Collaborative Research: Elasto-Granular Interactions Between Morphing Skins and Soils

该奖项将支持岩土工程和结构力学交叉领域的研究，着眼于实现用于现场调查和地下挖掘等应用的柔性挖洞探头。柔性探针和机器人通常包括一个线性执行器和一个柔性皮肤——一个壳状结构，经过精心设计，可以实现理想的、通常是极端的变形行为。当执行器拉长或缩短时，皮肤与周围的土壤相互作用，赋予探针以生物启发形式在洞穴中移动的能力。为了克服当前蒙皮设计的局限性，本研究引入了多模态蒙皮的概念，该蒙皮可以径向扩展，同时产生弹出式特征，从而诱导洞穴内运动所需的各向异性摩擦。为了避免在蒙皮设计中出现大量的试验和错误，该项目旨在提供对这种变形蒙皮（例如，产生各向异性摩擦的弹出板）的基本特征与颗粒介质之间的“弹性颗粒”相互作用的理解。利用这一认识来实现挖洞探针，该探针将进行广泛的测试，以评估皮肤的挖洞性能及其与周围土壤以有意义的方式相互作用的能力。这个项目中的想法将促进灵活的岩土系统的利用，利用结构的灵活性来实现创新的功能。此外，在这个项目中创建的关于弹性颗粒相互作用的知识可以输出到其他领域，如农业和生物医学工程。我们的外展及教育活动将围绕“灵活的土木工程系统”的主题，让学生有机会从新的角度看待土木工程系统，并了解灵活的结构，就像自然界中的结构一样，在各种土木工程应用中非常有用。本研究的主要目的是提供对“建筑”形状变形壳与颗粒介质之间微观和宏观相互作用的理解，并利用这些知识来指导实现地下挖洞和勘探的探针。为了实现这一目标，我们的工作旨在探索柔性结构的非线性力学与颗粒介质和土壤力学之间的界面。本研究将采用整体方法：i)利用结构力学和运动学理论对皮肤变形能力进行理论研究；Ii)利用有限元法进行应力预测；iii)通过离散元模型和x射线CT扫描辅助直接剪切实验研究微观弹性-颗粒相互作用；v)通过可视化槽实验和配备该皮肤的探针挖洞的离散元模拟，对皮肤行为进行宏观验证。本课题将为结构壳作为穴居探针的变形表皮的合理应用奠定基础。该项目由土木、机械和制造创新工程（CMMI）部门和刺激竞争研究的既定计划（EPSCoR）共同资助。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award will support research at the intersection of geotechnical engineering and structural mechanics, with an eye toward the realization of flexible burrowing probes for applications including site investigation and underground excavation. Flexible probes and robots typically comprise a linear actuator and a compliant skin – a shell-like structure that is carefully patterned to achieve desired and usually extreme morphing behaviors. As the actuator elongates or shortens, the skin interacts with the surrounding soil, endowing the probe with the capacity of moving through the burrow following bioinspired forms. To overcome limitations imposed by current skin designs, this research introduces the idea of multi-modal skins, that can radially expand while generating pop-up features that induce the anisotropic friction necessary for motion within the burrow. To avoid extensive trial and error in the skin design, this project aims at providing an understanding of the “elasto-granular” interactions between elementary features of such morphing skins (e.g., the pop-up plates that yield anisotropic friction) and granular media. This understanding is leveraged to realize a burrowing probe that will be subjected to extensive tests to evaluate the burrowing performance of the skin and its capacity to interact with the surrounding soil in meaningful ways. The ideas within this project will promote the utilization of flexible geotechnical systems, that leverage structural flexibility to achieve innovative functionalities. Moreover, the knowledge on elasto-granular interactions created in this project can be exported to other fields, such as agriculture and biomedical engineering. Our outreach and educational activities, revolving around the theme of “flexible civil engineering systems”, will give students opportunities to see civil engineering systems under a new light and to understand that flexible structures, like those found in nature, are extremely useful in a variety of civil engineering applications.The primary objective of this research is to provide an understanding of the microscopic and macroscopic interactions between “architected” shape-morphing shells and granular media and to leverage this knowledge to guide the realization of probes for underground burrowing and exploration. To reach this objective, our work aims at exploring the interface between the nonlinear mechanics of flexible structures and the mechanics of granular media and soils. This research will use a holistic approach based on: i) theoretical studies on the skins’ morphing capacity using structural mechanics and kinematic theories; ii) stress predictions using the finite element method; iii) studies on microscopic elasto-granular interactions via discrete element modeling and X-ray CT scan-assisted direct shear experiments; and v) macroscopic validation of skin behavior via visualization tank experiments and discrete-element simulations on the burrowing of a probe equipped with such skin. This project will lay the foundation for the rational application of architected shells as morphing skins for burrowing probes.This project is jointly funded by the Engineering for Civil, Mechanical and Manufacturing Innovation (CMMI) Division and the Established Program to Stimulate Competitive Research (EPSCoR).This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.