| 引用本文: | 吴兵,孙韵韵,巫世晶.纳米级粗糙界面法向接触特性的分子动力学模拟[J].中国表面工程,2024,37(4):262~272 |
| WU Bing,SUN Yunyun,WU Shijing.Molecular Dynamics Simulation of Normal Contact Characteristics Between Nanoscale Rough Surfaces[J].China Surface Engineering,2024,37(4):262~272 |
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| 摘要: |
| 精密仪器的应用推动了机械零部件的纳米化，然而关于纳米级粗糙形貌与接触参量之间映射关系的研究有限，且不同外加负载下粗糙界面接触参量的动态变化特性尚未完全被揭示。采用分子动力学方法研究纳米级粗糙界面的法向接触特性。 首先，通过对表面功率谱密度函数进行逆傅里叶变换构建随机粗糙表面，建立具有纳米级粗糙度的铜-金刚石界面法向接触分子动力学模型。然后，从原子尺度模拟纳米级粗糙界面的法向动态接触过程，分析纳米级粗糙界面在不同外加负载作用下的动态变化特性，包括法向接触力、实际接触面积、界面等效变形量等关键参量。最后，模拟不同粗糙度的界面法向接触过程， 建立等效接触变形量与实际接触面积间的映射关系。纳米级粗糙界面法向接触特性研究表明：接触界面粗糙形貌恒定时，法向接触力、实际接触面积、接触变形量与外加负载呈正相关；相同外加负载时，表面粗糙度的增加会使实际接触原子数量减少，进而导致法向接触力、实际接触面积和界面等效变形量的减小；原子间相互作用力和原子扩散效应直接导致接触参量的动态变化受表面形貌影响；实际接触面积随界面等效变形量呈非线性增长，且两者间存在幂律映射关系。通过分子动力学模拟，揭示纳米级粗糙界面实际接触面积与等效变形量之间的函数关系，研究成果可为微纳尺度界面接触研究提供理论参考。 |
| 关键词: 接触界面 纳米级粗糙度 法向接触特性 分子动力学模拟 |
| DOI：10.11933/j.issn.1007-9289.20220701001 |
| 分类号:TH111 |
| 基金项目:国家自然科学基金（52105270） |
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| Molecular Dynamics Simulation of Normal Contact Characteristics Between Nanoscale Rough Surfaces |
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WU Bing，SUN Yunyun，WU Shijing
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School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072 , China
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| Abstract: |
| The use of precision instruments facilitates the miniaturization of mechanical components, enhancing their efficiency and performance. Deformation at contact interfaces composed of mechanical components essentially derives from the interaction between nanosized asperities. Under external loading conditions, the presence of these nanosized asperities on rough interfaces can significantly reduce the actual contact area compared to the nominal area, leading to the localized stress concentration within the contact region. Similarly, contact parameters such as the normal contact force, contact pressure, and deformation directly impact the operational lifespan of mechanical components. Establishing an equivalent mechanical model for rough interfaces is a prerequisite to elucidate the underlying deformation mechanisms governing contact behaviors at the nanoscale. Therefore, understanding the normal contact behavior between nanoscale rough interfaces under various external loading conditions is crucial. At the nanoscale, the dispersion of atoms leads to the breakdown of the continuum mechanics theory. However, studies investigating the mapping relationship between the nanoscale roughness morphology and contact parameters are limited. In addition, very little information is available on the dynamic variations in the contact parameters of nanoscale rough interfaces under different applied loads. Furthermore, the application of the finite element method is restricted to microcontact processes and does not encompass contact analysis at the nanoscale. With advancements in computer technology, molecular dynamics has emerged as a widely employed approach for investigating nanoscale contact behaviors. The normal contact behaviors between nanoscale rough interfaces have been investigated through molecular dynamics simulations. First, random rough surfaces are constructed by applying an inverse Fourier transform to the surface power spectral density function, thereby establishing a molecular dynamics model for normal contact between nanoscale rough copper-diamond interfaces. Subsequently, the dynamic process of normal contact between nanoscale rough interfaces is simulated at an atomic scale. The dynamic variations in key parameters such as the normal contact force, actual contact area, and interface equivalent deformation are analyzed under various external loads. Finally, comprehensive simulations are conducted to study the normal contact process between nanoscale rough interfaces with varying surface roughness, inducing the establishment of a mapping relationship between the equivalent deformation and actual contact area. The results provide a qualitative understanding of the normal contact characteristics of nanoscale rough interfaces. The applied load shows a positive correlation with the normal contact force, actual contact area, and contact deformation when the surface roughness remains constant. This finding is consistent with the observed characteristics of interfaces featuring micron-scale roughness. Under identical loads, the surface roughness of the contact interfaces increases, resulting in reduced resistance to the deformation of nanosized asperities and facilitating deformation. This results in a decrease in the number of atoms in contact as well as a reduction in both the magnitude of the normal contact force and the size of the effective contact area. At the nanoscale, surface morphology significantly influences interatomic forces. As the contact interface becomes smoother, the interaction force between the atoms intensifies, leading to a wider fluctuation in the normal contact parameters such as the normal contact force and actual contact area. The actual contact area of the nanoscale rough interfaces exhibits a power-law mapping relationship with the equivalent deformation under external loading. Moreover, larger surface roughness leads to a smaller contact area. Normal contact analysis of nanoscale rough interfaces reveals variations in key parameters, including the normal contact force, actual contact area, and equivalent deformation under an external load. The establishment of a mapping relationship between the surface morphology and contact parameters not only offers a theoretical framework for investigating micro-nano scale contact behaviors but also provides invaluable support for enhancing the interface characteristics of precision instruments. |
| Key words: contact interface nanoscale roughness normal contact characteristics molecular dynamics |
