Effects of Nominal Duty Cycle and Delayed Energization on the Reciprocating Friction and Wear Performance of GCr15 Bearing Steel

Abstract

Under intermittent source-side excitation, electric-drive systems can maintain mechanical operation, so nominal energization parameters do not directly represent the interfacial electrical state. GCr15 ball-on-disk tests compared dry and polyalphaolefin (PAO 40)-lubricated conditions at 6 N under 5 V, 1 Hz switching. Tests covered nominal duty cycles from D = 0 to 1.00, where D is the ratio of the voltage on-time to the voltage period. Equal-on-time friction tests compared periodic D = 0.50, on→off and off→on. Wear was compared among periodic D = 0.50, off→on, and continuous direct current (DC). Friction increased overall with D. Longer on-time prolonged concurrent microcontact Joule heating and mechanical friction. Dry-sliding wear volume varied non-monotonically, peaking at D = 0.50 with changes in surface-layer removal and O-containing debris retention. Under PAO 40 boundary/mixed lubrication, wear-track width and volume increased monotonically with electrical-heating-related changes in oil film support and separation, microcontact, plowing, and plastic deformation. Equal-on-time friction histories differed. Periodic D = 0.50 and off→on produced similar wear volumes but different morphologies. Dry off→on and continuous DC wear volumes were close. Wear depended on timing and interface state at energization. Interface evolution altered contact resistance and voltage division, feeding back on wear. These findings support energization-parameter and bearing wear risk assessment under intermittent source-side excitation.