Wear Mechanism Research And Simulation Analysis Of Internal Combustion Engine Piston Ring With Self-lubricating Coating

Cylinder-piston ring is the core component of internal combustion engine.In the use of internal combustion engine,the friction pair of cylinder liner-piston ring works in high temperature,high pressure,variable load and corrosion environment for a long time.The harsh working environment also puts forward higher requirements on the wear resistance of piston ring.Because the friction and wear is a surface phenomenon,so surface coating is employed to treat the piston ring to improve its wear resistance.In this thesis,with thermosetting polyimide（TPI）as the matrix and reduced graphene（r-GO）decorated with silicon carbide（Si C）as filler,r-GO/Si C/TPI composites was synthesized by using in situ polymerization method.The tribological and mechanical properties of these composites were investigated.The simulation of the piston ring-cylinder liner system after coating,furthermore,was carried out by the Workbench analysis software under the thermodynamic coupling state.The specific research work is as follows:（1）Through a simple analysis of the working conditions of the piston ring,the performance requirements of the coating materials in the work were obtained,and TPI and its composites were selected and prepared.Through the related characterization,it can be found that in the prepared r-GO/Si C/TPI,the r-GO and Si C are not simply mixed,but there is a certain chemical bond.The compression properties of the prepared materials were analyzed.Co MPared with the pure TPI,the compression modulus and compressive strength of the materials were significantly improved by the addition of filling particles,especially by the addition of r-GO/Si C material.Co MPared with the pure TPI,the compression modulus and compressive strength were increased by 47.32%and 37.7%,respectively.The thermal properties of the modified material showed that the THRI of r-GO/Si C/TPI was increased by5.42%co MPared with that of pure TPI,and the decomposition temperature was much higher than the working temperature of the piston ring,which indicated that this composite had excellent mechanical properties and thermal properties,and could meet the requirement of piston ring coating.（2）Tribological properties of TPI composites was studied under different load.It is concluded that the friction coefficient and wear rate of TPI were reduced after adding a certain amount of filler.The r-GO/Si C/TPI composites demonstrate lowest friction coefficient and the lowest reachable wear rates of pure TPI,r-GO/TPI and r-GO/Si C/TPI composites are5.28×10^-7mm3N^-1m^-1,2.13×10^-7mm³N^-1m^-1 and 6.41×10^-8mm³N^-1m^-1,respectively.Co MPared with pure TPI,the wear rate of r-GO/Si C/TPI composites is reduced by an order of magnitude.By further observation of the worn surface,it is found that the worn surface of pure TPI sample has much defects as peeling,fracture and furrow,while the surface of R-GO/Si C/TPI composite does not have these defects.It was found that the density of the transfer films formed on the dual ring was different of materials,and the transfer films formed by R-GO/Si C/TPI were the most uniform and dense.Further study of transfer film composition can be concluded that r-GO/Si C/TPI in the formation of the transfer film on the surface of the duality of the main elements for Si,this is because in the process of wear and tear on the surface of the Si C adhere to the dual form of transfer film with self-lubricating properties,effectively form change.These phenomena indicate that r-GO/Si C composites have synergistic effect on the tribological properties of polyimide composites.（3）The simulation analysis of the piston ring-cylinder liner system after coating is carried out in the thermodynamical coupling state.The results show that the application of coating will not cause the temperature anomaly of the piston ring-cylinder liner system,and the heat dissipation performance of each component is ba Si Cally unchanged.The application of the coating significantly improves the working stress of the piston ring,which decreases from 193.72MPa to 168.55MPa and are 13%lower than previous.This indicates that the application of the coating can effectively improve the working conditions of the piston ring,thus extending its working life.The application of coating can also improve the stress and strain of piston and cylinder liner to some extent,which provides a reference for the application of coating in engineering practice.