Steric Effects on Tribochemical Reactivity in Detergent-Containing Lubricants under Nanoconfinement

Modified Reynolds Equation for Thin Film Lubrication with Arbitrarily Enhanced Viscosity Surface Layers and Lubrication Analysis of Micro-Tapered Pad Bearing

“…3.1 Viscosity function when the effective viscosity is saturated below a large film thickness A previous study [17,18] indicated that a high-viscosity surface layer on the moving surface could simulate the effective viscosity characteristics of engine oil comprising metallic detergent additive, which were measured by Shibasaki et al [11] and Tamura et al [12]. This high-viscosity surface layer for the one-side model is expressed by Eq.…”

“…where r 0 is the ratio of viscosity at the solid surface (µ 0 ) to bulk viscosity (µ b ). In a previous study [17,18], r 0 = 1000 and 100 were used for calculation examples, whereas r 0 = 500 was used in this study based on the effective viscosity measured by Tamura et al [12]. The quantities Z c and z c are referenced film thicknesses close to the saturated viscosity film thickness when the viscosity at z = Z c and z c becomes (r 0 +1)/2 = ~r0 /2.…”

“…Subsequently, Sakuma et al [9,10] developed a resonance shear surface force measurement system and measured the rheological properties of various liquid-thin films. Furthermore, Shibasaki et al [11] and Tamura et al [12] measured the rheological properties of engine oil using the resonance shear force measurement system. In contrast, Itoh et al [13,14] measured the rheological properties of various lubricant films using the fiber-wobbling method.…”

“…The effective viscosity ratios µ ef /µ b given in Eqs (20). and(12) are shown in black thick lines as a function of h/z c . The viscosity function ratio µ z /µ b is nearly equal to 250 = r 0 /2 when z/z c = 2 for the one-side model in Fig.2(a) and z/z c = 1 for the two-side model in Fig.2(b), regardless of the power N. The viscosity functions in the two-(18)…”

Modified Reynolds Equation for Confined High Viscosity Film Lubrication and Lubrication Analysis of Micro-Tapered Pad Bearing

“…Viscosity reduction at high temperatures and increased friction force in mixed and boundary lubrication regimes at low speeds have been mitigated by adding viscosity-and friction-modifying additives to the base oil [1][2][3]. The use of additives to increase the viscosity of the surface layer, increase the fluid lubrication pressure at small clearances, and reduce the friction coefficient in mixed and boundary lubrication regimes is considered an increasingly important lubrication technology for engines and power transmission mechanisms in the future [4,5]. However, the reduction in friction and wear in the mixed and boundary lubrication regimes by additives has been conducted exclusively through experimental research, and a quantitative evaluation of the rheological properties of lubricants with additives has not yet been incorporated into the Reynolds equation to evaluate the texture and piston ring bearing characteristics.…”