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文章描述的声学测微计是以监测伪Sezawa波为基础的。假定在半无限大介质的上表面有一薄的复盖层,当层介质中的横波声速较底下介质的横波声速小时,可有许多表面波模式沿层状介质的表面传播,其中基模为瑞利波,第二个模为Sezawa波。实验所用样品中,基片材料为42-合金,上面薄层材料是金。当一平面超声波通过水耦合斜入射到样品上时,在样品表面层激发的前两个模的相速度色散曲线如图1所示,图中k为波数,d为薄层厚度。Sezawa波有一个截止波数,在这个波数,Sezawa波的相速度等于基片中的
The article describes the acoustic micrometer is based on the monitoring of pseudo-Sezawa wave. Assuming that there is a thin covering layer on the upper surface of semi-infinite medium, when the shear wave velocity in the medium is lower than the shear wave velocity in the medium, there are many surface wave modes that propagate along the surface of the layered medium. The fundamental mode is Rui The second wave is Sezawa Wave. In the sample used in the experiment, the substrate material is 42-alloy and the thin layer above is gold. When a plane ultrasonic wave is obliquely incident on the sample through water coupling, the phase velocity dispersion curves of the first two modes excited on the sample surface layer are shown in Fig. 1, where k is the wavenumber and d is the thickness of the thin layer. The Sezawa wave has a cutoff wave number at which the Sezawa wave has a phase velocity equal to that of the substrate