High resolution electron microscopy of fatigue behavior in high performance concrete and multiscale modelling using a bonded particle model

高性能混凝土疲劳行为的高分辨率电子显微镜和使用粘合颗粒模型的多尺度建模

• 批准号: 353408149
• 负责人: Dr.-Ing. Martin Ritter
• 金额: --
• 依托单位: Betriebseinheit Elektronenmikroskopie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/353408149?language=en
• 关键词: resolution; electron; microscopy; fatigue; behavior

The project focuses on two objectives: Firstly, the analysis of structural damage caused by fatigue in cementitious high performance materials using high resolution analytical electron microscopy. The second aim of the project is the multiscale modelling of fatigue in high performance concrete using a bonded particle model (BPM). The project focuses on UHPC. In the first period, specimens of the priority program´s reference UHPC and of the binder were produced and fatigue experiments under compressive load carried out. Afterwards the structures of UHPC and binder specimens in different fatigue states were examined. To characterize the transition zone, specimens with quartzite-binder interface were produced and shear tests performed. Quartzite was used as model substance for the quartz sand of the UHPC. By means of transmission electron microscopy (TEM) characteristic structural changes of UHPC and binder specimens caused by the fatigue process could be observed on the nanoscale for the first time, whereas the UHPC does not show any characteristic changes on the microscale. To perform modeling of mechanical behavior with BPM, different rheological bond models were developed and their parameters were calibrated by means of static mechanical tests with the binder, the sand and the quartzite-binder specimens and microscopic investigations. The current model is able to predict well both the deformation and the fracture behavior. In the second period we plan to analyze the structural changes with TEM in greater detail and to quantify or at least to categorize the damage. For this purpose TEM tomography will be used intensively, as FIB-tomography was found to be not very helpful for the investigation of the system. Furthermore, in-situ tensile tests in the TEM are planned. During the second period the project will focus also on UHPC with fibers and coarse aggregate. The contact of both components with the matrix will be analyzed with high resolution TEM. These investigations will provide important information for the modeling. The modelling in the second period will be focused on homogenization methods to transfer data between different scales as well as on cyclic-jump based methods to simulate the complete fatigue behavior. A novel BPM-based approach for load extrapolation and regeneration of structure is proposed. Other focus of the work lies on further development of rheological models to describe mechanical behavior of different components and to consider changes occurring due to cyclic loading. In addition to the components investigated in the first project period, structural and functional models of fibers and coarse millimeter-sized aggregate will be developed. The project is strongly interconnected with other projects of the priority program. It uses their experimental data and shares own results, developed methods and simulation framework within the priority program. The project will furthermore participate in the planned benchmarks 4 and 5.

本项目主要有两个目标：第一，利用高分辨率分析电镜对胶结高性能材料的疲劳结构损伤进行分析。该项目的第二个目标是使用粘合颗粒模型（BPM）对高性能混凝土中的疲劳进行多尺度建模。该项目侧重于UHPC。第一阶段制作了优先方案参考UHPC和粘结剂试件，并进行了压载疲劳试验。然后对不同疲劳状态下UHPC和粘结剂试样的结构进行了研究。为了表征过渡带，制作了具有石英岩-粘结剂界面的试样并进行了剪切试验。以石英岩作为UHPC石英砂的模型物质。通过透射电镜（TEM）首次观察到疲劳过程引起的UHPC和粘结剂试样的纳米尺度特征结构变化，而UHPC在微观尺度上没有表现出任何特征变化。为了利用BPM进行力学行为建模，建立了不同的流变黏结模型，并通过黏结剂、砂和石英岩黏结剂样品的静态力学试验和微观观察来校准其参数。目前的模型能够很好地预测变形和断裂行为。在第二个阶段，我们计划用透射电镜更详细地分析结构变化，并量化或至少对损害进行分类。为此，TEM断层扫描将被广泛使用，因为fib断层扫描被发现对系统的研究不是很有帮助。此外，计划在TEM中进行原位拉伸试验。在第二个阶段，该项目还将侧重于纤维和粗骨料的UHPC。两种成分与基体的接触将用高分辨率透射电镜进行分析。这些调查将为建模提供重要的信息。第二阶段的建模将集中在均匀化方法上，以在不同尺度之间传输数据，以及基于循环跳的方法来模拟完整的疲劳行为。提出了一种新的基于bpm的结构荷载外推和再生方法。其他工作的重点在于进一步发展流变模型，以描述不同部件的力学行为，并考虑由于循环加载而发生的变化。除了第一个项目期间研究的组件外，还将开发纤维和粗毫米级骨料的结构和功能模型。该项目与其他优先项目紧密相连。它使用他们的实验数据，并在优先计划中共享自己的结果、开发的方法和仿真框架。该项目将进一步参与计划的基准4和基准5。