摘要
本文提出一种定量无损估计超薄弹性层声速、厚度和密度参数的低频超声波频域定征方法。这里“超薄”的概念是指材料厚度远小于材料中声波波长，导致在时域上材料前后界面的多次回波信号相互混迭。本文采用超声纵波垂直入射超薄层材料，分析了水浸耦合和耦合剂耦合两种情况下，材料反射波和透射波的组成，定义和推导了材料的反射与透射传递函数，提出了在最小二乘误差意义上分别使用材料传递函数幅度谱、相位谱和复谱对各参数进行反向估计的算法，分析了影响估计准确性的各种因素，研究了灵敏度函数在误差传递中的意义。实验结果表明该方法能够对厚度小于百分之一声波波长的超薄弹性层进行无损定征。
A frequency domain characterization method using low frequency ultrasound is put forward to estimate parameters of ultra thin elastic layers, such as: the sound velocity, thickness and density. The ‘ultra thin’ means that the thickness of specimen is much less than the ultrasound wavelength so that two successive echoes from the specimen can not be separated in the time domain using previous method. An analysis of the composition of the reflected and transmitted signals of the layer immersed in the water as well as coupled with ultrasonic coupler is given. The transfer functions of transmission and reflection mode are derived. In the least squares error sense, an inverse algorithm is used to estimate the parameters mentioned above on the basis of the amplitude, phase and complex spectrum. An analysis of main sources of the estimate deviation is presented. The sensitivity of the transfer function to parameters and its significance in the transfer of errors have been well discussed. It is observed that the agreement between the nominal and estimation values is excellent.
出处
《计量学报》
CSCD
北大核心
1998年第4期291-298,共8页
Acta Metrologica Sinica
基金
中国国家教委跨世纪人才基金
