Molecular Dynamics Study On Sliding Friction Behavior Of Cotton Cellulose And Chromium Metal

Cotton fiber material is an indispensable part of the development of human civilization.Xinjiang's unique geographical conditions make it the main cotton producing area in China.The whole process of mechanized cotton harvesting and textile processing is the fundamental way to promote the sustainable development of Xinjiang's cotton industry.However,the frictional behavior involved in the cotton harvesting and spinning process not only controls the quality of the cotton fiber material and its textile products,but also affects the high precision,stability,long life and reliability of metal components.Therefore,an in-depth understanding of the friction and wear between cotton fibers and metals is of great significance for the production and processing quality of cotton fibers and for improving the damage protection of metal parts.In this study,cotton fiber and chromium metal were taken as the research objects,and the sliding friction behavior of the friction pair was explored by molecular dynamics method.The main research contents and results are as follows:(1)The visualized atomic three-dimensional models of crystalline cotton fibers and chromium metal and amorphous cotton fibers and chromium metal under dry friction vacuum conditions were constructed by using Materials Studio molecular simulation software,and the model structures were optimized.(2)The evolution of the microstructure of the contact interface between cotton fibers and chromium metal was investigated.The slip process between cotton fiber and chromium metal was simulated by LAMMPS software at different temperatures(300 K,320 K and 340 K)and loads(0.3 MPa and 50.6MPa),and the microstructure of the contact interface in the simulated system was calculated by OVITO software.Visual monitoring of the evolution.The results show that the molecular chain of cotton cellulose is broken during the sliding friction process,and the oxygen atoms in the free functional groups interact with the chromium atoms at the contact interface to generate a new chemical bond,the chromium-oxygen bond.In the simulation system,under high load and temperature conditions,the structural failure of the contact surface of the chromium layer occurs earlier;under constant load,the temperature change has no significant effect on the structure of the chromium layer.(3)The variation law of the number of Cr-O bonds in the simulated system was studied under different temperature and load conditions.The evolution of the number of chromium-oxygen bonds in the simulation process was calculated with the help of Fortran software,and the number of chromium-oxygen bonds under different temperatures and loads was compared.At the same time,the existence of chromium-oxygen bonds was verified by using the radial distribution function.The results show that the number of chromiumoxygen bonds in the simulation system of crystalline cotton cellulose and chromium metal increases with the increase of temperature conditions under the same loading conditions,while the simulation system of amorphous cotton cellulose and chromium metal shows a U-shaped distribution.(4)The evolution of the friction force and friction coefficient in the simulated system with the simulation time under different temperature and load conditions is studied.By plotting the evolution of friction force and friction coefficient with the simulation time during the sliding process of the simulated system under different temperatures and loads,the effects of different temperatures and loads on the friction force and friction coefficient are summarized.At the same time,the research shows that the friction laws of amorphous cotton fibers in different mechanical states are different in the process of sliding friction.