Effective oil replenishment to the lubrication track of a running bearing is crucial to its sustainable operation.Reliable practical solutions are rare despite numerous theoretical studies were conducted in the last f...Effective oil replenishment to the lubrication track of a running bearing is crucial to its sustainable operation.Reliable practical solutions are rare despite numerous theoretical studies were conducted in the last few decades.This paper proposes the use of surface effect,wettability gradient,to achieve the goal.This method is simple and can be nicely implemented using femtosecond laser ablation.A periodic comb-tooth-shaped pattern with anisotropic wetting capability is devised and its effect on the anisotropic spreading behaviour of an oil droplet is studied.Results show that the comb-tooth-shaped pattern enables the rearrangement of oil distribution,thereby escalating oil replenishment to the lubrication track.The effect is due to the unbalanced interfacial force created by the surface pattern.The influence of the shape and the pitch of teeth,which are the two governing factors,on oil transport is also reported.The effects of the newly devised surface pattern on lubrication are experimentally evaluated under the conditions of limited lubricant supply.These results are promising,demonstrating the reduction in bearing friction and the increase in lubricating film thickness.展开更多
The effects of boundary (liquid/solid) slip on hydrodynamics are well recognized.However,it is extremely difficult to quantify in-situ boundary slip in a lubrication contact.Therefore,an effective interfacial paramete...The effects of boundary (liquid/solid) slip on hydrodynamics are well recognized.However,it is extremely difficult to quantify in-situ boundary slip in a lubrication contact.Therefore,an effective interfacial parameter that is well correlated with the lubrication effect is of practical significance.This paper presents an examination of common interfacial parameters,including surface tension,contact angle,contact angle hysteresis,and a recently proposed spreading parameter.Specimen surfaces of different hydro/oleophobicity were prepared and characterized using the aforementioned interfacial parameters.These samples were further used as bearing surfaces in hydrodynamic lubrication tests.The correlations of these parameters with the measured lubricating film thickness were examined and compared.The key parameter closely related to the hydrodynamic effect was identified.展开更多
It has been well accepted that the lubrication in tribopairs is dominated by different regimes under different conditions,mainly involving hydrodynamic lubrication (HDL),elastohydrodynamic lubrication (EHL),thin film ...It has been well accepted that the lubrication in tribopairs is dominated by different regimes under different conditions,mainly involving hydrodynamic lubrication (HDL),elastohydrodynamic lubrication (EHL),thin film lubrication (TFL),and boundary lubrication (BL).Thin film lubrication is a lubrication regime with lubricant film thickness ranging from a few nanometers to tens of nanometers,which bridges the gap between boundary lubrication and elastohydrodynamic lubrication.展开更多
基金The authors would like to express their gratitude to the National Natural Science Foundation of China(No.51775286)the Research Grants Council of Hong Kong(Project No.CityU11269216)for the financial support.
文摘Effective oil replenishment to the lubrication track of a running bearing is crucial to its sustainable operation.Reliable practical solutions are rare despite numerous theoretical studies were conducted in the last few decades.This paper proposes the use of surface effect,wettability gradient,to achieve the goal.This method is simple and can be nicely implemented using femtosecond laser ablation.A periodic comb-tooth-shaped pattern with anisotropic wetting capability is devised and its effect on the anisotropic spreading behaviour of an oil droplet is studied.Results show that the comb-tooth-shaped pattern enables the rearrangement of oil distribution,thereby escalating oil replenishment to the lubrication track.The effect is due to the unbalanced interfacial force created by the surface pattern.The influence of the shape and the pitch of teeth,which are the two governing factors,on oil transport is also reported.The effects of the newly devised surface pattern on lubrication are experimentally evaluated under the conditions of limited lubricant supply.These results are promising,demonstrating the reduction in bearing friction and the increase in lubricating film thickness.
基金The work described in this paper was fully supported by the Research Grants Council of Hong Kong，Natural Science Foundation of China
文摘The effects of boundary (liquid/solid) slip on hydrodynamics are well recognized.However,it is extremely difficult to quantify in-situ boundary slip in a lubrication contact.Therefore,an effective interfacial parameter that is well correlated with the lubrication effect is of practical significance.This paper presents an examination of common interfacial parameters,including surface tension,contact angle,contact angle hysteresis,and a recently proposed spreading parameter.Specimen surfaces of different hydro/oleophobicity were prepared and characterized using the aforementioned interfacial parameters.These samples were further used as bearing surfaces in hydrodynamic lubrication tests.The correlations of these parameters with the measured lubricating film thickness were examined and compared.The key parameter closely related to the hydrodynamic effect was identified.
文摘It has been well accepted that the lubrication in tribopairs is dominated by different regimes under different conditions,mainly involving hydrodynamic lubrication (HDL),elastohydrodynamic lubrication (EHL),thin film lubrication (TFL),and boundary lubrication (BL).Thin film lubrication is a lubrication regime with lubricant film thickness ranging from a few nanometers to tens of nanometers,which bridges the gap between boundary lubrication and elastohydrodynamic lubrication.
