Codrignani Andrea, Peeters Stefan, Holey Hannes, Stief Franziska, Savio Daniele, Pastewka Lars, Moras Gianpietro, Falk Kerstin, Moseler Michael
Microtribology Center μTC, Fraunhofer Institute for Mechanics of Materials IWM, Wöhlerstraße 11, 79108 Freiburg, Germany.
Freiburg Materials Research Center, University of Freiburg, Stefan-Meier-Straße 21, 79104 Freiburg, Germany.
Sci Adv. 2023 Dec;9(48):eadi2649. doi: 10.1126/sciadv.adi2649. Epub 2023 Dec 1.
The Reynolds lubrication equation (RLE) is widely used to design sliding contacts in mechanical machinery. While providing an excellent description of hydrodynamic lubrication, friction in boundary lubrication regions is usually considered by empirical laws, because continuum theories are expected to fail for lubricant film heights ≪ 10 nm, especially in highly loaded tribosystems with normal pressures ≫ 0.1 GPa. Here, the performance of RLEs is validated by molecular dynamics simulations of pressurized (with = 0.2 to 1 GPa) hexadecane in a gold converging-diverging channel with minimum gap heights = 1.4 to 9.7 nm. For ≤ 0.4 GPa and ≥ 5 nm, agreement with the RLE requires accurate constitutive laws for pressure-dependent density and viscosity. An additional nonlinear wall slip law relating wall slip velocities to local shear stresses extends the RLE's validity to even the most severe loading condition = 1 GPa and = 1.4 nm. Our results demonstrate an innovative route for continuum modeling of highly loaded tribological contacts under boundary lubrication.
雷诺润滑方程（RLE）被广泛用于设计机械中的滑动接触。虽然它能很好地描述流体动力润滑，但边界润滑区域的摩擦通常由经验定律来考虑，因为对于润滑膜高度≪10 nm的情况，连续介质理论预计会失效，特别是在法向压力≫0.1 GPa的高负荷摩擦系统中。在此，通过在最小间隙高度 = 1.4至9.7 nm的金制收敛 - 发散通道中对压力为（ = 0.2至1 GPa）的十六烷进行分子动力学模拟，验证了RLE的性能。对于≤0.4 GPa且≥5 nm的情况，与RLE的一致性要求有精确的与压力相关的密度和粘度的本构定律。一个将壁面滑移速度与局部剪应力相关联的附加非线性壁面滑移定律，甚至将RLE的有效性扩展到了最苛刻的负荷条件 = 1 GPa和 = 1.4 nm。我们的结果展示了一种在边界润滑下对高负荷摩擦接触进行连续介质建模的创新途径。
