Synchronized Cu-Cantilever Structure for Kinetic Friction Characterization

A synchronized Cu-cantilever structure, used for characterizing the kinetic friction, is proposed by integrating frictional motion with synchronized amplification for the first time in this paper. A theoretical expression is further derived to predict the entrainment range of synchronization under periodically variable perturbation, rather than the invariable one. A two-cantilever resonator system, mainly consisting of a long cantilever and a short one coupled by an overhang, is designed in this paper. A friction block is fixed on the free end of the long cantilever to contact with target surfaces. The kinetic friction force representing a periodically varying perturbation is applied to the long cantilever via the friction block. The resonance frequency shift of the long cantilever, found to be related to the kinetic friction force, is magnified multiple times by that of the short cantilever. This not only implies the feasibility of applying the synchronized amplification to periodically variable perturbation but also improves the sensitivity of detecting such kind of perturbations. If both the frictional pair and tribological conditions are fixed, the abovementioned periodically variable perturbation, kinetic friction force in this paper, tribologically correlates to the surface feature, which is an invariable parameter like surface roughness and surface hardness. This paper validates that the proposed method based on the synchronized amplification is capable of characterizing extremely small differences in invariable parameters which cannot be detected by conventional imaging methods, especially those out of identification limits (like no change in color or surface feature) of conventional imaging methods.