Fundamental Study of Friction with Hierarchically Ruga-controlled Surfaces

该奖项支持适用于现代纳米技术以及岩土科学和工程的摩擦力学的基础研究。自达·芬奇时代以来，摩擦--两个物体之间的滑动阻力--一直是最具挑战性的课题之一，尽管人们对它的理解仍然不完整，但对现代科学技术的进步却至关重要。例如，它在控制纳米机械手中的滑动机制以及测量和预测构造断层线上积聚的力方面至关重要。在这里，首席研究者计划发展一个创新的力学框架-摩擦重正化，即连续评估较大长度尺度的摩擦行为与较小长度尺度的摩擦行为，并通过控制实验进行验证。本项目的基础研究将建立一个调控纳米级摩擦以控制宏观摩擦的系统框架。摩擦的多尺度框架不仅对于发展纳米机械设备技术，而且对于发展机器人和生物医疗设备工程中的摩擦控制技术，以及解决地质中的科学问题都是必不可少的。它还将提高对生产行业中广泛遇到的摩擦控制敏感的制造过程的计算建模和设计能力。此外，在这个项目下，首席研究员将在布朗大学开发一个外展计划，通过暑期实习计划教育未被充分代表的学生，并开发新的课程材料。在过去的25年里，对多尺度摩擦过程的研究非常活跃，以揭示这些过程的分子起源，并在不同长度尺度上沟通对现象的理解。最近，主要研究小组发现，摩擦的重整化软化/强化取决于分子粘结摩擦应力的降低、粗糙度相关的扁平化或表面的硬化。这种独特的摩擦重整化方案对于研究粗糙表面的多尺度摩擦过程是非常有效的。获得该奖项的首席研究员将研究(I)粗糙表面摩擦中的重整化强化；(Ii)分级粗糙度的RUGA(表面波纹)控制，以研究摩擦的重正化；(Iii)粗糙度谱的演变以及由粗糙塑性和磨损引起的摩擦。

This award supports fundamental research on the mechanics of friction applicable to modern nanotechnology as well as geotechnical science and engineering. Since the time of Leonardo da Vinci, friction - sliding resistance between two objects - has been one of the most challenging subjects still incomplete in understanding but crucial in advancement of modern science and technology. For example, it is critical in controlling sliding mechanisms in nano-manipulators as well as in measuring and predicting forces building up at tectonic fault lines. Here, the principal investigator plans to develop an innovative mechanics framework - renormalization of friction, i.e. successive evaluation of larger length scale friction with smaller length scale friction behavior, and verify it with controlled experiments. The fundamental studies of this project will establish a systematic framework for regulating nanoscale friction to control macroscopic friction. The multi-scale framework of friction will be essential for developing not only nano-mechanical device technology but also friction-control technology in robotics and bio-medical device engineering, as well as for solving scientific problems in geology. It will also advance computational modeling and design capabilities for manufacturing processes sensitive to friction control, widely encountered in production industries. In addition, under this project, the principal investigator will develop an outreach program at Brown, to educate underrepresented students through summer internship programs, and to develop new course material.Over the past two and half decades, research on multi-scale frictional processes has been very active to uncover the molecular origin of these processes and to bridge understanding of the phenomena at different length scales. Recently the principal investigator's group revealed that renormalization softening/strengthening of friction develops depending on the reduction of molecular adhesive friction stress, scale-dependent flattening of asperities or stiffening of the surface. This unique scheme of friction renormalization is very powerful in investigating multi-scale friction processes of rough surfaces. With this award, the principal investigator will study (i) renormalization strengthening in rough-surface friction; (ii) Ruga (surface corrugation) control of hierarchical roughness to study renormalization of friction; (iii) evolution of roughness spectra and friction due to asperity plasticity and wear.