An Adaptive Sensor for Detecting Hybrid Defects on Steel Plate With Unknown Thickness

Hybrid defects of the oil and gas pipelines with unknown thickness occur frequently influenced by the complex working environment. Due to the mutual interference between hybrid-surface and hybrid-back defects and the lack of thickness information, it is difficult to accurately detect hybrid defects with unknown wall thickness. The integrated method has been widely developed for detecting hybrid defects due to its high detection efficiency and integrity. However, existing methods are unable to accurately detect hybrid defects with unknown wall thickness due to the difficulty in detecting completely covered hybrid-back defect and the nonadaptation to unknown thickness perfectly. To the above issues, an adaptive sensor is proposed, which does not require hybrid-surface and hybrid-back defects to be staggered or the known thickness in advance. First, an integrated structure is proposed by sharing magnetic source to synchronously collect multiple signals, which extends the information dimension without changing the excitation. Second, a circuitous strategy is proposed by energy detour to overcome the difficulty in detecting completely covered hybrid-back defect. Third, an adaptive strategy is proposed by matching the best frequency for unknown thicknesses. Finally, the experimental results indicate that the proposed sensor can accurately detect hybrid defects with unknown wall thickness.