Frictional Characterization of Emulsions under Hydrodynamic Lubrication

doi:10.3901/JME.260830

Abstract

Abstract: Based on the slider-on-disc contact oil film measurement system, the friction force measurement system is added and combined with the dichromatic fluorescence method to investigate the friction characteristics of emulsion in the conformal contact lubrication process. Using optical interferometry to measure the film thickness of emulsions with different concentrations and friction measurement system to measure the friction force in the lubrication, the results show that under the same case, the friction force of deionized water is the highest, the friction force of deionized water and emulsion with concentration p≤5% demonstrate the pattern of decreasing initially and subsequently increasing in correspondence with an escalation in velocity, which can be seen by the Stribeck curve, and the state of lubrication of deionized water has experienced the transition from mixed lubrication to hydrodynamic pressure lubrication; emulsion concentration ≥40%, friction force increases with speed, and is in the hydrodynamic lubrication state in the speed interval (0＜u≤200 mm/s); when the emulsion concentration 5%＜p≤30%, the alteration in speed results in a dissimilar frictional force, and the pattern of presentation becomes increasingly intricate. Observing the oil and water distribution in the contact area using dichromatic fluorescence method, utilizing p=30% as a baseline, at low velocities (u≤10 mm/s), the contact area predominantly comprises the oil phase, with only a minimal presence of the water phase at the inlet edge. As the velocity increases, the ingress of water into the contact area escalates, resulting in a transition from a single-phase oil environment to a composite of oil and water phases. At elevated velocities (u≥120 mm/s), the contribution of the water phase within the contact area becomes pronounced, leading to a reduction in friction. Consequently, the lubrication regime transitions from hydrodynamic lubrication to oil-water phase lubrication system. Using confocal microscope to observe the friction wear on the surface of the steel block, the degree of wear caused by emulsion lubrication of different concentrations on the surface of the steel block is different, when the oil content in the lubricant rises, the viscosity rises, and the degree of wear caused on the surface of the steel block will be reduced accordingly.

Key words: emulsion lubrication, friction, light interference, dichromatic fluorescence method, mixed lubrication, hydrodynamic lubrication

CLC Number:

TH117

LÜ Chunfeng, HAN Suli, GUO Feng, JING Zhaogang. Frictional Characterization of Emulsions under Hydrodynamic Lubrication[J]. Journal of Mechanical Engineering, 2026, 62(15): 475-483.

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