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Purpose: This study aims to propose an optimization framework using deep neural networks (DNN) coupled with nondominated sorting genetic algorithm II and technique for order preference by similarity to an ideal solution method to improve the tribological properties of camshaft bearing pairs of internal combustion engine. Design/methodology/approach: A lubrication model based on the theory of elastohydrodynamic lubrication and flexible multibody dynamics was developed for a V6 diesel engine. Setting DNN model as fitness function, the multi-objective optimization genetic algorithm and decision-making method were used to optimize the bearing pair structure with the goal of minimizing the total friction loss and the difference of the average values of minimum oil film thickness. Findings: The results show that the lubrication state corresponding to the optimized bearing pair structure is elastohydrodynamic lubrication. Compared with the original structure, the optimized structure significantly reduces the total friction loss. Originality/value: The optimized performance and corresponding structural parameters are obtained, and the optimization results were verified through multibody dynamics simulation. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-12-2023-0417/ [ABSTRACT FROM AUTHOR]

The variation of friction coefficient (μ) of model wine and model saliva mixtures with entrainment speed (VR) on simulated oral surfaces was evaluated by oral tribology. Combined with techniques of dynamic light scattering (DLS), atomic force microscopy (AFM), rheometer, and quartz crystal microbalance with dissipation monitoring (QCM‐D), the correlation between characteristics of the model wine and model saliva mixtures (particle size and morphology, suspension viscosity, adsorption film thickness, and viscoelasticity) and the oral lubrication loss was established. The results showed that the higher the concentration of tannin in the model wine, the larger the size of the complexes with the model saliva, and the higher the thickness, viscoelasticity, and roughness of the adsorption film formed, which resulted in the increase of friction coefficient in the boundary lubrication regime. Different from previous results, it is found that the maximum value of the friction coefficient (μmax) in the boundary regime has the best positive correlation with the astringency perception intensity of the model wine accordingly. [ABSTRACT FROM AUTHOR]

In this paper, a tribo‐dynamic model of a helical gear is established. For the lubrication sub‐model, a finite line thermal elastohydrodynamic lubrication model of helical gear is adopted. The lateral vibration, axial vibration of gear and torsional vibration of the gear shaft are considered in the dynamic sub‐model. Results show that the tribological parameters of helical gear under the tribo‐dynamic model deviate significantly from that of the quasi‐static model, especially in the engaging‐in region of tooth pair. The friction excitation mainly affects the vibration along the off‐line‐of‐action direction of the gears. The influence of operating conditions on the tribological and dynamic properties of a helical gear pair is significant, especially in the case related to the characteristic frequency of gears. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study is to investigate the use of micro-pits technology to the problem of tribological performance in a sliding motion. Design/methodology/approach: Vegetable oil is a sustainable and economically viable alternative to both mineral and synthetic oils, offering significant savings in both the cost of research and manufacturing. To solve the depriving issue and boost lubrication film thickness, the micro-pits on the surface may function as reservoirs that provide the oil to the contact inlet area. In this research, an aluminium block is used as the workpiece material in an evaluation of a through pin-on-disc tribotester. Lubricating oil in the form of super olein (SO) was used in the experiment. Findings: The results show that the friction performance during a rubbing process between a hemispherical pin and an aluminium block lubricated with SO using aluminium alloy materials, AA5083, was significantly improved. Originality/value: In this study, a material that breaks down called SO, which is derived from the fractionation of palm olein, was used to use a modified aluminium micro-pit sample that will serve as a lubricant reservoir in pin-on-disc tribotester. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2023-0200/ [ABSTRACT FROM AUTHOR]

The rheological and tribological properties of environmentally compatible lubricants of different bases (native oil, synthetic ester, polyalkylene glycol‐containing oil) compared to a conventional, mineral oil‐based lubricant are investigated in order to develop toxicologically harmless and technically suitable lubricants for electromechanical drives. The aging of the oil is also considered. The results of this study reveal that the properties of polyalkylene glycol‐containing and synthetic ester‐based lubricants have the potential to act as substitutes for lubricants containing mineral oil. By examining and improving the properties of sustainable lubricants, gear oils that are partially or totally non‐mineral oil based will be highly attractive in the future. [ABSTRACT FROM AUTHOR]

A series of polyimide (PI)/V2CTx MXene composites was synthesized via polyamide acids (PAA) and two‐dimensional (2D) V2CTx MXene obtained by etching precursor V2AlC. PI/V2CTx MXene composites with different mass ratios were obtained by blending and heating with PAA. The results showed that V2CTx MXene has excellent dispersion in PI. In particular, V2CTx MXene exhibited excellent friction reduction and anti‐wear properties as a solid lubricant additive, and the wear rate (WR) was reduced by 43.2% by incorporating only 0.8 wt% of V2CTx MXene in the pristine PI and 71.9% by incorporating 1.2 wt%. Scanning electron microscopy (SEM) and x‐ray photoelectron spectroscopy (XPS) analyses showed that the continuous transfer film consisting of a high proportion of tribo‐chemical products formed on the contact surface is significant to improve the lubrication performances of the PI composites. This work broadens the application of MXene in the field of tribology and contributes to energy conservation and sustainable development of human society. Highlights: The tribological properties could be tuned by changing the ratio of PI to V2CTx MXene.The WR of PI composites was reduced by 71.9% with incorporating 1.2 wt% of V2CTx MXene.The formation of transfer films on the contact surface is significant for improving anti‐wear of PI. [ABSTRACT FROM AUTHOR]

Laser texturing with a dimple pattern was applied to modify a Ti6Al4V alloy at the micro level, aiming to improve its friction and wear resistance in combination with oil lubrication to optimize the performance in demanding industrial environments. The tribological analysis was performed on four different dimple-textured surfaces with varying dimple size and dimple-to-dimple distance and under lubrication with three different oils, i.e., T9, VG46, and VG100, to reflect the oil viscosity's influence on the friction/wear of the laser-textured Ti6Al4V alloy. The results show that the surfaces with the highest texture density showed the most significant COF reduction of around 10% in a low-viscosity oil (T9). However, in high-viscosity oils (VG46 and VG100), the influence of the laser texturing on the COF was less pronounced. A wear analysis revealed that the laser texturing intensified the abrasive wear, especially on surfaces with a higher texture density. For low-texturing-density surfaces, less wear was observed for low- and medium-viscosity oils (T9 and VG46). For medium-to-high-texturing densities, the high-viscosity oil (VG100) provided the best contact conditions and wear results. Overall, reduced wear, even below the non-texturing case, was observed for sample 50–200 in VG100 lubrication, indicating the combined effect of oil reservoirs and increased oil-film thickness within the dimples due to the high viscosity. [ABSTRACT FROM AUTHOR]

Purpose: Tantalum is a kind of metal material with moderate hardness, high ductility, small thermal expansion coefficient, excellent corrosion resistance and outstanding biocompatibility. The purpose of this study is that its tribological performance could be tested and analyzed so as to use it in different fields. Design/methodology/approach: The friction resistance of a-Ta under dry friction conditions was tested at different roads. The relationships between load and friction coefficient, wear rate and two-dimensional shape of wear scars were studied. Findings: The stable Ta2O5 film with lubrication effect was generated in the process of friction. And, the larger the test load, the more Ta2O5 would be generated. Originality/value: This work lays a theoretical foundation for tantalum as an excellent wear-resistant material. Peer review: The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-02-2023-0047/ [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the effect of compound pit textures on the tribological properties of thrust cylindrical roller bearings (TCRBs) using several parameters, such as compound type, pit diameter, pit depth and pit area density. Design/methodology/approach: The surface texture parameters of the shaft washer (WS) raceway include pit diameter (D; 100, 300 and 500 µm), pit depth (H; 10 and 20 µm) and pit area density (S; 10%, 13% and 18%). Pits were produced on the WS of the TCRBs using laser marking equipment. The friction and wear performances of compound pit-textured TCRBs under starved lubrication conditions are studied using a friction and wear test rig. The influence mechanisms of the compound pit texture on the friction and wear properties of TCRBs are discussed through real tests and discussions. Findings: Compared with nontextured bearings, the average coefficient of friction (ACOFs) and wear loss of TCRBs with single/compound pit textures are reduced when rotating under starved lubrication. D has the greatest effect on the COFs curve. When D = 300 µm, H = 10 µm and S = 10%, the ACOF and wear loss are the lowest, that is, 0.0207 and 3.38 mg, respectively. Under the same lubrication conditions, compared with the nontextured bearing group, the COF and wear loss are reduced by 41.4 and 59.6%, respectively. Originality/value: This study provides a useful reference for the raceways of textured TCRBs. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to study the influence of dimple textures on the friction and wear properties of tapered roller bearings (TRBs) with many pattern parameters, e.g. diameter, depth and area density under starved lubrication. Design/methodology/approach: The pattern parameters include the dimple diameter (D; 60, 100 and 200 µm), dimple depth (H; 5, 10 and 20 µm) and area density (S; 6%, 12% and 24%). Dimples were fabricated on the outer ring (OR) of TRBs using a laser marking machine. The tribological properties of dimple-textured TRBs under starved lubrication were studied on a vertical universal friction wear tester with special friction pairs. The effect mechanisms of dimple textures on the tribological properties of TRBs are presented and summarized through experiments and discussions. Findings: When dimple-textured TRBs revolve under starved lubrication, the average coefficients of friction (ACOF) and wear losses are markedly lower than those of non-textured bearings. S has the greatest influence on the COF curve. When D is 100 µm and S is 24%, the ACOF and wear losses are both lowest, i.e. 0.00426 and 0.51 mg, respectively. Under the same test conditions, compared with the non-textured group, its COF and wear loss decreased by 35.6% and 62.5%, respectively. Originality/value: This work provides a useful reference for the research on the raceways of textured TRBs. [ABSTRACT FROM AUTHOR]

To improve the tribological characteristics of the face seal, the squamous groove micro textures with different area proportion and the circular dimple micro texture were designed and manufactured. The disc‐disc friction and wear experiments and numerical simulation were carried out in oil lubrication. The pressure distribution, friction coefficient, fluid temperature and wear morphology are investigated. The study show that the friction coefficients of the micro textured and untextured samples decline with the increase of load, but first increase and then decrease with the rise of rotational speed. Micro textured samples could decline the friction coefficient effectively, and the asymmetric structure in the lubricant inflow and outflow region of the squamous groove micro texture makes it have better tribological performance. In addition, the micro texture can increase heat dissipation area, reduce heat production and collect wear debris, which could modify the lubricant temperature and wear morphology effectively. [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]

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]

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]

The main idea of this study was to utilize the pressure and heat produced in the friction process to make Mo nanoparticles mixed in lubrication oil into the multi-layered tribo-film. An in-house developed reciprocating wear rig was used for the tribo-film deposition and associated tribological tests. By design of experiment, the optimal deposition parameter was obtained. Results indicate that the multi-layered film consists of a Mo-based concrete structure layer and a carbon-based film. The carbon-based film was produced by the dehydrogenation and carbonization of the lubricating oil catalyzed with Mo nanoparticles. The consumption and deposition of the carbon-based film was dynamically balanced during the wear process, resulting in the outstanding tribological performance. [Display omitted] • A great amount of Mo nanoparticles were ultrasonically mixed in the base oil. • Film fabricated by utilizing the heat and pressure produced in friction process. • The film consists of Mo-based film mixed with amorphous carbide. • Realize carbon film formation and restoration in lubrication. [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]

Adaptive calibration for ultrasound reflectometry methods used in the detection of lubrication film thickness is of great research interest. This is mainly due to the versatile non-destructive implementation of the technology in industrial applications, allowing for measurements of the lubrication film thickness, which directly relates to the friction, wear, and overall efficiency of the system. This study reviews and compares a curve fitting, extended Kalman filter, and resonance frequency detection adaptive calibration approach. Furthermore, the study compares two different regression models, used for the curve fitting and the extended Kalman filter approach. The study compares the methods and regression models based on both a theoretical and experimental analysis. The experimental analysis is based on data with varying lubrication film thickness. The lubrication film thickness is varied such that the resonance frequency is both detectable and non-detectable within the ultrasound transducer bandwidth. It is found that all three methods give results very similar to those achieved through manual calibration. However, since the extended Kalman filter approach is the only method that allows for continuous calibration, this method is found to have the greatest potential of the methods compared. [ABSTRACT FROM AUTHOR]

Purpose: Cold forging operation is one of the widely used techniques in industry production. This paper aims to present a case study in highlighting and modelling the use of different type of palm oil-based [palm stearin (PS), palm kernel oil (PKO) and palm mid olein (PMO)] as a bio-lubricant in cold forging process using experimental and finite element method. Design/methodology/approach: Ring compression test plays a fundamental role in the understanding of materials science and engineering because of the deformation, friction and wear behaviour. Aluminium (A6061) was used in this test to observe the deformation of the ring with different palm oil and its derivatives by comparing with commercial metal forming oil. Findings: The presence of certain type of palm oil-based lubricant has a good performance compared to mineral-based oil in terms of surface roughness but when observed in terms of friction the result shows that palm oil-based lubricant has poor friction performance compared to mineral oil-based lubricant (m = 0.25), where PS has the lowest friction at m = 0.3 compared to PKO (m = 0.35) and PMO (m = 0.38). Research limitations/implications: This research is using palm oil in cold forging test to study the friction, formation and stress at certain levels of stroke. The detail of the test is explained in the manuscript as attached. Social implications: This research is trying to promote the use of biodegradable material to reduce pollution to the surrounding. Originality/value: The originality of this paper has been checked using Turnitin and the result is 13%. [ABSTRACT FROM AUTHOR]

In mixed lubrication, material wear is inevitably caused due to solid contact. Simultaneously, the surface morphology after wear will affects the lubrication performance. To understand this coupling process, virtual surface reconstruction technology and mixed lubrication sliding wear model were applied to predict the evolution of wear characteristics and lubrication characteristics during wear in this study. The effects of the roughness root mean square (RMS), roughness direction and wavelength ratio on the contact area ratio, the contact load ratio, accumulated wear, film thickness and the friction coefficient were analysed. The results indicated that the contact area ratio and the contact load ratio and the friction coefficient decreased and average film thickness increased with the increase in the number of the wear cycles. In addition, a surface with low‐roughness RMS, longitudinal roughness texture and high‐wavelength ratio is suitable for improving lubrication performance and reducing wear. [ABSTRACT FROM AUTHOR]

A Ni–Cr–MoS 2 coating with trivalent Cr was prepared on the surface of the cylinder liner by the composite co-deposition method to modify its tribology performance. The effects of MoS 2 concentration on the properties of the coatings and tribological properties of cylinder liners were studied by surface detection methods and reciprocating wear tests. The results show that Ni–Cr–MoS 2 coating has a smaller grain size, higher micro-hardness, and greater coating thickness, compared with Ni–Cr coating. Doping by MoS 2 effectively reduces the friction coefficient of Ni–Cr coating from 0.142 to 0.107, the wear amount of coating decreases from 7.9 mg to 7.1 mg, and the scuffing time increases from 19 min to 56 min. It is found that the doping of MoS 2 provided more nucleation sites and promoted the deposition of ions, which resulted in the refined grain and thicker coating. The formation of solid lubrication film by MoS 2 during the wear process and more coating thickness are mainly responsible for the modification of the tribology performance of cylinder liners. This research provides a practical approach to prolong the service life of friction pairs. • The inclusion of MoS 2 significantly increased the Ni–Cr coating thickness. • The doping of MoS 2 increased nucleation sites and changed the coating structure. • The friction and scuffing properties of cylinder liner were significantly improved. • A solid lubrication film produced on the surface of composite coating by MoS 2. [ABSTRACT FROM AUTHOR]

The lubrication regime of a hip implant is influenced by various parameters, including material, geometry, roughness, relative angular movement, and loading circumstances. These factors impact friction and wear performance, ultimately limiting the implant's longevity. In this study, a ball-on-plane model is considered to predict the lubrication regime across the entire gait cycle for the metal-on-metal and ceramic-on-ceramic hip implants. According to ISO 14242-1, a normal walking gait cycle is considered for the loads and rotations in the hip implant for this study. A comprehensive analysis is done to estimate the lubrication regime by considering different material combinations, body weights, femoral head sizes, clearances, and roughness across the entire gait cycle. The correlation coefficients show that the geometrical parameters are dominant in affecting the lubrication film thickness compared to the operational and material parameters. The femoral head size and body weight are found to be the most dominant and least dominant parameter respectively. Among the hard-on-hard tribo-pairs, ceramics operate predominantly in the full-film lubrication regime compared to metals due to its fine surface finish. The present research suggests that in order to maximise the longevity of a hip implant, an orthopaedic surgeon should choose one with a larger femoral head diameter, less clearance, and an ultra-fine surface finish, regardless of any material tribo-pair. • Comprehensive analysis on minimum film thickness for hard-on-hard hip implants. • Geometrical parameters are more dominant than operational and material parameters. • Larger head size, less clearance and fine surface finish are preferred for longevity. • Ceramic contacts perform predominantly in full-film lubrication regime than metals. [ABSTRACT FROM AUTHOR]

The increasing application of diamond-like carbon (DLC) coatings in engine mechanical parts requires the investigation on interaction mechanism between DLC and fully formulated engine oil. This study shows that the friction can be controlled by monitoring the load for a steel/DLC contact, lubricated by a fully formulated 5W30 engine oil in boundary/mixed lubrication regime. A calcium carbonate-rich patchy tribofilm, mainly formed on steel ring, was characterized by multiple surface analyses. X-ray photoelectron spectroscopy (XPS) indicates an increase quantity of calcium carbonate (CaCO 3) with increasing contact load. Transmission Electron Microscope (TEM) showed that the original calcium carbonate in the overbased detergent additive within the lubricant itself was amorphous. However, the amorphous calcium carbonate crystallizes in vaterite (low load), aragonite (medium load) and calcite (high load) during the tribological tests. The intrinsic lubricity of each calcium carbonate polymorph was estimated by density functional theory calculations, while the tribological properties of the sliding interface composed by H-passivated diamond and CaCO 3 polymorphs were investigated by ab initio molecular dynamic simulations. The in-depth investigation presented here sheds light into the main factors leading to the unexpected pressure-induced friction reduction. [ABSTRACT FROM AUTHOR]

The wealth of soft contact tribological (SCT) investigations utilising ball-on-disc tribometers assume Hertzian contact model to describe substrate deformation. We hypothesise this is invalid for soft-adhesive viscoelastic discs with a finite thickness. Here, we uniquely use the wear transducer in the mini-traction machine to indirectly measure the load-dependent deformation and fluid film thickness of rigid-soft, soft-rigid, and soft-soft contacts across a range of loads, speeds and viscosities. Macroscopic deformation within these configurations and compliance of the respective tribopairs vary considerably, which is not predicted by the Hertzian model. We consider how to account for these deformation effects in SCT. [Display omitted] • MTM wear transducer measures film thickness in EHL regime for soft contacts (ball-disc). • MTM wear transducer measures substrate deformation in BL-ML regime. • Hertzian contact mechanics is invalid for viscoelastic substrates with finite thickness. • A large effective gap arises in BL-ML regime due to the deformation of VE substrates (disc). [ABSTRACT FROM AUTHOR]

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]

Eco-friendly waterborne bonded solid lubricating coating (BSLC) has attracted increasing concern for surface protection engineering. However, the development of BSLC with outstanding comprehensive performance (lubrication, wear resistance and flexibility) remains challenging. In this study, surface-partitioned Janus nanoparticles (JNPs) was specially designed and applied to modify waterborne epoxy (EP) BSLC, in which the hydrophobic polytetrafluoroethylene (PTFE) and hydrophilic silica acted as soft side and hard side of PTFE@Silica JNPs, respectively. With unique amphipathicity, the hydrophobic PTFE can be uniformly dispersed in waterborne EP. The attained EP-JNPs composite coating with a moderate additive amount of JNPs (i.e., EP-JNPs-20 wt%) has desirable lubrication and anti-wear (coefficient of friction and wear volume are about 80 % and 90 % lower than EP, respectively.). The formed PTFE tribofilms and the stiffening effect of silica lobes collaborate together to realize the outstanding self-lubrication of EP-JNPs composite coating. This drives the application of waterborne BSLC in the fields of wear-resistance coatings. [Display omitted] • Janus nanoparticles were specially designed to modify waterborne epoxy coating. • Friction and wear are reduced by about 80 % and 90 % with Janus nanoparticles. • Silica lobes enhances the dispersibility of PTFE in waterborne epoxy. • PTFE tribofilms and stiffening of silica lobes dominate the tribological behavior. • This study provides novel strategy to design nanofillers for tribology applications. [ABSTRACT FROM AUTHOR]

Graphene-encased copper particles (GE@Cu) with fluctuating particle sizes ranging from 3 to 15 nm, 80-210 nm, 270-530 nm, and 1.2–3.5 μm are prepared by metal-organic chemical vapor deposition using cupric tartrate and cupric acetylacetonate as precursors.The reaction temperature has been found a significant effect on the decomposition of the organocopper compounds, the coalescence of Cu/C clusters, and the morphology evolution of GE@Cu particles. Thus, the size of copper particles and thickness of the graphene cladding layer (few-layer and multi-layer) can be strictly controlled by modulating the pyrolysis temperatures of the organocopper compounds. The optimized GE@Cu particles with 0.5 wt% mass ratio in lubricants exhibit the reduction of wear track depths and coefficient of friction comparing with the pure lubricants. The corresponding wear rate for the 0.5 wt% few-layer graphene@Cu (FLGE@Cu) and 0.5 wt% multi-layer graphene@Cu (MLGE@Cu) decreases by 60.3 % and 62.5 %, respectively. Additionally, Raman spectroscopy illustrates the formation of a self-lubricating graphene layer on the wearing surface during the friction with GE@Cu as the lubricant additives. The hybridized structure of this nanoadditive introduces synergistic lubrication effects, involving sliding friction (graphene) and rolling friction (copper particles) at the friction contact surface, leading to enhanced lubrication performance. The comprehensive encapsulation of copper particles by GE established the suitability of this lubricant additive for enduring prolonged and intricate environments. In conclusion, GE@Cu lubricant additives hold great promise across the fields of mechanical equipment, bearings, and engines. Graphene-encased copper particles are synthesized through metal-organic chemical vapor deposition with organocopper compounds as precursors for application in lubricant additives and friction testing. [Display omitted] • Graphene-encased copper particles (GE@Cu) with controllable particle sizes and a tunable thickness of graphene cladding layer were synthesized by modulating the pyrolysis tempretures of organocopper compounds. • Composite lubricant with optimized mass ratio of GE@Cu additives demonstrates excellent friction resistance properties. • GE@Cu particles contribute to synergistic lubrication via the bearing/rolling effect of copper particles and the excellent self-lubrication of graphene sheet. [ABSTRACT FROM AUTHOR]

Food oral tribology plays an important role in studying the oral processing behavior of foods. This article explores the lubricity of different mass fractions of honey-water solutions (HWS) combining experimental and simulation study. Friction experiments are performed in simulated soft oral environment, and the complete Stribeck curve is successfully constructed. It is found that as the mass fractions of honey increase, the friction coefficients decrease and the curves move towards higher Vη (speed × viscosity) values. Higher viscosity and wettability enhance the film-forming and entrainment ability of the fluid, while reducing the friction coefficients in the boundary and mixed regimes. However, changes in wettability have little impact on the elastohydrodynamic lubrication regime of pure honey. In addition, a lubrication model is established using finite element method to examine the fluid movement in the lubrication area. The distribution of lubrication film exhibits a horseshoe shape. Influences of the sliding speed, fluid viscosity, and solid viscoelasticity on the distribution of fluid pressure and film thickness are revealed. This study provides guidance for exploring the oral processing behavior of fluid foods and improving the pleasure of eating. • Friction of honey-water is revealed combining experiment and simulation study. • Rising honey mass fractions improves its lubrication. • 100% honey is mainly in the elastohydrodynamic lubrication during oral processing. • The viscoelasticity of tongue-palate substitutes affects the movement of fluid food. [ABSTRACT FROM AUTHOR]

To enhance the tribological properties of Si 3 N 4 based ceramics, surface textures of dimples combined with DLC coatings are fabricated on Si 3 N 4 /TiC ceramic surface by nanosecond laser and plasma enhanced chemical vapor deposition (PECVD). The dry friction and wear performances are evaluated by unidirectional sliding friction tests using a rotary ball-on-disk tribometer. Results reveal that the friction and wear properties of Si 3 N 4 /TiC ceramics are significantly enhanced by DLC coatings or dimpled textures, and the DLC coatings combined with dimpled textures show the best efficiency in reducing friction, adhesion and wear. This improvement can be explained by the synergistic effect of DLC coatings and surface textures, and the synergistic mechanisms are attributed to the formation of lubrication film and secondary lubrication, debris capture of dimpled textures, increased surface hardness and mechanical interlocking effect, and reduced contact area. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to investigate the effects of surface texture with roughness orientation considered on tribological properties under a mixed lubrication state numerically and experimentally. Design/methodology/approach: Based on the average Reynolds equation and asperity contact model, the impacts of surface texture parameters and roughness orientation on lubrication properties have been calculated using finite difference method. Tin–bronze samples with various prescribed surface texture geometric parameters and roughness orientation were fabricated by laser surface texturing technique, and the tribology performance of the textured surface was studied experimentally. Findings: The effects of surface geometric parameters and roughness orientation parameters have been discerned. The experimental observations are in good agreement with the numerical prediction, which suggests that the numerical scheme adopted in this work is suitable in capturing the surface texture and roughness effect under mixed lubrication state. Originality/value: By meticulously controlling the surface roughness and surface texture geometric characteristics based on the laser surface texturing process, samples with prescribed surface texture parameters and roughness orientation consistent with that in theoretical studies were fabricated and the theoretical model and results were verified experimentally. [ABSTRACT FROM AUTHOR]

The design of existing tribometers mainly focuses on normal contact and lubricant conditions and aims to evaluate the effect of the load, speed, and environmental conditions on the rubbing pair properties. The effect of the contact angle and variable speed on the rubbing pair properties is often not considered. In this study, a multidirectional adjustment tribometer is developed to evaluate the tribological behavior of cylinder liner–piston rings under dry sliding or oil lubrication conditions. The dynamic, specimen clamping, measuring, and control systems are redesigned according to the structural characteristics of the SKODA-SAVIN tribometer and special requirements of research on the net texture effect on tribological properties. Using LabVIEW software, a man–machine interface is designed to achieve converter control, data acquisition, and other functions. A fail-safe analysis is performed through reproducibility, comparability, and sensitivity tests. From the experiments, it is proved that the tester can provide more detailed, abundant, and reliable data for the performance testing and development of cylinder liner–piston ring materials. [ABSTRACT FROM AUTHOR]

This study proposes a tribo‐dynamic model for point contacts under lubrication, focusing on the excitations caused by surface movement, defect and load impact. Surface movement and load impact can cause changes in contact force, resulting in acceleration and dynamic displacement, which may affect the flow of the lubricant. The traditional lubrication model is usually steady or transient, and load balance is used to correct the normal height, ignoring a series of influences such as the mass, stiffness and damping. It requires repeated corrections to obtain a balanced position, which is very time‐consuming. By combining tribology and dynamics, dynamic excitation is introduced in the contact process in this study. After determining the initial value, the normal height can be directly obtained from the dynamic equation. Besides, a comparison between the tribo‐dynamic model and the steady‐state model is presented. It is found that the film thickness and pressure distribution calculated by the two models are almost the same at medium and low speeds, while the calculation results of the two models are different at high speed or under load impact, which emphasises the importance of considering the dynamic behaviour in the study of contacts. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this paper is to investigate the effects of surface texture with roughness orientation considered on tribological properties under a mixed lubrication state numerically and experimentally. Design/methodology/approach: Based on the average Reynolds equation and asperity contact model, the impacts of surface texture parameters and roughness orientation on lubrication properties have been calculated using finite difference method. Tin–bronze samples with various prescribed surface texture geometric parameters and roughness orientation were fabricated by laser surface texturing technique, and the tribology performance of the textured surface was studied experimentally. Findings: The effects of surface geometric parameters and roughness orientation parameters have been discerned. The experimental observations are in good agreement with the numerical prediction, which suggests that the numerical scheme adopted in this work is suitable in capturing the surface texture and roughness effect under mixed lubrication state. Originality/value: By meticulously controlling the surface roughness and surface texture geometric characteristics based on the laser surface texturing process, samples with prescribed surface texture parameters and roughness orientation consistent with that in theoretical studies were fabricated and the theoretical model and results were verified experimentally. [ABSTRACT FROM AUTHOR]

Background: Soft tribology is increasingly important in the design and engineering of materials used in robotics, haptics, and biomechanics studies. When patterned surfaces are part of a lubricated tribopair that undergoes sliding and compressive deformation, the patterns experience a bending strain that affects the lubrication film thickness and elastohydrodynamic friction. The contribution of bending patterns to soft tribology is not well understood because earlier studies focused on hard tribopairs with effectively flat surfaces. Objective: We investigate and model the differences in lubricated friction for poly(dimethyl siloxane) (PDMS) elastomer and PEGDA/alginate double network hydrogel patterns in order to determine the effect of height-to-width aspect ratio and bending angle on the elastohydrodynamic friction. Methods: Photoresists of two different viscosities are spin coated onto silicon substrates to fabricate molds with pattern heights ranging from 20 μm to 50 μm. Results: Tribological characterization of the tribopairs in the elastohydrodynamic lubrication regime shows that the patterns generate a friction peak that is independent of aspect ratio for short patterns but displays a "power-law fit" decrease with increasing aspect ratio for taller patterns. Two independent models are used to estimate the theoretical bending and deflection angles for the tribopairs. Conclusions: The decrease in lubricated friction is attributed to taller patterns having large bending angles and a reduced effective surface for fluid load bearing. Results suggest that the bending of micropatterns could be harnessed to engineer lubricated friction in a variety of applications. [ABSTRACT FROM AUTHOR]

Purpose: This paper aims to improve the tribological performance of grease-lubricated spherical plain bearings (SPBs) under heavy load, dimple-type textures were prepared by laser on the outer surface of the inner ring. The influence of roughness parameters of a textured surface on reducing friction coefficient and temperature rise was also explored. Design/methodology/approach: This study adopts a laser processing method to fabricate dimple-type textures. Three-dimensional roughness parameters were used to characterize the textured surfaces. The friction coefficients of five SPBs with surface texture and one original commercially available SPB without surface texture under different nominal loads were measured on a self-established test rig. The data of temperature rise were obtained by nine embedded thermal couples. Findings: The results indicate that SPBs with textures generally exhibit lower friction coefficients than the original SPB without textures. The dimple depth has a significant influence on improving the tribological performance, which coincides with the analysis by surface roughness parameters. A textured surface with negative Ssk and high Vvc has the minimum temperature rise. Originality/value: As it is too difficult to arrange sensors into heavy-load SPBs, there are few reports about the temperature characteristics. Through nine embedded thermal couples, the distribution of temperature rise on the inner ring of SPBs was given in this study. The positive effect of surface texture on reducing temperature rise and friction coefficient was verified, which is beneficial for the design of heavy-load SPBs. [ABSTRACT FROM AUTHOR]

As lubricating materials, the tribological performance of laminar transition metal dichalcogenides (TMDs), can be improved by compound oxide particles. In this study, MoSe2/MoOx heterogeneous nanostructures are easily obtained from a solvothermal reaction followed by an annealed process in O2/N2 atmosphere. The MoSe2/MoOx composite, as a lubricant additive, shows better performance than those of pristine base oil, which includes friction coefficient and antiwear capability. The enhanced performance of MoSe2/MoOx heterogeneous nanostructures can be attributed to the lubrication layer and tribochemical reaction films formed on the worn surface, which prevents the direct contact of the friction surface and improves tribological performance. [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]

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]

This paper investigated the effect of oil‐air lubrication on contact temperature and sliding tribological properties. On the basis of heat transfer theory, a numerical simulation model of forced convection was established. Experiments were conducted using the tribology machine. Results show that in oil‐air lubrication, forced convection can significantly reduce the temperature at the contact position. Nonlinear decline and decrease in the descent rate of contact temperature were observed with the increase in convective heat transfer coefficient. The convective heat transfer between friction pairs increased with air supply velocity, whereas the sliding friction coefficient initially decreased and then increased. The friction flash temperature reached its lowest value with proper heat dissipation capacity. With the increase in ambient temperatures of the friction pairs, the sliding friction coefficient decreased, whereas the friction flash temperature increased. Influenced by the oil‐air lubrication heat dissipation in the test, the wear mechanism of point contact sliding friction was abrasive wear. [ABSTRACT FROM AUTHOR]

Current requirements for the reduction of CO2 emissions, as well as for the improvement of durability and reliability of sociotechnical systems such as passenger cars, lead to an increase in development effort in order to increase efficiency and system lifetime. Tribological systems play an essential role in the development of sociotechnical systems, but have proved to be particularly complex. The development of tribological systems, as part of the overall system under development, is an interdisciplinary effort. Involvement of solid mechanics, fluid mechanics, rheology, and many more scientific disciplines is essential to cope with the high number of nonlinear relationships, which often cause unpredictable system behavior. This paper contributes to the scientific field of tribology by introducing concepts of model‐based systems engineering for the specific case of elastohydrodynamic lubrication states. The elastohydrodynamic lubrication state of tribological system has been chosen as example to show how system models can be used to better describe the behavior of a system by connecting several specific models. In order to gain an overview of the models used in tribological system development, a system cube was used to structure the models. The system cube enabled gaps and overlapping model zones to be identified. Finally, the role of system models in development and the benefit of using system models to solve problems that cannot be solved by a single technical discipline but only in an interdisciplinary effort are discussed. An approach to connect models and methods to describe a system in an elastohydrodynamic lubrication state is presented. [ABSTRACT FROM AUTHOR]

This work is on the study of the synergetic effect of anodized Al alloy surfaces, with thin tungsten disulphide films alloyed with carbon and fluorine (WS-CF) deposited by magnetron sputtering. The surface roughness and surface chemistry were changed to tune the surface wettability and improve the frictional behaviour of the hybrid surfaces. The SEM analysis of these surfaces showed that, although the film growth has led to the progressive pore narrowing, pores were still visible after deposition of an ~ 200 nm thick film. Even though the film deposition has induced the surface smoothening, the surface free energy (SFE) of the hybrid surfaces was not substantially altered, when compared to bare anodized surface with large dimple (LD). Accordingly, the contact angles measured with water (WCA) and α-bromonaphthalene (OCA) on the hybrid surfaces suggested that the film surface chemistry was the main responsible for the wettability results, having the bottom dimple-shaped surface roughness just a low effect. LD surface coated with pure WS2 coating (LD + WS2) showed a remarkable high hydrophobicity combined with a high oleophilicity. Pin-on-disc testing carried out at room temperature in dry conditions showed much lower coefficient of friction (COF) values for the coated samples (hybrid surfaces), comparatively to uncoated ones. Furthermore, the friction performance of the hybrid surfaces was better for the F-alloyed thin film (sample named as WS-CF5 and having 9.5 at% of F) than for the WS2 film. In lubricated testing with a polyalphaolefin oil (PAO-8), the soft uncoated surfaces presented lower COF values, since the rapid smoothening of the contact surface turned the lubrication regime from mixed to hydrodynamic-like. For the LD surfaces coated with the F-alloyed WS film (named as LD + WS-CF5), the higher hardness of WS-CF5 was responsible for keeping the lubrication regime in partial lubricated conditions, leading to higher initial COF. Afterwards, a WS2-based tribolayer is formed in the solid-solid contacts which, together with the progressive film smoothening, change the lubricated regime toward hydrodynamic. Therefore, the friction of LD + WS-CF5 was reduced with the elapsed time and approached the one of the uncoated samples (LD). Concluding, both these hybrid surfaces can have a role on oil-water separation processes, self-cleaning of building outdoors or on microfluidic and printing applications. [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]

This paper presents the results of research, which are the effect of national and international projects carried out at the Łukasiewicz Research Network -- Metal Forming Institute, concerning both tribological and biotribological topics. The research results, the effect of which is the development of a new generation of forging tools (the design of cold forging tools with a properly prepared work surface and the development of new multilayered, nanostructured gradient coatings) and the solution to the problem of early wear of the parts working in difficult conditions are presented. For friction elements operating at high temperature, a solution has been developed that has found practical applications in the industry in the field of improving lubrication technology. The development of the technology of introducing solid lubricant particles onto the surfaces of tribologically cooperating parts operating at elevated temperatures has become extremely important for many industries that daily face problems with the early wear of cooperating elements. The second part of the work focuses on biotribological problems and the main challenge is to extend the durability of hip joint endoprostheses. In connection with this, work was carried out to thoroughly understand the process of endoprosthesis wear. Examination of the tribological properties of new materials intended for elements of endoprostheses is also a very important issue. The research was conducted on a specially designed and built hip joint simulator, which meets the requirements of the ISO standard. [ABSTRACT FROM AUTHOR]

Gears typically operate in mixed lubrication conditions, where the lubricant film is too thin to prevent opposing surface asperities from interacting with each other. The likelihood/intensity of interactions is indicated by the Λ ratio: the ratio of smooth surface film thickness to surface roughness. Researchers have asserted that asperity interactions are the predominant cause of acoustic emission (AE) in healthy gear contacts. However, direct experiments on gears have yet to yield a clear relationship between the Asperity AE (AAE) and Λ ratio, this is in part due to the complexity of gear tooth contacts. In this paper, a disc rig was used to simulate a simplified gear contact so that the fundamental relationship between AAE and Λ could be investigated more effectively. By varying oil temperature and entrainment speed, a wide spectrum of lubrication conditions was generated. In contrast to other published studies, an independent measurement technique, the contact voltage (CV), was used to verify the amount of interactions, and repeated roughness measurements were used to confirm minimal surface wear. A simple, consistent and precise relationship between AAE amplitude and Λ was identified and defined for changes from full-film to mixed lubrication. Within the mixed lubrication regime, the AAE amplitude increased exponentially as Λ decreased at all speeds tested. It was also observed that an increase in speed always resulted in an increase in AAE amplitude, independently of any changes in Λ. This direct effect of speed was modelled so that the AAE could be predicted for any combination of speed and Λ within the tested envelope. This paper links gear contact tribology and AE with new precision and clearly demonstrates the potential of using AAE as a sensitive monitoring technique for the lubrication condition of gears. [ABSTRACT FROM AUTHOR]

Abstract In this work the fat mimicking mechanism of microparticulated whey proteins (MWP) in milk-based systems was studied using rheological and tribological techniques. Flow curves and friction measurements in a soft contact of skim milk-MPW dispersions (SM-MPW) and skim milk-dairy fat emulsions (SM-DF) at different concentrations (3, 6, 9, 12, 15, 18 and 20% w/w) and temperatures (25 °C and 37 °C) were carried out and compared. Friction coefficient curves of SM-MPW dispersions as a function of the product of entrainment speed and viscosity collapsed into a single master curve in the mixed and elastohydrodynamic (EHL) regimes when the high shear viscosity values as obtained through Carreau-Yasuda model were used. This suggests that the dispersions as a whole entrained in the contact. However, in the case of SM-DF emulsions, a very good collapse is obtained if only SM is assumed to pass through the contact. Simulations of friction coefficient within the EHL region showed a reasonably good continuity of the experimental data for SM-MPW dispersions and SM-DF emulsions. Finally, it was observed that friction levels attained with MPW proteins and DF at typical speeds involved in oral processing were comparable, hence demonstrating the capability of SM-MPW proteins dispersions to imitate DF in milk-based systems from a lubrication point of view. Highlights • Fat mimicking mechanism of microparticulated whey (MPW) proteins in milk-based systems studied by rheology and tribology. • Comparison between Skim milk-MPW dispersions and Skim milk-dairy fat (DF) emulsions. • Stribeck curves and simulations help to infer about the viscosity contribution to the friction coefficient. • Typical friction coefficient values attained by MPW proteins and DF in oral environment conditions. [ABSTRACT FROM AUTHOR]

Due to scarce resources coupled with increasing mobility requirements, resource-efficient machine and motor elements are vital. Therefore, surfaces in lubricated tribological contacts can be microtextured, enabling improved lubricating conditions and friction behavior. While this has already been shown for lower loaded contacts, the effects for higher loaded, application-oriented EHL contacts are topic of basic research. Therefore, geometrically defined microtextures are adapted to the tribological system of the tappet/camshaft contact in the valve train of combustion engines as a demonstrator. The tribological performance in respect to lubricating conditions, friction and wear behavior is analyzed on single cam/tappet component test-rigs. EHL simulation is used as ‘numerical zoom’ into a section of the contact area contributing to better understanding of effects and observed phenomena. [ABSTRACT FROM AUTHOR]

Abstract: Considering the tribology design theory of arbitrary intersecting line gear (AILG) is still a blank, the equivalent ellipsoid model of contact area of the AILG pair was built and then improved by 3 modification methods of line teeth profile. Based on the improved model, semiquantitative analyses of the relationship between the parameters of the AILG and the ratio of principal curvature radii of equivalent ellipsoid Rx/ Ry were presented, and design criteria for the parameters of AILG based on elastohydrodynamic (EHL) point contact model were proposed. The results of the theoretical calculation and the optical EHL experiment proved that the modifications of teeth profile and the parameters design criteria for the AILG are conducive to improving its EHL performance. [ABSTRACT FROM AUTHOR]

Transient effects in elastohydrodynamic lubrication occur due to varying operating conditions and surface features moving through the contact. For rolling/sliding contacts the lubricated contact behaviour is determined by a unifying mechanism characterized by the inlet length (boundary layer). Roughness deformation depends on a single dimensionless parameter representing the ratio inlet length to wavelength. This behaviour is shown to generalize to the pure impact problem. The bell shaped film thickness near the periphery of the contact is directly related to the boundary layer velocity profile. Also, the waviness deformation under impact conditions is shown to depend on the same parameter as in rolling contacts when the rolling velocity is replaced by the local boundary layer velocity in the impact problem. [ABSTRACT FROM AUTHOR]