Development and Characterisation of the structure of cohesive bulk solids

粘性散装固体结构的发展和表征

• 批准号: 169536439
• 负责人: Professor Dr.-Ing. Arno Kwade
• 金额: --
• 依托单位: Institut für Partikeltechnik
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2010
• 资助国家: 德国
• 起止时间: 2009-12-31 至 2018-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/169536439?language=en
• 关键词: Development; Characterisation; structure; cohesive; bulk

When sheared, cohesive powders develop an inhomogeneous and anisotropic structure. Microscopically this is due to fragmentation and agglomeration of particle clusters within the bulk. The particles themselves remain largely intact, but contacts among them open or close. An important distinction can be made between instantly sticking contacts (adhesion dominated) and those, which need time to age (cementation dominated). Corresponding model materials are KCl-powders (cementation dominated), respectively SiO2- or limestone powders (adhesion dominated). The KCl-particles can be well described by an elasto-plastic contact model, while the SiO2-particles behave viscoelastically. The aim of this project is to understand the effect which these contact properties have on the shear induced inhomogeneity and anisotropy. Experiments are performed which correlate properties on the level of individual particles with the shear induced structure formation in the bulk. They are complemented by computer simulations to establish physical models for the phenomena. A crucial experimental tool to validate the simulation models in order to relate the particle dynamics to macroscopic phenomena is a micro shear-tester, which can be used in combination with X-ray microtomograpy (XMT) to get a detailed picture of the three dimensional structure of the particle network. Based on the experimental and theoretical analysis of the first series of three dimensional snapshots the third funding period will focus on the influence of particle size distribution, particle shape and cohesion strength on quasi-dynamic processes. In order to extract individual particle trajectories and rotations, the digital processing of time resolved images with high spatial resolution will be improved, especially also for non-spherical particles. These experimental and corresponding simulation-based data will be analyzed statistically in order to identify relevant structural signatures for the rheological behavior of cohesive bulk materials. The outcome of this research will be an enhanced understanding of contact mechanical behavior based on structural information.

当剪切时，粘性粉末形成不均匀和各向异性的结构。在显微镜下，这是由于本体内颗粒簇的破碎和团聚。粒子本身基本上保持完整，但它们之间的接触打开或关闭。可以在即时粘附接触（粘附为主）和需要时间老化的接触（胶结为主）之间进行重要的区分。相应的模型材料是KCl粉末（胶结为主），分别为SiO2或石灰石粉末（粘附为主）。KCl颗粒可以很好地描述了弹塑性接触模型，而SiO2颗粒表现为粘弹性。本项目的目的是了解这些接触特性对剪切引起的不均匀性和各向异性的影响。进行实验，其相关的单个颗粒的水平上的性能与剪切诱导的结构形成的散装。它们还辅之以计算机模拟，以建立这种现象的物理模型。验证模拟模型以将颗粒动力学与宏观现象联系起来的关键实验工具是微观剪切测试仪，该测试仪可与X射线显微断层扫描（XMT）结合使用，以获得颗粒网络三维结构的详细图像。在第一系列三维快照的实验和理论分析的基础上，第三个资助期将侧重于颗粒尺寸分布、颗粒形状和凝聚强度对准动态过程的影响。为了提取单个颗粒的轨迹和旋转，将改进具有高空间分辨率的时间分辨图像的数字处理，特别是对于非球形颗粒。这些实验和相应的基于模拟的数据将进行统计分析，以确定相关的结构签名的粘性散装材料的流变行为。这项研究的成果将是一个加强了解接触力学行为的基础上的结构信息。