High-performance simulations of wave propagation for structure analysis of concrete

试验证明，超声波对不同荷载作用下的钢筋混凝土(RC)是敏感的。相应分析的一个工具是尾波干涉术(CWI)。然而，混凝土是一种强烈的非均质和密实的复合材料。由于高密度的散射成分和夹杂物，超声波在该材料中的传播由多次散射、模式转换和扩散能量传输的复杂混合物组成。为了更好地理解骨料、孔隙率和裂缝分布对混凝土中弹性波传播的影响，并优化反演技术，在时间域中显式地模拟波的传播和散射过程是有用的。为此，我们使用旋转交错网格(RSG)有限差分技术来求解弹性、各向异性和/或粘弹性介质的波动方程。第一个集中于超声模拟作为一项服务，为合作伙伴(特别是与RUB1、BAM和TUM2)提供服务。通过这项任务，我们继续在研究股第一阶段就这一问题进行密切合作。在第二个工作包中，我们将通过X射线计算机断层扫描(XRCT)图像进一步开发数字双胞胎。利用该工具，我们估计了不同荷载(湿度、温度和机械荷载)对混凝土微观结构的影响。基于物质知识的图像分割是这一过程中的关键一步。通过几种数字岩石物理方法从地球物理到混凝土的转化，我们可以估计相应的对混凝土有效性能的影响。在第四工作包中，我们使用WP3的结果来估计对尾波信号的相应影响。在国际合作伙伴的帮助下，我们还将应用进一步的机器学习技术来解释合成结构和真实结构中的尾波信号。第四个工作包旨在将用于声学事件定位和表征的时间反向成像(TRI)技术扩展到有源TRI，它将使用尾波信号来定位和表征损伤区。WP 5的目标是应用机器学习技术来识别不同的载荷(WP 3)和主动TRI技术来定位损伤区(WP4)到研究单位(Gänstorbrücke和ScheidPlatz站)的主要建议中建议的测试侧。总之，我们将借助高性能计算机模拟和地球物理反演技术的应用来优化CWI。将进一步开展对RC的定性和定量长期评估。

It is experimentally demonstrated that ultrasonic waves are sensitive to different loadings of Reinforced Concrete (RC). A tool for the corresponding analysis is the Coda wave Interferometry (CWI). However, concrete is a strongly heterogeneous and densely packed composite material. Due to the high density of scattering constituents and inclusions, ultrasonic wave propagation in this material consists of a complex mixture of multiple scattering, mode conversion and diffusive energy transport. For a better understanding of the effect of aggregates, porosity, and of crack distribution on elastic wave propagation in concrete and to optimize inverse techniques it is useful to simulate the wave propagation and scattering process explicitly in the time domain. For this purpose, we use the Rotated Staggered Grid (RSG) finite-difference technique for solving the wave equations for elastic, anisotropic, and/or viscoelastic media.The subproject BU of the research unit is subdivided into five Work Packages (WP). The first one concentrates on ultrasound simulations as a service for collaborating partners (especially with RUB1, BAM and TUM2). With this task we continue the close collaboration on this issue during the first phase of the research unit. In the second work package we will further develop digital twins by X-Ray Computed Tomographic (XRCT) images. With this tool we estimate the influence of different loads (moisture, temperature, and mechanical load) to the microstructure of concrete. Image segmentation based on material knowledge is a crucial step in this procedure. By the transformation of several Digital Rock Physics approaches from geophysics to concrete we can estimate the corresponding influence on effective properties of concrete. In work package four we use the results of WP 3 to estimate the corresponding influence on the Coda signal. With the help of an international partner, we also will apply further machine learning techniques to interpret the coda signal in synthetic as well as in real structures. The fourth work package aims to extend the Time Reverse Imaging (TRI) technique for localization and characterization of Acoustic Events to an Active-TRI which will use the Coda signals to localize and characterize damage zones. The goal of WP 5 is to apply the machine learning techniques to identify the different loads (WP 3) and the Active-TRI technique to locate damage zones (WP4) to the test sides suggested in the main proposal of the research unit (Gänstorbrücke and station Scheidplatz).In summary we will optimize CWI with the help of high-performance computer simulations and the application of geophysical inversion techniques. Qualitative and quantitative long-term assessment of RC will be further developed.