Aix Marseille Univ, CNRS, Centrale Marseille, LMA, 13453 Marseille, France; Electricity of France Research and Development (EDF R&D), 78400 Chatou, France.
Aix Marseille Univ, CNRS, Centrale Marseille, LMA, 13453 Marseille, France.
Ultrasonics. 2019 Feb;92:21-34. doi: 10.1016/j.ultras.2018.07.018. Epub 2018 Aug 2.
Several non-destructive evaluation techniques to characterize concrete structures are based on ultrasonic wave propagation. The interpretation of the results is often limited by the scattering phenomena between the ultrasonic wave and the high concentration aggregates contained in the cement matrix. Numerical simulations allow for further insights. This study aims to build a two-dimensional numerical model in order to reproduce and interpret ultrasonic wave propagations in concrete. The model is built in a spectral-element software package called SPECFEM2D. The validation of the numerical tool is based on the use of resin samples containing different amount of aluminum rods from low (5%) to high concentration (40%), the last one being representative of aggregate concentration in concrete. These samples are characterized using an ultrasonic testing bench (ultrasonic water tank) from 150 kHz to 370 kHz. The measured results are analyzed in terms of phase velocity and attenuation which are the main parameters of coherent waves. As homogenization models such as the Waterman-Truell or Conoir-Norris models are usually used to model coherent waves in two-phase systems, we also compare the experimental and numerical results against them. We confirm that the use of these homogenization models is limited to low concentration of scattering phase, which is not adapted to applications to concrete. Finally, we use our numerical tool to carry out a parametric study on scatterer concentration, shape, orientation and size distribution of aggregates in concrete. We show that aggregate orientation has an influence on coherent wave parameters, but aggregate shape has not.
有几种用于描述混凝土结构的无损评估技术是基于超声波传播的。结果的解释通常受到超声波与水泥基体中高浓度骨料之间散射现象的限制。数值模拟可以提供更深入的了解。本研究旨在建立一个二维数值模型，以再现和解释混凝土中的超声波传播。该模型是在称为 SPECFEM2D 的谱元软件包中构建的。数值工具的验证基于使用含有不同数量铝棒的树脂样品，从低浓度（5%）到高浓度（40%），最后一个浓度代表混凝土中的骨料浓度。这些样品使用从 150kHz 到 370kHz 的超声波测试台（超声波水箱）进行表征。根据相干波的主要参数，即相速度和衰减，对测量结果进行分析。由于诸如 Waterman-Truell 或 Conoir-Norris 模型等均匀化模型通常用于模拟两相系统中的相干波，我们还将实验和数值结果与它们进行了比较。我们证实，这些均匀化模型的使用仅限于散射相的低浓度，这不适用于混凝土的应用。最后，我们使用我们的数值工具对混凝土中骨料的浓度、形状、取向和尺寸分布进行了参数研究。我们表明，骨料取向对相干波参数有影响，但骨料形状没有影响。
