School of Mechanical Engineering, The University of Adelaide, SA 5005, Australia.
School of Mechanical Engineering, The University of Adelaide, SA 5005, Australia.
Ultrasonics. 2021 Jul;114:106369. doi: 10.1016/j.ultras.2021.106369. Epub 2021 Feb 11.
Engineering structures are often composed of thin elements containing features such as free edges, welds, ribs, and holes, which makes distant safety inspections based on guided waves difficult due to wave scattering. However, these features can themselves generate so-called 'feature-guided' waves, which can potentially be utilised for damage detection. One such example are flexural wedge waves, which have been investigated extensively both theoretically and experimentally in the past. Another example is edge waves. These waves, which are a natural analogue of Rayleigh waves propagating in a finite thickness plate, have received relatively little attention, specifically with respect to their possible use in distant damage inspections and Structural Health Monitoring systems. The current paper is aimed to address this gap, and it is focused on the investigation of the fundamental mode of edge waves (ES), which is the most promising for practical applications. The features of the transient ES mode are investigated experimentally and numerically, and compared with previous theoretical studies. It was demonstrated that the ES mode can be effectively excited with the wedge excitation method, and distant damage detection with this wave mode at low frequency-thickness values (FTV < 5) is readily achievable. In particular, in a laboratory environment the ES mode propagated several meters with almost no decay. However, at higher frequency-thickness values, a wave amplitude modulation, significant energy decay and strong coupling between the ES and S wave modes were observed. These phenomena may restrict the defect resolution as well as the range of damage inspections based on the fundamental edge wave mode.
工程结构通常由含有自由边缘、焊接、肋骨和孔等特征的薄元件组成，由于波的散射，基于导波的远距离安全检测变得困难。然而，这些特征本身可以产生所谓的“特征导波”，这些波可能被用于损伤检测。其中一个例子是弯曲楔形波，过去已经在理论和实验方面进行了广泛的研究。另一个例子是边缘波。这些波是在有限厚度板中传播的瑞利波的自然类似物，它们受到的关注相对较少，特别是在远距离损伤检测和结构健康监测系统中的潜在应用方面。目前的论文旨在解决这一差距，重点研究边缘波（ES）的基本模式，该模式在实际应用中最有前途。实验和数值研究了瞬态 ES 模式的特征，并与以前的理论研究进行了比较。结果表明，ES 模式可以通过楔形激励方法有效地激发，并且在低频厚度值（FTV <5）下，这种波模式可以实现远距离损伤检测。特别是在实验室环境中，ES 模式传播了数米，几乎没有衰减。然而，在更高的频率厚度值下，观察到了波幅调制、能量显著衰减以及 ES 和 S 波模式之间的强耦合。这些现象可能会限制基于基本边缘波模式的缺陷分辨率和损伤检测范围。
