Research On Fractal Characterization Of Surface Topography And Anti-Friction Performance Of Piston Ring-Cylinder Liner System

The friction pair of the piston ring-cylinder liner system is one of the most important friction pairs in internal combustion engines.With the development of technology and the requirements of environmental,economic,and energy aspects,more and more scholars are conducting research on the wear resistance,friction reduction performance,and physical characterization of surface morphology of the piston ring-cylinder liner system friction pair.This thesis studies the friction reduction performance of surface texture and fractal characterization method of anti-friction texture surface morphology in the piston ring-cylinder liner system,providing technical support for the anti-wear and anti-friction technology of internal combustion engine piston ring-cylinder liner system and the fractal characterization of rough surfaces.The main research content and work of this thesis are as follows:(1)Considering the composite load and lubrication conditions of the piston ring-cylinder liner system during the running-in period,a slice friction and wear test of the piston ring-cylinder liner friction pair is designed.The friction coefficient,three-dimensional surface morphology,and worn surface profile of the piston ring-cylinder liner friction pair at different working conditions are tested by a multifunctional friction and wear tester and a three-dimensional confocal laser microscope.The effect of processing single piston ring textures,single cylinder liner textures and piston ring-cylinder liner coupled textures on the tribological performance of the piston ring-cylinder liner friction pair is studied.(2)Based on the Archard wear model and transient dynamics theory,Workbench software is used to study the effects of processing single piston ring textures,single cylinder liner textures and piston ring-cylinder liner coupled textures on the equivalent stress,strain and wear amount of the friction pair of the piston ring cylinder liner system at different working conditions,verifying the accuracy of the friction and wear test results.Based on the distribution of contact stress during the motion of the piston ring-cylinder liner friction pair,the optimal processing position of the anti-friction texture was obtained.(3)Based on the fractal characteristics such as multi-scale and anisotropy of the cylinder liner anti-friction texture surface,the cylinder liner is machined by plateau honing technology and the non-destructive image acquisition system is used to obtain the cylinder liner anti-friction texture surface images after rough honing and plateau honing.On this basis,cylinder liners anti-friction texture surfaces with different physical characteristics are processed by a laser marking machine,and their images are collected.The fractal dimensions of each image group are calculated by the power spectral density method,the differential box-counting method and the partitioned iterated function system method,and their corresponding MSEs(mean square errors)are compared to determine the method with the highest accuracy for calculating the fractal dimension of the cylinder liner anti-friction texture surface.