Directional friction surfaces through asymmetrically shaped dimpled surfaces patterned using inclined flat end milling

• Production of asymmetrically shaped dimples through micro-end milling.
• Validation of machine model through experimental measurement of milling forces.
• Observed asymmetry in the machine tool used to create dimpled surfaces.
• Measured lower friction coefficient on dimpled surface compared to flat surface.
• Direction dependent friction coefficient.

In this study, directional friction effects by creating asymmetrically shaped dimpled surfaces on an aluminum workpiece were investigated. The surfaces were created using the inclined micro-flat end milling process. Inclined micro-milling forces were modeled, and subsequent comparisons with the measured forces have provided validation. These simulations also showed that the flat end mill used to produce these dimpled surfaces was not symmetric. Tribological characterization of the friction properties of the surface using reciprocating tribometer and a hemispherical ruby counter surface indicated that these asymmetrically shaped dimples lowered the overall friction coefficients measured under both dry and lubricated sliding conditions. Moreover, the results also demonstrated a sliding direction dependent response, in terms of the measured friction coefficients.