Tao Yi, Sun Chengdong, Huang Shuyu, Dong Yun, Kan Yajing, Wei Zhiyong, Zhang Yan, Ni Zhonghua, Chen Yunfei
Southeast University, Jiangsu Key Laboratory for Design and Manufacture of Micro-Nano Biomedical Instruments, School of Mechanical Engineering, Nanjing 211189, China.
Lanzhou University of Technology, School of Mechanical and Electrical Engineering, Lanzhou 730050, China.
Phys Rev E. 2025 May;111(5-2):055506. doi: 10.1103/PhysRevE.111.055506.
Friction, defined as the resistance to relative motion between two contacting objects, has historically been regarded as a consequence of mechanical energy dissipation. However, the precise mechanism by which it operates in the context of phonon excitation has not been fully elucidated. In this study, we present a theoretical framework based on the atomistic Green's function method that connects friction-excited phonons to the resulting friction force. Our analysis reveals that phonons are primarily excited at bi-washboard frequencies and their harmonics when relative motion occurs in arbitrary directions. The theoretical predictions are validated through detailed molecular dynamics simulations and further supported by experimental evidence. A key finding of our work is the identification of a spectral function that links the normalized number densities of friction-excited phonons to their frequencies. This relationship is intrinsic to the friction system and remains independent of specific factors such as sliding velocity or direction. Our discovery enables a quantitative explanation of anisotropic friction, nonmonotonic velocity dependence of friction, and fluctuations in friction, all without relying on additional assumptions. By resolving the spectral characteristics of phonon excitations, this study provides systematic insights into the fundamental nature of friction.
摩擦力被定义为两个相互接触的物体之间相对运动的阻力，在历史上一直被视为机械能耗散的结果。然而，在声子激发的背景下，其作用的精确机制尚未完全阐明。在本研究中，我们提出了一个基于原子格林函数方法的理论框架，该框架将摩擦激发的声子与产生的摩擦力联系起来。我们的分析表明，当相对运动在任意方向发生时，声子主要在双搓板频率及其谐波处被激发。理论预测通过详细的分子动力学模拟得到验证，并得到实验证据的进一步支持。我们工作的一个关键发现是确定了一个光谱函数，该函数将摩擦激发声子的归一化数密度与其频率联系起来。这种关系是摩擦系统所固有的，并且独立于诸如滑动速度或方向等特定因素。我们的发现能够对各向异性摩擦、摩擦的非单调速度依赖性以及摩擦波动进行定量解释，而无需依赖额外的假设。通过解析声子激发的光谱特征，本研究为摩擦的基本性质提供了系统的见解。
