Origins of Damping in Biomimetic Scale Exoskeletal Metamaterials and their Influence on Limit Cycles

该补助金将支持对仿生尺度结构中新型阻尼的发现和量化的研究。这些结构是合成的软基质，具有硬板状外骨骼突起，类似于鱼类和爬行动物的鳞片。阻尼可以严重影响一系列动态系统的性能，例如软自主系统和机器人，可穿戴技术，航空结构和微系统。通常，阻尼是不期望的或控制不良的。然而，外骨骼结构利用几何形状、变形和滑动来提供对阻尼响应的前所未有的控制。这可以将阻尼从一个讨厌的东西变成一个设计元素，从而调整操作效率和动态。这将直接有助于开发下一代航空航天结构、协作机器人（COBOTS）和具有上级性能的智能皮肤。这些成果将提高运营效率，加速自动化并深化人机集成。这项研究将广泛造福美国经济，提高技术竞争力，加强国防，并对社会产生积极影响。这项研究的全面但基本的方法将导致新的科学，更大的跨工程思想的交叉授粉，扩大代表性不足的群体的参与，并改善工程课程。在这项研究中考虑的系统的结构阻尼的起源是从滑动外骨骼结构之间的摩擦，并显着重塑超材料由于复杂的相互作用的动力学，变形和拓扑结构。仿生鳞片外骨骼超材料的动力学，类似于在自然界中发现的鱼类和爬行动物的鳞片的形式，是由复杂的相互滑动运动学的刚性板状鳞片。然而，由于滑动摩擦引起的阻尼的出现知之甚少，因为摩擦具有双重性质-增强耗散和刚度。作为滑动复杂性的直接结果，该项目假设即使在尺度之间存在简单的库仑摩擦时，也会出现粘性、方向性和非线性阻尼行为。由于摩擦对刚度和阻尼的双重影响，它在极限环的产生-湮灭中起着核心作用。该研究将使用分析建模，计算模拟（包括有限元）和基于测试和成像的实验研究的组合来揭示结构-耗散-动力学关系。尺度滑动运动学与基底变形和边界条件的相互作用引起了这些新兴的属性，即使在小应变与复杂的振荡可定制的外骨骼分布和形状（架构）。通过揭示这些操作因素的耦合，将创建一个新的关于外骨骼结构动力学的变革性知识体系。该奖项反映了NSF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。

The grant will support research towards the discovery and quantification of new kind of damping in biomimetic scale structures. These structures are synthetic soft substrates with stiff plate like exoskeletal protrusion resembling scales on fishes and reptiles. Damping can critically affect the performance of a range of dynamic systems such as soft autonomous systems and robots, wearable technologies, aerostructures and microsystems. Typically, damping is either undesirable or poorly controlled. However, exoskeletal structures leverage geometry, deformation and sliding to provide unprecedented control over damping response. This can change damping from a nuisance to a design element that tailors operational efficiency and dynamics. This will directly contribute to the development of next generation of aerospace structures, collaborative robots (COBOTS) and smart skins with superior performance. These outcomes will improve operational efficiency, accelerate automation and deepen human-machine integration. This research will broadly benefit US economy, increase technological competitiveness, strengthen national defense, and positively affect society. The comprehensive but fundamental approach in this research will lead to new science, greater cross-pollination of ideas across engineering, broaden participation of underrepresented groups and improve engineering curriculum. The origins of structural damping for the systems considered in this study are from the friction between sliding exoskeletal structures, and are dramatically reshaped in metamaterials due to the intricate interplay of dynamics, deformation and topology. The dynamics of biomimetic scale exoskeletal metamaterials, resembling the form of scales found in nature on fishes and reptiles, is dictated by the complex mutual sliding kinematics of the stiff plate-like scales. However, the emergence of damping due to sliding friction is poorly understood as friction has a dual nature – enhance both dissipation and stiffness. As a direct consequence of sliding complexity, this project hypothesizes the emergence of viscous, directional and nonlinear damping behavior even when simple Coulomb friction exists between scales. Due to the dual effect of friction on both stiffness and damping, its central role in limit cycle creation-annihilation is postulated. The research will reveal the architecture-dissipation-dynamics relationships using a combination of analytical modeling, computational simulations including finite elements and testing and imaging based experimental studies. The interplay of scale sliding kinematics with substrate deformation and boundary conditions give rise to these emergent properties even in small strains with complex oscillations tailorable from the exoskeletal distribution and shape (architecture). By revealing the coupling of these operating factors, a new body of transformative knowledge on the dynamics of exoskeletal structures will be created.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.