Gunderson Aaron M, Daniel Timothy D, Marston Philip L, Isakson Marcia J
Applied Research Laboratories, University of Texas at Austin, Austin, Texas 78758, USA.
Department of Physics and Astronomy, Washington State University, Pullman, Washington 99164, USA.
J Acoust Soc Am. 2018 May;143(5):3036. doi: 10.1121/1.5038256.
Acoustic backscattering from a rubber spherical shell in water is observed to contain a delayed enhancement, demonstrated to be associated with a waveguide path along the shell. This path is somewhat analogous to that of the Lamb wave observed on metallic shells. Rubber is a unique material because of its subsonic sound speed relative to water, and because shear coupling is often small enough to be neglected in typical models, making it fluid-like. This makes rubber a material of interest for coating and cloaking underwater devices and vehicles. Both fluid and elastic rubber partial wave series models are tested, using experimentally measured longitudinal and shear speeds, attenuation, and rubber density. A finite element model for the shell is also developed. Comparison of the models and experiments highlights the importance of the waveguide path to the overall scattering. Estimates for the group and phase velocities of the lowest order propagating mode in the shell are determined through waveguide normal mode analysis and Sommerfeld-Watson theory, and are shown to give good agreement with experiments in predicting the time of arrival of the waveguide path.
观察到水中橡胶球壳的声学反向散射包含延迟增强现象，证明其与沿球壳的波导路径有关。该路径在某种程度上类似于在金属壳上观察到的兰姆波路径。橡胶是一种独特的材料，因为其相对于水的声速低于音速，且在典型模型中剪切耦合通常小到可以忽略不计，使其具有类似流体的性质。这使得橡胶成为用于水下设备和车辆涂层与隐形的一种有吸引力的材料。使用实验测量的纵向和剪切速度、衰减以及橡胶密度，对流体和弹性橡胶的部分波系列模型进行了测试。还开发了球壳的有限元模型。模型与实验的比较突出了波导路径对整体散射的重要性。通过波导正常模式分析和索末菲 - 沃森理论确定了球壳中最低阶传播模式的群速度和相速度估计值，结果表明在预测波导路径的到达时间方面与实验结果吻合良好。
