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Lubrication is essential to minimize wear and friction between contacting surfaces in relative motion. Oil based lubricants are often enhanced via polymer additives to minimize self-degradation due to the shear thinning effect. Therefore, an accurate estimate of the load carrying capacity of the thin lubricating film requires careful modeling of shear thinning. Available models such as the generalized Reynolds equation (GR) and the approximate shear distribution have drawbacks such as large computational time and poor accuracy, respectively. In this work, we present a new approach, i.e., the modified viscosity (MV) model, based on calculating the strain rate only in one point along the vertical direction. We investigate, for both MV and GR, the load, the maximum pressure, and the computational time for (i) sliding (non-cavitating) contacts, (ii) cavitating, and (iii) squeezing contacts. We observe that the computational time is reduced (i) considerably for non-cavitating sliding and rolling contacts and (ii) by several orders of magnitudes for cavitating and squeezing contacts. Furthermore, the accuracy of MV is comparable with the GR model within an appreciable range of bearing numbers. Finally, for each type of boundary motion, we have determined the optimal vertical location to calculate the shear strain rate for MV; while this optimal value is close to half the height of the contact for sliding configurations, for rolling dominated and squeezing contacts it is around one quarter (or three quarter) of their height. We finally provide an analysis to a priori estimate the optimal location of the strain rate. [ABSTRACT FROM AUTHOR]

Motion of three-phase contact lines is one of the most relevant research topics of micro- and nano-fluidics. According to many hydrodynamic and molecular models, the dynamics of contact lines is assumed overdamped and dominated by localized liquid–solid friction, entailing the existence of a mobility relation between contact line speed and microscopic contact angle. We present and discuss a set of non-equilibrium atomistic molecular dynamics simulations of water nanodroplets spreading on or confined between silica-like walls, showing the existence of the aforementioned relation and its invariance under wetting modes ("spontaneous" or "forced"). Upon changing the wettability of the walls, it has been noticed that more hydrophilic substrates are easier to wet rather than de-wet; we show how this asymmetry can be automatically captured by a contact line friction model that accounts for the molecular transport between liquid layers. A simple examination of the order and orientation of near-contact-line water molecules corroborates the physical foundation of the model. Furthermore, we present a way to utilize the framework of multicomponent molecular kinetic theory to analyze molecular contributions to the motion of contact lines. Finally, we propose an approach to discriminate between contact line friction models which overcomes the limitations of experimental resolution. This work constitutes a stepping stone toward demystifying wetting dynamics on high-friction hydrophilic substrates and underlines the relevance of contact line friction in modeling the motion of three-phase contact lines. [ABSTRACT FROM AUTHOR]

Guideways accommodate tool or workpiece translations, and their dynamic behavior and associated sliding effects have great impact on the precision, stability, and performance of the machine tool. During machining, guideway rollers experience oscillatory excitations because of cutting forces, which necessitate considering their pre-sliding behavior along with the sliding characteristics to compensate for the associated tracking errors using the position control system. This study considers friction effects in pre-sliding and sliding regimes of lubricated linear roller guideway systems to provide an accurate dynamic model of the machine tool element. To model the dynamic characteristics of frictional contact in the lubricated linear roller guideway, the LuGre model, commonly used in the machine tool positioning control system to estimate the compensating drive force, is modified considering the roller-raceway contact physics and the lubricant film dynamics. The proposed model also includes coupling effects between normal and tangential forces in the contact interface. Experimental studies were performed on a lubricated linear roller guideway to verify the performance of the presented modified LuGre model. In the experimental observations, the dynamic behavior of friction in the lubricated linear guideway is well illustrated. A comparison of the experimentally measured data and proposed modified LuGre model predictions shows the model can accurately predict dynamic behaviors of the frictional contact interface. [ABSTRACT FROM AUTHOR]

Modelling hydrodynamic lubrication helps engineers and material scientists designing lubricants that minimize viscous energy losses without compromising the durability of engine components. This type of modelling requires selecting lubricant rheological constitutive equations that provide realistic information on fluid behaviour within tribological contact zones. Due to complexity of differential constitutive equations the modelling effort was limited to generalized Newtonian or Oldroyd-B fluids. In this paper, we present more realistic description of hydrodynamic lubrication using the Giesekus fluid capturing both viscous shear thinning and the development of elastic stresses at high Weissenberg numbers. The problem analysis is done using a modified regular perturbation method with respect to the small mobility parameter |$\alpha $|⁠. The perturbation analysis modification is caused by the fact that the problem contains several a priori unknown boundaries. The actual perturbation solutions for functions of pressure and gap, as well as the coordinate of exit from the contact and the exit film thickness, are obtained as linear functions of |$\alpha $|⁠. The effects of the model parameters such as the mobility factor, relaxation time and the polymer contribution to viscosity on pressure, shear and extensional viscosities within the contact zone are analysed. It is shown that the presence of polymers helps to increase the gap and reduce the viscous losses associated with hydrodynamic friction. This result is consistent with empirical observations of fuel economy enhancement for polymer-containing lubricants. [ABSTRACT FROM AUTHOR]

Reciprocating spur gear rack is prone to lubrication failure near the reversing dead center position. Ree‐Eyring lubrication fluid, multigrid method and multigrid integral method were used to calculate the pressure profile, film thickness and oil temperature rise. Compared with linear motion, the process of reciprocating commutative movement is more complicated and the lubrication state are more unstable. The effects of different reversing duration time and commutation meshing state on lubricant film were analysed. The results show that, the oil thickness during the gear reversing process is significantly reduced. While shortening the reversing time can improve the lubricating film thickness, it causes the instantaneous oil temperature to rise. Therefore, the gear tooth damage caused by high temperature can be avoided by prolonging the reversing duration time properly. The longer the reversing duration time, the minimum value of central film thickness and central pressure is closer to the meshing outlet area. No matter what the reversing time change, the minimum lubrication film thickness is in the reversing dead center position. So the reversing dead center is still the dangerous point for the lubrication failure of the spur gear rack mechanism. When the reversing dead center is in the leading tooth of double‐tooth meshing, the gear has the largest film thickness and the largest contact area. In addition, the synthetic radius of curvature and entrainment velocity become larger so the lubrication conditions have been improved. The results provide the theoretical basis and guidance for the reasonable design of the spur gear rack and the improvement of its lubricating performance. [ABSTRACT FROM AUTHOR]

Adjacent segment degenerative diseases are a major clinical concern for anterior cervical corpectomy with fusion surgery. In this study, a hybrid motion-preserving cervical prosthesis consists of two articulating joints and one porous fusion body is designed to provide motion ability and reduce the occurrence of degenerative diseases. The hybrid design is fabricated from Ti–6Al–4V (TC4) alloy using selective laser melting (SLM) technology. After carburization pretreatment, two types of bearing couple SLM-TC4 self-mating and SLM-TC4/UHMWPE were studied in terms of lubrication regime, contact mechanics and wear performance. According to the ISO 18192-1 standard, five million cycles (Mc) of in vitro spine simulator wear tests were conducted in bovine serum lubricated condition. Hamrock-Dawson minimum lubrication film thickness analysis stated that both bearing was likely under boundary lubrication only, with extensive surface asperities contact. And, the contact stress encountered during in vitro condition was not enough to cause surface fatigue failure of any bearing couple. In term of wear performance, the obtained steady state wear rates were 0.160 ± 0.004 mm3/Mc for SLM-TC4 self-mating and 8.57 ± 0.06 mm3/Mc for SLM-TC4/UHMWPE bearing couples, respectively. According to these outcomes, SLM-TC4 self-mating couple was more promising for the articulating joint bearing design. For SLM-TC4 self-mating couple, the initial wear mechanism was abrasion with potential third-body abrasion wear. As the wear cycle proceeding, the TiC cermet layer was gradually damaged and exposed the local bare metal. Under this circumstance, material loss was consisted of abrasion wear, adhesion wear, and tribo-corrosion. In comparison, the wear mechanism of SLM-TC4/UHMWPE bearing was always abrasion-adhesion of UHMWPE. The surface of UHMWPE socket was severely plowed by the hard micro bulge of the TiC layer, and material loss and plastic deformation occurred only on the UHMWPE socket. In conclusion, carburization pre-treatment causes a hard TiC cermet layer formation on the SLM-TC4, which enhance its hardness and protect underling material from corrosion damage. The thickness and quality of the TiC layer directly affect the longevity of the joint prosthesis in vivo. [ABSTRACT FROM AUTHOR]

Fiber-reinforced materials or 3D printed parts feature transversely isotropic elasticity. Although its influence on pressures, shapes, and sizes has been studied extensively for dry contacts, the transferability to lubricated contacts is fragmented. This numerical study investigates how the content and orientation of short fibers in fiber-reinforced polymers (FRP) affect elastohydrodynamic lubrication (EHL) of point contacts. Material properties are modeled with Tandon-Weng homogenization. For EHL modeling, a fully-coupled approach based on finite element discretization is used. Results on hydrodynamic pressure and film thickness as well as material stress distribution are analyzed and compared to common approximations using the effective contact moduli. It is shown that the combination of fiber content and orientation defines the effective contact stiffness that determines the contact shape, size, and film thickness. Furthermore, the contact regime can change if a contact-specific stiffness threshold is reached. [ABSTRACT FROM AUTHOR]

Most EHL numerical calculation methods considering both starved and flooded conditions, employ a fixed multiple of the Hertzian radius for the normalization of the computational domain. These methods are often used to investigate the influence of the lubricant supply on friction etc., but the solutions obtained might be numerically starved. The present numerical calculation method utilizes an optimized normalization of the computational domain to ensure that the solutions obtained are not numerically starved. With this normalization method, the computational domain can be appropriately meshed, regardless of the variability in the inlet length due to changes in the operating conditions. This method can, therefore, be used to obtain accurate EHL film thickness and pressure data over a wide range of operating conditions. [ABSTRACT FROM AUTHOR]

Using boric acid, polyols and long-chain fatty acids, a high temperature salt resistant drilling lubricant SOB has been developed to deal with high torque high friction encountered in deep and ultra-deep well drilling. SOB has good lubricity at high temperatures and high salinities. A 5% base mud treated with 1% SOB has its friction coefficient reduced by 92.7%, and the adhesion coefficient of the mud cake produced by that mud is reduced to 0.0405, meaning that SOB has a sustainable lubricity under extreme pressure condition. Percent reduction of friction coefficient at 210 ℃ is generally 90.2%, percent reduction of friction coefficient of a mud containing 35%NaCl at 210 ℃ is generally 81.3%. At high temperature and high salinity conditions, SOB has good compatibility with other components of a high density drilling fluid. After aging at 200 ℃, the rheology of the drilling fluid was not affected, the mud filtration rate can be reduced, and the coefficient of friction of the mud was reduced by 45.09%, meaning that SOB has better lubricity than conventional drilling lubricants. The reason for this phenomenon is that SOB can be effectively adsorbed on the surfaces of the drill strings, forming a layer of film with strong hydrophobicity. The existence of this film changes the direct contact between the drill strings and the borehole wall to a contact between two films of the lubricant, thereby effectively reducing the friction therebetween. [ABSTRACT FROM AUTHOR]

This paper aims to develop a mathematical model for investigating the nonlinear dynamic mixed friction behaviors, including hydrodynamic force, contact force, deformation, and displacements, of the novel coupled bearing lubricated with low-viscosity fluid. The model fully couples the five-degrees-of-freedom rotor dynamic model with the mixed elastohydrodynamic lubrication model of the novel coupled bearing, considering the unbalance and exciting forces/comments caused by the propeller rotor. A comparative analysis is carried out to validate the effectiveness of the present model. Through the numerical simulation, the dynamic nonlinear mixed friction behaviors of the novel coupled bearing under low-viscosity lubricant are revealed. Based on the established mathematical model, a series of parametric studies are conducted to explore the effect of the structural parameters on the nonlinear mixed friction behavior of the novel coupled bearing. Numerical results demonstrate that the exciting moments increase the range of the journal orbit, thereby generating the edge asperity contact for both the journal and thrust bearings. The angular displacement along the y axis improves the transient mixed friction performances of the thrust bearing. Furthermore, numerical results reveal that the increasing length–diameter ratio of the journal bearing (the specific pressure remains constant) improves the nonlinear dynamic mixed friction behaviors of the thrust bearing. In addition, the nonlinear dynamic mixed friction performance of the journal bearing becomes better with the increase in the thrust bearing radius. [ABSTRACT FROM AUTHOR]

The paper examines variation in the structure and properties of an antifriction composite produced from grinding waste of the R6AM5 high-speed steel with additives of CaF2 solid lubricant depending on the quantitative composition of the main components. The composite is intended to perform in friction units of offset and press cylinders of printing machines that operate in self-lubrication conditions at high rotation speeds (up to 5,000 rpm) and increased loads (up to 5 MPa) in air. The developed production modes allowed the R6AM5 steel grinding waste composite to be appropriately structured. The composite structure is a metal matrix in which CaF2 solid lubricant particles are evenly distributed. The composite's metal matrix consists of pearlite–carbide and carbonitride phases formed in the presence of R6AM5 steel doping elements. The appropriate amount of the CaF2 solid lubricant, which contributes to reaching the maximum antifriction properties, was determined by a series of experimental mechanical and tribotechnical tests and by fractographic analysis of the materials containing from 3.0 to 10.0 wt.% CaF2. The microstructural, fractographic, mechanical, and tribotechnical tests showed that content of the CaF2 solid lubricant that ensured high mechanical properties and significantly increased the antifriction characteristics of the composites varied from 4.0 to 8.0 wt.%. Electron microscopy studies of the friction surfaces of the R6AM5 + (4.0–8.0)% CaF2 composites confirmed the formation of uniform continuous protective antifriction films that completely covered the contact pair's friction surfaces and provided self-lubrication. Field tests showed the feasibility of using antifriction bushings made of the new composites produced from R6AM5 steel grinding waste and (4.0−8.0)% CaF2 in the friction units of offset and press cylinders of roll newspaper offset printing machines. The research identified prospects for expanding studies over a wide range of valuable metal waste for the development of new effective antifriction composites with a well-grounded content of components. This would also make another important contribution to protecting the environment against contamination. [ABSTRACT FROM AUTHOR]

In this study, the influence of the in-situ tribo-oxide-layer on non-lubricated tribological behaviours of LM27/SiCp composites was studied at different applied loads. For this purpose, LM27/SiCp composites were manufactured by stir casting route with reinforcement of different amounts (3–12 wt.%) and different sizes (fine: 1–20 µm and coarse: 106–125 µm) of SiCp. A comprehensive characterization of the friction and wear mechanisms ranging from mild to severe wear for oxidative and delamination at a contact pressure of 0.125–0.624 MPa was discussed. Results indicate that the friction and wear behaviour is strongly influenced by the morphology and the nature of the oxide scale on the wear track. In-situ formation of oxide layers on the contact region of the specimen supports the self-lubrication which supports better wear performance of LM27/SiCp composites. However, these study portraits that composite with 12wt. % fine size SiCp exhibits better wear performance in comparison to the other developed composites. [ABSTRACT FROM AUTHOR]

This paper investigates the strong coupling between friction power losses and film thickness that prevent from clearly identifying the mechanism of scuffing through classical test procedures. As the film thickness appears of great influence on the phenomena, a new test method is presented, allowing scuffing initiation study with the film thickness as a key parameter. This new test method allows film thickness variation with minimal friction losses and bulk temperature variations. This procedure has been developed with nitrided steels and a synthetic base oil on a twin disks test rig. Even though asperity contact is considered necessary in literature for scuffing, the test result shows that it can be reached in full film lubrication, potentially through the collapse of the oil film. Different test methods allowing triggering scuffing through different parameters are identified, which shows that a variety of parameters is able to influence scuffing. [ABSTRACT FROM AUTHOR]

Using pure water in comparison to water-based lubricant containing 4% TiO2 nanoparticles (NPs), the hot rolling tests of 304 stainless steel were carried out at a rolling temperature of 1050 °C under varying rolling reductions and speeds. The effects of lubrication on rolling force, torque, power and contact friction were systematically investigated. The coefficient of friction (COF) during steady-state hot steel rolling was inversely calculated using a developed flow stress model. The COF models including the effects of rolling reduction and speed were proposed via multiple linear regression. The results indicated that the use of the nanolubricant enabled a reduction of rolling force up to 6.1% and decreases in rolling torque and power up to 21.6%, compared to that of water condition. The results obtained from the linear regression agreed well with those from the inverse calculation, suggesting the developed COF models had high accuracy. The lubrication mechanisms were derived from a boundary lubrication regime, owing to ball bearing and mending effects of TiO2 NPs, and formation of thin lubricant film under high rolling pressure. [ABSTRACT FROM AUTHOR]

In this study, a three-dimensional numerical model of an ejector is established, which is based on a 40 W power proton exchange membrane fuel cell (PEMFC) system. Computational Fluid Dynamics (CFD) technique is used to analyze the ejector in low power condition. The effects of two key structural parameters (distance from the mixing chamber to the nozzle and the mixing chamber diameter) on the ejector performance at different currents are investigated. It is found that ejector entrainment ratio changes slightly with the distance from mixing chamber to nozzle. The ejector entrainment ratio increases first and then decreases with the mixing chamber diameter. Moreover, with the increase of mixing chamber diameter, the turbulent kinetic energy and turbulent dissipation rate decrease obviously. [ABSTRACT FROM AUTHOR]

Friction has been a significant research concern for decades. Most of the energy input into an internal combustion (IC) engine is wasted because it is used to overcome friction. Scientific developments have been made to reduce friction, including surface coatings and surface textures, which have emerged as potential solutions to reducing friction throughout the lubricating regimes. This study combines surface texturing with the coating approach to investigate the frictional response. Realistic tribo-dynamics (secondary motion of the piston skirt) are considered during actual engine-like conditions to explore the effects of pattern-based coating on friction in hydrodynamic lubrication. Results show a remarkable reduction in friction and encourage the pattern-based development of surface coatings to extend the benefit across lubricating regimes. Consequently, the surface coated with optimized patterns had 7.98 ± 0.34 % reduced energy loss per engine cycle as compared with the surface coated without a pattern. [ABSTRACT FROM AUTHOR]

Cylindrical gear with variable hyperbolic circular arc tooth trace (VH-CATT) is a new type of gear. Sliding wear is the main mode of the surface failure of multiple mechanical parts. Both the lubrication state and contact temperature considerably influence wear characteristics, which may aggravate the transmission performance of gear pairs. Wear, contact temperature, as well as lubrication states are jointly explored. Therefore, an integrated wear prediction model was proposed through taking into account flash contact temperature and surface roughness of VH-CATT cylindrical gears in mixed elastohydrodynamic lubrication. According to the equivalent ellipse contact model of VH-CATT cylindrical gears and tooth surface equation, normal curvature and velocity relations for VH-CATT cylindrical gears were observed, and the normal meshing force was obtained through the consideration of load sharing coefficients and quality grades. Flash contact temperature was estimated by using the literature. This study proposes analytical solutions for investigating how various surface roughness, operation, and geometric parameters affect asperity contact ratio (ACR), asperity contact pressure (ACP), flash contact temperature (FCT), as well as wear depth (WD) related to driving gears. ACR, ACP, FCT, as well as WD initially decrease and then increase from engaging-in to engaging-out processes. The minimum occurs at the pitch point. The WD declines as module, cutter radius, and rotational velocity increase while augmenting when surface roughness and torques increase. The maximum and minimum wear depths in driving gears occur at the dedendum and pitch point, respectively. Its overall wear is reduced by 23.16 % compared to the wear of spur gears. The results are valuable for the studies of tooth pitting, wear resistance, and fatigue life improvement for VH-CATT cylindrical gear. These studies can provide verification data and references required for engineering designs and VH-CATT cylindrical gear operations. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to report the tribological behavior of dimples textured rolling element bearings (REBs) under variable load and starved lubrication. Design/methodology/approach: The pattern parameters include line-diameter of dimples (200 µm, 250 µm, 300 µm), depth of dimples (10 µm, 20 µm, 30 µm). Dimple patterns were prepared on the raceways of the shaft washers of cylindrical roller thrust bearings (CRTBs). A vertical wear test rig was used to obtain their coefficients of friction (COFs) under stepped load (1200–6000 N, with a manually increase of 1200 N every 3600 s) and starved lubrication. The wear losses and worn surfaces were characterized. The tribological performance between stepped load and fixed load (4000 N) was compared. The influence mechanism of dimples on the friction and wear properties of CRTBs under stepped load and starved lubrication was also discussed. Findings: Compared with the data of smooth ones, the average COFs of the dimples textured bearings are almost all reduced under stepped load and starved lubrication, while their mass losses almost all get higher. The depth−diameter ratio and the effective volume coefficient of dimples are the important factors. In this work, compared with the smooth group, when the line-diameter of dimple is 250 µm and the depth is 20 µm, i.e. the depth−diameter ratio is 0.08, its average COF is reduced by 46.8% and its mass loss is reduced by about 7%, showing wonderful friction-reducing effect and good wear resistance. Originality/value: This work can provide a reference for the raceway design of REBs. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to compare the spherical protruded and dimple textured journal bearings performance characteristics with the untextured bearing. Design/methodology/approach: The governing Reynolds equation considering the mass conserving (JFO) boundary conditions is solved using the computationally efficient progressive mesh densification (PMD) method. The central difference scheme is used for the discretization of the governing Reynolds equation. The numerical code developed is validated with the experimental results available in the literature. Findings: From this numerical study, it has been observed that the protruded textured journal bearing gives better performance compared to the dimple textured and untextured journal bearing for friction variable, whereas dimple textured journal bearing provides better performance compared to the protruded textured and untextured journal bearing for load carrying capacity and flow coefficient. For better performance, dimple and protruded textured bearings must be textured in second-half textured region configuration. Practical implications: The results shown here would be quite useful for the researchers generally and the bearing designers particularly. Originality/value: The load carrying capacity should be maximum whereas, the friction coefficient should be minimum and also the adequate flow of lubricant is necessary to maintain hydrodynamic lubrication and to remove the heat generated within the bearing due to friction, which impacts the bearing performance and life. Thus, this study would be significant in effective bearing design aspect. [ABSTRACT FROM AUTHOR]

In this study, an interfacial slip model including the limiting shear stress is proposed and applied to the thermal elastohydrodynamic lubrication (EHL) analysis of a helical gear pair. The main difference between the proposed model and the classical EHL model is that, the term of entrainment velocity in Reynolds equation is modified. The influences of interfacial slip, thermal effect, initial limiting shear stress and operating conditions on the tribological properties are evaluated. Due to the interfacial slip, the pressure distribution moves towards the inlet region, and the fluctuation distributions of entrainment velocity and film thickness are similar to the trigonometric function. The influence of thermal effect on interfacial slip cannot be ignored, especially in the case of high speed and heavy load. As the input torque and input rotational speed increase, the interfacial slip gradually extends to the whole meshing process. [ABSTRACT FROM AUTHOR]

As a medium and low pressure gear machine without automatic compensation structure for axial and radial clearances, the friction pairs in the straight conjugate internal gear pumps (SCIGPs) depend on the fixed small clearances to seal, lubricate and transfer the force. The oil film design of the friction pairs has become an important part of gear pump design. However, there has never been a publicly published research on the oil film design of the SCIGP in past literature. This paper applies orthogonal test to the oil film design of the SCIGP for the first time to determine the best working clearances. With this goal, the paper first provides the mathematical models for analyzing the internal leakage flow and the viscous friction loss, which elucidate the relationships between the leakage and the friction loss with working conditions. After that, the orthogonal test scheme for numerical simulation was designed on the basis of determining the range of oil film thickness. The paper also propounds the viewpoints of using the range-method to estimate the primary and secondary relationship of factors and determining the optimal combination according to the test target. Based on this concept, the main factors affecting the target are procured and the optimal working clearances of the friction pairs are determined. For the purpose of verifying the model, the redesigned prototype was tested and compared with the simulation results. The results validate the applicability of the simulation model and the correctness of the simulation method. Finally, the paper summarizes the ways to improve the total efficiency and the working conditions at the highest efficiency. [ABSTRACT FROM AUTHOR]

To improve the meshing performance and increase the bearing capacity and service life of spiral gear pairs, a cutterhead approximation machining method based on controlling geometric topological deviations was proposed to solve the problem where line contact spiral bevel gears with tapered teeth depth cannot be machined by cutterheads. First, a mathematical model of the line contact conjugate flank was established, and the geometric topological deviations model of the comparison between the machining tooth flank and the theoretical tooth flank was obtained. Second, the deviation of each tooth flank point was calculated by the topological differential calculus analysis. Finally, with the machining tooth flank approaching the theoretical tooth flank as the modification objective, the additional cutting motions and machining compensation parameters of cutterheads were obtained to control the machining tooth flank deviations and reduce them to the allowable deviations of the theoretical tooth flank, and the cutterhead approximation machining of line contact spiral bevel gear pairs with tapered teeth depth was realized. The contact simulation analysis and rolling test verified the correctness of the line contact conjugate flank model and the feasibility of the cutterhead approximation machining method. [ABSTRACT FROM AUTHOR]

[Display omitted] The structure of the slippery layer and the evolution of functional properties of a lubricant infused substrate (LIS) is determined by the isotherm of disjoining pressure in the lubricant film. The macroscopic theory of van der Waals forces was applied to the layered system used to model the structure and properties of LIS. For a lubricant layer sandwiched between the flat substrate and air or water, the isotherms of disjoining pressure were calculated and their analysis was used to conclude about stability of LIS. The results obtained for silicone oil and perfluorodecalin on smooth and porous hydrophilic and hydrophobic solids allow selecting the LIS components corresponding to stability of lubricant films in air and water. It was found that for hydrophilic substrates in conditions of lubricant depletion, silicone oil and perfluorodecalin show lubricant film stability in both air and water. On flat or post microtexture hydrophobic substrate with flat tops, the perfluorodecalin lubricating layer is typically stable in air and unstable in water. In contrast, silicone oil lubricating layer demonstrates the stability in a wide range of lubricant film thicknesses for the hydrophobic substrate with flat-top textures in water, however, it can be unstable in air. [ABSTRACT FROM AUTHOR]

Slippery liquid‐infused porous surface (SLIPS) has received widespread attention in the antifouling field, while its controllability of surface lubricity and durability of lubricant are relatively insufficient. In this study, inspired by the hagfish's defensive behavior of secreting mucus to escape from predators, a smart SLIPS marine antifouling coating is prepared, which possesses responsively switching lubrication modes and self‐healing property. The responsive supramolecular interaction between azobenzene (Azo) and α‐cyclodextrin (α‐CD) is introduced to regulate the lubricity of SLIPS. cis‐Azo is converted to trans and combined with α‐CD by supramolecular interaction under visible light or heating, driving the shrinkage of polymer chains to squeeze the stored lubricant to the surface. The responsive self‐replenishment of lubricant can adjust the surface lubricity to switch antifouling modes between "enhancive" and "normal" smartly, which adapts to different occasions. Moreover, disulfide and hydrogen bonds are introduced to enhance self‐healing performance (91.73%). In summary, it has efficient self‐cleaning, anti‐protein, antibacterial, anti‐algae properties, and 180‐day real marine field antifouling performance during boom season (the longest antifouling period in real marine field test of reported SLIPS materials), which demonstrates the promising application in neritic sea equipment and other antifouling fields. [ABSTRACT FROM AUTHOR]

Skid-resistance performance of a runway greatly influences aircraft landing safety. A wet runway significantly increases the incidence rates of aircraft overrun. To study the influence of the skid-resistance performance of a runway on aircraft landing, a co-simulation method is proposed. First, a finite element (FE) model of the local tire-water film-runway simulation is established to obtain the combination coefficient-slip ratio curve of a tire on a wet runway. Second, a global model of an Airbus A320 virtual prototype (VP) is created. Then, on the basis of fuzzy control theory, a two-dimensional (2D) fuzzy controller of the aircraft AB is established. The friction coefficient-slip ratio curve of the tire on the wet runway obtained in the local simulation is introduced into the full-scale hydroplaning simulation model of the aircraft. Finally, the global-local multiscale simulation method is used to analyze the skid-resistance behaviour of the aircraft on three types of runways. It is found that the increase of water film thickness of the pavement and the increase of the grounding speed cause the attenuation of the friction coefficient of a runway, finally causing the reduction of the deceleration rate of the aircraft and the increase of the braking distance. [ABSTRACT FROM AUTHOR]

The seepage behavior of lubricant on a porous surface has a significant influence on its lubrication characteristics. This paper studied the unsteady seepage response of a lubricant on a loading porous surface. The exudation and supply behaviors of lubricant to the porous surface are discussed. The results show that the lubricant infiltration and exudation all exist on the porous surface. The normal seepage velocity of the lubricant can be divided into the primary velocity and secondary velocity at different positions of the whole surface. In most loading times, the primary velocity is greater than the secondary velocity. The change of the principal velocity shows that the infiltration and exudation of the lubricant arise in the contact area and its inlet, respectively. On both sides away from the entrance of the contact area, the secondary velocity goes through a diffusion, fluctuation, and stability process within the loading period. During the fluctuation of the velocity, the phenomena of infiltration and exudation alternate repeatedly. The secondary velocity occasionally exceeds the principal velocity. The normal pressure gradient is the internal cause that drives the diffusion and fluctuation of the secondary velocity. The velocity fluctuation can regulate lubricant quantity on the porous surface spontaneously, thereby forming a closed-loop adaptive lubrication system. The research can provide a theoretical basis for the lubricant supply behavior and the self-lubricating mechanism of the squeezed porous interface. [ABSTRACT FROM AUTHOR]

Falling film technology has been widely applied in various industrial processes, but vapor shearing effects cause significant problems. The mechanism by which vapor affects the hydrodynamics of a falling film has not yet been fully understood, particularly for cross vapor streams. In this paper, a three-dimensional model is developed to investigate the hydrodynamics of a falling film on a horizontal tube with a cross vapor stream. The results indicate that (1) there are valley and peak zones during the spreading of the liquid film; (2) the effect of cross vapor flow on the hydrodynamics of the falling film depends on the film flow rate, the cross vapor velocity, and the position on the tube; (3) with increasing vapor velocity, the peripheral film thickness increases on both the upwind and downwind sides for values of z* (the dimensionless axial coordinate) from 0 to 0.1, while decreasing on the upwind side but increasing on the downwind side for values of z* from 0.2 to 0.5; and (4) under the action of the cross vapor stream, liquid film offset occurs, characterized by the formation of new stagnation and detachment zones on the downwind side of the tube. [ABSTRACT FROM AUTHOR]

A sharp metal needle used as the ionization emitter in conventional atmospheric pressure chemical ionization (APCI) mass spectrometry (MS) is usually required for analyte ionization through corona discharge (i.e., gas discharge). Nevertheless, we herein demonstrate that an insulating fiber (tip diameter: 10–60 µm; length: ~ 1 cm) made of glass or bamboo can function as an APCI-like ionization emitter. Although no direct electric contact is made on the fiber, the ionization of volatiles and semi-volatiles occurs when the fiber is placed close (~ 1 mm) to the inlet of the mass spectrometer. No analyte ion signals can be observed without placing the insulating fiber in front of the mass spectrometer. The generation of ion species mainly relies on the electric field provided by the mass spectrometer. Presumably, owing to the high electric field provided by the mass spectrometer, the dielectric breakdown voltages of gas molecules in the air and the fiber are overcome, leading to the ionization of analytes in gas phase. In addition, the insulating fiber can function as a holder for sample solutions. Electrospray ionization–like processes derived from polar analytes such as amino acids, peptides, and proteins can readily occur when the insulating fiber deposited with a sample droplet is placed close to the inlet of the mass spectrometer. The feasibility of using the current approach for the detection of nonpolar and polar analytes from complex fetal bovine serum samples without tedious sample pretreatment is demonstrated in this work. The main advantage of using the suggested fiber is that the fiber can be used as the sampling probe to pick up samples and placed in front of a mass spectrometer for direct MS analysis. The application of using a robust, insulating, and disposable probe to pick up samples from real samples such as onion, honey, and pork samples followed by direct MS analysis is also demonstrated. [ABSTRACT FROM AUTHOR]

Micro-cantilever beam are now widely used in modern micro and nano devices. This device includes micro-switches and microscopes which are operated by atomic force. The dynamic analysis of cantilever beams is of critical prior to manufacturing of the beams. Dynamic analysis is carried out using an energy technique based on Galerkin method and pull-in parameters are to be found out for prismatic cantilever. In squeeze film damping the air present between movable beam and fixed beam behave as squeezed fluid and producing the damping effect which lead to reducing in displacement. In case of fringing field the line of action of electrostatic force do not remain perpendicular at the boundaries. The effect of damping due to Squeeze film and fringing field on dynamic performance of beam is studied and found out the pull-in factors and matched with the published outcomes. This area opens novel opportunities for structural optimization of electrostatic micro-beams. [ABSTRACT FROM AUTHOR]

Tribological performance comparison of Graphene nanoplatelet and Halloysite clay nanotube-based nanolubricants in an aluminum-based hybrid composite/steel tribo-contact was addressed by suspending nanoparticles in concentrations of 0.025, 0.05, 0.1 and 0.5%wt within SAE 5W40 motor oil. Dispersion stability and thermophysical properties of the designed nanolubricants were also evaluated. In order to perform tribological experiments by using a pin-on-ring configuration tribometer at various loads and rotation speeds, a hybrid composite was fabricated by powder metallurgy-extrusion method and characterized. The lubrication regime was characterized using stribeck curves and minimum film thickness. The worn surfaces morphology of the pin materials were characterized by Scanning electron microscopy images, Energy-dispersive X-ray spectroscopy and surface roughness measurements. The obtained highest friction coefficient and wear rate reductions were 40 and 36% with 0.5%wt Graphene nanoplatelet, and 25 and 10% for 0.1%wt Halloysite clay nanotube-based nanolubricants, respectively, during a mixed lubrication regime. The wear mechanism on the worn surface of the hybrid composite was predominantly abrasive with plastic yielding and delamination. Scanning electron microscopy images, Energy-dispersive X-ray spectroscopy and surface roughness measurements confirmed the Graphene nanoplatelet and Halloysite clay nanotube deposition on the worn surfaces and the formation of tribo-films that protect the sliding contacts. [ABSTRACT FROM AUTHOR]

An equivalent lubrication model of line contact was established for the cam mechanism in air splicer when its steel roller rolls over the cam transition curve. Complete numerical solutions of the lubrication film thickness, pressure, and temperature rise were obtained by solving the control equations of the lubrication model, and the lubrication performance under isothermal and thermal conditions was analyzed. Results show that under isothermal and thermal conditions, increasing the stroke s and transition angle θ is disadvantageous for improving lubrication conditions at the transition curve. On the contrary, increasing the cam base circle radius R0 and roller radius R1 is favorable for improving the lubrication conditions. However, attention should also be paid to avoid the root-cutting phenomenon caused by excessive steel roller use. The changes of the above four parameters affect the EHL characteristics of the cam mechanism more significantly under thermal conditions than they do under isothermal conditions. [ABSTRACT FROM AUTHOR]

A comprehensive numerical model was proposed to investigate the disengaging process of a wet multi-disc clutch, which included the hydrodynamic lubrication, the micro elastic-plastic contact, the spline resistance, and the impact between the piston and clutch hub. The clutch disengaging process was divided into the boundary, mixed, and hydrodynamic lubrication stages to discuss the variations in friction pair gaps and friction torque. Moreover, the nonuniformity coefficient was employed to characterize the disengaging uniformity of friction pair gaps. During the disengaging process, the friction pair gaps increased slowly, increased rapidly, and stabilized after fluctuating. The increase in spline friction coefficient and the decline in pressure decrease rate dramatically deteriorated the disengaging uniformity; the decline in pressure decrease rate also significantly prolonged the disengaging time. This research demonstrated for the first time evidence for the dynamic characteristics of the clutch disengaging process. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to present a numerical model to examine the finite magneto-hydrodynamic (MHD) journal bearings performances including both non-Newtonian couple stress and bearing deformation impacts. Design/methodology/approach: Based upon the MHD and Stokes theories, a novel expression of modified Reynolds equation including bearing deformation is obtained. The bearing elastic deformation impact is predicted by means of the Winkler model. Using the numerical differentiation approach, the film pressure is iteratively solved. Different bearing characteristics are then numerically calculated. The validity of the proposed model was verified by comparing with some particular cases from literature. Findings: From the numerical presented results, it is demonstrated that the conducting couple stress lubricant with an applied radial magnetic field results in an induced electric current density and thus significantly improves the performances of elastic journal bearings. Particularly, the load-carrying capacity is increased, whereas a reduction in friction factor is observed. Originality/value: This numerical model is original, which combines both non-Newtonian couple stress and bearing deformation impacts on finite MHD journal bearings performances. It provides useful information in designing MHD journal bearings, given the lack of experimental studies. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to study the lubrication characteristics of double involute gear (DIG), compare its lubrication differences under quasi-static and tribo-dynamic conditions and study the influence of different factors on its lubrication characteristics under the tribo-dynamic condition. Design/methodology/approach: According to the meshing characteristics of DIG and elastohydrodynamic lubrication (EHL) theory, a tribo-dynamic model of DIG is established based on the "subsection method." The Runge-Kutta method and the multigrid method are integrated to solve the model, and the dynamic analytical model of lubricating oil is established in the iterative solution. Findings: The load and the transmission error fluctuate obviously under the tribo-dynamic condition, which is not conducive to the lubrication of DIG. The influence of rotational speeds and torque on the lubrication properties of DIG has obvious differences under tribo-dynamic and quasi-static conditions. Originality/value: This research can provide a theoretical basis for improving the lubrication performance, reducing the loss of mechanical efficiency and improving the bearing capacity and service life of DIG. [ABSTRACT FROM AUTHOR]

Purpose: Researchers have not reached an agreement on which biomimetic shape has the best lubrication performance. This paper aims to study the influence of microtexture size, shape and direction on bearing capacity, end leakage, friction coefficient and wear of oil film. Design/methodology/approach: Different oil film thickness equations considering the microtexture of bearing surface are gained. The two-dimensional finite difference equation and the calculation equation of wear are established. Findings: The theoretical research shows that the wear value and the wear ratio when long side is perpendicular to the axial direction of the bearing are generally lower than when the long axis is parallel to the axial direction of bearing. The theoretical and experimental results show that the appropriate microtexture shape, such as circular dimple, crescent-shaped dimple, triangular dimple and fish-shaped dimple can improve effectively the lubrication performance of journal bearing and reduce the friction coefficient. Originality/value: The research has great significance to reduce friction and improve the wear resistance of equipment. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to investigate the combined effect of surface force, solvation and Van der Waals forces and surface topography parameters of amplitude and wavelength on the formation of ultrathin films for elastohydrodynamic lubrication of point contact problems. Design/methodology/approach: The Newton–Raphson technique is used to simultaneously solve the Reynolds' film thickness including surface roughness and elastic deformation, surface force of solvation and Van der Waals forces and load balance equations. Different values of surface amplitude and wavelength were simulated in addition to the load variation. Findings: The simulation results revealed that roughness effects are important as the film thickness decreases. The oscillation in the pressure and film thickness is due to the combined action of the solvation force and surface topography parameters. The limiting values of the surface topography parameters of the amplitude and wavelength varied and depended on the load. For different values of wavelength and load, amplitude values up to 0.25 nm have no effect on ultrathin film formation. Originality/value: The combined effect of the surface force and surface roughness on the formation of ultrathin films was evaluated for elastohydrodynamic lubrication of point contact problems under different operating conditions of load and surface topography parameters of amplitude and wavelength. The limited surface topography parameters of the amplitude and wavelength are shown and analyzed. [ABSTRACT FROM AUTHOR]

Cashew Nut Shell Liquid (CNSL) has been explored in several applications within the sustainability principles and circular economy of agro-industrial product waste. To understand the anticorrosive and lubricant properties of CNSL solutions, a multi-faceted approach, incorporating electrochemical analyses, immersion test, tribological measurements, and tribochemical characterization was carried out for mild steel AISI 1012, stainless steel AISI 420 and Aluminium Alloy 6061. Electrochemical analyses reveal a positive impact of CNSL, inducing a shift in corrosion potential to more positive values and a decrease in corrosion current, indicating effective corrosion inhibition for stainless steel and aluminium alloy. In mild steel, CNSL exhibits a mixed-type inhibition with efficiency increasing in correlation with oil concentration. The lubricating properties of CNSL are evident according to the coefficients of friction (COF) obtained and the elastohydrodynamic lubrication regime observed during tribological tests. Tribochemical tests demonstrate a reduction in wear and an improvement in tribocorrosion behavior under sliding conditions. CNSL emerges as a promising tribocorrosion mitigator, demonstrating multifaceted benefits. The concentration-dependent effects highlight the need for optimization in specific applications, particularly for passive materials. CNSL not only inhibits corrosion through film formation but also provides effective lubrication, reducing friction, wear, and chemical-mechanical degradation. This research contributes valuable insights to corrosion science. It proposes practical applications for CNSL in diverse industrial contexts, showcasing its potential as an environmentally friendly and sustainable solution for tribocorrosion challenges. • The influence of Cashew Nut Shell Liquid (CNSL) on the tribocorrosion behavior across three metallic alloys (mild steel, stainless steel, and aluminium) is explored. • Electrochemical analyses, immersion test, tribological measurements, and tribochemical characterization was carried out for AISI 1012, AISI 420 and AA6061. • CNSL exhibited a positive impact on corrosion inhibition for stainless steel and aluminium alloy, inducing a shift in corrosion potential to more positive values and a decrease in corrosion current. • CNSL demonstrated lubricating properties according to the coefficients of friction (COF) obtained and the elastohydrodynamic lubrication regime observed during tribological tests. • CNSL emerges as a promising tribocorrosion mitigator, demonstrating multifaceted benefits. [ABSTRACT FROM AUTHOR]

Achieving macroscale superlubricity on engineering steel by utilizing aqueous green lubricants has gained growing interest, given its substantial potential to reduce energy consumption and carbon footprint. However, maintaining superlubricity under diverse sliding conditions over a prolonged duration is a major obstacle for real-scale applications. Herein, we report that a robust and durable tribofilm enabled by a unique lubrication mechanism based on carboxylated graphene quantum dots (CGQDs) in aqueous glycerol triggers macroscale superlubricity in self-mated steel contacts. A dedicated intermittent test was designed to show the superlubricity's robustness and the ability of the tribofilm to adapt to a variety of relevant sliding conditions. Moreover, the boundary film provides an average coefficient of friction of around 0.007 and up to 69 % wear reduction (compared to the base lubricant), resulting in the maintenance of superlubricity at a real final contact pressure of 123 MPa, which increases the upper limit of the contact pressure compared to current aqueous-lubricated steel contacts. The new superlubricity mechanism was enabled by the chemical adsorption of the CGQDs onto the worn metal surface, coupled with the tribo-induced structural degradation and transformation of the CGQDs into layered graphitic structures that generate an adaptable low-shear interface. This work provides new insights into the role of chemical adsorption and structural transformation of CGQDs in achieving superlubricity and is an important step forward for implementing energy-efficient and green lubrication technologies for industrial applications. [Display omitted] [ABSTRACT FROM AUTHOR]

MXenes induce excellent wear resistance under solid lubrication due to their distinctive surface chemistry, easy-to-shear ability, and capability to form low-friction and wear-resistant tribofilms. However, beyond the extensively studied Ti 3 C 2 T x , other promising members of the MXene family remain largely underexplored. Therefore, we spray-coated multi-layer vanadium carbide (V 2 CT x) coatings (thickness ∼10.8 μm) on steel substrates and studied their tribological performance for prolonged times (10,000 cycles) using a reciprocating ball-on-disk tribometer with acting contact pressure of 445 MPa in ambient conditions. Results show that V 2 CT x -coated substrates demonstrate an 8-fold reduction in friction (COF of 0.11) and a 10-fold wear rate reduction (1.405 × 10−6 mm3 N−1 m−1). High-resolution materials characterization confirmed that the remarkable tribological performance of these coatings can be traced back to the formation of protective films on the substrate (tribofilm) and counterbody (transferfilm) consisting of contact pressure and frictional heat-induced degraded, deformed, exfoliated V 2 CT x nanosheets, nanocrystalline oxides, and amorphous carbon debris. This work fully elucidates the tribological potential of V 2 CT x , which is of utmost relevance for designing high-performance lubricating materials. Our work has assessed the performance of multi-layer V 2 CT x (M 2 XT x) due to its remarkable thermal stability, low molecular weight, good mechanical properties, and high interlayer spacing, thus serving as an entry point into diverse MXene compositions, including M 4 X 3 T x (V 4 C 3 T x). [Display omitted] [ABSTRACT FROM AUTHOR]

• A novel simulation method is proposed to identify the causes of lubrication failure in high-speed coolant pumps for electric vehicles. • Experimental validation confirms the accuracy of simulations for both the pump and bearing. • The steady radial forces of the pump rotor are effectively balanced by the bearing load capacity. • The rotor–stator interaction results in unsteady radial forces, inducing substantial whirl in the bearing. • The bearing whirl reduces lubricant film pressure gradient and load capacity, ultimately leading to lubrication failure. The high-speed coolant pump is essential for electric vehicle thermal management, ensuring optimal module temperatures. The pump impeller and bearing are combined into a rotor and then fit on a fixed shaft with a clearance, aiming to generate a complete lubricant film between the stationary journal and rotating bearing during pump operations. However, during the pump durability test under off-design conditions, severe wear occurred on both the journal and bearing. A novel simulation method based on computational fluid dynamics and dynamic mesh is developed to investigate the lubrication failure. User-defined functions are programmed to articulate the simultaneous rotation and whirl of the bearing, and the effects of temperature and cavitation are considered. Both the pump and bearing simulations closely align with experimental results. When the radial force of the pump rotor is steady, the bearing only rotates without whirling, and the bearing load capacity can counteract the maximum radial force of the rotor. However, the rotor experiences fluctuating radial forces over time, primarily attributed to elevated pressure levels at the volute tongue caused by the rotor–stator interaction. This phenomenon results in the bearing to rotate and whirl simultaneously. The load capacity generated by the backward whirl of the bearing is greater than that of the forward whirl. Nevertheless, the bearing whirl initiates a decline in the extremum values of lubricant film pressure. Subsequently, both load capacity and minimum film thickness exhibit a continuous decrease, eventually culminating in the breakdown of the complete lubricant film and resulting in contact wear failure. These new findings contribute to proposing measures to reduce wear under unsteady excitations. [ABSTRACT FROM AUTHOR]

Hybrid journal bearings are crucial components in many equipment, such as nuclear reactor cooling pumps and hydraulic motors. However, there exists a significant challenge to understand the lubrication behaviors of hybrid bearings with multiple thermal effects at low-speed, heavy-load conditions. Therefore, a composite thermal lubrication model is proposed, which includes four thermal effects: edge suction heat, hydrostatic pressure loss heat, oil viscous friction heat, and asperity friction heat. The lubrication and contact model are modified by actual rough surfaces to evaluate friction heat accurately. The experiments from a homemade testing rig verify the model well. Friction and temperature characteristics of the hybrid bearing are obtained, and the influence of hydraulic pressure and speed on four types of heat are analyzed. • The composite thermal oil film lubrication model is proposed to predict the overall performance of hybrid journal bearings. • The model contains edge suction heat, hydrostatic pressure loss heat, oil viscous friction heat, and asperity friction heat. • The flow factors and contact coefficients from the actual rough surfaces are used to correct the lubrication and contact model. • The four types of heat play a role in specific conditions and correspondingly cannot be ignored. [ABSTRACT FROM AUTHOR]

Laser surface texturing is an effective method to enhance gear lubrication by improving lipophilic properties, thereby increasing transmission performance and longevity. This study investigated the effects of laser parameters on lipophilicity using a grid texture and found that a scanning speed of 100 mm/s maximized diffusion and climbing. The textured specimens showed higher wetting hysteresis and adsorption, forming a thicker oil film for better lubrication. Wear tests indicated that the textured specimen had reduced friction, wear quality, and depth by 49.2% and 66.34% compared to unprocessed specimens. Gear efficiency is effectively increased, and gear oil temperature is significantly reduced. This research offers insights into lipophilic characterization and gear lubrication enhancement, potentially decreasing surface failures like pitting, adhesion, and wear. • A method for characterizing the lipophilicity of material surfaces is proposed. • Maximum wettability and adsorption force increased by 49.2% and 66.34% over US. • Minimum wear quality and depth decreased by 29.65% and 45.33% compared to US. • Textured gears increase efficiency > 3.67%, reduce oil temp > 7.45% vs. untextured. [ABSTRACT FROM AUTHOR]

Surface micro-texturing involves creating microscopic pits or textures, serving as lubricant reservoirs to enhance lubrication distribution, potentially reducing friction and wear. This study specifically delves into the influence of varied depth patterns of pits on the operational performance of textured rolling bearings under severe lubrication conditions. Five distinct patterns with a fixed pit diameter (250 µm) and different depth variations (concave, decreasing, increasing, convex, and horizontal) were introduced on the shaft rings of cylindrical roller thrust bearings using the laser marking method. Wear tests were conducted under starved lubrication condition. Wear loss and signal analysis highlight the profound effect of depth variations, whereby bearings with shallow pits near the outer side of their working surfaces exhibit longer lubrication times, improved tribological performance, and enhanced vibration characteristics. Notably, the convex pattern stands out for providing comprehensive and favorable tribological and vibration properties. This research contributes valuable insights for the optimal design of micro-textures for rolling bearings, paving the way for enhanced efficiency and reliability in mechanical systems. [ABSTRACT FROM AUTHOR]

The lubricated non-conformal contact generally works under the mixed-EHL regime. Optimizing the surface topography or selecting the right coating is an effective way to improve its performance. This paper presented an improved mixed-TEHL model for the lubricated non-conformal contacts with the effects of roughness and coating in consideration. The effect of coating was solved analytically by employing the Papkovich–Neuber potentials. It was found that the properties of coatings, especially their elastic modulus, significantly affect the pressure and stress distribution. In comparison to other roughness parameters, standard deviation and kurtosis have a significant impact. As expected, the present model can provide an efficient analysis of the tribological behavior and the stress distribution of the lubricated non-conformal contacts. [ABSTRACT FROM AUTHOR]

A sulfur-containing carbon nanosphere (SCN) with the corrosion inhibitor M16 (M16 @SCN) was successfully prepared through post-carbonization and then electrostatic adsorption. The as-prepared SCN have rich pore and high specific surface area of 578.9 m2g−1 due to high-temperature carbonization of polythiophene (PT), which as a nanocontainer could upload corrosion inhibitor M16 to obtain M16 @SCN. The M16 @SCN exhibits anti-corrosion performance via controlled release of M16 and improved tribological performance, with friction coefficient of 0.1, extreme pressure of 850 N, and reduction in wear volume of 88.6%. The M16 adsorbed on the nanosphere improves the dispersion of SCN in the lubricating oil, and the SCN acts as a nanocontainer to ensure the performance of M16 under harsh conditions. The good tribological properties are attributed to the synergistic effect between SCN and M16 in the friction process, resulting in a rigid protective oil film was produced on friction pair via tribochemical reactions and physical adsorption. [Display omitted] • Sulfur-containing carbon nanosphere with corrosion inhibitor (M16 @SCN) was prepared by electrostatic adsorption. • The as-prepared M16 @SCNs exhibit excellent tribological performance when used as oil additive. • The superior lubrication performance was attributed the oil film formed by the synergistic interaction during friction. [ABSTRACT FROM AUTHOR]

A fully coupled FE model for mixed EHL of finite line contacts is proposed, integrating all of the governing equations into a monolithic system. The solution reveals the fully coupled model achieves 5% higher accuracy and 50% greater efficiency compared to the weakly coupled one. Additionally, there is evidence to support the assertion that profiling contributes to the mitigation of surface roughness contact. Logarithmic profiling can increase the minimum film thickness by a factor of 30, resulting in a reduction of up to 64.6% in the maximum asperity contact pressure, and thus, the boundary friction force is decreased by more than 19%, under heavy-load low-velocity condition. This contributes to the reduction of abrasive wear. • A fully coupled FE model for the mixed EHL analysis of finite line contacts is developed. • Lubrication of mixed EHL film with straight, dub-off, and log profiles under different loads and velocities is analysed. • Influences of profiling on asperity contact and friction force are discussed and revealed. • A logarithmic profile has the potential to enhance the boundary lubrication condition at the free-end. [ABSTRACT FROM AUTHOR]

The journal-thrust coupled bearing (abbreviated as JTC bearing) works at the end of the crankshaft in diesel engine, with the function of carrying radial load and prevent axial movement of the crankshaft. The journal part and the thrust part of this special bearing both form the oil film lubrication when subjected to the time-varying loads in axial and radial directions during the working condition. In this work, the JTC bearing in marine diesel engines was analyzed using a transient thermal elastohydrodynamic (TEHD) lubrication model. The thermal and pressure (thermal-pressure) coupled effects were taken into consideration based on the flow, pressure, and thermal continuity conditions between the journal and thrust parts. Moreover, the transient time-varying load was considered in the lubrication analysis to explore the coupled effect under the actual operating conditions. A test rig was built to validate the established transient TEHD lubrication model for the JTC bearing. The thermal-pressure coupled effect between the journal and thrust parts was found to significantly affect the transient lubrication behaviors of the JTC bearing, which cannot be ignored. Also, different boundary conditions were investigated for the influence of the coupled effect on transient lubrication characteristics, including axial clearances, radial clearances, waveforms of radial load, incline angles and inlet oil temperatures. This work could theoretically support the lubrication design of the JTC bearings used in the diesel engine crankshafts. [ABSTRACT FROM AUTHOR]