โ Scribed by J.A. Bares; N. Argibay; P.L. Dickrell; G.R. Bourne; D.L. Burris; J.C. Ziegert; W.G. Sawyer
No coin nor oath required. For personal study only.
Decoupled graphite lubrication of monolithic silver brushes on a copper rotor was studied in an ambient air environment under current varying from 0 A/cm 2 to 200 A/cm 2 using a custom designed electrical contact tribometer. Bifurcation of the positive and negative brush wear rates was observed at a current density of 200 A/cm 2 . Energy dispersive spectroscopy showed transfer of copper from the rotor to the lower wear negative brush. Scanning electron microscopy of worn brush surface cross-sections created by focused ion beam milling revealed a fine-grained metallic layer below the graphite transfer layer on the negative brush surface; no such layer was found on the positive brush surface. At 40 A/cm 2 , steadystate brush wear rates were very low (<10 -11 m/m). Friction coefficient at steady state was measured to be 0.15 ยฑ 0.02 and was independent of current direction. Using a scanning white light interferometer, the thickness of the graphite transfer layer on the rotor surface was estimated to be โผ5 m. Ultimately, the goal is to model lubricant buildup and removal as a competitive rates problem.
๐ SIMILAR VOLUMES
Apparatus and techniques are described which are capable of producing reliable controlled-environment data for low speed stick-slip friction. Such data have demonstrated their value in the study of various boundary friction and lubrication problems. Experiments performed with the original apparatu