LAUSR

Purpose This paper aims to compare the tribological performances of four different types of tooth surface finishing, namely, form grinding, generating grinding, super finishing and grinding and coating, and to reveal the details at dry contact nodes. Design/methodology/approach Real measured roughness is input to a finite line contact mixed elastohydrodynamic lubrication model developed for helical gear pairs. Their tribological performances are compared. The variation throughout one meshing period is analyzed. The influence of the root mean square (RMS) is studied. The textures are also scaled to the same RMS values to make comparisons while excluding the influence of roughness amplitude. Findings Roughness is directly reflected in pressure and film thickness. Average film thickness sees major changes while entering and leaving the single-tooth-contact region. The textures have different performances even under the same RMS. Roughness peaks incurring dry contact are those higher than the smooth-situation film thickness plus the sum of variation in normal approach and elastic deformation compared with the smooth situation. To lower dry contact severity, the surface finishing process should take care of both the overall amplitude and the portion of peaks with maximum height. When RMS value is the same, the latter plays a decisive role. Originality/value This paper interprets the differences between the tribological performances of four different types of tooth surface finishing from the aspect of roughness features and presents a way to analyze the details at dry contact nodes.