Shen Yanfeng, Cesnik Carlos E S
University of Michigan-Shanghai Jiao Tong University Joint Institute, Shanghai Jiao Tong University, Shanghai 200240, China.
Department of Aerospace Engineering, University of Michigan, Ann Arbor, MI 48109, USA.
Ultrasonics. 2019 Apr;94:202-217. doi: 10.1016/j.ultras.2018.09.011. Epub 2018 Sep 25.
This article presents an efficient numerical approach to the investigation of nonlinear scattering and mode conversion phenomena of Lamb waves as they interact with breathing cracks. A Local Interaction Simulation Approach (LISA) is adopted, which possesses the versatility to capture arbitrary damage profiles. The stick-slip contact dynamics is implemented in the LISA model via the penalty method, which captures the nonlinear interactions between Lamb waves and breathing cracks. The LISA framework achieves remarkable computational efficiency with its parallel implementation using Compute Unified Device Architecture (CUDA) executed on powerful GPUs. A small-size LISA model with absorbing boundaries is tailored for the purpose of extracting the Lamb wave scattering and mode conversion features. Due to the explicit parallel CUDA implementation and the small-size model setup, the computation is highly efficient. Numerical case studies on nonlinear scattering of Lamb waves from breathing cracks are given. Distinctive higher harmonic generation and selective mode conversion phenomena are presented using the complex-valued Wave Damage Interaction Coefficients (WDICs) containing both amplitude and phase information of the scattered wave field. The effect of oblique incident angle on nonlinear scattering phenomenon is investigated. The rough crack surface feature with initial openings and closures is also considered to better approximate fatigue cracks in practical engineering scenarios. In addition, the wave amplitude effect on the nonlinear scattering and mode conversion is studied. This research may provide guidelines for the effective design of sensor arrays utilizing nonlinear Lamb waves for fatigue crack detection.
本文提出了一种高效的数值方法，用于研究兰姆波与呼吸裂纹相互作用时的非线性散射和模式转换现象。采用了局部相互作用模拟方法（LISA），该方法具有捕获任意损伤轮廓的通用性。通过罚函数法在LISA模型中实现了粘滑接触动力学，该方法捕获了兰姆波与呼吸裂纹之间的非线性相互作用。LISA框架通过在强大的图形处理器（GPU）上使用统一计算设备架构（CUDA）进行并行实现，实现了显著的计算效率。为提取兰姆波散射和模式转换特征，定制了一个具有吸收边界的小型LISA模型。由于采用了显式并行CUDA实现和小型模型设置，计算效率很高。给出了关于呼吸裂纹引起的兰姆波非线性散射的数值案例研究。使用包含散射波场幅度和相位信息的复值波损伤相互作用系数（WDIC），展示了独特的高次谐波产生和选择性模式转换现象。研究了斜入射角对非线性散射现象的影响。还考虑了具有初始开口和闭合的粗糙裂纹表面特征，以更好地近似实际工程场景中的疲劳裂纹。此外，研究了波幅对非线性散射和模式转换的影响。本研究可为利用非线性兰姆波进行疲劳裂纹检测的传感器阵列的有效设计提供指导。
