IEEE Trans Ultrason Ferroelectr Freq Control. 2022 Jan;69(1):330-339. doi: 10.1109/TUFFC.2021.3114432. Epub 2021 Dec 31.
Most of the existing ultrasonic-guided wave tomography approaches to map structural changes in plate-like waveguides are based on the assumption of an isotropic material model. However, there are many other engineering applications that are made of anisotropic materials and structures. Applying these techniques on such structures becomes complicated due to the anisotropic wave propagation behavior. The main challenge is to develop a suitable forward model that describes the wave propagation in such material, thereby enabling accurate reconstruction of the material properties. The present study proposes an anisotropic formulation of the acoustic forward model to map velocity variations induced by defects in anisotropic plates. The anisotropic behavior of the waves along the plate is simulated by implementing approximate anisotropic parameters. The velocity reconstruction is based on a full-waveform inversion algorithm, and its performance is investigated in the case of different degrees of anisotropy of the plate material and the defect. The results suggest that the method is highly suitable for imaging velocity changes due to defects. This is found to be the case when the defect has a similar anisotropic structure to the surrounding plate material. The validation experiment is performed on a multilayered composite plate with a circular defect of stiffness reduction using A mode, showing a very good performance of the reconstruction algorithm.
大多数现有的用于对板状导波结构变化进行成像的超声导波层析成像方法都基于各向同性材料模型的假设。然而，还有许多其他的工程应用是由各向异性材料和结构制成的。由于各向异性波传播行为，将这些技术应用于此类结构变得复杂。主要的挑战是开发合适的正演模型来描述这种材料中的波传播，从而能够准确地重建材料特性。本研究提出了一种各向异性的声传播正演模型来对各向异性板中缺陷引起的速度变化进行成像。通过实现近似各向异性参数来模拟波在板中的各向异性行为。速度重建基于全波形反演算法，并在板材料和缺陷的各向异性程度不同的情况下研究了其性能。结果表明，该方法非常适合成像由于缺陷引起的速度变化。当缺陷具有与周围板材料相似的各向异性结构时，就会出现这种情况。通过使用 A 模式对具有刚度降低的圆形缺陷的多层复合材料板进行了验证实验，该重建算法表现出了非常好的性能。
