Study of the influence of surface roughness parameters on the frictional characteristics of materials

The study of surface roughness parameters and their correlation with coefficient of friction (COF) is of great importance for metal-mechanic applications. Evidence suggests that R_a (surface roughness average) is not directly related to COF under sliding conditions. In this study, the relation between surface roughness parameters, namely R_a, R_t (maximum height of the profile), Δa (mean slope of the profile), and COF, as well as their interactions, were particularly studied. The materials were of an aluminium alloy Al A380. Samples were chemically attacked to modify their surface roughness characteristics. Six different conditions were tested: Al A380 with the surface attacked with an alkaline substance for 0, 2.5, 5, 15, 30 and 60 min. The value of COF was determined using a T-05 block-on-ring tribotester, and surface roughness data was obtained using an optical 3D surface measurement system. MathWorks MATLAB software was used to process the data. Results show that Δa has a strong positive correlation with COF during sliding conditions, whereas both R_a and R_t may vary without directly affecting COF, contrary to the commonly used industry standard.