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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。
With the wide application of plate structure in the petrochemical, aerospace and power industries, it is urgent to develop corresponding non-destructive testing technology to evaluate the structural integrity periodically to ensure the safe operation of the structure. Based on Lamb wave technology of air-coupled transducer, the plate structure can be scanned non-contactly and quickly, which has broad application prospects in the field of structural safety testing. In this paper, based on the potential function method of air-coupled plate-shaped structure of the acoustic propagation model, obtained through the theoretical solution of the Lamb wave critical angle with the thickness of the product change rule. In the experiment, the air-coupled transducer was used to excite and receive the Lamb wave. The Fourier transform and signal filtering techniques were used to identify the S0 and A0 modes and confirmed by comparison with the theoretical results. Finally, the S0 and A0 modes were used to locate the semi-through-hole defects on the back of the plate. The results show that the non-contact ultrasonic non-destructive testing method can be used to detect the back defects of the plate structure.