| The tangential micro deflection between contacting machined surfaces was studied by{09} experiments and theoretical analysis. Two types of experiments were performed to identify the characteristics of the tangential micro deflection before mechanical breakaway. The experimental results show that the nonlinear tangential stiffness between contacting machine surfaces should be considered in the elasto-plastic deformation stage before micro-breakaway occurs. The experimental results further indicate that the tangential force has a linear relationship with tangential micro displacement only in the stage of elastic deformation at submicron level, or below 100 nm, and a strong nonlinear relationship is observed beyond 100 nm. This linear range of sub-micrometer is much smaller than the previously reported 2∼5 μm, which has been widely used in various theoretical models for friction and motion controls. The experiments also show that the contact interface only resumes a certain amount of tangential deflection in unloading cycle when tangential displacement exceeds the range of elastic stage, under various loading conditions. Based on the experimental study, the tangential micro deflection of the interface formed by contacting machined surfaces is modeled as elasto-plastic and micro-slip stages by viewing each asperity as an object with certain attributes (e.g. height of asperity, contact area of summit, normal deflection, tangential deflection, etc.). Tribological influence on machined contact interface was quantitatively represented by the model through the variances of the surface height, the surface slope and the surface curvature, which all depend on the characteristics of contact surfaces, mainly surface roughness. |
