板背部缺陷的单侧非接触式超声无损检测方法

随着板状结构在石化、航空航天和电力等工业领域中的广泛应用,急需发展相应的无损检测技术,对其结构完整性进行定期评估,以保证结构的安全运行。基于空气耦合换能器的Lamb波技术,可以非接触快速地对板状结构进行扫描,在结构安全检测领域有广阔的应用前景。本文采用基于势函数法的空气耦合板状结构声传播模型,通过理论求解得到其Lamb波临界角随频厚积的变化规律。实验中采取空气耦合换能器激发和接收Lamb波,采用傅里叶变换和信号滤波技术识别S0和A0模式,并通过与理论结果比较进行确认。最后,分别采用S0和A0模式对板背部半通孔缺陷进行定位,结果显示该单侧非接触式超声无损检测方法可用于板状结构背部缺陷的检测。

On the One-Side Non-Contact Ultrasonic Non-Destructive Testing Method for Detection the Defects on Backside of Plate

Along with wide application of plate like structure in petrochemical, aerospace and power industry etc, it is urgent to develop corresponding nondestructive detecting technology to evaluate periodically the integrity of structure to ensure safe operation of the structure. Lamb wave technology, based on air-coupled transducers, can non-contactly and quickly scan plate structure, therefore has broad application prospect in the area of structure safety detection. In this paper, adopting acoustic propagation model of air-coupled plate like structure based on potential function method, the variation of Lamb wave critical angle along with the frequency thickness product was obtained through theoretical solution. In experiment, Lamb wave was excited and received by air-coupled transducers; S0 and A0 mode were identified by Fourier transform and signal filtering technique, which was confirmed by comparing experimental data with theoretical results. Finally, the location of a half through hole at the backside of plate was detected by using S0 and A0 mode respectively. Results show that the one-side non-contact ultrasonic non-destructive testing method can be used for detection the defects at backside of plate like structure.