Shan Shengbo, Cheng Li
Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong Special Administrative Region; The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen 518057, China; Hong Kong Branch of National Rail Transit Electrification and Automation Engineering Technology Research Center, The Hong Kong Polytechnic University, Kowloon, Hong Kong Special Administrative Region.
Department of Mechanical Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong Special Administrative Region; The Hong Kong Polytechnic University Shenzhen Research Institute, Shenzhen 518057, China; Hong Kong Branch of National Rail Transit Electrification and Automation Engineering Technology Research Center, The Hong Kong Polytechnic University, Kowloon, Hong Kong Special Administrative Region.
Ultrasonics. 2022 Feb;119:106554. doi: 10.1016/j.ultras.2021.106554. Epub 2021 Aug 20.
Inspection of incipient structural damage is of great significance. Existing techniques based on nonlinear guided waves have shown great promise for the detection of incipient damage due to material microstructure changes, but with only limited success for damage localization, which is technically more challenging. Our previous work uncovered the existence of the second harmonic A0 mode Lamb waves in a PZT-driven system, as a result of the mixing of the primary A0 and S0 mode Lamb waves, thus pointing at the possibility of performing damage localization through tuning the size of the wave mixing zone. In the present study, a two-dimensional incipient damage localization method is proposed based on this newly discovered wave phenomenon. By visualizing the nonlinear wave field, damage-induced nonlinear wave scattering features are first investigated. A dedicated localization algorithm is then proposed and evaluated. Numerical results show that the energy of the scattered nonlinear wave is mainly confined to a narrow region along the actuator-damage path, the spatial variation of which can be approximated by a simple Gaussian function. Embedding this information into the proposed localization strategy, damage localization can be achieved using a simple physical system. Experiments are finally carried out to validate the 2nd A0 wave scattering features and the proposed damage localization method.
早期结构损伤检测具有重要意义。现有的基于非线性导波的技术在检测由于材料微观结构变化引起的早期损伤方面显示出巨大潜力，但在损伤定位方面仅取得了有限的成功，而损伤定位在技术上更具挑战性。我们之前的工作发现了在压电陶瓷驱动系统中存在二次谐波A0模式兰姆波，这是由于一次A0和S0模式兰姆波的混合所致，从而指出了通过调整波混合区大小来进行损伤定位的可能性。在本研究中，基于这一新发现的波现象提出了一种二维早期损伤定位方法。通过可视化非线性波场，首先研究损伤引起的非线性波散射特征。然后提出并评估了一种专用的定位算法。数值结果表明，散射非线性波的能量主要集中在沿着激励器 - 损伤路径的一个狭窄区域，其空间变化可以用一个简单的高斯函数近似。将此信息嵌入到所提出的定位策略中，可以使用一个简单的物理系统实现损伤定位。最后进行实验以验证二次A0波散射特征和所提出的损伤定位方法。
