空气耦合超声斜入射均匀弹性层状介质材料的传播特性

针对空气耦合超声非接触、无损伤技术在均匀弹性层状介质材料中应用缺少相关理论依据的问题，从波动方程入手，利用传递矩阵法及声波气体与固体边界条件研究了空气耦合超声波以不同的入射角和检测频率在均匀弹性层状介质中的声传播规律，建立了基于空气耦合的均匀层状弹性材料检测方法。模拟结果表明：斜入射时，透射系数分布呈现多模式形态；当入射角超过横波临界入射角时，发生全反射现象；随着检测频率的逐渐增大，入射临界角逐渐变小；随着声入射角逐渐增大，截止声波频率与介质厚度积也逐渐增大。实验验证表明，实验结果与数值模拟结果基本吻合。

Propagation Characteristics of Oblique Incidence Air Coupling Ultrasonic Wave in Uniform Elastic Layered Medium

The propagation rules of air coupling acoustic wave in uniform elastic layered medium are studied at the different incident angles and testing frequency according to the wave equation. The transfer matrix method and the gas-solid boundary conditions of acoustic wave are used to solve the problem which lacks theoretical support in the application of non-contact ultrasonic test technology in uniform elastic material. A testing method of uniform elastic medium is developed. The stimulated results show that the transmission coefficient distribution presents a form of multimode. The total reflection occurs when the incident angle exceed the critical angle of transverse wave. The incident critical angle decreases with the increase in testing frequency. The cutoff frequency-thickness product increases with the increase in incident angle. The experimental results are in agreement with the numerical results.