论文部分内容阅读
本文提出低频超声类瑞利波定征方法来估计覆层/基层层状复合结构超薄覆层的纵波声速、横波声速、厚度和密度等参数。这里“超薄”的概念是指覆层厚度h远小于覆层中的声波波长λ,导致在时域上覆层前后界面的各次回波信号相互混迭。文章采用水楔耦合方式,利用超声漏类瑞利波频域分析方法获取层状复合结构超声类瑞利波色散曲线,提出以色散特性为基础的低频超声类瑞利波覆层定征方法和在最小二乘意义下以色散曲线为基础的反向算法对覆层进行了参数估计。文中分析了影响估计准确性的各种因素,研究了低频超声类瑞利波定征方法对覆层各参数的灵敏度及其在误差传递中的意义。实验结果证实,对于银箔/玻璃层状复合结构,该方法能够准确估计厚度小到26μm银箔覆层的声学参数。
In this paper, the low frequency ultrasound Rayleigh wave characterization method is proposed to estimate the parameters such as the longitudinal wave velocity, transverse wave velocity, thickness and density in the ultrathin overlay of the clad / base layered composite structure. The concept of “ultra-thin” here means that the thickness h of the coating is much smaller than the wavelength λ of the acoustic wave in the coating, so that the respective echo signals at the interface before and after the coating overlap with each other in time domain. In this paper, the water-wedge coupling method is adopted to obtain the ultrasonic Rayleigh wave dispersion curve of layered composite structure by using the ultrasonic leaky Rayleigh wave frequency domain analysis method. The method of low frequency ultrasonic Rayleigh wave cladding identification based on the dispersion characteristics is proposed. The inverse algorithm based on the dispersion curve in the least squares sense estimates the coating parameters. In this paper, various factors that influence the accuracy of the estimation are analyzed, and the sensitivity of the low frequency ultrasound Rayleigh wave characterization method to the parameters of the cladding and its significance in error transmission are studied. The experimental results show that the method can accurately estimate the acoustic parameters of the silver foil with the thickness as small as 26μm for the silver / glass layered composite structure.