小曲率半径弧面涡流检测中探头提离干扰的抑制方法  

Suppression Method of a Probe-coil's Lift-off Noise for the Curved Specimen With Small Curvature Radius in Eddy-current Testing

作　　者：张玉华[1] 孙慧贤[1] 罗飞路[1] 

机构地区：[1]国防科学技术大学机电工程与自动化学院,湖南省长沙市410073

出　　处：《中国电机工程学报》2009年第27期126-132,共7页Proceedings of the CSEE

摘　　要：研究弧面检测中探头提离干扰的抑制方法是涡流检测实践中一个重要课题。针对3类检测表面(凹面、平面和凸面),建立对应的三维涡流场问题的有限元模型,计算分析了检测表面形状、曲率半径大小以及提离变化对线圈反射阻抗的影响。结果表明,试件形状和曲率半径大小仅改变线圈反射阻抗的值,并不影响其变化规律,由提离改变所形成的阻抗轨迹始终为一条直线。当试件上出现缺陷时,探头提离的增加使缺陷信号的幅值明显变小,相位几乎不变,但随着检测频率增大,缺陷信号和提离轨迹之间的相位差Φ发生改变,并存在一个频率点f⊥使Φ=90°,根据此特征给出了实际检测中能有效抑制提离干扰的频率范围,并提出利用相位旋转和信号增强相结合的方法消除提离干扰,实验数据说明了数值结果及理论分析的正确性。It is key problem that the research of suppressing a probe-coil＇s lift-off noise for the curved specimen in practical eddy current testing. For three different detected surfaces---concave, plane and convexity, the relevant finite element models of three-dimensional eddy current field problem have been built. The surface shape, curvature radius and lift-off variation effects on coil＇s reflected impedance have been analyzed. The results show that the reflect impedance magnitude is changed by the specimen＇s shape and curvature radius, but its characteristics is not affected by them. The impedance loci produced by lift-off variation are always straight line. When a probe-coil＇s lift-off to the specimen with a defect is increased, the amplitude of defect signal is decreased obviously, but its phase is almost unchanged. The phase difference, Ф between defect signal and lift-off loci is shifted with frequency. And defect signals are vertical to lift-off loci at a well-selected frequency. On this merit, the range of frequency for suppressing effectively lift-off noise in practical testing is attained. Furthermore, phase rotation and signal enhancement technique are presented to eliminate lift-off noise. Numerical results and theoretical analysis are validated by experiments.

关 键 词：涡流检测 弧面试件 提离干扰 相位旋转 检测频率 有限元模型 

分 类 号：TH878[机械工程—仪器科学与技术]