Study on Evaluation System of Mechanical Properties of Coating Materials using Wavelet Analysis of Surface Wave

板材或涂层的超声无损检测通常采用兰姆波和类瑞利波。这些波的色散特性造成了激发和检测超声波以及分析检测信号的困难。在这项研究中，开发了一种接触式线聚焦换能器，该换能器由1/4圆柱形的PMMA楔形板制成，并在其上粘贴PVDF薄膜。结果表明，该换能器能成功地激发和探测平板或涂层中的色散波。采用两种利用小波变换的方法从检测信号中确定兰姆波或类瑞利波的频散关系。此外，应用最优化技术，从色散关系中估计了板或涂层的弹性性能。

Lamb waves and Rayleigh-like waves are often used for ultrasonic NDE of plates or coatings. The dispersive nature of these waves causes difficulties in excitation and detection of ultrasonic waves as well as in the analysis of detected signals. In this study, a contact-type line-focused transducer made of a quarter-cylindrical PMMA wedge with a PVDF film adhered to the wedge is developed. It is shown that dispersive waves in plates or coatings are successfully excited and detected by this transducer. Two techniques utilizing the wavelet transform are employed to determine the dispersion relation of Lamb or Rayleigh-like waves from detected signals. In addition, the elastic properties of plates or coatings are estimated from the dispersion relation by applying an optimization technique.