Computational Tools, 4275 Chatham Avenue, Gurnee, Illinois 60031, USA.
J Acoust Soc Am. 2011 Jun;129(6):3661-75. doi: 10.1121/1.3583540.
Prior work has proposed the use of ultrasonic angle-beam shear wave techniques to detect cracks of varying angular location around fastener sites by generating and detecting creeping waves. To better understand the nature of the scattering problem and quantify the role of creeping waves in fastener site inspections, a 3D analytical model was developed for the propagation and scattering of an obliquely incident plane shear wave from a cylindrical cavity with arbitrary shear wave polarization. The generation and decay of the spiral creeping waves was found to be dependent on both the angle of incidence and polarization of the plane shear wave. A difference between the angle of displacement in 3D and the direction of propagation for the spiral creeping wave was observed and attributed to differences in the curvature of the cavity surface for the tangential and vertical (z) directions. Using the model, practical insight was presented on measuring the displacement response in the far-field from the hole. Both analytical and experimental results highlighted the value of the diffracted and leaky spiral creeping wave signals for nondestructive evaluation of a crack located on the cavity. Last, array and signal processing methods are discussed to improve the resolution of the weaker creeping wave signals in the presence of noise.
先前的工作提出了使用超声波角束剪切波技术，通过产生和检测爬行波来检测紧固件周围不同角度位置的裂纹。为了更好地理解散射问题的本质，并量化爬行波在紧固件检测中的作用，开发了一个用于传播和散射具有任意剪切波极化的圆柱形腔中斜入射平面剪切波的 3D 分析模型。发现螺旋爬行波的产生和衰减既取决于平面剪切波的入射角，也取决于其偏振角。观察到 3D 中的位移角与螺旋爬行波的传播方向之间存在差异，并将其归因于切向和垂直（z）方向上腔表面曲率的差异。利用该模型，对从孔中测量远场的位移响应提出了实际的见解。分析和实验结果均强调了用于检测位于腔上的裂纹的衍射和泄漏螺旋爬行波信号的价值。最后，讨论了阵列和信号处理方法，以提高存在噪声时较弱的爬行波信号的分辨率。
