| Copper-zinc alloy has excellent wear resistance and is an important material for the manufacture of tiny precision instruments.The parts of micro-precision instruments are small in size,and the adsorption effect and interface effect have become the dominant factors affecting the tribological performance of micromechanical parts,higher requirements are put forward for the wear resistance of mechanical parts.Therefore,an in-depth understanding of the friction and lubrication behavior of copper-zinc alloys at the nanometer scale is of great significance for optimizing the design and manufacturing of micro/nano devices and improving the reliability and life of micro/nano devices.In this paper,molecular dynamics simulation method is used to analyze the friction and lubrication behavior between copper-zinc alloy and n-hexadecane lubricating film from molecular and atomic scale.The effect of zinc content and friction speed in copper-zinc alloy on the microstructure and rheological properties of n-hexadecane molecules was systematically studied.The content is as follows.(1)The significance of friction and lubrication was expounded.Simulation software and related modules were briefly introduced.The basic theory and condition setting of molecular dynamics were discussed.Lubrication and friction model of micro/nano Cu-Zn alloy was established,and the geometric optimization of lubrication friction,annealing and lubrication friction process were discussed.(2)The microscopic properties of thin film lubrication were studied.The thin film lubrication model with thickness of 30 (?) n-hexadecane was established for simulation analysis.The results showed that during the lubrication process,the lubricating film presents a multi-layered structure,and a solid adsorption film is generated on the alloy wall,while some molecules in the lubricating film still exhibit fluid characteristics.The increase in the molar content of zinc atoms in the alloy changes the adsorption capacity of the alloy to the n-hexadecane lubricating film,which in turn affects the structure delamination,interfacial slippage,shear viscosity and friction of the lubricating film.The friction speed of the friction pair has little effect on the layering of the lubricating film structure,but the interface slip and friction force increase with the increase of the friction speed,and the shear viscosity inside the lubricating film decreases with the increase of the friction speed.(3)On the basis of decreasing the thickness of lubrication film,the microscopic characteristics of boundary lubrication were investigated.The boundary lubrication model of n-hexadecane with thickness of 20 (?) was established,and explored the influence of copper-zinc alloy zinc atom molar content and friction speed on the structure and rheological properties of the lubricating film.The results showed that during the lubrication process,the lubricating film also presents a multi-layered structure,and the layered structure is more obvious than thin film lubrication,but there is no liquid flow characteristic in the middle area of the lubricating film.The interface slip and friction between the alloy and the lubricating film have larger values,and the shear viscosity is smaller.The molar content of zinc atoms in copper-zinc alloys has little effect on these results.The friction speed of the friction pair has the same effect on the structure delamination,shear viscosity,interface slip and friction force of the lubricating film.(4)The microscopic properties of hybrid lubrication were studied.The results showed due to the presence of rough peaks,the n-hexadecane molecules in the lubricating film are adsorbed in the gap,so there is no interface slip between the alloy and the lubricating film.Because of the mutual contact between the rough peaks in the lubrication process,cracks and large contact stresses different from thin film lubrication and boundary lubrication are produced.The influence of the number of n-hexadecane molecules in the lubricating film on the friction is considered.The contact stress between the rough peaks decreases with the increase of the number of lubricating film molecules.The existence of the n-hexadecane lubricating film protects the interface to a certain extent morphology. |
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