【摘要】 利用超声波回波法对薄膜的声学特性进行了研究,提出了一种薄膜介质的超声波衰减评价方法。结果表明,超声回波信号的尾部产生大量的细小杂波,这些杂波包含着反应薄膜物性的声学参量。采用解析法建立了基于频谱分析的无薄膜时回波信号和有薄膜时回波信号频谱比值的恢复函数H(f),该方法考虑了超声波在薄膜介质中的衰减系数特征参量,获得了薄膜介质的密度、弹性模量等物理参量及超声波在薄膜中传播衰减系数与频率的关系。克服了超声波低频检测法无法测量厚度小于入射波波长的薄膜介质或涂层声学特性的缺点。更多还原

【Abstract】 Acoustics characteristic of thin layers was studied by the ultrasonic wave propagation theories. An evaluation method of ultrasonic attenuation of the thin layer was proposed. The result indicated that there were a large number of small clutters in the tail of ultrasonic echo, which contained the acoustic characteristic. An analytic method was built based on the restoration function H(f) of frequency spectrum ratio of ultrasonic echoes under the condition of substrate material uncovered and covered with the rubber thin layer, which considered attenuation coefficient parameters in course of the propagation in the rubber thin layer. The supersonic wave propagation velocity in the rubber thin layer, the thin layer acoustic impedance, density and relationship between attenuation coefficient and frequency can be acquired. This method overcomes the shortcomings that the traditional ultrasonic does not evaluate acoustics characteristic of the thin layer or coat medium which the thickness is less than motivation wavelength.更多还原