Effect of waviness and roughness on cylinder liner friction

The tribological performance of piston ring-cylinder bore was investigated through deterministic mixed-lubrication modeling. Bore topographies measured from regular honed Gray Cast Iron (GCI) to “Mirror-Like” coated bore surfaces were used in the investigation. In contrast with typical honed GCI bores composed of relatively well-distributed peaks and valleys, coated bores are composed of a much smoother plateau and localized deep pores. Simulation results indicated that coated bore surfaces generate significantly higher hydrodynamic pressure and lower asperity contacts when compared with regular GCI topographies. The influence of roughness filtering and the associated cut-offs values were also considered in the analysis, showing that the choice of cut-off affects both the predicted hydrodynamic and asperity contact pressures. Furthermore, the simulation results also revealed that most of the fluid pressure was generated by the honing grooves rather than by the localized pores present on coated bore surfaces.