Phase-dependent force dynamics and surface roughness variations in two-stage plateau honing of cast-iron engine cylinder liners

This study elucidates the mechanisms behind tribologically relevant surface roughness variations in a two-stage honing process for cast-iron engine cylinder liners. By decomposing the honing stroke into six kinematic phases, analytical force models are developed to relate hydraulic mandrel pressure to phase-dependent radial feed forces at the stone–liner interface. Surface roughness measurements at multiple axial locations show that, for both single-stage rough honing and two-stage rough plus plateau honing, the top sections of the liners remain approximately 10% rougher than the middle regions (mean over all test conditions; standard deviation 1.8%). After plateau honing, the surface parameters exhibit a substantial reduction: Ra decreased by a factor of 4.5 and additional reductions of 3.2 in R3z, 7.8 in Rpk, 6.4 in Rk, 3.4 in Rvk, 2.6 in Mr1 and 1.1 in Mr2, confirming the strong bearing-area enhancement of the plateau step. The force model predicts approximately 30% higher radial expansion pressure in the upper stroke phases compared with the central phases (evaluated over the hydraulic-pressure range P = 40–80%), which is identified as the primary driver of systematic axial roughness variations. Scanning electron microscopy and energy-dispersive X-ray spectroscopy reveal deep hemispherical pits associated with graphite excavation, shown to be a major source of random roughness fluctuations in grey cast-iron liners. The combined insights from phase-resolved force modelling and detailed surface characterisation provide a basis for improved measurement strategies and process control aimed at stabilising cylinder-liner topography for enhanced lubrication and friction performance in piston ring–liner systems.