Yuan Peilong, Xu Xiaodong, Glorieux Christ, Jia Kangning, Chen Jiaming, Chen Xianmei, Yin Anmin
Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Department of Physics, Nanjing University, Nanjing 210093, China; Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200D, B3001 Leuven Belgium.
Key Laboratory of Modern Acoustics, MOE, Institute of Acoustics, Department of Physics, Nanjing University, Nanjing 210093, China.
Ultrasonics. 2024 May;140:107306. doi: 10.1016/j.ultras.2024.107306. Epub 2024 Mar 23.
To characterize fatigue crack, an analytical calculation and finite element (FE) simulation of Lamb wave propagating through the region of a breathing crack in a two-dimensional(2D) isotropic plate were studied. Contact surface boundary conditions between the two surfaces of the vertical crack were considered to study contact acoustic nonlinearity (CAN) from the breathing contact crack in conjunction with the modal decomposition method, Fourier transform, and variational principle-based algorithm. Reflection and transmission coefficients in the fundamental frequency and second harmonic frequency were calculated and analyzed quantitatively. Different ratios of incident wave amplitude to crack width were studied to calculate CAN results related to micro-crack width. In addition, a low-frequency (LF) vibration(10 Hz) excitation was introduced to perturb the free surface vertical crack to close, and an interrogating Lamb wave(1 MHz) was used to study crack-related CAN in different conditions for interpreting the modulation mechanism. The contact boundary conditions between two surfaces of vertical crack were set which were dynamically changed due to the low frequency modulation. The clapping effects when the crack closed due to the modulation of the contact boundary conditions between the crack surfaces were studied and analyzed to get the quantitative correlation between CAN and LF modulation. The results obtained from the analytical model were compared with those from the FE simulation, showing good consistency. Knowledge of these effects is essential to correctly gauge the severity of surface cracks in the plate, which can be spotlighted in its application to quantitative evaluation of micro fatigue cracks in structural health monitoring(SHM).
为了表征疲劳裂纹，研究了兰姆波在二维各向同性板中穿过呼吸裂纹区域的解析计算和有限元（FE）模拟。考虑垂直裂纹两个表面之间的接触表面边界条件，结合模态分解方法、傅里叶变换和基于变分原理的算法，研究呼吸接触裂纹的接触声非线性（CAN）。对基频和二次谐波频率下的反射系数和透射系数进行了定量计算和分析。研究了不同的入射波振幅与裂纹宽度比，以计算与微裂纹宽度相关的CAN结果。此外，引入低频（LF）振动（10 Hz）激励来扰动自由表面垂直裂纹使其闭合，并使用探测兰姆波（1 MHz）研究不同条件下与裂纹相关的CAN，以解释调制机制。设置了垂直裂纹两个表面之间的接触边界条件，该条件因低频调制而动态变化。研究和分析了由于裂纹表面之间接触边界条件的调制导致裂纹闭合时的拍击效应，以获得CAN与LF调制之间的定量相关性。将解析模型得到的结果与有限元模拟结果进行比较，显示出良好的一致性。了解这些效应对于正确评估板中表面裂纹的严重程度至关重要，这在其应用于结构健康监测（SHM）中的微疲劳裂纹定量评估时可以凸显出来。
