Stick-slip motion is often observed in out-of-equilibrium disordered systems as a yield response to a smoothly-varying external force. Earthquakes on faults and the mechanical failure of materials are two extreme examples of stick-slip events. A common feature of stick-slip events is their broad range of slip sizes, manifest as power-law distributions of many orders of magnitude. Observations that many different systems behave similarly have prompted many theoretical, numerical, and experimental investigations aimed at finding some common mechanism or universal law underpinning these phenomena, which are also referred to as avalanche dynamics. In this talk, I will present our recent experimental efforts in developing a hang-beam atomic force microscope (AFM) to study the stick-slip dynamics of a moving three-phase contact line [1] and dry friction between two (rough) solid surfaces in mesoscale contact [2]. The hanging-beam AFM provides a versatile experimental framework at the mesoscale that is small enough to resolve individual slip events but is also large enough to examine a broad range of slip sizes in a well-characterized disorder landscape with a single-slip resolution. With this framework, we can resolve depinning force fluctuations generated by individual slip events and provide a statistical description of the stick-slip motion, which bridges the gap between the microscopic behavior of individual slips and the macroscopic laws of stick-slip motion for a moving contact line and solid interfaces. In particular, the measured probability density functions (PDFs) of the slip length x obey a power law distribution, and the power-law exponent is explained by a new theoretical model for the under-damped spring-block motion under a Brownian-correlated pinning force field. This model provides a long-sought physical mechanism for the avalanche dynamics in stick-slip friction at the mesoscale.

*This work was done in collaboration with Caishan Yan, Hsuan-Yi Chen, Pik-Yin Lai, D.-S. Guan and Y. Wang, and was supported in part by the Research Grants Council of Hong Kong SAR.

[1] C.-S. Yan, D.-S. Guan, Y. Wang, P.-Y. Lai, H.-Y. Chen and P. Tong, Avalanches and extreme value statistics of a moving contact line, Phys. Rev. Lett. 132, 084003 (2024) (Editors’ Suggestion).

[2] C.-S. Yan, H.-Y. Chen, P.-Y. Lai, and P. Tong, Statistical laws of stick-slip friction at mesoscale, Nature Communications 14:6221 (2023).

报告人简介

Professor Penger TONG is currently Chair Professor in the Department of Physics at the Hong Kong University of Science and Technology (HKUST). He received his PhD from the University of Pittsburgh in 1988. After a period of post-doctoral training at Exxon Research & Engineering Company, he served successively as Assistant Professor, Associate Professor and then full Professor of Physics at Oklahoma State University before joining HKUST as full Professor in 2003. Professor Tong is an experimental soft condensed matter physicist. His interdisciplinary research in this field has resulted in significant advances on several topics in four key areas: turbulent convection, physics of living matter, colloidal diffusion, and liquid interfacial phenomena. His high esteem in the professional community is reflected in the large number of invited talks he has presented, election as Fellow of the American Physical Society in 2010. Professor Penger TONG was appointed as the Associate Provost (Mainland Affairs) in January 2023.

邀请人

孟凡龙 研究员