In recent years, polymer materials are widely used in aerospace, microelectronicsand other fields. However, wear resistance of the surface is becoming the key factorconstraining its extensive application. Thus, the research of friction behavior, surfacemicrostructure and their relationship is urgently required.In this paper, conical indentation and scratch on amorphous polymer surfaces,coarse-grained models of amorphous polymer films, were simulated using a large-scalemolecular simulation approach. The indentation behavior and scratch behavior of filmswere studied, the change of polymer microstructure during the sliding process wasanalyzed, and polymer friction behavior and molecular mechanism wereexplained.These main contents are as follows:The rubbery and glassy of amorphous polymer with different weights wereprepared through melt-cooling process. The glass transition temperature of the film wasgotten by analyzing and calculating the variation of film’s thickness during the coolingprocess. The probe model was prepared, and the details of setting parameters involvedin the process of the conical indentation and scratch on amorphous polymer surfaceswere described.Considering these factors, such as repulsive and attractive between probe andsubstrate, load, sliding velocity,temperature and the length of the chains and so on, theimpaction on contact behavior and friction behavior of the substrate wasstudied.Thesimulatedload-depth behavior and friction-load behavior showed that it islinear correlation between depth, friction and load with repulsive, ultra-linearcorrelation between depth and load with attractive. Observing and analyzing atomicconfiguration,it is shown that monomers of surface layers are not only stacking in frontof the probe, but also adhering to the side-surface of the probe with attractive comparedwith repulsive.Considering these factors, such as repulsive and attractive between probe andsubstrate, load, sliding velocity,temperature and the length of the chains and so on, thebond orientation and chain conformation of polymer’s surface were calculated duringscratch tests. And surface microstructure of a polymer film and relationship withfriction behaviorwere studied during sliding process. It is shown that, surfacemicrostructure wasn’t changed after sliding with repulsive, however, changed greatly with attractive. After statisticalanalyzingstretchof chains that caused by friction, thecontribution of chain ends and chain loops were compared during the sliding. Finally,variousvariation of molecular structure of surface was caused by the different lengths ofmolecular chain. And different friction behaviors of amorphous polymers wereexhibited. |