Effects of texture patterns on hydrodynamic and mixed lubrication characteristics

Abstract

Surface texturing effects on the friction characteristics under hydrodynamic and mixed lubrication conditions are investigated experimentally and theoretically. The experiments are conducted by using a ring-on-plate type test rig, where a ring with a flat ring end is rotated against the plate with the engraved texture patterns of longitudinal, transverse and herringbone grooves and of square dimples. It is found that the friction characteristics significantly depend on the texture patterns even though the depth and the groove area ratio are identical in all the texture patterns; among them, the herringbone grooves show the lowest friction coefficients under any lubricating conditions. On the one hand, it is found that the longitudinal grooves and the square dimples effectively reduce the friction; on the other hand, the transverse grooves hardly reduce the friction. The experiments are compared with the calculations and it is found that higher pressure is generated with the herringbone grooves than other patterns, which avoids solid contact and results in friction reduction.