EAPSI: Modeling of Forces Within Sand During Compression Based on X-Ray Images

散粒体的工程特性在岩土工程、国防和工业中具有重要意义，一直是研究的热点。粒状材料的例子有：地基下的沙粒，暴露于地下爆炸的沙粒流，加工过程中的药物粉末，或筒仓内的颗粒。这些颗粒之间的相互作用和力对颗粒材料的力学行为非常重要，但仍然没有得到很好的理解。来自澳大利亚墨尔本大学的Antoinette托尔德西利亚博士是颗粒材料微观力学领域的领先专家，并开发了一套强大的数学工具来分析颗粒材料数据和测量结果。这项研究将结合由提案人提供的颗粒材料在加载过程中的三维X射线图像，在托尔德西利亚博士的模型中进行测试和分析。当外部载荷施加到大量颗粒材料上时，被称为力链的颗粒的细观尺度柱状结构以近似线性的方式排列，以抵抗大部分施加的载荷，并且在载荷增加期间，力链将继续抵抗载荷或弯曲。理解力链在特定边界条件下的行为将有助于解释材料的宏观尺度特性，并有助于用微观力学方法来建模多尺度行为。复杂的颗粒形态和粒状织物，从三维X射线计算机断层扫描（CT）数据的天然砂在模型中进行分析，并比较理想化的颗粒。这项研究有望深入了解影响力链形成和崩溃的因素，这对涉及颗粒材料的计算机模型和实际应用产生了深远的影响。这个NSF EAPSI奖是与澳大利亚科学院合作资助的。

The engineering behavior of granular materials has significant importance to geotechnical engineering, defense, and industry, and has been the subject of extensive research. Examples of granular material are: sand particles under a foundation, the flow of sand particles exposed to a buried explosion, pharmaceutical powders during processing, or grains within a silo. The interaction and forces between these particles is extremely important to the mechanical behavior of granular material but is still not very well understood. Dr. Antoinette Tordesillas, from the University of Melbourne in Australia, is a leading expert in the micro-mechanics of granular material and has developed a robust suite of mathematical tools to analyze granular materials data and measurements. This research will incorporate three-dimensional x-ray images of granular material during loading, provided by the proposer, to test and analyze in Dr. Tordesillas's models.As external loads are applied to mass of granular material, meso-scale columnar structures of particles known as force chains align in a nearly quasi-linear manner to resist the bulk of the applied load, and during the increase of loading the force chains will either continue to resist the load or buckle. Understanding how force chains behave given certain boundary conditions will help explain the macro-scale properties of the material and contribute to a micro-mechanical approach to modeling multi-scale behavior. Complex particle morphology and granular fabric, obtained from 3D X-ray computed tomography (CT) data of natural sand during, will be analyzed in the model and compared to the idealized particles. The research is expected to provide an insight into the factors that affect the formation and collapse of force chains which has a profound impact on computer models and practical applications that involve granular materials. This NSF EAPSI award is funded in collaboration with the Australian Academy of Science.