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This study investigates lubricating performances of oils through altering the working conditions in accelerated aging tests, observing the degradations on the lubricants' performances and incorporating in-time detections for verification. To meet the aims, a new measuring system has been developed to observe alterations of the recorded viscosity index, color difference, thermal coefficient and torque transmission in the oil film under electrical discharges. To resolve the quality of lubricating oil in real time, the discharging waveforms and the acoustic indexes were applied to the marginal Hilbert spectrum for characterizing the time-frequency domain features. The Fisher score of the selected features successfully differentiated the new and used lubricants. The physical effects in association with the degradations of oil films are reported in detail. [ABSTRACT FROM AUTHOR]

Cavitation in hydrodynamic bearings is a fundamental factor in the behavior of the fluid film and in the equilibrium position the journal will have after the application of external loads. The calculation of these parameters by robust tools is an active research topic even though accuracy, stability and conservativeness are not so often discussed. This work shows the results obtained through the implementation of a novel model developed from first principles that allows characterizing the pressure field of a liquid–gas lubricant mixture avoiding the reported instabilities with the time derivative of the mixture density. The formulation also relies on a coupled transport equation describing the evolution of the liquid fraction, ensuring mass conservation. This model is applied to study cases with gaseous, vaporous or pseudo-cavitation through the use of the Rayleigh–Plesset equation to characterize the physical behavior of the bubbles formed taking into account the characteristic time of each phenomenon. High resolution schemes are used for the spatial treatment of the advection and a temporal discretization based on the Strang splitting method which allows for a second order convergence in space and time. The numerical results obtained are contrasted and discussed with experimental data found for static and dynamic bearings for the three types of cavitation mentioned, obtaining a very good agreement. • A two-phase model for cavitation in journal bearings is developed. • The physical behavior of each cavitation phenomenon can be modeled correctly. • High resolution schemes are used to obtain a higher convergence order. • Cavitated region depends on saturation pressure, not bubble advection. • Cavitation model impacts vapor region, pressures, shaft stability and final position. [ABSTRACT FROM AUTHOR]

Understanding the behaviour of engine and gear oils, especially the viscosity, under temperature and shear is important to improve machine operation. A novel viscometer using ultrasound is presented and used under a range of temperatures. A single cross-temperature (between 20 ° C and 60 ° C) ultrasonic calibration is shown to be sufficient. Next, the ultrasonic viscometer is compared to a conventional viscosity measurement technique for Newtonian and non-Newtonian lubricants. Newtonian viscosity standard fluids and shear-thinning engine oils are studied. Both viscosity measurement techniques match for Newtonian fluids but ultrasonic measurements are consistently lower for shear-thinning fluids. It suggests that the ultrasonic viscometer is similar to a high-shear viscometer with a shear rate of about 1 0 6 s − 1 . [ABSTRACT FROM AUTHOR]

In this study, we demonstrated hydration lubricity improvement via the synergistic effects of free polymers and brush films formed on a surface. We analyzed the hydration interfacial structure using neutron reflectometry and measured the shear viscoelasticity of the film using the fiber wobbling method. The results revealed that the volume fraction of the free polymer adsorbed on the brush film increased, leading to an improvement in the load-carrying capacity. Additionally, a water-rich layer formed on the surface owing to the brush film's exclusion-volume effect, and this layer reduced the shear resistance and increased the lubricity. These insights into the composite films of polymer brushes and adsorbed free polymers offer new perspectives and design principles for the development of hydration lubrication. [Display omitted] • Synergistic effects of free polymers and brush films improve hydration lubricity. • Volume fraction increase in free polymer on brush film increased loading capacity. • Water-rich layer on the surface reduced shear resistance and increased lubricity. • Results offer new perspectives for development of hydration lubricants. [ABSTRACT FROM AUTHOR]

Research on numerical methods for reciprocating seals, including revealing leakage rate mechanism under the elastic-hydraulic lubrication (EHL) regime are mature. However, micro convex bodies contact behaviors and their effect on lubrication transition mechanism are still used under the mixed lubrication (ML) and wear model insufficiently. Seal model with micro convex bodies deformation should be updated to reflect the lubrication transition from EHL to ML and reveal leakage failure mechanism. Reciprocating speed ranging from 0.1 m/s to 0.2 m/s and working pressure of 100 MPa can characterize the seal performance and failure of leakage mechanism especially in low speed and harsh film formation condition. The updated leakage rate formula and the Reynolds equation are modified considering contact factor and reveal leakage mechanism through macro and micro numerical method. [Display omitted] • The seal convex bodies thermal contact is considered and related to the macro and micro simulation. • Contact factor is added to the Reynolds equation and the leakage rate formula considering the thermal and wear effect. • Seal leakage rate formula is related to contact factor and wear model and numerical method. • The implication of updated model and numerous method from EHL to ML is discussed through updated leakage rate criterion. • Seal experimental workbench is described and nearly conformable to numerous results considering contact factor in Reynolds equation. [ABSTRACT FROM AUTHOR]

The current research examines how a long cylinder, and an infinitely flat surface are affected by surface roughness, MHD, couple stress, and slip velocity using the stochastic theory of hydrodynamic lubrication of rough surfaces as developed by Christensen. Squeeze film time, load carrying capacity, and pressure are calculated using a derived mathematical form of Reynolds' modified equation that accounts for surface roughness and coupling stress. The amount of time needed to squeeze a film under a specific pressure and load can be determined using an analytical method called Reynolds' equation. The lubrication characteristics are graphically represented for various parameters. When a magnetic field occurs and the slip velocity increases, the pressure of the squeeze film, its capacity to carry loads, and the time it takes are all significantly increased. The lubricating properties caused a decrease or increase in the values of the longitudinal (transverse) roughness parameter. [ABSTRACT FROM AUTHOR]

In order to investigate the interaction effect between the transient wear behavior and the lubrication characteristics of the main bearing in low-speed diesel engine under the actual working condition, a coupling model of mixed elastohydrodynamic transient lubrication and time-varying wear is constructed. The transient lubrication model considering the journal misalignment and elastic-plastic asperity contact is used to consider the lubrication characteristics of the main bearing. The wear mechanism of the main bearing material (Babbitt alloy) is found to be surface fatigue wear mainly by the experiments under the equivalent lubrication state, thus the wear model is based on the fatigue damage theory. Several experiments were conducted to verify the accuracy of the coupled model. It is found that the wear gradually increases with increases with wear time, and meanwhile, the lubrication characteristics also change with the wear status. In addition, the effect of the parameters including radius clearance, rotation speed, journal misalignment and bearing loads on the properties of lubrication and wear were investigated. This work would provide practical support for the investigation of wear and lubrication behavior under actual low-speed diesel engine operation. • A coupling analysis model of mixed elastohydrodynamic transient lubrication and time-varying wear of the main bearing under actual dynamic load was established. • The wear mechanism of the main bearing material is found to be surface fatigue wear mainly by the experiments under the equivalent lubrication state of actual condition in low-speed diesel engine. • The verifications of axis orbit, friction coefficient and wear depth indicate the accuracy of the coupling model. • The improvement of bearing lubrication performance after stable wear under actual working conditions was revealed. [ABSTRACT FROM AUTHOR]

In this study, free radical polymerization was employed to prepare a supramolecular polymer gelator called PUMA-PSMA, containing urea groups. The incorporation of this gelator is anticipated to enhance the heat resistance of the gel lubricant. The resulting PUMA-PSMA gels demonstrate favorable mechanical strength and the ability to recover from deformation. Additionally, the PUMA-PSMA gel has a greater film thickness compared to the base oil when the oil supply is abundant. In cases of limited lubricant supply, the PUMA-PSMA gel effectively undergoes shear thinning, reducing the duration of oil starvation. These gel lubricants help prevent the loss of lubricant to some extent and are poised to serve as an innovative type of lubricant. [Display omitted] • The manuscript reports a novel, simple and low-cost method for the preparation of supramolecular polymer gel lubricants. • The addition of synthesized PUMA-PSMA gelator to the 500SN base oil can result in self-assembly to form gels. • Optical interferometric are used to study the oil film thickness and oil pool during the experiment. • The PUMA-PSMA gel can reducing the duration of oil starvation under limited oil supply conditions. • The PUMA-PSMA gel can not only provide effective lubrication but also prevent lubricant loss. [ABSTRACT FROM AUTHOR]

This study presents a numerical model that incorporates the actual micro morphology of sealing lip and rotating shaft to elucidate the sealing behavior in high-speed rotating lip seals operating under mixed lubrication conditions. The model explores the intricate interplay between hydrodynamics at the interface, macro-scale solid mechanics, micro-contact mechanics of surfaces, and the heat generated by friction at the lip. Based on this model, this paper quantitatively predicts the leakage rates and friction torque under various operating conditions and lip seal structural parameters, shedding light on the influence of high-speed frictional heat on sealing performance. • Improved mixed lubrication model is proposed to reveal high-speed leakage. • Revealed the influence mechanism of frictional heat on high-speed rotating lip seal. • Increasing the thickness and length of sealing lip can reduce the leakage rate. • Increasing the inner diameter and lip angle can decrease the frictional torque. [ABSTRACT FROM AUTHOR]

The contact properties of gear rough surfaces during meshing are influenced by various factors. The analysis of rough surface thermoelastoplastic hydrodynamic lubrication (TPEHL) considering micro-scale effect and thermal effect has not been addressed in the literature. This study establishes a new TEPHL model with multi-factor coupling of thermal field, fluid lubrication, stress-strain, and geometric profile. Based on strain gradient theory (SG), a new thermoelastoplastic material constitutive considering micro-scale effect is developed. Subsequently, the three-dimensional rough surface TPEHL-SG analysis of gear is conducted. The paper investigates the impact of thermal and micro-scale effects on various parameters during the meshing of gear in the full oil film lubrication condition, including surface pressure, oil film thickness, surface temperature, surface deformation, and friction coefficient. [ABSTRACT FROM AUTHOR]

Bio-inspired surface microtexture has been adopted in mechanical systems for its advanced lubrication performance. In this study, we discerned the aerodynamic characteristics of different parts of the peregrine falcon's wing, summarized the influence of its distinctive shape on the fluid flow, and, based on simplified geometries and the bionic concept, designed a novel wing-shaped microtexture to enhance lubrication performance in friction pairs. Its shape was simplified by the following parameters: area ratio S p , dimensionless depth h *, and orientation angle α. Using a multiphase flow model, we investigated the effect of the above geometrical parameters on the lubrication performance of the wing-shaped microtexture by numerical simulation. The corresponding geometrical parameters of the wing-shaped microtexture to achieve optimum lubrication performance were: S p = 30%/ h *=1.75/ α = 0°. The wing-shaped microtexture's friction coefficient(COF) corresponded to a reduction of 18.8% and 20.7%, respectively, compared to the triangle and rectangular microtexture, which had the best lubrication performance for existing applications. The results showed that the wing-shaped microtexture enhanced the lubrication performance for three reasons: 1. The biomimetic leading edge created more negative pressure and cavitation zones; 2. The interference between positive and negative pressure zones was effectively mitigated; 3. The sharp design of the biomimetic trailing edge and tail wing concentrated the positive pressure zone while increasing its area. Two double-layer composite wing-shaped microtextures were further introduced to maximize friction reduction. The impact of inner-outer layer area ratio S p * and inner-outer depth ratio h * on the lubrication performance was investigated. Their simulation results revealed that the optimal geometric parameters for the composite microtextures were S p *=6.3%/ hp *=3.0 and S p *=12.7%/ hp *=2.0, respectively. The configurations led to additional COF reductions of 7.6% and 10.56% compared to the single-layer wing-shaped microtexture. These insights offer valuable guidance for reducing friction and wear in mechanical systems. • A novel bio-inspired peregrine falcon wing-shaped microtexture was designed, reaching an effective friction reduction. • Compared to the triangular and rectangular microtextures, the COF decreased by 18.8% and 20.7%, respectively. • The lubrication performance of the double-layer composite microtextures were further promoted compared to the single-layer. [ABSTRACT FROM AUTHOR]

The thermal elastohydrodynamic lubrication (TEHL) model considering pivot deformation and journal misalignment is proposed for the pivot-supported structure of tilting pad thrust bearings. The influence of pivot deformation under journal misalignment on static lubrication performance is analyzed. Meanwhile, the transient response under different dynamic loads is investigated. An electromagnetic hydraulic collaborative controllable loading technology is applied in experiments to verify the model. Results show that the pivot deformation of tilting pad thrust bearings can reach the order of magnitude of minimum film thickness and not be ignored in numerical calculations. Moreover, the pivot deformation can improve the uneven load phenomenon under the journal misalignment, but increase the swing amplitude of tilting pads and the axial vibration of the thrust disk. [ABSTRACT FROM AUTHOR]

When the glass transition is considered in an EHL traction analysis, shear-thinning is not sufficient to explain experiments because there is no liquid behavior to shear-thin and a limiting stress is required. The usual approach of ignoring the glass transition and the associated previtreous pressure dependence has concealed the role of vitrification in establishing the minimum film thickness in real contacts. For the first time, the glass transition is considered in an elastohydrodynamic lubrication simulation along with the glass compressibility. Vitrification and the previtreous pressure response are necessary to predict the minimum film thickness in a point contact. Future numerical simulations should include the glass transition, both for the film thickness and, of course, friction. [ABSTRACT FROM AUTHOR]

Liquid-solid triboelectric behaviors often involve varied liquid-solid and gas-liquid interfaces. However, applications submerged in lubricants haven not been extensively studied. This paper studies the triboelectric behaviors of continuous rotary friction pairs in liquid lubrication. Triboelectric signals are observed from friction pairs made of graphite and stainless-steel with polytetrafluoroethylene (PTFE) coatings. The mechanism lies in the generated streaming current, with constant circumferential velocities and variable radial velocities induced by the variation of film thickness. Pulse signals of electric outputs of 0.26 V are observed as the film thickness changes suddenly. Further discussions about electrode configurations and sealing mediums are conducted for potential applications in film thickness monitoring of mechanical seals. This work expands theories and applications of conventional liquid-solid triboelectric performances. [ABSTRACT FROM AUTHOR]

In spiral bevel gears, the entraining velocity, contact load and radii of curvature along tooth surface are always changed dramatically, which results in remarkable transient squeezing effect on lubricating performance, especially it operates in high-speed and heavy-load conditions. Available elastohydrodynamic lubrication (EHL) and mixed EHL studies for spiral bevel gears are mainly performed under quasi-static (steady-state) assumptions which ignores these transient influences. Therefore, in this paper, a transient mixed EHL model for spiral bevel gears is presented, in which takes into account most variable parameters along meshing surface including contact load, contact radii of curvature, entraining and sliding velocity vectors. Note that all these transient parameters of spiral bevel gears are employed from the results of loaded tooth contact analysis (LTCA). In order to improve the computational efficiency and convergent accuracy with a relatively dense grids, the progressive mesh densification (PMD) method for this transient mixed EHL model is also introduced. A comparison between the present transient mixed EHL model and those data from literature is executed to verify the correctness of the newly developed model. After that, systematically investigations of transient squeezing impact are carried out for spiral bevel gears and compared with the corresponding steady-state EHL results with and without real machined surface roughness. The obtained results reveal that the transient squeezing action can significantly affect the film thickness distribution in each contact zone and along the meshing track line in spiral bevel gears, and lead to dramatic growth in asperity contact area as well. Besides, the steady-state EHL appears to be greatly overestimated the lubricating characteristics for spiral bevel gears. • A transient mixed EHL numerical simulation model for spiral bevel gears is developed. • The progressive mesh densification (PMD) method for this transient mixed EHL model is also presented. • The results from present transient EHL model show a good agreement with those data from literature. •.The steady-state EHL appears to be greatly overestimated the lubricating characteristics of spiral bevel gears. • The contact area ratio and contact load ratio of steady-state mixed EHL are both massively underestimated. [ABSTRACT FROM AUTHOR]

A numerical contact fatigue model combining the effects of rolling contact fatigue and wear has been developed based on mixed elastohydrodynamic lubrication (EHL) theory, continuum damage mechanics (CDM) and the Archard's wear law. A series of benchtop tests were conducted using a triple-contact test rig to study the influence of surface roughness, speed and load on micropitting. The proposed surface damage model was used to simulate the rolling-sliding line contact of surfaces having different surface topography. The film thickness, contact pressure and sub-surface stress were determined by solving the generalized Reynolds equation and using the well-developed discrete convolute and fast Fourier transformation (DC-FFT) method. The jump-in-cycle was assumed to evaluate the accumulated damage based on the tested fatigue life and sub-surface stress histories. Surface topography was updated by calculating the wear height with the Archard's wear equation. Results reveal that micropitting occurs under the combined effect of wear and contact fatigue. The micropitting rate increased then turn to decreased as the lambda ratio (λ) increased. The contact pressure significantly affected the contact fatigue life and the micropitting rate. • The combining effect of contact fatigue and wear on micropitting was investigated. • A series of contact fatigue tests were conducted using the triple-contact rig to investigated the micropitting behavior. • The surface damage was predicted based on CDM, which shows a qualitative agreement with test results. [ABSTRACT FROM AUTHOR]

The attention is focused on high-performance Mg alloys due to their favorable biocompatibility, lightweight, physicochemical and mechanical properties. Here, the fretting performance of Mg–Sn–Y alloy was evaluated under fluids lubrication, and the fretting mechanism was explored in detail via analysis of wear track/debris using SEM and XPS depth profile. The results illustrate that the friction reduction is superior to wear resistance for lubricated Mg–Sn–Y/Steel contact under fretting conditions, mainly depending on the oil-film induced transformation of fretting running regime and transition of fretting wear (from adhesive/oxidation wear and delamination under dry friction to abrasive wear and delamination under fluids lubrication). Hence fretting performance of Mg–Sn–Y alloy under fluids lubrication depends on fretting running regime and synergy of oil-film/protective film. Image 1 • The fretting running regime and wear mechanism of Mg–Sn–Y alloy under lubrication conditions are first investigated in detail. • The introduction of lubricants can transform the fretting running state of Mg–Sn–Y/Steel contact. • Wear debris and transfer layer can enhance the mechanical properties of mating interfaces, change the fretting regime, and reduce friction and wear. • XPS depth profile reveals the tribo-chemical reaction films composed of MgO, Mg(OH) 2 , MgCO 3 , MgF 2 and Y 2 O 3. [ABSTRACT FROM AUTHOR]

In a nuclear power plant, the thermal energy from the reactor chamber is transported out to the steam generators through a fluid called reactor coolant. Pumps circulating the reactor coolant in a closed loop have a multistage sealing system including a controlled leakage face seal. It is crucial to understand and predict the performance of this mechanical seal to prevent exposure of this radioactive fluid to the environment. This paper introduces a novel modeling approach that allows fast and accurate prediction of the operation of an axisymmetric seal. Thermal and mechanical parameters governing the performance of the seal have been shown to match well with previous experiments. The new model allows investigation of yet unexplored process variables. • The results from the integrated TEHL model match well with published data. • Changes in the shaft speed are predicted to cause little variation in leak rate. • Thermal deformations cause the leak rate to increase linearly with taper angles. • Leak rate is impacted by the operational history through friction at the dynamic seal. [ABSTRACT FROM AUTHOR]

A transient Mixed Lubrication-Wear coupling model (MLW coupling model) is developed to investigate the mixed lubrication and wear performances of journal bearings, and a wear experiment for journal bearing is performed to support the validity of the developed numerical model. In the coupling numerical model, the transient interaction between the behaviour of mixed lubrication and wear is considered by incorporating the wear depth distribution, which is determined by the developed friction fatigue wear model, into the film gap equation. The evolutions of the worn surface profile, wear rate, fluid pressure and asperity contact pressure over operating time are calculated by the developed numerical model. The simulated results demonstrate that the transient wear process affects the distribution trend of lubrication performances significantly, and a worn surface profile may exist that provides an optimal tribology performance of journal bearings. The simulated results also demonstrate that there are two wear stages, identified by initial and steady wear stage, of journal bearings under mixed lubrication condition. Furthermore, the effects of the input parameters, including the radius clearance(C), surface roughness (σ), asperity curvature radius (β) and boundary friction coefficient(μ c), on the predicted mixed lubrication and wear performance are evaluated. • A transient Mixed Lubrication-Wear coupling model (MLW coupling model) for journal bearings is developed. • The effects of transient mixed lubrication performance on the wear are considered by a developed fatigue wear model. • The evolution of the lubrication and wear performance over operating time is determined. [ABSTRACT FROM AUTHOR]

This paper reports a comprehensive study of soft lubrication in a porous layer whose thickness ranges from 3.1 mm to 19.0 mm, using two experimental setups for different scales of porous media. We demonstrate that the lubrication theory for soft porous media (Feng and Weinbaum, J. Fluid Mech. 422, 282, 2000) is valid in describing the fluid pressurization, while the theory by Toll (Polym Eng Sci 38, 1337, 1998) is appropriate in predicting the solid phase lifting force. A new model is then developed for estimating the contribution of the fluid pressure to the total lift, which, along with extensive dimensional analysis, provides critical insights for the application of soft porous lubrication in industrial applications. • A novel experimental study of soft porous lubrication in multiscale materials. • Experimentally verified theories for both fluid and solid pressure generation. • A new model for predicting the lubrication behavior in soft porous media. • The new model is verified experimentally. • Dimensional analysis provides guidelines for the design of porous bearings. [ABSTRACT FROM AUTHOR]

The behaviour of n -alkanes confined and sheared between iron oxide surfaces has been studied using nonequilibrium molecular dynamics simulations. The molecular extension, orientation, film structure, flow, and friction have been investigated for a range of n -alkane chain lengths under conditions representative of the elastohydrodynamic lubrication regime. At high pressure, the molecules show strong layering and long-range order, suggesting solid-like films. Conversely, high shear rates result in less elongated, layered, and ordered molecules; indicating more liquid-like films. Although Couette flow is usually observed for short n -alkanes, the flow is often non-linear for long n -alkanes. The friction coefficient increases logarithmically with shear rate, but the slope decreases with increasing pressure such that it becomes insensitive to shear rate for long n -alkanes. [ABSTRACT FROM AUTHOR]

In this work a stable and reliable numerical model based on complementary variables is developed to study lubricated contacts characterised by slip at one or both surfaces and in the presence of cavitation. This model can be used to predict surface behaviour when cavitation induced by e.g. the presence of surface texture, slip, or a combination of the two is encountered, with varying surface parameters. For this purpose, two different algorithms are coupled to predict the formation of cavitation, through a mass-conserving formulation, and the presence of slip at the wall. The possible slippage is described by a limiting shear criterion formulated using a Tresca model. To show the flexibility of our model, several bearing geometries have been analysed, such as a twin parabolic slider, a cosine profile used to mimic a bearing, and a pocketed slider bearing employed to study the effect of surface texture. We observe that the lubrication performance (i.e. low friction coefficient) can be improved by using materials that promote slippage at the moving wall. The location of the slippage region can be optimised to find the lowest value of friction coefficient. Our theoretical developments and numerical implementation are shown to produce useful guidelines to improve and optimise the design of textured superoleophobic surfaces in the presence of lubricated contacts. • Proposal of a simulation framework for lubricated contact in the presence of wall slip and cavitation. • Robust and efficient solver developed for flexible exploration of engineering solutions. • Validation of results against existing state-of-the-art. • Use of the numerical simulation to optimise bearing performances. • Consideration of operating condition that may benefit from specific solutions proposed. [ABSTRACT FROM AUTHOR]

In this study, a lubricant was utilized to improve the performance of an injection molded PA66 gear, and evaluations were carried out using a power absorption test rig. The observation of scuffing on the test gear under lubricated conditions in the gear tooth between the start of active profile (SAP) and the lowest point of single tooth contact (LPSTC) confirmed the maximum predicted gear tooth temperature in this region. A lower film thickness between the SAP and LPSTC region compared to the pitch region also contributed to the scuffing failure. The failure morphology of the test revealed tooth subsurface cracking in the pitch region and scuffing in the flank region under dry and lubricated condition respectively. • Injection molded PA 66 gears were evaluated under dry and lubricated conditions using a power absorption test rig. • Contact temperature of the gear tooth pair and film thickness under lubricant conditions were computed using AGMA standards. • The scuffing under lubricated conditions between the SAP and the LPSTC confirms the maximum predicted gear tooth temperature. • Tooth cracking near the pitch region and scuffing in the flank region under dry and lubricated condition were observed. [ABSTRACT FROM AUTHOR]

A numerical investigation was performed, with single axisymmetric asperities passing through lubricated rolling contacts at different slip. Two explanatory and cooperating phenomena were found as to why the damage develops more frequently at negative than positive slip. Metal contact occurred in the inlet, where tractive asperity contacts at negative slip provided a large tensile surface stress outside the contact. As the asperity moved through the contact, sliding supplied it with lubricant and heated the lubricant along the contact. The shear tractions were thus higher near the inlet than the outlet, making them more detrimental for negative than positive slip. • The asymmetry of pitting was explained by asperities in thermal-EHL. • The temperature increase through the contact yielded asymmetric shear tractions. • Separation of the real defect and complementary effect gave asymmetric metal contact. • Explanation of rolling contact fatigue by the asperity point load mechanism. [ABSTRACT FROM AUTHOR]

Micro-textures applied on rubbing surfaces have gained tremendous attention in the tribological community. Numerous studies deal with the deduction and testing of beneficial micro-textures. Nevertheless, not all questions have been answered yet. Will texturing really deliver as good effects as frequently claimed? Are there optimum texture designs? Are there occasions where texturing could enhance the tribological performance but is questionable from other perspectives? Therefore, ball-on-disc experiments are carried out with a special emphasis on the relative position of micro-texture and counter body. Furthermore, transient EHL simulations are performed, addressing the effects of structural parameters and relative texture's position on the tribological performance. Finally, meta-modeling with subsequent optimization is applied to predict numerically derived optima and robust texture designs. • The relative position between micro-texture and contact area influences friction and wear. • Structural texture parameters determine the tribological behavior. • Tribo-simulations and Meta-Modeling support the deduction of robust texture designs. • Appropriate micro-texture designs depend on the applied load. • Shallow textures with a diameter close to contact area are considered to be beneficial. [ABSTRACT FROM AUTHOR]

The purpose of this research is to indicate the potential differences in bearing characteristics resulting from the application of different lubricant types with the same viscosity grade. The effect of different environmentally acceptable lubricants (EALs) on hydrodynamic journal bearing properties is studied experimentally and compared to the properties obtained after lubrication with a reference mineral oil. The results of the studies proved that a bearing lubricated with EALs had practically the same properties as one lubricated with mineral oil. The calculations for the tested bearing system showed that the variations of selected lubricant parameters, such as specific heat or thermal conductivity, do not significantly affect the properties of the bearing, i.e. the minimum film thickness or power losses. • Theoretical and experimental work was conducted. • Theoretical part – calculations – FSI modeling was used for calculations. • Experimental research – was conducted for real scale journal bearings on unique test rig designed and build on University. • Journal bearing lubricated by different type oils properties were studied and compared. [ABSTRACT FROM AUTHOR]

Porous aerostatic bearings (PABs) are widely used in high-speed applications and ultra-precision machinery owing to their frictionless motion and remarkable stability. In this paper, a novel parallel capillary-cavity model based on the intricate pore structure characteristics is established to characterize air flow in PABs and analyze the pneumatic hammer vibration. An experimental setup is constructed to measure the pneumatic hammer vibration of PABs. The experimental results exhibit a strong agreement with the predictions. The effects of various factors, including different loads, air pressures and porosities on the pneumatic hammer vibration are thoroughly discussed. The results show that higher air supply pressures, larger loads, and increased porosity are more likely to trigger pneumatic hammer vibration in PABs. • This paper proposes a novel parallel capillary-cavity model to analyze the pneumatic hammer vibration. • A numerical analysis on the vibration of PABs is presented by coupling the lubrication and motion equations of PABs. • By building test rigs, the pneumatic hammer vibration of porous aerostatic bearings is measured. • The experimental results show a remarkable agreement with numerical values. • The experimental results show that the newly proposed model can effectively predict the pneumatic hammer vibration of PABs. [ABSTRACT FROM AUTHOR]

Rotary compressor, which contains different types of friction pairs, is widely applied in refrigeration equipment. With its development towards high power density and long life, the multi-body interactions and the surface deformation have increasing impacts on the compressor performance. To reveal the working state of the compressor comprehensively and conduct optimal design, a new tribo-dynamic model considering multi-body coupling and bearing deformation is established in this study. Based on the analysis under high ambient pressure, the moving characteristics of the rolling piston and the effects of the crankshaft shoulder profile are presented. It is found that the direction and magnitude of the piston rotation speed highly depend on the working frequency, and an asymmetric crankshaft shoulder profile can dramatically increase the minimum oil film thickness and reduce the wear load. In addition, the impacts of the oil supply structures for the crank, the main bearing and the sub bearing are also given. By comparing different design schemes, the optimized oil supply structures are determined. This work provides a comprehensive analysis method for optimizing the lubrication design of high-performance compressors. • A new tribo-dynamic model of the whole rotary compressor is established. • The effects of multi-body coupling and bearing deformation are considered. • The variation of piston rotation speed highly depends on working frequency. • An asymmetric crankshaft shoulder profile can dramatically reduce wear load. • Compressor performance can be improved with the optimized oil supply structures. [ABSTRACT FROM AUTHOR]

The paper aims to reveal the lubrication bearing mechanism of double-film bearing under different conditions. Modified lubrication models of double-film bearing with laminar/turbulent effect, cavitation and other conditions are established. The function reflection relations between lubrication behavior and structural parameters, working condition parameters are illuminated. The regulations of influences of coupling factors (eccentricity ratio, speed, length-diameter ratio, misaligned angle and operating models) on lubrication characteristics are explored. The lubrication mechanism of double-liquid film interface is elucidated. The variation rules of bearing performance are summarized. The research is important to the optimal design (load-carrying capacity enhancement & friction-reduction) of the double-film bearing. [Display omitted] [ABSTRACT FROM AUTHOR]

This study aims to investigate the lubrication behavior of asphalt binder on the basis of Stribeck tribology theory, employing viscosity test, gyratory compaction test, and image processing techniques. The quantification of the lubrication regimes and their transformation was performed by an image processing algorithm that measures the thickness of the mortar film based on the minimum distance. The hydrodynamic regime transforms into the elasto-hydrodynamic regime by 23.2% below 60 gyrations. 11.6% of the elasto-hydrodynamic regime transforms into the mixed regime above 60 gyrations, causing an increase in friction. The slope of the compaction curve follows the variation rule of the Stribeck friction coefficient. Asphalt viscosity in the range of 380–460 mPa·s is recommended for optimum compaction. [ABSTRACT FROM AUTHOR]

This study focuses on the relationship between meniscectomy and osteochondral junction health, and their integrity on cartilage lubrication. Using a previously published multi-component joint computational model, we explored the impact of increasing degree of meniscectomy and osteochondral flow conductivity on joint lubrication. Results suggest a greater effect of meniscectomy on joint lubrication when the osteochondral junction is healthy. However, the impact is less pronounced when the osteochondral junction is already diseased due to compromised lubrication capability. This research provides a first-time quantitative analysis of this interaction, which highlights the importance of adequately evaluating the osteochondral junction's condition before meniscectomy surgery. It also suggests that reducing post-surgery activity level may be beneficial for patients with diseased junctions undergoing meniscectomy. [ABSTRACT FROM AUTHOR]

The research on Ti 3 C 2 T x as a liquid lubricating additive is still in its infancy, and some problems exist, such as ambiguous relationship between Ti 3 C 2 T x structure and lubricating performance. Herein, Ti 3 C 2 T x was adjusted to improve its tribological properties in polyethylene glycol 200 (PEG200). Hydrothermal method was employed to prepare spherical Ti 3 C 2 T x quantum dots (MQDs), with size of approximately 6 nm. The additive of MQDs significantly improved the tribological properties of pure PEG200, where the average friction coefficient was reduced by 20.0 % and the wear volume was reduced by 69.1 %. MQDs can provide a rolling effect to reduce the friction and repair the worn interfaces by forming an adsorption film through electrostatic adsorption, thereby effectively improving the tribological behaviors of sliding interfaces. [Display omitted] • Spherical Ti 3 C 2 T x quantum dots (MQDs) with particle size of 6 nm were successfully prepared by hydrothermal method. • The optimum addition amount of 0.3 % MQDs into PEG200 can reduce the friction coefficient and wear volumes by 20.0 % and 69.1 %, respectively. • Lubricating mechanisms of MQDs was derived from the synergistic lubrication of Ti 3 C 2 T x , oil-film, and tribo-film. [ABSTRACT FROM AUTHOR]

To reveal the thermal-fluid-structure interaction characteristics of water-lubricated slipper/swash plate interface, a transient mixed thermoelstohydrodynamic (MTEHD) lubrication model incorporating asperity contact, elastic deformation, heat transfer and viscosity temperature effect is originally presented. The change in fluid properties caused by cavitation is considered for solution the piston chamber pressure. Distributions of pressure, temperature, deformation and tilting state of slipper simulated by MTEHD show strong reasonableness. Effect of operating and structural parameters on energy consumption characteristics calculated by MTEHD and hydrodynamic lubrication is contrastively analyzed. The results show that energy consumption is different in delivery and suction stroke due to different degrees of MTEHD effects and transient contact. Besides, the optimal dimension for the width of studied sealing surface is determined. [Display omitted] • A TFSI model for water hydraulic slipper/swash plate interface is originally presented. • Lumped parameter method for flow properties is coupled with MTEHD lubrication model. • Transient MTEHD lubrication behavior is obtained. • Effects of working and structural parameters on energy loss characteristics are investigated. [ABSTRACT FROM AUTHOR]

this paper presents a stacked perforated foil bearing to address plastic deformation and complex processes of traditional gas foil bearing, which consists of a top foil, three stacked perforated foils and a bearing sleeve. Three layers of perforated foils are stacked to form a stacked perforated foils as the elastic structure of the SPFB, providing sufficient structural deformation and multi-point friction. The theoretical model of the SPFB, which couples a structural model based on a single supported beam with Reynolds equation, is solved using FDM, and the predicted results are validated against experimental results. The static and dynamic characteristics of the SPFB are analyzed under multiple structural and operational parameters, which improves the theoretical basis for commercial application. • This paper presents a novel SPFB that utilizes three perforated foils to distribute the bearing circumferentially, providing sufficient structural stiffness and multi-point contact friction effect. • The theoretical model of the SPFB coupling the simply supported beam model for the perforated foil and the finite shell model for top foil with Reynolds equation is founded to predict the static and dynamic characteristics. • The static and dynamic characteristics of SPFBs are investigated under different speeds, loads, circumferential interval angle and axial distance of the perforated foil, nominal clearance, rotor tilt angles, and installation preload. • The dynamic coefficients of the SPFB with different circumferential interval angles and axial distances of the foil structure show similar behavior, larger interval angle and distance are recommended to improve stability. The effect of nominal clearance on bearing performance is segmented, and a small clearance is preferred. Selecting appropriate installation preload and rotor tilt angle can improve bearing stability. [ABSTRACT FROM AUTHOR]

Owing to the simple structure, large load-carrying capacity and long life, journal bearings supporting planet gears (JBSP) are increasingly used in the wind turbine gearbox. The moment caused by the asymmetric meshing leads to the misalignment of the JBSP and further deteriorates its lubrication behaviors. A thermal-elastohydrodynamic (TEHD) model is developed for the misaligned JBSP, where the finite element method (FEM) and influence coefficient method are used to compute the temperature and deformation of this bearing, respectively. Besides, the above model is also experimentally verified. It is found that the misalignment of the JBSP can be suppressed through reducing its modification amount, helix angle and radial clearance, which have the optimal values to improve the TEHD behavior of the JBSP. • The thermal-elastohydrodynamic model of the misaligned journal bearing in the wind turbine gearbox is proposed. • Selecting an appropriate elastic modulus can suppress the misalignment and improve the lubrication behavior of the bearing. • Reasonably reducing the radial clearance, modification amount and helix angle can suppress the planet misalignment. • The radial clearance, modification amount or helix angle has an optimal value to improve the bearing lubrication behavior. [ABSTRACT FROM AUTHOR]

The objectives of this investigation are to determine the effects of cage pocket conformality on lubrication in a cylindrical roller bearing (CRB) cage. A custom Bearing Cage Friction Test Rig (BCFTR) was configured with a sealed enclosure to emulate a lubricant bath environment. The enclosure was designed to accommodate CRB raceway segments and swappable cage pockets with adjustable roller-pocket clearance. Three transparent cage segments were fabricated with differing pocket conformality with respect to the roller surface. A high-speed camera was used to visualize the in-situ lubricant flow within the roller-pocket contact for all cage types. An equivalent two-phase computational fluid dynamics (CFD) model was developed using Ansys Fluent software. The CFD results corroborated well with the experimentally observed trends of lubricant distribution and cage pocket friction. The findings demonstrated that the impact of pocket conformality was two-fold. The least conformal pocket design experienced minimum pocket friction. However, the same design introduced challenges with retaining lubricant at the roller-pocket contact and increasing air entrapment in the oil. [ABSTRACT FROM AUTHOR]

The two-dimensional piston pump with flat roller/cam transmission mechanism enables high-speed operation, frequent load-carrying start-ups, and rotational direction changes, making it suitable for electro-hydrostatic actuators. This study investigates the rolling friction loss and starting torque characteristics of the friction pair under high-speed and high-load conditions. Numerical simulations show that the flat roller/cam friction pair is unsuitable for elastohydrodynamic lubrication when the roller surface hardness exceeds the cam surface. Experimental results reveal a friction coefficient of 0.0042 during load-carrying start at 1400 N, equivalent to 28 MPa pump load pressure, and 0.001 at 10000 rpm and 1400 N. The study highlights the high transmission efficiency of the designed mechanism, allowing load-carrying start-ups without relying on an oil film. [ABSTRACT FROM AUTHOR]

High-carbon chromium steel is a main material to make bearings, owing to the notable wear resistance. However, researches on the abradability of this material in mixed lubrication are rarely available. Therefore, an approach by combining mixed lubrication simulation and ball-disc wear experiment was proposed to determine the correlation between oil film parameter and wear coefficient of GCr15 (AISI52100) bearing steel. Generous of ball-disc wear experiments were conducted under varied lubrication conditions to obtain matching wear coefficient. In terms of the simulations and experiments, the relationship between oil film parameter and wear coefficient was quantified. Furthermore, the analysis of the variation of wear coefficient with the factors in operating conditions demonstrated that the normal load and rotation velocity significantly affects wear coefficient. [ABSTRACT FROM AUTHOR]

Tackling fluid-flow problems involving intricate surface geometries has been the catalyst for a plethora of numerical investigations aimed at accommodating curved complex boundaries. An example is the application of body-fitted curvilinear coordinate transformation, where the one-to-one correspondence of grid points from a non-orthogonal curvilinear grid in the physical domain to an orthogonal grid in the computational domain is achieved. In lubricated interfaces, such conversion is challenging due to the complexity of the governing equations in the mapped-grid, the numerical instabilities exhibited by their non-linearities and the severity of the operating conditions. The present contribution proposes a Reynolds-based, finite volume fluid–structure interaction (FSI) framework for solving thermal elastohydrodynamic lubrication (TEHL) problems mapped onto orthogonal grids in the computational domain. We demonstrate how the strong conservation form of the pertinent governing equations can be expressed in three-dimensional curvilinear grids and discretised using the finite volume method to ensure fluid-flow conservation and enforce mass-conserving cavitation conditions. Numerical and experimental benchmarks showcase the robustness and versatility of the proposed framework to simulate a diverse range of lubrication problems, hence achieving a predictive computational tool that would enable a shift towards tribology-aware design. [ABSTRACT FROM AUTHOR]

Journal bearings are the most commonly used load elements in rotating systems and have a long history in tribology research. However, the relatively new surface modification technique of femtosecond laser texturing has rarely been used to increase the efficiency of journal bearings. We used a 300-fs laser to create chevron-shaped microstructures in different circumferential texture locations on half-bearing shells to investigate the effect of partial texturing on the tribological performance of journal bearings. With a customized shaft-bearing shell setup, the coefficient of friction and lubrication film thickness was tracked in two load scenarios at varying rotational speeds. In fully film conditions, the findings demonstrate that textures in the high-load region of journal bearings provide the highest lubricant film thickness and lowest friction compared to textures in the pressure build-up, divergent zone, and unstructured reference. Moreover, surface textures in the high-load area also perform better in boundary and mixed lubrication. Experimental data have also shown that asymmetric texture designs have a detrimental effect on lubrication performance. In contrast to symmetric designs, the lubrication film build-up is hindered. The research results represent a step toward transferring laboratory findings on laser surface texturing for tribological optimization in real applications. [Display omitted] • Textures in the high-load region provide the highest lubricant film thickness and lowest friction in hydrodynamic lubrication. • Textures in the high-load area also perform better in boundary and mixed lubrication. • Asymmetric texture designs can be detrimental for the lubrication performance of journal bearings. [ABSTRACT FROM AUTHOR]

Drawing process, with the advantages of high accuracy and efficiency, is a common process for tube production. The high friction in tube drawing leads to high drawing forces, easy breakage of tube and high production costs, etc. It is urgent to reduce friction coefficient during the tube drawing. However, the effect of contact area on friction (friction-related size effect) along with the coupling effects of surface roughness, lubricants, and coatings is still unclear or even contradictory, which causes the reduction of the friction coefficient in tube drawing to become a challenge. In this study, taking IN718 tube drawing as the research object, the influence mechanism of contact area (1.25–12.06 mm2) as well as the coupling effects of surface roughness (0.513–0.622 µm), lubrication status, and coatings on friction was explored to reduce the friction coefficient as much as possible. Firstly, a new multi-sensor drawing device is designed to obtain contact pressure and drawing force, combined with finite element model, to characterize friction coefficient during the tube drawing. Secondly, the finite element model considering pits and lubricant is designed to reveal the friction mechanism in tube drawing. The results indicate that as the nominal contact area increases, the proportion of actual contact area decreases, leading to a decrease in friction coefficient, from 0.1102 to 0.0502, a decrease of 54.36%. The reduction of roughness leads to the weakening of plough effect, the coating leads to a transformation of the friction pair, and the lubricant bears some pressure, all of which can lead to a decrease in the friction coefficient, from 0.1203 to 0.0351, a decrease of 70.79%. By designing appropriate contact area (12.06 mm2), surface roughness (0.513 µm), lubrication status (graphite), and coating (sodium fluoride), the friction coefficient is sharply reduced from 0.1203 to 0.0014, a decrease of 98.79%. This in turn leads to a significant increase in the deformation amount, viz., the single pass drawing deformation amount is greatly improved from 14.22% to 49.65%. The research results have significantly reduced production costs. [Display omitted] • The friction coefficient is reduced from 0.1203 to 0.0014. • The influence mechanism of the size effect on friction in the drawing process has been obtained for the first time. • A new drawing device has been designed to solve the problem of difficult characterization of the friction coefficient. • The reduction of the friction coefficient causes an increase in the drawing deformation amounts from 14.22% to 49.65%. [ABSTRACT FROM AUTHOR]

Experimental research was conducted on mechanical seals with pressurized lubricated-oil, focusing on lubrication and leakage inhibition of herringbone-grooved face seals. Through the visualization experiments and axial displacement tests, this study evaluated the performance of the inner-diameter-side (IDS) and middle-diameter-side (MDS) herringbone grooved seals based on the measured cavitation region, leakage rate, friction torque, surface temperature of stator, and axial displacement of the primary ring. The experiment results show that, increasing the width of the seal dam can reduce the hydrodynamic effect and cavitation development of the liquid film but enhance the hydrostatic effect, maintain a small leakage range, the maximum leakage rate is less than 19 mL∙min−1. Zero-leakage can be achieved in MDS due to cavitation suction. The axial displacement curves indicate that the runout amplitude of IDS is smaller than that of MDS, the maximum axial displacement difference is about 25 µm, the stability of IDS is better than MDS. Comparisons of surface temperature and friction torque demonstrates that the lubrication of MDS is better than that of IDS. [ABSTRACT FROM AUTHOR]

Electric current discharge in motor bearings is becoming more of a concern with the move toward electric vehicles (EV), since it can damage bearing surfaces and potentially cause premature failures. Electric discharge (ED) tests were carried out utilizing a self-improved ball-on-disc instrument under elastohydrodynamic lubrication (EHL) regime to better understand the nature of electric discharge in EV motor bearings. The experiments prove that the discharge behaviour is related to the lubricant film thickness and the discharges appear at the minimum film thickness area. An electric discharge energy model was developed to describe the relationship between working conditions and the energy of a single discharge. The model was qualitatively verified by comparing the predicted ED damages with the ball-on-disc test results. • The modified ball-on-disc test equipment can mimic the electric discharge that occurred in EV motor bearings. • Discharge behaviour is lubricant film thickness dependent and the discharges appear at the minimum film thickness area. • A model was developed to link working conditions and the energy of a single discharge. • A mitigation measure to avoid/reduce electric erosion is proposed by controlling the lubricant film thickness. [ABSTRACT FROM AUTHOR]

Utilizing environmentally-friendly magnesium silicate hydroxide (MSH) nanoparticles as a lubricant additive is considered a promising concept. However, whether large particle agglomerates would enter the small lubrication contact area is a worthwhile issue to consider. This study aimed to investigate in situ visualization the lubrication behaviour of MSH-containing oil in rolling contact. The results indicate that MSH nano-additives can enter the contact zone in granular, sheared, and unrestricted states as the velocity increases. The MSH tribofilm can spontaneously grow on the lubrication track regardless of whether the lubrication is in the boundary, mixed, or elastohydrodynamic (EHD) regime. A mass fraction of 0.50% MSH produces a tribofilm thickness of approximately 200 nm, significantly improving tribological properties under rolling conditions. With the velocity increasing, the MSH-based tribofilm thickness decreases. The size of aggregates and the sheared effect affect tribofilm growth. In addition, the interferogram presents that the lubricant flow also affects tribofilm growth. The velocity profile of the lubricant flow is obtained by numerical calculation. The results show that the tribofilm decreases because the backflow in the inlet reduces the probability of MSH particles entering the contact. [ABSTRACT FROM AUTHOR]

Polyurethane, as one versatile family of material, has been studied widely for water-lubricated bearings material. However, the connection between tribological performance and their internal material structure, in particular, crosslinks, remains elusive. Here, the effect of crosslink on the tribological performance of thermoplastic polyurethane (TPU) has been elucidated. TPUs with different crosslink degree were obtained by strengthening hydrogen bonded effect via Gamma-ray. The result shows that the friction coefficient increases with the increase of crosslink degree overall. It is because that enhanced crosslink means more molecular chains crosslink together by hydrogen bonds, resulting in more energy consumption during the friction process. In addition, incremental and larger particles produced during friction leads to third-body mechanism, acting on wear behavior of TPU. • Intermolecular hydrogen bonds forming in thermoplastic polyurethane reflects its crosslinking density. • Increased dose of Gamma-ray radiation causes enhanced crosslinking density, causing higher friction coefficient overall and different wear behaviors. • Higher crosslinking density means more molecular chains to move restrictively and it costs more energy during the friction process. • Many TPU particles produced during friction, which suggests a possible third-body mechanism. [ABSTRACT FROM AUTHOR]

Boundary slippage modeling and optimization of the hydrophobic tilting pad thrust bearing with elastic deformation are conducted to obtain the optimal lubricating film geometry and power loss. The modified Reynolds equation combining with a nonlinear slip control equation of the limiting shear stress model is transformed to a series of linear complementary problems to be solved by the parametric quadratic programming technique. An optimization approach based on the Kriging surrogate model is developed to optimize the slip/no-slip configuration of the thrust pad. The effect of homogeneous slipping and heterogeneous slip/no-slipping coupled with elastic deformation on minimum film thickness and power loss is studied for the tilting pad thrust bearing with the flexible lining materials. • Boundary slippage model with considering elastic deformation is developed. • Limiting shear stress model is used to accurately describe the boundary slippage. • Parametric quadratic programming technique is used to avoid numerical difficulty. • Kriging surrogate model is used to efficiently optimize slip/no-slip configuration. • An improved design of slip/no-slip configuration of thrust pad is carried out. [ABSTRACT FROM AUTHOR]

Lubrication conditions have significant influences on the formation of tribofilms and then affect tribological behavior. In this work, the influence of tribofilm formation on the tribological behavior of textured surfaces with oval shapes was measured using a pin-on-plate tribometer. The results show that, under full lubrication, the adsorbed oil film controlled the friction and wear behavior of steel/steel tribopairs but under starved lubrication, the formation of a tribofilm significantly influenced the tribological behavior. The appropriate textured surfaces with oval-shaped dimples contribute to obtaining excellent antifriction and antiwear behavior. However, excessively high ratios of the major to the minor axis of the oval can result in high contact stresses which can destroy the tribofilm. • Textured surfaces with oval-shaped dimples were facilely fabricated. • Influence of tribofilm formation on the surface tribological behavior was investigated. • The adsorbed-film controlled the friction and wear behavior of tribo-pairs under full lubrication. • The formation of tribofilm dominated the interface behavior under starved lubrication. [ABSTRACT FROM AUTHOR]

This paper theoretically investigates the lubricant film build-up in a Newtonian, isothermal wide EHL rolling contact with a small transverse oscillating speed of constant frequency and amplitude. By increasing either elliptical contact width or roller-end gap smoothness, it is found with the aid of perturbation techniques that a) film fluctuations introduced by the transverse speed become smaller in amplitude and limited to the contact edges and, b) the overall minimum film thickness position shifts from the side lobes to the centerline outlet. As a result, the central, average and minimum film thickness values might then all appear to be unaffected by the transverse speed. • This paper investigates film build-up in wide EHL rolling contacts with small superimposed transverse oscillating speed. • The effect of increasing contact ellipticity or roller-end smoothness is discussed. • Film fluctuations due to the transverse velocity become smaller in amplitude and remain localized at the contact edges. • The central, average and minimum film thickness values might then appear to be all unaffected by the transverse speed. [ABSTRACT FROM AUTHOR]

To investigate the effect of the inlet starvation severity on the flash temperature, which dictates the scuffing failure, a thermal mixed elastohydrodynamic lubrication model is developed for line contacts operating under the starved lubrication condition. Utilizing a generalized Newtonian Reynolds equation, the lubricant viscosity dependence on the shear rate, as well as on the pressure and temperature, is incorporated for the proper and accurate modeling of the tribological behavior under the high sliding condition. A film fraction parameter is employed in the Reynolds equation to include the starvation and cavitation description. Considering different operating and surface roughness conditions, a parametric study is performed to show an asymptotic relationship between the flash temperature and the inlet starvation severity. • Develop a mixed EHL model for line contacts under starved condition.. • Include lubricant viscosity dependence on shear rate, pressure, and temperature. • Use film fraction parameter to describe starvation/cavitation. • Parametric simulation to show flash temperature dependence on starvation severity. [ABSTRACT FROM AUTHOR]

In the journal-bearing system, the journal inevitably moves along the bearing axis, and the axial movement of journal may affect the performance of misaligned journal bearing. In this article, a numerical model for the thermohydrodynamic lubrication of bearing considering the axial movement of journal is established, and based on which a comprehensive analysis on the performance of misaligned journal bearing is conducted by solving the generalized Reynolds equation, heat conduction equation and energy equation. The results show that axial movement of misaligned journal has more obvious influence on the bearing lubrication characteristics at the lower speed, larger inclination angle and eccentricity. The impact of axial movement on the bearing lubrication performance is greatly affected by the thermal effect and surface roughness. • A numerical model of thermohydrodynamic lubrication considering the axial movement of misaligned journal which moves along the bearing axis is built. • When the axial movement of misaligned journal takes place, the bearing lubrication performance will change significantly. • The impact of axial movement on the bearing lubrication performance is greatly affected by the thermal effect and surface roughness. [ABSTRACT FROM AUTHOR]