In this article, a damage localization method in concrete materials based on time reversal theory and meso-scale finite element simulation considering random heterogeneous properties is developed. In this article, concrete is regarded as a multiphase composite material consisting of cement mortar matrix, coarse aggregates, and interface transition zones. Compared to other methods, which assume that concrete is homogeneous, the meso-scale model considers the intricacies of concrete inhomogeneity and can therefore better characterize the interaction between stress waves and internal structures of concrete material. Through the meso-scale method, acoustic phenomena including reflection, transmission, and diffraction among internal structures of concrete can be modeled. Furthermore, a novel time reversal based, damage imaging method is developed using the envelope of the refocused damage scattering signal to monitor the health condition of concrete. The scattered signal received by each sensor is time reversed and reemitted via numerical computation. To decrease the dispersion effect, the autocorrelation function of the refocused signals is computed to generate an image of the estimated damage. A time correction factor is introduced to decrease the influence of the elongated wave packet. Numerical and experimental results indicate that the proposed damage imaging method can locate damage with high spatial resolution in heterogeneous concrete material. Moreover, owing to the meso-scale modeling, the propagation of high-frequency stress waves in concrete can be analyzed more accurately.

中文翻译：

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基于二维细观模型的混凝土时间反演损伤定位

在本文中，开发了一种基于时间反演理论和考虑随机异质特性的细观有限元模拟的混凝土材料损伤定位方法。在本文中，混凝土被视为由水泥砂浆基体、粗骨料和界面过渡区组成的多相复合材料。与假设混凝土是均质的其他方法相比，中尺度模型考虑了混凝土非均质性的复杂性，因此可以更好地表征应力波与混凝土材料内部结构之间的相互作用。通过中尺度方法，可以模拟混凝土内部结构之间的反射、透射和衍射等声学现象。此外，基于新颖的时间反转，损伤成像方法是利用重新聚焦的损伤散射信号的包络来监测混凝土的健康状况。每个传感器接收到的散射信号经过时间反转并通过数值计算重新发射。为了减少色散效应，计算重新聚焦信号的自相关函数以生成估计损坏的图像。引入时间校正因子以减少拉长波包的影响。数值和实验结果表明，所提出的损伤成像方法可以在异质混凝土材料中以高空间分辨率定位损伤。此外，由于中尺度建模，可以更准确地分析混凝土中高频应力波的传播。