Multi-Scale Experimental Investigation of Sliding Friction

***9908218 glaser工程师一直依赖于速率和状态相关的本构模型（行为标准）。最近由凝聚态物理界取得的进展已经产生了对滑动摩擦阻力负责的假设理论机制。这些模型解释了从埃级到千米长的地震错位的行为，并为理解物质蠕变以及圣安德烈亚斯断层的自愈滑动提供了理论框架。由于几乎没有直接的实验证据证明假设的基本物理机制确实在起作用，pi将利用他们的实验和解释能力来描绘这些微观机制。鉴于摩擦结的基本运动学导致声子（振动，因此声学，能量）的产生，定量声发射和波形反演的结合是唯一能够成像这些运动学的。Glaser开发了表面和嵌入式传感器，经NIST验证，能够测量从10 kHz到1 MHz到3 dB内的皮计位移。研究表明，这些传感器的动态记录与理论运动学波形非常匹配，可以实现源运动学的全波形反演，而不是单点矩张量反演。该项目的研究成果将在若干层面上推动科学和工程的发展。基本了解滑动摩擦背后的物理机制，从而提高对物理世界的基本认识。这将有助于完善目前对摩擦的经验理解，并允许从纳米机器到亚千米尺度结构的机械设计的巨大改进。此外，将回答有关千米尺度震源机制的基本问题，特别是围绕自愈滑移的概念的问题，从而提高对地震位错机制的理解，并最终提高地震安全性

***9908218GlaserEngineers have always relied on rate- and state-dependent constitutive models(behavioral criteria). Recent advances by the condensed-matter physicscommunity have resulted in hypothetical theoretical mechanisms responsible forfrictional resistance to sliding. These models explain behaviors from angstromscale to kilometers-long earthquake dislocations, and provide a theoreticalframework for understanding material creep as well as self-healing slip on theSan Andreas fault. Since there has been little direct experimental proof thatthe posited fundamental physical mechanisms indeed are at work, the PIs willleverage their experimental and interpretive ability to image thesemicro-mechanisms. Given that the fundamental kinematics of frictional junctionsresults in production of phonons (vibrational, hence acoustic, energy), thecombination of quantitative acoustic emission and waveform inversion isuniquely able to image these kinematics. Glaser has developed surface andembeddable sensors proven capable by NIST of measuring picometer displacementsfrom 10 kHz to 1 MHz to within 3 dB. Studies show that the dynamic recordtransduced by these sensors match the theoretical kinematic waveformsremarkably well, allowing whole-waveform inversion for source kinematics ratherthan single-point moment tensor inversion. The results of this project will further science and engineering on severallevels. Fundamental understanding of the physical mechanisms behind slidingfriction, leading to improvement of basic understanding of the physical world. This will help refine current empirical understanding of friction and allowgreat improvement in mechanical design from nanomachines to sub-kilometer-scalestructures. In addition, fundamental questions about kilometer-scaleearthquake source mechanisms will be answered, in particular the issuessurrounding the notion of self-healing slip, thereby leading to an improvedunderstanding of the earthquake dislocation mechanism, and ultimately improvedseismic safety.***