Lubricant Distribution Research Articles

Lubricant flow analysis for effective lubrication of tractor forward/reverse clutch.

Owing to the high power requirements of tractors, their low-power transmission gears often experience durability problems such as burning of the clutch. The operation of tractors under high load conditions also causes clutch slip, with the consequent longer operation duration exacerbating the burning of the friction plate. Solving this problem requires effective lubricant distribution. This was achieved in the present study by the development of an analysis model for predicting the lubricant flow rate. The reliability of the model was verified by comparing its predictions for various operation conditions with experimental measurements. Using the model, it was determined that effective distribution of the lubricant could be achieved without significant modification of the system, by only adjusting the gaps between the clutch piston and the housing, and between the separation plates and the case.

Metallurgical Aspects of Self-lubricating Composites Containing Graphite and MoS2

The performance of dry self-lubricating bulk materials is directly related to microstructural aspects such as solid lubricant chemical composition and distribution. In this paper, dry powder mixtures were prepared from iron powder and 9-16.5 vol.% of solid lubricants (graphite and MoS2), both combined and isolated. The results showed that interactions and reactions occurred during processing, either between the solid lubricants or between the lubricants and the matrix, generating carbides and sulfides. On account of that, the lubricant distribution in the microstructure is greatly altered, and the microhardness, friction coefficient and wear rate are increased. The best results were achieved by adequate powder particle size, solid lubricant content and sintering temperature control. In the composite containing 9%MoS2 + 2.5%C, values of friction coefficient and wear rate lower than 0.08 and 8 × 10−6 mm3 N−1 m−1 were reached.

Effect of the External Lubrication Method for a Rotary Tablet Press on the Adhesion of the Film Coating Layer.

External lubrication is a useful method which reduces the adhesion of powder to punches and dies by spraying lubricants during the tableting process. However, no information is available on whether the tablets prepared using an external lubrication system can be applicable for a film coating process. In this study, we evaluated the adhesion force of the film coating layer to the surface of tablets prepared using an external lubrication method, compared with those prepared using internal lubrication method. We also evaluated wettability, roughness and lubricant distribution state on the tablet surface before film coating, and investigated the relationship between peeling of the film coating layer and these tablet surface properties. Increasing lubrication through the external lubrication method decreased wettability of the tablet surface. However, no change was observed in the adhesion force of the film coating layer. On the other hand, increasing lubrication through the internal lubrication method, decreased both wettability of the tablet surface and the adhesion force of the film coating layer. The magnesium stearate distribution state on the tablet surface was assessed using an X-ray fluorescent analyzer and lubricant agglomerates were observed in the case of the internal lubrication method. However, the lubricant was uniformly dispersed in the external lubrication samples. These results indicate that the distribution state of the lubricant affects the adhesion force of the film coating layer, and external lubrication maintained sufficient lubricity and adhesion force of the film coating layer with a small amount of lubricant.

Optical analysis of ball-on-ring mode test rig for oil film thickness measurement

There are few experimental results available on film thickness at speeds above 5 m/s and they are almost all based on the optical ball-on-disc test rig. In contrast to the contacts in a rolling bearing, in which the lubricant in the oil reservoir distributes symmetrically, ball-on-disc contact shows asymmetry of lubricant distribution due to centrifugal effects. In order to closely imitate the contact occurring between the ball and the outer ring of a ball bearing, this study proposes an experimental model based on ball-on-glass ring contact. An optical matrix method is used to analyze the optical system, which is composed of a steel ball-lubricant-chromium-coated glass ring. Based on the optical analysis, the measurement system is improved in order to obtain a high quality interference image, which makes it possible to measure the film thickness at high-speeds conditions.

Spatial distributing lubricants from Raman mapping and scanning electron microscopy–energy dispersive X-ray spectroscopy on cetirizine dihydrochloride fast disintegrating tablet properties

Recently, the fast disintegrating tablet (FDT) has started gaining popularity and acceptance as a new drug delivery system. Lubricants could influence on disintegration time (DT), hardness, wetting time (WT) and dissolution of FDT. This study investigated the effects of amount and type of lubricants (magnesium stearate and sodium stearyl fumarate) as well as compression force on characteristics of the cetirizine dihydrochloride (CD) FDT. The spatial distribution of lubricants in tablets had been analyzed using Raman mapping and scanning electron microscopy–energy dispersive X-ray spectroscopy. The more concentration of lubricants or higher compression force resulted in more distribution of lubricant therefore hindering water penetration into the tablet. In addition, CD FDT was prepared by direct compression method. A 32 full factorial design was applied for the optimization of CD FDT. By adopting a systematic formulation approach, the closeness between predicted and observed values (DT, WT, contact angle, surface free energy, hardness) indicated the validity of derived equations for the dependent variables. Sodium stearyl fumarate had less impact on hardness and disintegration time than magnesium stearate. Therefore, FDT containing sodium stearyl fumarate as lubricant showed higher drug release than that containing magnesium stearate.

Analysis of the effect of grooves in single and twin axial groove journal bearings under varying load direction

Multi-axial groove hydrodynamic journal bearings are often preferred over single grooved ones to improve lubricant distribution. However, when assessing the influence of loading angle for a twin axial groove bearing, the authors detected the occurrence of phenomena such as strong negative flow rate in one of the grooves for a broad range of loading angles which was deleterious to bearing performance. Conversely, single groove bearings display acute starvation for specific loading ranges.The authors use a previously proposed thermohydrodynamic approach to compare the role of single and twin groove bearings under variable loading direction. Results show that a groove deactivation strategy (using check valves) might be a best-of-both-worlds strategy, optimizing groove flow rate distribution, reducing temperature and eccentricity levels.

Development of Ni/h-BN Self-Lubricating Composite Powder by High-Energy Ball Milling

Solid lubricants have had good acceptance when used in problem areas where the conventional lubricants cannot be applied: under extreme temperatures, high charges and in chemically reactive environments. In case of materials manufactured by powder metallurgy, particles of solid lubricants powders can be easily incorporated to the matrix volume at the mixing stage. In operation, this kind of material provides a thin layer of lubricant that prevents direct contact between the surfaces. The present study aimed at incorporating particles of second phase lubricant (h-BN) into a matrix of nickel by high-energy ball milling in order to obtain a self-lubricating composite with homogeneous phase distribution of lubricant in the matrix. Mixtures with 10 vol.% of h-BN varying the milling time of 5, 10, 15 and 20 hours and their relationship ball/powder of 20:1 were performed. The effect of milling time on the morphology and microstructure of the powders was studied by X-ray diffraction, SEM and EDS. The composite powders showed reduction in average particle size with increasing milling time and the milling higher than 5 hours resulted in equiaxial particles and the formation of nickel boride.

Viscoelastic behaviour effect of hyaluronic acid on reciprocating flow inside mini-channel

One of the most successful surgeries during the 21st century is total joint replacement (TJR) with material combination of polymer-on-metal (PoM). Despite its success, wear particle generation at the interface of the polymer and metal causes eventually implant loosening. Investigating and understanding the wear particles distribution should help in designing implants with better performances. First step towards characterising wear particle distribution is deriving the lubricant behaviour and velocity distribution inside implant gap. Different hyaluronic acid (HA) solutions were subjected to a sinusoidal movement in straight rectangular channels. The velocity profiles along the channel width were measured with Micro Particle Image Velocimetry. HA solution behaviour was found to be dependent on the concentration. Results showed significant differences between the water (Newtonian) and HA behaviour in unsteady flow. The unsteady behaviour of the lubricant depended strongly on its non-Newtonian viscoelastic behaviour which was due to the time dependent nature of HA solution. Copyright © 2016 John Wiley & Sons, Ltd.

Effect of size and dimensional tolerance of reverse total shoulder arthroplasty on wear: An in-silico study

Although huge research efforts have been devoted to wear analysis of ultra-high molecular weight polyethylene (UHMWPE) in hip and knee implants, shoulder prostheses have been studied only marginally. Recently, the authors presented a numerical wear model of reverse total shoulder arthroplasties (RTSAs), and its application for estimating the wear coefficient k from experimental data according to different wear laws. In this study, such model and k expressions are exploited to investigate the sensitivity of UHMWPE wear to implant size and dimensional tolerance. A set of 10 different geometries was analysed, considering nominal diameters in the range 36–42mm, available on the market, and a cup dimensional tolerance of +0.2, −0.0mm (resulting in a diametrical clearance ranging between 0.04–0.24mm), estimated from measurements on RTSAs. Since the most reliable wear law and wear coefficient k for UHMWPE are still controversial in the literature, both the Archard law (AR) and the wear law of UHMWPE (PE), as well as four different k expressions were considered, carrying out a total of 40 simulations.Results showed that the wear volume increases with the implant size and decreases with the dimensional tolerance for both the wear laws. Interestingly, different trends were obtained for the maximum wear depth vs. clearance: the best performing implants should have a high conformity according to the AR law but low conformity for the PE law. However, according to both laws, wear is highly affected by both implant size and dimensional tolerance, although it is much more sensitive to the latter, with up to a twofold variation of wear predicted. Indeed, dimensional tolerance directly alters the clearance, and therefore the lubrication and contact pressure distribution in the implant. Rather surprisingly the role of dimensional tolerance has been completely disregarded in the literature, as well as in the standards. Furthermore, this study notes some important issues for future work, such as the validation of wear laws and predictive wear models and the sensitivity of k to implant geometry.

Effects of head wear performance with respect to the lubricant thickness on hard disk media for ultra-thin lubricants

Magnetic head wear performance was studied using various thicknesses of D-4OH lubricant that covers hard disk media. The characteristic head wear behavior to over-push the dynamic flying height power differed for each lubricant thickness. The difference in the behavior was highly dependent on the media friction coefficient. The surface free energy also varied as a function of the lubricant thickness. According to the lubricant coverage analysis, we found that the head wear behavior and the friction were dependent on the lubricant coverage change as a function of the lubricant thickness. Furthermore, the molecular dynamics method was applied to investigate the lubricant molecular distribution; the coverage changed with the lubricant thickness similar to that in the experiment. Finally, a head---disk interface mechanism under an over-pushed state was discussed, and meniscus bridge formation was suggested to have occurred at touchdown power for each lubricant thickness.

液体ナノ薄膜の変形流動特性

In the head-disk interface (HDI) of a hard disk drive (HDD), the effects of lubricant deformation on the flying characteristics of a head slider increase as the flying height decreases. Therefore, it is very important to investigate the deformation and flow characteristics of lubricant on a recording disk. In particular, in heat-assisted magnetic recording (HAMR), laser heating of the lubricant induces surface tension distribution and evaporation of lubricant, which may cause deformation of the lubricant film. In this paper, deformation and flow characteristics of liquid nano-film of perfluoropolyether (PFPE) film on solid substrate is investigated numerically and experimentally. Calculation results are compared with experimental results, and validity of the analytical model is investigated.

A study on the tribological behavior of surface texturing on the nonflat piston ring under mixed lubrication

In this study, the performance of surface texturing on nonflat surfaces is numerically investigated. A one-dimensional mixed-lubrication model considering the oil supply is employed. The cases of the nonflat ring lubrication with full and partial texturing are conducted in steady-state and engine-like conditions. By considering the oil transport for lubricant distribution along the liner, the simulation for the whole ring pack is also conducted. As a main conclusion, the textured surface can obtain a special benefit on the tribological properties under not only the mixed lubrication, but also starved lubrication. In addition, it also suggests that the reduction of the ring-pack friction is possible if the nonflat top compression ring is textured.

Problematics of empowerment: sex worker HIV prevention in the Pacific.

A recent overview of HIV/STI prevention programmes for sex workers in the Pacific region indicates that, despite a regional policy shift from universal to targeted interventions, Pacific Island countries currently lack core HIV/STI prevention services for sex workers. Across the region, condom distribution, peer outreach and support services for sex workers have ceased even in countries where such programmes had previously existed. This article cautions that the endorsement of empowerment projects does not negate the important role of condom access in HIV and STI prevention efforts for Pacific sex workers. While community empowerment underpins, and is essential to the sustainability of, effective interventions, it does not constitute an adequate form of HIV and STI prevention in and of itself. We contend that in the context of the Pacific Islands, timely and effective HIV prevention measures must specifically attend to the implementation of, and sustained support for, behavioural interventions such as sex-worker-specific peer education, condom and lubricant distribution, and access to appropriate sexual health services. Further, the responsibility for delivery of these should not be borne solely by fledgling sex worker organizations and communities. The evolution of targeted interventions in the Pacific and the current lack of funded condom distribution programmes highlight a more generalizable imperative within HIV prevention to ensure that behaviour change efforts are not considered to be extraneous to, or rendered redundant by, empowerment-based interventions.

INFLUENCE OF ENGINE LOAD ON PISTON RING PACK OPERATION OF A MARINE TWO-STROKE ENGINE

A set of piston rings is used to form a dynamic gas seal between the piston and cylinder wall. Many physical phenomena are associated with the operation of the system piston-ring-cylinder (PRC), such as: inter-ring gas dynamics for the labyrinth seal, hydrodynamic lubrication and mixed friction in gaps between the rings and cylinder liner, oil flow and distribution of lubricant along the liner, twist motion of rings, liner temperature influence on the oil viscosity. A complex model of the PRC system has been developed by the author. Among own models it includes several sub-models taken from literature, like: a model of viscous oil flow between rough gap surfaces formulated by Patir & Cheng and an elastic contact model of Greenwood & Tripp. The main parts of the mathematical model and software have been experimentally verified abroad by the author at the marine engine-designing centre. A relatively good qualitative and quantitative compatibility between the experimental measurements and calculated results has been achieved. In contrast to the previous papers of the author, new calculation results for a marine two-stroke engine have been presented. These results concern influence of engine load on piston ring pack operation of the analysed engine. They include basic physical quantities associated with gas and oil flow in the piston-ring-cylinder system of the engine. The developed model can be utilized for: evaluation of gas leakage through the sealing ring set, prediction of lubrication conditions of piston rings and oil consumption, defining areas of the possible cylinder liner wear and profile changes of piston rings sliding surfaces, and thus can be useful for optimization of the PRC system design.

Effect of surface topography of disk on lubricant distribution and lubricant transfer between disk and slider

Lubricant transfer from the disk to the slider can affect the slider flying ability. Based on molecular dynamics simulation, we investigated the effects of the roughness of diamond like carbon (DLC) and disk surface protrusion on lubricant distribution on a disk surface and lubricant transfer between the disk and the slider using modified coarse-grained, bead-spring model. The simulation results showed that the effect of DLC roughness on the average lubricant thickness and on the disk surface roughness is small. However, the effect of disk surface protrusion on lubricant distribution on a disk surface is more significant. The roughness of DLC layer and disk surface protrusion result in an increase in the volume of lubricant transfer. Between these two, the effect of the disk surface protrusion is much more important than that of the DLC layer roughness.

Effect of Asperity Plastic Deformation on the Interface Friction in Metal Forming

This paper investigates the effect of the plastic deformation of surface asperities on the interface friction in metal forming involving multi-scale deformation with random surface topography. The equivalent interfacial layer (EIL) introduced by the authors previously was used to integrate the Reynolds equation with the plastic deformation of the randomly distributed surface asperities. The contributions of solid-lubricant interaction, lubricant viscosity and microscopic deformation were therefore included efficiently in a conventional macroscopic finite element analysis. The merit of the method was demonstrated by an investigation into the metal strip rolling, whose friction, lubrication and pressure distribution are otherwise hard to be characterized accurately.

Characterization of Lubricant Distribution of Die Wall Lubricated Tablets by Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy

Characterization of Lubricant Distribution of Die Wall Lubricated Tablets by Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy

Effect of Flying Pitch and Roll Angles on Lubricant Transfer Between Disk and Slider

In this paper, the effect of flying pitch angle and flying roll angle on lubricant transfer from the disk to the slider was experimentally studied. A flying height tester, which can measure flying pitch angle and flying roll angle of a slider, was used to study lubricant transfer from the disk to the slider without head/disk contacts. Transparent glass disks with a thin layer of lubricant were used. A charge-couple device camera was used to observe in situ, the lubricant transfer and lubricant flow on the slider surface, while time-of-flight secondary ion mass spectrometry was used to identify lubricant distribution on the slider surface after the test. The experimental results showed that lubricant flow follows the slider skew direction, i.e., lubricant flow goes toward the outer trailing edge (TE) of the slider when it flies at the inner diameter, and toward the inner TE of the slider when it flies at the outer diameter. In addition, flying roll angle plays a more dominant role than flying pitch angle on lubricant transfer from the disk to the slider.

A-P-1 液体ナノ薄膜の流動特性に関する実験的研究

In the head-disk interface (HDI) of a hard disk drive (HDD), the effects of lubricant deformation on the flying characteristics of a head slider increase as the flying height decreases. Therefore, it is very important to investigate the deformation and flow characteristics of lubricant on a recording disk. In particular, in heat-assisted magnetic recording (HAMR), laser heating of the lubricant induces surface tension distribution and evaporation of lubricant, which may cause deformation of the lubricant film. In this paper, flow characteristics of liquid nano-film of perfluoropolyether (PFPE) film on solid substrate is investigated experimentally. Using the modified Boltzmann-Matano method, diffusion coefficients of liquid nano-step are calculated. In addition, thicknesses of mobile layer and bonded layer of PFPE are measured.

20pm3-PM009 液体ナノ薄膜の流動特性の加熱による影響

In the head-disk interface (HDI) of a hard disk drive (HDD), the effects of lubricant deformation on the flying characteristics of a head slider increase as the flying height decreases. Therefore, it is very important to investigate the deformation and flow characteristics of lubricant on a recording disk. In particular, in heat-assisted magnetic recording (HAMR), laser heating of the lubricant induces surface tension distribution and evaporation of lubricant, which may cause deformation of the lubricant film. In this paper, flow characteristics of liquid nano-film of perfluoropolyether (PFPE) on solid substrate is investigated experimentally. Using the modified Boltzmann-Matano method, diffusion coefficients of liquid nano-step, which shows the flow characteristics, are calculated. As a result, effects of initial film thickness and temperature on the flow characteristics were clarified.