Friction, Fatigue and Failure: a Multiscale Approach Linking Physics, Fabrication and Geophysical Phenomena

技术概述：该奖项支持跨学科的理论研究和教育，以促进对物理的基本理解，这些物理是本质上异构的、内部结构的、在压力下的、远离平衡的材料的基础。重点研究领域包括摩擦、疲劳、非晶固体和颗粒材料的动力学和非均匀性之间相互作用的基础理论和多分辨率研究，以及在地球物理学和摩擦补偿与控制方面的应用。该项目从最小的尺度开始，计划继续对剪切颗粒材料进行数值模拟。在PI最近的工作基础上，使用接触动力学来探索在稀（动力学理论）和密（剪切转变区）限制下推导的本构定律的有效性范围，计划包括调查漏斗和其他几何形状的流动，以及对密集状态下力相关性和干扰的详细研究。结果将与实验室摩擦研究以及速率和状态本构定律进行比较。模拟还将扩展到更复杂的颗粒形状和更广泛的尺寸分布，颗粒的老化和磨损，详细的局部摩擦模型，以及与流体相关的流体动力耗散的影响。在中间尺度上，研究重点是推导和验证描述颗粒系统、非晶固体、凝胶和润滑界面的本构定律。描述了一种统一的、多尺度的本构定律方法，作为微观动力学和更大尺度（粘滑不稳定性、瞬态超调、剪切带形成和可控性）的最终含义之间的中介。该方法利用计算机科学和工程系统理论的方法扩展了非平衡统计物理的基本理论。该项目还侧重于与最近的实验室实验的定量联系，这些实验直接探测了接触、老化、闪热和流体的微观时空动态。在宏观尺度上，该提案描述了持续的地球物理应用以及摩擦补偿和控制技术应用的新工作。在地球物理应用方面的工作包括动态裂纹前缘和材料不均匀性之间的相互作用，以及存在空间材料梯度（可能是由于温度或压力变化、老化或磨损）的断裂动力学。摩擦控制方面的工作代表了PI的一个新领域，并利用她的团队在物理摩擦模型和控制理论方面的综合专业知识来开发和测试设备制造的控制器。智力优势：对致密非晶材料的变形、耗散、老化、磨损和断裂的研究，涉及到新的理论和模拟工具的发展和实施，涵盖了广泛的尺度。这既扩展了对远离平衡的物理系统的基本理解，又为描述其他复杂的、相互关联的系统提供了新的方法，这些系统表现出老化和级联分解现象。更广泛的影响：了解摩擦、疲劳和失效是目前开发新技术和预测自然灾害的主要限制因素。这里提出的工作将导致设备应用控制器和地震危害估计模型。将为公共和K-12教育和推广活动开展相关的实践示范，旨在提高公众意识和安全，并增加妇女和少数民族在物理科学领域的代表性。非技术总结：该奖项支持跨学科的理论研究和教育，以促进对固体和颗粒材料摩擦、疲劳和断裂的基本理解。对这些现象的预测能力的基本理解仍然是难以捉摸和具有挑战性的，并且将在许多情况下从材料失效到地球物理灾害中找到广泛的应用。在更深的层次上，摩擦、疲劳和断裂广泛地作为某些复杂系统的典型例子，在这些系统中，人们寻求控制其行为的基本原理。这样的普遍原则将适用于许多复杂的系统，而不仅仅是发现它们的系统。他们的发现将推动统计物理学领域的发展，该领域关注的是远离平衡的系统。PI的方法将跨越这些现象所特有的许多长度尺度。它本质上是多学科的；它将计算科学、工程学、地球物理、物理学和材料科学的元素结合在一起，以促进对基本系统的理解。了解摩擦、疲劳和失效是目前开发新技术和预测自然灾害的主要限制因素。这里提出的工作将导致设备应用控制器和地震危害估计模型。将为公共和K-12教育和推广活动开展相关的实践示范，旨在提高公众意识和安全，并增加妇女和少数民族在物理科学领域的代表性。

TECHNICAL SUMMARY:This award supports interdisciplinary theoretical research and education to advance the basic understanding of the physics which underlies materials which are intrinsically heterogeneous, internally structured, under stress, and far from equilibrium. Focus areas of the research include basic theory and multiresolution studies of the interplay between dynamics and heterogeneity in friction, fatigue, and failure of amorphous solids and granular materials, with applications in geophysics and friction compensation and control.The project begins at the smallest scales, with plans for continuing numerical simulations of sheared granular materials. Building on the PI's recent work using contact dynamics to probe the range of validity of constitutive laws derived in the dilute (kinetic theory) and dense (shear transformation zones) limits, plans include investigation of flows in hoppers and other geometries, as well as detailed studies of the emergence of force correlations and jamming in the dense regime. Results will be compared to laboratory friction studies, as well as rate and state constitutive laws. The simulations will also be expanded to investigate effects of more complex particle shapes and broader size distributions, aging and wear of particles, detailed local friction models, as well as hydrodynamic dissipation associated with fluids.At intermediate scales, investigations focus on derivation and verification of constitutive laws describing granular systems, amorphous solids, gels, and lubricated interfaces. A unified, multiscale approach to constitutive laws as an intermediate between microscopic dynamics, and the ultimate implications for larger scales (stick-slip instabilities, transient overshoots, shear band formation, and controllability) is described.The approach expands basic theory for nonequilibrium statistical physics using methods from computer science and engineering systems theory. The project also focuses on quantitative connections with recent laboratory experiments, which directly probe the microscopic spatio-temporal dynamics of contacts, aging, flash heating, and fluids.At macroscopic scales, the proposal describes continuing geophysical applications as well as new work on technological applications in friction compensation and control.Work on geophysical applications includes interactions between dynamic crack fronts and material inhomogeneities, as well as rupture dynamics in the presence of spatial material gradients (which may be due to temperature or pressure variations, aging, or wear). Work on control of friction represents a new area for the PI, and leverages her group's combined expertise in physical friction models and control theory to develop and test controllers for device fabrication.Intellectual Merit: The research on deformation, dissipation, aging, wear, and fracture in dense, amorphous materials, involves development and implementation of new theory and simulation tools spanning a broad range of scales. This both expands basic understanding of physical systems far from equilibrium, and provides new methodologies for describing of other complex, interconnected systems which exhibit aging and cascading breakdown phenomena.Broader Impact: Understanding friction, fatigue, and failure is currently a primary limiting factor both in developing new technologies and forecasting natural hazards. The work proposed here will lead to controllers for device applications, and models for seismic hazard estimation. Related hands on demonstrations will be developed for public and K-12 education and outreach activities, aimed at public awareness and safety, and increasing representation of women and minorities in the physical sciences.NON-TECHNICAL SUMMARY:This award supports interdisciplinary theoretical research and education to advance the fundamental understanding of friction, fatigue, and fracture in solids and granular materials. A fundamental understanding with predictive power of these phenomena remains elusive and challenging, and would find widespread applications from materials failure in many settings to geophysical hazards. At a deeper level, friction, fatigue, and fracture serve broadly as prototypical examples for some classes of complex systems for which fundamental principles governing their behavior are sought. Such universal principles would be applicable to many complex systems, not just the one in which they were discovered. Their discovery would advance the area of statistical physics that focuses on systems that are far from equilibrium. The PI's approach will span the many length scales characteristic of these phenomena. It is inherently multidisciplinary; it brings to bear elements of computational science, engineering, geophysics, physics, and materials science on well characterized systems to advance understanding at a fundamental level. Understanding friction, fatigue, and failure is currently a primary limiting factor both in developing new technologies and forecasting natural hazards. The work proposed here will lead to controllers for device applications, and models for seismic hazard estimation. Related hands on demonstrations will be developed for public and K-12 education and outreach activities, aimed at public awareness and safety, and increasing representation of women and minorities in the physical sciences.