State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
J Acoust Soc Am. 2012 Mar;131(3):2048-62. doi: 10.1121/1.3682033.
This paper first reviews a method of simulating the propagation characteristics of guided waves in multilayered coaxial cylindrical elastic solid media. Secondly, this method is used to investigate the properties of the guided waves for the ultrasonic long-range non-destructive evaluation techniques for rockbolts. To do so, the special case of non-leaky guided modes in open waveguides is considered. The method explains how the complex dispersion function is converted into a real function: hence the bisection technique can be employed to search for all the real roots. The model is used to (i) characterize the low dispersion range and anomalous dispersion of normal and Stoneley modes and (ii) analyze the excitation mechanisms of guided waves from axisymmetric and non-axisymmetric acoustic sources. The results are used to select suitable excitation frequency ranges associated with dominant modes with large amplitudes, low dispersion, and distinguishable propagation velocities to reduce signal distortion. The results suggest the lowest order flexural mode, excited by a radial force source, has potential to be used in practice. Also, the highly dispersive Stoneley mode propagating along a cylindrical interface is defined and distinguished from the normal mode using two properties, velocity high-frequency asymptotes and amplitude distributions along the radial direction.
本文首先回顾了一种模拟多层同轴线弹性固体中导波传播特性的方法。其次，该方法用于研究用于锚杆超声远程无损评估技术的导波特性。为此，考虑了开波导中非泄漏导模的特殊情况。该方法解释了如何将复频率分散函数转换为实函数：因此可以采用二分法搜索所有实根。该模型用于(i) 表征正常模态和斯通利模态的低分散范围和异常分散，以及 (ii) 分析轴对称和非轴对称声源激励导波的机制。结果用于选择与具有大振幅、低分散和可区分传播速度的主导模式相关的合适激励频率范围，以减少信号失真。结果表明，径向力源激励的最低阶弯曲模式具有在实际中应用的潜力。此外，定义了沿圆柱界面传播的高分散斯通利模态，并使用两个特性，即速度高频渐近线和沿径向的振幅分布，将其与正常模态区分开来。
