Effects of abrasive-grain vibration modes on the ultra-precision polishing of Invar

To investigate the influence of a diamond abrasive grain on the ultra-precision polishing of polycrystalline Invar under different vibration modes, we established a scratching contact model of polycrystalline Invar using the molecular dynamics method. The study analysed the influence of vibration factors during ultra-precision scratching on the polishing quality and machining performance of Invar from the perspectives of contact force, internal structure, temperature, and energy changes. The scratching results show that under the vibration-free condition, the average contact force between the abrasive grain and the Invar substrate increases with scratching speed; the resulting groove profiles are exceptionally flat; the atoms undergoing lattice reconstruction within the substrate are predominantly concentrated in the near-surface region. Under the conditions of vertical vibration and combined vibration, the instantaneous contact force shows periodic fluctuations; after being squeezed by the abrasive grain, irregular pits form on the upper surface of the substrate. Under horizontal vibration conditions, severe plastic deformation occurs on the upper surface of the Invar substrate, resulting in grooves with a harmonic curve profile.