Significance of Dimple Parameters on the Friction of Sliding Surfaces Investigated by Orthogonal Experiments

Surface texturing has proven to be an effective method to improve tribological performance of sliding surfaces. The pattern of microdimples is the most popular surface texture because it is supposed to obtain additional hydrodynamic pressure easily.

In order to evaluate the significance of the dimple parameters, including dimple diameter, depth, and area ratio, to the frictional performance, the dimple patterns with dimple diameter from 50 to 300 μm, dimple depth from 5 to 20 μm, and area ratio from 5 to 20% were manufactured on chromium-coated specimens by through-mask electrochemical micromachining. Experiments were designed using an L ₁₆ (4 ⁵ ) orthogonal array, which contained the above three factors and four levels for each factor. The frictional tests on the above-textured specimens against the specimens of cast iron with oil lubrication were carried out under the contact pressures of 0.2 and 1 MPa and sliding velocities of 0.1 s and 0.5 m/s.

The range analysis showed that the optimum dimple pattern was that with dimple diameter of 100–200 μm, dimple depth of 5–10 μm, and area ratio of 5%, which induced the friction reduction up to 77.6% compared to that of untextured surfaces.

Both the range analysis and analysis of variance suggested that dimple area ratio is the most important parameter influencing friction coefficient under the test condition of this research.