基于激光超声表面波的盆式绝缘子表面开口缺陷成像与定量

Imaging and Quantification on Insulating Spacer Surface Opening Defect Based on Laser Ultrasonic Surface Wave

针对盆式绝缘子表面开口缺陷精准检测的迫切需求,文中提出一种基于激光超声表面波的盆式绝缘子成像检测及缺陷定量方法,利用高速振镜实现超声信号的非接触式扫描激励和快速采集,利用声场互易原理实现超声传播及其与缺陷相互作用过程的动态显示,以相邻信号相关度为指标实现表面开口缺陷的高对比度成像,基于中值滤波和索贝尔算子边缘提取实现缺陷尺寸的精确测量。设计和制造圆孔和刻槽两类缺陷对所提出方法进行验证,结果表明:所提成像方法可以同时检出位于探头正前方以及具有一定偏转角度方位上的缺陷,所提定量方法对位于探头正前方表面开口缺陷的定量精度达到95%。

In view of the urgent need of accurate defection of insulating spacer surface opening defect,a kind of imaging detection and defect quantitative method of insulating spacer based on laser ultrasonic surface wave is proposed in this paper. The non-contact scanning excitation and fast acquisition of ultrasonic signal are achieved by using highspeed galvanometer. The dynamic display of interaction between ultrasonic propagation and defect is realized by the use of sound field reciprocity principle. The adjacent signal correlation is taken as indicator so to realize the high contrast imaging of defect,and the accurate measurement of defect size is achieved by edge extraction based on median filter and sobel operator. The proposed method is verified by designing and manufacturing such two defects as circular hole and grooving defects. It is shown by the result that the proposed imaging method can simultaneously detect the defects directly in front of the probe and with a certain deflection angle,and the quantitative accuracy of the proposed method for the defects directly in front of the probe reaches 95%.