Hansen Jonny, Björling Marcus, Larsson Roland
Division of Machine Elements, Luleå University of Technology, 97187, Luleå, Sweden.
Transmission Development, Scania CV AB, Södertälje, Sweden.
Sci Rep. 2020 Dec 17;10(1):22250. doi: 10.1038/s41598-020-77434-y.
A ball-on-disc machine was employed in a highly idealised setting to study the interplay between oil film formation and surface irregularities in single-sided rough elasto-hydrodynamic lubricated (EHL) conjunctions. The tests were operated under GPa pressures and high slide-to-roll ratios in a situation where the separating gap was smaller than the combined surface roughness height. Under the initial state of solid contact interference and with the operating conditions held fixed, surfaces were found to gradually conform such that a fully separating oil film of nanometre thickness eventually developed-a thin film lubrication state known as micro-EHL. Additionally, with a previously developed approach for 3D surface re-location analysis, we were able to very precisely specify the pertained nature of surface transformations, even at the asperity scale, by comparing the post-test surfaces to those in the virgin state. The surface roughness Sq was reduced by up to 17% after running-in, while the speed required for full film EHL was reduced by a remarkable 90%. Hence, full film EHL is possible even in cases where the Λ-ratio falsely suggests boundary lubrication. This discrepancy was attributed to the way surfaces are deformed inside the contact, i.e., through the establishment of micro-EHL.
在高度理想化的环境中使用球盘试验机，以研究单面粗糙弹流润滑（EHL）接触中油膜形成与表面不规则性之间的相互作用。试验在吉帕压力和高滑动-滚动比下进行，此时分离间隙小于组合表面粗糙度高度。在固体接触干涉的初始状态下，且操作条件保持不变时，发现表面会逐渐贴合，最终形成厚度为纳米级的完全分离油膜——一种称为微EHL的薄膜润滑状态。此外，通过先前开发的三维表面重新定位分析方法，通过将试验后的表面与原始状态的表面进行比较，我们能够非常精确地确定表面转变的相关性质，即使在微凸体尺度上也是如此。磨合后表面粗糙度Sq降低了高达17%，而全膜EHL所需的速度显著降低了90%。因此，即使在Λ比错误地表明是边界润滑的情况下，全膜EHL也是可能的。这种差异归因于接触内部表面的变形方式，即通过微EHL的建立。
