Recurrence evolvement of brass surface profile in lubricated wear process

• A specially-designed apparatus is utilized to measure the same area of wear surface.
• Three recurrence patterns of surface profile during wear are analyzed and identified.
• The evolvement of wear surface is studied by recurrence quantification analysis.

This investigation exemplifies how recurrence analysis can be applied to characterize the non-linear dynamic evolution of Cu–30%Zn brass surfaces when sliding under boundary lubricated conditions against AISI 52,100 steel. Roughness profiles of the wear surface of the brass specimen were measured periodically using a specially-designed apparatus to locate the same area of the wear surface. Recurrence plots of these changing surface profiles measured are presented. Two recurrence parameters, average diagonal length (ADL) and correlation dimension (CD), are also computed. The recurrence plots depict conditions before wear testing, during steady-state wear, and after severe wear begins. These sequential plots evolve from a periodic-like pattern, to a partially homogeneous pattern, and then to a disrupted pattern. During wear, the ADL first decreases, stabilizes at a small value, and then finally increases significantly, corresponding, respectively, to a wear-in stage, a steady-wear stage, and a severe wear stage. By contrast, the CD parameter tends toward two dimensions at first, then fluctuates around a large value and then rapidly decreases toward one dimension. The computation of ADL and CD reveals changes in randomness and complexity as the wear surface of the brass specimen passes through three stages. It reveals the non-linear dynamic behavior of the brass-on-steel sliding wear process particularly, but the method may be useful for studies of other metallic wear surface as well.