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Tribological failures come in different forms, and there are many parameters (e.g. speed, pressure, sliding, roughness, viscosity, etc.) that affect which failure mode will be realized in testing. It is not uncommon to have two apparently identical tests produce different failure modes. In this study, the failure modes of pitting, micropitting, and abrasive wear were evaluated for rolling/sliding contacts and mapped at low lambda conditions (λ < 0.5). These tests were conducted with a disc-type machine using carburized steel specimens with a circumferential lay direction and oil with anti-wear additives under variable conditions typical in rotating machinery. The surface condition of the specimens was evaluated periodically throughout testing using non-contact profilometery. The data demonstrate that a transition point exists where the primary failure mode switches from abrasive wear/pitting to micropitting, driven primarily by the lambda ratio. The data further shows that (1) increasing film thickness, and thus reducing asperity contact, does not necessarily reduce the likelihood of micropitting in low lambda conditions, and (2) when the lambda ratio is less than 0.1, there exists a sensitivity where one cannot predict the resultant failure mode, most likely due to competing failure modes between abrasive wear and pitting. Additionally, some recommendations will be discussed for replicating gear tests with a disc test stand.
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Wagner, Jeremy J. and Sundararajan, Sriram, "Failure mode mapping for rolling/sliding contacts under low lambda conditions" (2021). Mechanical Engineering Publications. 491.
Available for download on Tuesday, July 18, 2023