Granular Materials Design and Optimization

Jaeger颗粒物的处理和加工对国家的经济基础和技术基础非常重要。对于颗粒材料的性能至关重要或制造成本很高的应用，组成颗粒的优化成为一项关键任务。然而，对颗粒状材料表现出的复杂行为的理解和控制带来了巨大的挑战，特别是对于非球形材料。最先进的方法是预测给定颗粒类型或形状的集合体属性。正确的设计需要的是一种解决逆问题的通用方法：一种识别那些粒子属性的方法，这些属性将优化给定的聚合属性。该项目的目标是制定和实施这种方法。该项目将进化优化策略、数值模拟、三维(3D)快速成型、测试机械载荷响应的实验和非侵入性x射线成像集成到一个全面的、紧密耦合的方法中，能够为这一逆问题提供解决方案。该项目直接解决到目前为止难以回答的问题，包括如何根据给定的性能目标优化颗粒形状，或者设计出属于典型性能区域之外的具有独特集合体特征的颗粒材料。该项目的一个重点将是设计随机颗粒集料系统的机械载荷响应，这一方面的研究比静态填充特性要少得多。除了简单的凸粒子，该项目还将探索由更小的积木组成的广泛类别的复合粒子。任意颗粒形状将由颗粒分子表示，颗粒分子的构型可以变异和进化，以优化性能。这种进化是通过调用DEM模拟的优化算法来执行的。该项目将探索除形状外的一系列不同的颗粒级变量，如尺寸、体积模数和弯曲刚性(对于更复杂的颗粒状聚合物类型的颗粒)。其中的具体目标将是设计颗粒材料，不仅要考虑集料的有效弹性系数或屈服应力等特性，而且要设计整个应力应变曲线。3D打印将使制造大量优化的颗粒用于直接实验验证成为可能。X射线将在无法模拟颗粒的情况下提供微观结构信息，并检查从模型颗粒(如3D打印的颗粒)获得的设计规则在颗粒材料改变时是否仍然有效。优化设计的颗粒的可用性将使其有可能克服目前限制颗粒材料使用的一些瓶颈，并开辟广泛的新用途。这可能包括用于软机器人的轻质、易堵塞和形状一致的材料；用于医疗植入物的高韧性、高孔隙率的材料；或者具有应力-应变特性并可以倒在敏感设备周围的减震材料。该项目将培训研究生和本科生在科学和工程的交界处进行前沿研究。这项研究将与一系列多方面的教育和外联活动相结合，包括与附近的芝加哥科学与工业博物馆的活动。

1334426PI: JaegerThe handling and processing of particulate matter is important to the economy and technology base of the nation. For applications where either the performance of the granular material is critical or the fabrication cost is substantial, optimization of the constituent particles becomes a key task. Yet the understanding and control of the complex behavior exhibited by granular material poses formidable challenges, in particular for non-spherical shapes. The state-of-the-art approach is to predict the aggregate properties for given particle type or shape. What is needed for proper design, but so far has been lacking, is a general approach to the inverse problem: a methodology that identifies those particle attributes that will optimize given aggregate properties. The objective of the project is to develop and implement such methodology. The project integrates evolutionary optimization strategies, numerical simulations, three-dimensional (3d) rapid prototyping, experiments testing the mechanical load response, and non-invasive x-ray imaging into a comprehensive, tightly coupled approach capable of providing solutions to this inverse problem.This project directly addresses questions that so far have been difficult to answer, including how to optimize particle shape for given performance goals or design granular materials with unique aggregate characteristics that fall outside the typical performance regions. A focus of the project will be on designing the mechanical load response of random granular aggregate systems, an aspect much less studied than the static packing properties. Going beyond simple convex particles, the project will explore a wide class of compound particles composed from smaller building blocks. Arbitrary particle shapes will be represented by granular molecules, whose configuration can be mutated and evolved to optimize performance. This evolution is performed by an optimization algorithm that calls up DEM simulations. The project will explore a range of different particle-level variables besides shape, such as size, bulk modulus, and bending rigidity (for more complex, granular-polymer-type particles). Among the specific goals will be to design granular materials not only with respect to characteristics like the effective modulus or the yield stress of the aggregate, but to design the whole stress strain curve. 3d-printing will make it possible to fabricate large numbers of optimized particles for direct experimental validation. X-rays will provide microstructural information in cases where particles cannot be simulated and to check whether design rules obtained from model particles, such as 3d-printed ones, remain valid when the particle material is changed.The availability of optimized designed particles would make it possible to overcome a number of bottlenecks currently limiting the use of granular materials and open up a wide range of new uses. This might include lightweight jammable and shape-conforming materials for soft robotics; high-toughness high-porosity materials for medical implants; or shock absorbing materials that have designed stress-strain characteristics and can be poured around sensitive equipment. The project will train graduate and undergraduate students in forefront research at the interface of science and engineering. The research will be integrated with a multi-faceted set of education and outreach activities, including activities with the nearby Chicago Museum of Science and Industry.