脉冲涡流检测中三维磁场量的特征分析与缺陷定量评估

为获取更多更明显的特征量以提高脉冲涡流检测技术对缺陷的检测能力,采用一种新型的均匀脉冲涡流探头能将三维磁场量分离开来实现各自的独立测量,将传统的仅利用一维分量进行检测扩充到同时利用三维分量实现检测,大大地增加了可用的信息量,且该探头在平行涡流流向的方向和垂直于导体表面的方向上还具有自差分的特点,使它对缺陷的几何参数变化具有很高的检测灵敏度。实验和数值结果均表明在有缺陷存在时,三维响应信号能直观地反映缺陷深度的大小变化,取信号的幅值作为检测特征量,分析不同时刻信号幅值按空间位置的分布特征发现,通过三个信号幅值变化的特征位置和幅值变化的程度可以实现缺陷深度和边缘轮廓的定量评估,这为进一步实现飞机机身上多层结构中缺陷(如腐蚀、坑、铆钉孔附近的裂纹等)的成像检测提供了有实用价值的参考。

Detection of a Defect Based on 3D Magnetic Field Measurement for Pulsed Eddy Current Testing

To improve detectability of Pulsed Eddy Current Testing(PECT) for surface/subsurface defects,the paper presents a novel uniform PEC probe.It is greatly advantageous to pickup three-dimensional magnetic field components for detection.Moreover it is characteristic of self-difference in the directions,parallel to induced eddy-current's flow paths and perpendicular to the conductor's surface.So the probe is highly sensitive to shape and dimension of a defect.The three-dimensional transient responses due to a defect have been calculated and compared with the experimental results.The results show that a defect's depth and edges can be evaluated quantitatively by analyzing the magnitude of the three-dimensional transient signals.These merits are valuable for imaging inspection of defects(such as corrosion,dent,rivet hole,etc) in the aircraft structures.