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

颗粒材料的工程性能对岩土工程、国防和工业具有重要意义，是广泛研究的课题。颗粒状物质的例子有：地基下的沙粒、暴露在地下爆炸中的沙粒流、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，但仍然没有很好地理解。来自澳大利亚墨尔本大学的Antoinette Tordesillas博士是颗粒材料微观力学方面的权威专家，他开发了一套强大的数学工具来分析颗粒材料的数据和测量。这项研究将结合由提议者提供的颗粒材料在加载过程中的三维x射线图像，在Tordesillas博士的模型中进行测试和分析。当外部载荷被施加到大量颗粒材料上时，被称为力链的颗粒的中观尺度柱状结构以近乎准线性的方式排列以抵抗所施加的大部分载荷，并且在载荷增加期间力链将继续抵抗载荷或弯曲。了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特性，并有助于用微力学方法来模拟多尺度行为。该模型将分析从天然砂的三维x射线计算机断层扫描（CT）数据中获得的复杂颗粒形态和颗粒结构，并将其与理想颗粒进行比较。该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具有深远的影响。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.