Crack Defect Detection Based on Multi-frequency Balanced Electromagnetic Field Measurements

Traditional eddy current detection technology has a good detection effect on pipeline cracks, but it is limited by the skin effect only to detect cracks on pipeline surface. This paper proposes a multi-frequency balanced electromagnetic field measurement (MF-BEFM) method to detect crack defects. First, the principle of balanced electromagnetic detection is introduced. Secondly, the multi-frequency excitation strategy of synchronous additive synthesis is adopted to achieve different skinning depths by using response signals of different frequencies. Finally, through the MF-BEFM test, the multi-frequency method can be verified by comparison to realize the detection of surface and buried defects. The results show that the peak value of the multi-frequency balanced electromagnetic signal increases approximately linearly with the increase of the defect depth.