under the same depth and width, the abnormal variables of Bx and Bz signals increase with the increase of the defect length.