Zhang Guangdong, Li Xiongbing, Kundu Tribikram
School of Traffic and Transportation Engineering, Central South University, Changsha, Hunan 410075, China; Department of Civil and Architecture Engineering and Mechanics, University of Arizona, Tucson, AZ 85721, USA.
School of Traffic and Transportation Engineering, Central South University, Changsha, Hunan 410075, China.
Ultrasonics. 2023 Aug;133:107028. doi: 10.1016/j.ultras.2023.107028. Epub 2023 May 6.
Since it is almost impossible to carry out a comprehensive parametric investigation experimentally for internal cracks with different geometry and orientation, a good numerical modeling and simulation technique is necessary to have a clear understanding of the physics of wave propagation and its interaction with cracks. Such investigation is helpful for structural health monitoring (SHM) with ultrasonic techniques. This work presents a nonlocal peri-ultrasound theory based on ordinary state-based (OSB) peridynamics for modeling elastic wave propagation in three-dimensional (3-D) plate structures containing multiple cracks. A relatively new and promising nonlinear ultrasonic technique called Sideband Peak Count - Index (or SPC-I) is adopted to extract the nonlinearity generated from the interactions between elastic waves and multiple cracks. Effects of three main parameters - the distance between the acoustic source and the crack, the crack spacing and the number of cracks are investigated using the proposed OSB peri-ultrasound theory together with the SPC-I technique. For each of these three parameters investigation, different crack thicknesses were considered - 0 mm (crack-free), 1 mm (thin crack), 2 mm (intermediate thickness) and 4 mm (thick crack); thin and thick cracks are defined after comparing the crack thickness value with the horizon size mentioned in the peri-ultrasound theory. It is found that for obtaining consistent results the acoustic source should be placed at least one wavelength away from the crack and crack spacings also play an important role on the nonlinear response. It is concluded that the nonlinear response diminishes when the cracks become too thick, and thin cracks show higher nonlinearity than that of thick cracks and no cracks. Finally, the proposed method which is combining the peri-ultrasound theory and SPC-I technique is used for monitoring cracks' evolution process. The numerical modeling results are compared with the experimental findings reported in the literature. Consistent qualitative trends in SPC-I variations predicted numerically and obtained experimentally are observed, thus it gives confidence in the proposed method.
由于通过实验对具有不同几何形状和取向的内部裂纹进行全面的参数研究几乎是不可能的，因此需要一种良好的数值建模和模拟技术，以便清楚地了解波传播的物理过程及其与裂纹的相互作用。这种研究有助于采用超声技术进行结构健康监测（SHM）。本文提出了一种基于普通状态基（OSB）近场动力学的非局部近场超声理论，用于模拟含多个裂纹的三维（3-D）板结构中的弹性波传播。采用一种相对较新且有前景的非线性超声技术——边带峰值计数指数（或SPC-I）来提取弹性波与多个裂纹相互作用产生的非线性。利用所提出的OSB近场超声理论和SPC-I技术，研究了三个主要参数——声源与裂纹之间的距离、裂纹间距和裂纹数量的影响。对于这三个参数中的每一个参数的研究，都考虑了不同的裂纹厚度——0毫米（无裂纹）、1毫米（薄裂纹）、2毫米（中等厚度）和4毫米（厚裂纹）；薄裂纹和厚裂纹是在将裂纹厚度值与近场超声理论中提到的水平尺寸进行比较后定义的。研究发现，为了获得一致的结果，声源应放置在距离裂纹至少一个波长的位置，并且裂纹间距对非线性响应也起着重要作用。得出的结论是，当裂纹变得太厚时，非线性响应会减弱，薄裂纹比厚裂纹和无裂纹显示出更高的非线性。最后，将近场超声理论和SPC-I技术相结合的所提出的方法用于监测裂纹的扩展过程。将数值模拟结果与文献中报道的实验结果进行了比较。观察到数值预测和实验获得的SPC-I变化具有一致的定性趋势，因此这为所提出的方法提供了信心。
