Lateral traction of laminar flow between sliding pair with heterogeneous slip/no-slip surface

et al. 2019

Micro & Nano Letters

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This paper explores the synergy mechanisms that are associated with the coexistence of multiple textures, to improve the precision control of a hydraulic servo cylinder. Based on the classical Reynolds equation, it establishes a single-texture and a nine-texture model to compare and study the synergy of surface textures. The film thickness is obtained under different working conditions for 1 N. Based on this parameter, it compares the simulation results from the two models with the experimental results to determine if the friction coefficient is reduced when multiple textures exist. When multiple textures exist, the inlet pressures of the central texture increase, but the peak pressure and cavitation pressure decrease. The synergy of the textures acts as an 'average pressure' and causes the pressure to decrease, which directly decreases the shear force. As the area ratio of the texture increases, the beneficial effect from the synergy gradually increases and then decreases, which implies that there is an optimum area ratio. The depth of the texture was 10 μm and the optimum depth-to-diameter ratio was 0.009. When the speed increases for a light load, the oil film thickness increases. However, this phenomenon does not substantially change the synergistic effect.

Section: Introductionmentioning

confidence: 99%

Synergy of surface textures on a hydraulic cylinder piston

Zhang

et al. 2019

Micro & Nano Letters

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“…The above mathematical model is solved by the relaxation iteration method in the MATLAB environment (Wu et al, 2017). Referring to the range of typical lubricating film thickness of hydrodynamic pressure lubrication (Wen and Huang, 2012), and the dynamic viscosity of 46 anti-wear hydraulic oil at 20°C measured by the test (Wu et al, 2018).…”

Section: Analysis Resultsmentioning

confidence: 99%

Study on curved surface design of sliding pair based on stepped topography model

Nguyen

2019

ILT

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Purpose The stepped topography of the friction pairs mainly causes the fluid film thickness to change in the direction of motion. In this region, there have very few topographical design methods for continuous or non-linear distribution of the fluid film. The purpose of this study is to analyze the effect of the curved surface on the performance of the liquid film. Design/methodology/approach First, a numerical simulation is used to solve the optimal bearing capacity and friction coefficient of the liquid film under the condition of the minimum film thickness. Then, the curved surface described by the sinusoidal curve equation is applied in the transitional region of maximum and minimum film thickness. The bearing capacity and the friction coefficient of the liquid film are respectively simulated and compared in the same condition of the minimum film thickness. Findings The research results show that the liquid film using the curved surface transition model, the optimal bearing capacity is significantly increased by 32 per cent while the optimal friction coefficient is clearly reduced by 38 per cent in comparison with using stepped surface model. Originality/value The friction pair with curved transition enables better lubrication performance of the liquid film and better adaptability under unstable conditions.

“…21,23 However, it is entirely possible to use a better surface treatment to achieve a true slip length b of tens of microns. 14 In the case of heterogeneous surface, 30 the use of such a surface can get better lubrication performance with unchanged film thickness. Taking into account the pressure flow and other factors to further improve the simulation model, the temperature distribution of the fluid and wall at each time will be predicted.…”

Section: Discussionmentioning

confidence: 99%

“…These equations are discretized according to the method of Ref. 30 and are solved in two steps in the MATLAB environment using the relaxation iteration method. For the experimental model of this study and the parameters given in Refs.…”

Section: -7mentioning

confidence: 99%

The effect of energy accumulation and boundary slip on laminar flow between rotating plates

Chen

et al. 2018

AIP Advances

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The poor operating conditions of fluid lubrication equipment during the start-up process are due to the resistance of the high-viscosity lubricating liquid. Moreover, the excessive reduction in fluid viscosity due to the elevated temperature resulting from power consumption during prolonged operation is not conducive to the generation of dynamic pressure. In this study, we examine the effect of energy accumulation and boundary slip on the laminar flow of a liquid between a pair of rotating plates. The experiments are conducted using a rotary rheometer, with polymethyl methacrylate (PMMA) as the thermal insulation material and polytetrafluoroethylene (PTFE) as the slip drag reduction material, and a three-dimensional simulation model is established. This model is derived by combining the energy equation including the slip length and the heat conduction equation. Thus, the temperature changes over time are predicted by this model, and the model accuracy is verified by experiments. The results reveal the following points: 1) boundary slips function as a drag reduction mechanism for short-time continuous operation; 2) under prolonged operation, the slip reduces the extent of the oil viscosity decrease and clear control of the elevated temperature by the boundary slip is observed.