M. D. Bryant, York, D., and Tewari, A., “Effects of Micro (Rocking) Vibrations and Surface Waviness on Wear and Wear Debri,” Journal of Wear, vol. 216, no. 1, pp. 60–69, 1998.
Recent studies have shown that micro-vibrations (10-100 μm amplitude. 10 to 100 Hz) can reduce sliding wear 50%, especially rigid body rockings of the slider. In this article. clearances between a carbon brush ( called a carbon sample in this article) and its holder were reduced while sliding over a slightly wavy (8 to 20 μm) steel surface. Undulations of the counter surface induced rigid body vibrations of the slider. including rocking. Tighter fits restricted rocking. looser fits permitted it. Plotted were wear (μg s -1 rate vs. speed (rpm) with clearance between brush and holder a parameter. Normal and nicking motions were measured. we found: (a) Micro-vibrations reduced brush wear on steel: (b) No rocking gave higher levels of wear: (c) An optimal fit (150 to 200 μm clearance), which kinematically permitted optimum rocking, 10 1 to 10 1 degrees, gave maximum wear reduction: (d) Fits too loose increased wear beyond smooth rotor levels: (e) Rocking with rotation vectors parallel or perpendicular to the sliding direction gave similar wear reduction, 50% or more; (f) Rocking with a rotation vector perpendicular to the sliding direction generated 'chatter', audible acoustic noise: (g) Rocking with a rotation vector parallel to sliding was quiet: (h) Wear reduction can occur at low waviness amplitudes (8 μm). Also in this article, wear particles were inspected under Scanning Electron Microscope. At low to moderate speeds particles shed from wavy and smooth copper counter surfaces were similar. At higher speeds, smooth surface particles were larger than wavy surface particles: often snowball like compactions of sub-particles similar to those shed from the wavy surface. This is consistent with a hypothesis wherein small wear particles shed from a slider running over a wavy surface escape the sliding interface through gaps opened by vibrations without gaps, particles become entrapped and compacted, In addition, clearances optimal for wear reduction correlated to the size of the gaps required for particles to escape.