Wear characterization under sliding–rolling contact using friction-induced vibration features

Skidding in rolling bearings often causes unexpected surface wear and early failures. Although vibration monitoring is widely used for bearing fault diagnosis, it is much less developed for wear analysis. This paper presents an investigation into characterizing the surface wear of a simplified sliding–rolling contact using friction-induced vibration features. The friction vibration mechanism under a rough sliding–rolling contact is explored by a mixed elastohydrodynamic lubrication model. It is found that the friction coefficient has a positive correlation with the surface roughness, which indicates that the friction behaviour can be used to track the wear state under the sliding–rolling contact. Furthermore, the vibration excited by different rough surfaces is studied experimentally on a roller–ring test rig. The friction-induced vibration signal is extracted and a feature parameter ( K) is defined for quantitative wear characterization. Results show that the friction-induced vibration can well reflect the surface wear under the sliding–rolling contact. Compared with traditional time-domain parameters, the proposed parameter has a better linear relationship with the surface roughness.

Asperity level characterization of abrasive wear using atomic force microscopy

Using an atomic force microscope, a nanoscale wear characterization method has been applied to a commercial steel substrate AISI 52100, a common bearing material. Two wear mechanisms were observed by the presented method: atom attrition and elastoplastic ploughing. It is shown that not only friction can be used to classify the difference between these two mechanisms, but also the ‘degree of wear’. Archard's Law of adhesion shows good conformity to experimental data at the nanoscale for the elastoplastic ploughing mechanism. However, there is a distinct discontinuity between the two identified mechanisms of wear and their relation to the load and the removed volume. The length-scale effect of the material's hardness property plays an integral role in the relationship between the ‘degree of wear’ and load. The transition between wear mechanisms is hardness-dependent, as below a load threshold limited plastic deformation in the form of pile up is exhibited. It is revealed that the presented method can be used as a rapid wear characterization technique, but additional work is necessary to project individual asperity interaction observations to macroscale contacts.