Department of Civil, Architectural, and Environmental Engineering, the University of Texas, Austin, TX, USA.
IEEE Trans Ultrason Ferroelectr Freq Control. 2011 Feb;58(2):427-36. doi: 10.1109/TUFFC.2011.1820.
Previous studies show that the surface wave transmission (SWT) method is effective to determine the depth of a surface-breaking crack in solid materials. However, nearfield wave scattering caused by the crack affects the reliability and consistency of surface wave transmission measurements. Prior studies on near-field scattering have focused on the case where crack depth h is greater than wavelength λ of surface waves (i.e., h/λ > 1). Near-field scattering of surface waves remains not completely understood in the range of h/λ for the SWT method (i.e., 0 ≤ h/λ ≤ 1/3), where the transmission coefficient is sensitive to crack depth change and monotonically decreases with increasing h/λ. In this study, the authors thoroughly investigated the near-field scattering of surface waves caused by a surface-breaking crack using experimental tests and numerical simulations for 0 ≤ h/λ ≤ 1/3. First, the effects of sensor locations on surface wave transmission coefficients across a surface-breaking crack are studied experimentally. Data are collected from Plexiglas and concrete specimens using air-coupled sensors. As a result, the variation of transmission coefficients is expressed in terms of the normalized crack depth (h/λ) as well as the normalized sensor location (x/λ). The validity of finite element models is also verified by comparing experimental results with numerical simulations (finite element method). Second, a series of parametric studies is performed using the verified finite element model to obtain more complete understanding of near-field scattering of surface waves propagating in various solid materials with different mechanical properties and geometric conditions. Finally, a guideline for selecting appropriate sensor arrangements to reliably obtain the crack depth using the SWT method is suggested.
先前的研究表明，表面波透射（SWT）方法在确定固体材料表面裂纹的深度方面非常有效。然而，裂纹引起的近场波散射会影响表面波透射测量的可靠性和一致性。先前对近场散射的研究主要集中在裂纹深度 h 大于表面波波长 λ 的情况（即 h/λ > 1）。在 SWT 方法的 h/λ 范围内（即 0 ≤ h/λ ≤ 1/3），表面波的近场散射仍然没有完全理解，在该范围内，透射系数对裂纹深度变化敏感且随 h/λ 的增加而单调减小。在这项研究中，作者使用实验测试和数值模拟对 0 ≤ h/λ ≤ 1/3 范围内的表面裂纹引起的表面波近场散射进行了彻底研究。首先，实验研究了传感器位置对表面波穿过表面裂纹时透射系数的影响。数据是使用空气耦合传感器从有机玻璃和混凝土试件中收集的。结果，以归一化裂纹深度（h/λ）和归一化传感器位置（x/λ）的形式表示了透射系数的变化。通过将实验结果与数值模拟（有限元法）进行比较，验证了有限元模型的有效性。其次，使用经过验证的有限元模型进行了一系列参数研究，以更全面地了解在具有不同力学性能和几何条件的各种固体材料中传播的表面波的近场散射。最后，提出了一种选择适当的传感器布置的指南，以便使用 SWT 方法可靠地获取裂纹深度。
