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，着眼于实现灵活的钻探探头，应用于现场勘察和地下挖掘。柔性探头和机器人通常包括一个线性致动器和一个柔顺的皮肤--一个壳状结构，经过精心的图案设计，以实现所需的、通常是极端的变形行为。随着致动器的拉长或缩短，皮肤与周围的土壤相互作用，赋予探头以生物灵感形式穿过洞穴的能力。为了克服当前皮肤设计的局限性，本研究引入了多模式皮肤的概念，这种皮肤可以径向扩展，同时生成弹出式特征，导致洞穴内运动所需的各向异性摩擦。为了避免蒙皮设计中的大量试验和错误，本项目旨在了解这种变形蒙皮的基本特征(例如，产生各向异性摩擦的弹出板)与颗粒介质之间的“弹性颗粒”相互作用。这种理解被用来实现挖洞探头，该探头将接受广泛的测试，以评估皮肤的挖洞性能及其以有意义的方式与周围土壤相互作用的能力。该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，该项目中创造的关于弹性-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。我们的推广和教育活动，围绕“灵活的土木工程系统”的主题，将使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，就像那些在自然界中发现的那样，在各种土木工程应用中非常有用。这项研究的主要目的是提供对“建筑”变形壳和颗粒介质之间的微观和宏观相互作用的了解，并利用这些知识来指导实现地下挖掘和勘探的探测。为了达到这一目标，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的力学之间的界面。这项研究将使用一种全面的方法，其基础是：i)使用结构力学和运动学理论对蒙皮的变形能力进行理论研究；ii)使用有限元方法进行应力预测；iii)通过离散元建模和X射线CT扫描辅助直接剪切实验研究微观的弹粒相互作用；v)通过可视化水槽实验和配备此类蒙皮的探头的离散元模拟来宏观验证蒙皮的行为。该项目将为合理应用建筑壳体作为挖掘探测的变形外壳奠定基础。该项目由土木、机械和制造创新工程(CMMI)分部和既定的激励竞争研究计划(EPSCoR)联合资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.