Search

In a MHCJB (multi-recessed hybrid conical journal bearings), the orientation of the pockets affects the oil film pressure dispersion in the clearance space of bearing thereby it affects the performance of bearing system. This article aims to analyse the influence of pocket orientation on the characteristics of MHCJB operating with PVP (piezo-viscous-polar) lubricant. To analyse the effect of pocket orientation, the study considers two configurations of MHCJB with different pocket arrangement. The modified form of Reynolds equation governing the flow of PVP lubricant in MHCJB is numerically solved by using Galerkin's technique. The results have been computed for the value of semi-cone angle (γ = 10 o), piezo viscous parameter ( α ¯ p v = 0.0, 0.3) and polar parameter ( l ¯ c s = 0.0, 0.2). The results indicate that pocket orientation-II offers maximum enhancement of 11.77 % in stiffness coefficient ( S ¯ x x) and 2.45 % in damping coefficient ( C ¯ z z). Further, PVP lubricant offers substantial improvement in stability threshold speed. • Consideration of single cone and double opposed cone bearing configurations subjected to combined radial and axial loading. • Pocket orientation significantly affects the dispersion of oil film pressure in clearance of MHCJB. • PVP lubricant offers significant improvement in the performance of MHJCB. • Double opposed cone configuration of MHCJB may be preferred to support significantly varying axial load. • Shifting of radial load towards bearing of positive axial displacement may reduce shaft tilting in double opposed cone bearings. [ABSTRACT FROM AUTHOR]

Most mechanical systems have mating interfaces that require effective lubrication for smooth functioning. Thus, understanding and accurately modeling lubrication regimes is an essential research task. The present work proposes a set of normalized coefficients based on homogenization and stochastic theories to model the partial and full-film lubrication regimes between a smooth and a rough surface. The modified Greenwood and Williamson theory, considering inter-asperity-interactions, was used to model the contact-zones. Subsequently, the film-thickness was evaluated and the homogenized Reynolds equations were solved to compute the normalized coefficients. The estimated coefficients were compared with Patir and Cheng's flow-factors, and the similarities and disagreements between both approaches were discussed. New sets of coefficients for running-in surfaces were proposed for modeling their lubrication regimes. • Normalized homogenization coefficients are evaluated based on stochastic analysis. • Inter-asperity interactions have been considered to model the solid contacts. • New sets of homogenization coefficients for running-in surfaces are proposed. [ABSTRACT FROM AUTHOR]

Traditional methods of evaluating the performance of journal bearings, for example thermal-elastic-hydrodynamic- lubrication theory, are limited to simplified conditions that often fail to accurately model real-world components. Numerical models that include additional phenomena such as cavitation and fully coupled effects like deformation, temperature, pressure and viscosity can be more accurate but require a large amount of computational overhead, making analysis slower and more costly. To address this limitation, a novel machine learning-driven approach is developed to predict the 2D distribution of surface deformation, film thickness, temperature, and pressure across the bearing surface as a function of design variables such as load and speed. The training dataset, generated using a fully coupled Reynolds' Equation solver implemented in OpenFOAM, contains a significantly extended range of conditions than in previous studies with approximately 39 000 000 points encompassing 4925 different test cases. Modelled bearing speeds range from 2000 to 10 000 rpm, while load values are varied between 1 and 30 kN. Predicting surface deformation, film thickness, temperature and pressure across the bearing surface results in a mean absolute percentage error below 0.4 % or better. The work also demonstrates that the trained models have a strong ability to generalise the prediction beyond the original training data range with only a 1 % error at up to 200 % of the highest trained speed. This work also demonstrates that machine learning-based processes are a practical alternative to physics-based numerical modelling, especially in cases where rapid performance evaluation is desired as real-time calculation is possible with significantly reduced computational cost. This has the potential to enable development of rapid design optimisation tools and real-time performance monitoring at high resolution and with low latency. Using consumer hardware, it is found that the neural network-based approach is faster than the existing numerical modelling technique by a factor of over 10 000, enabling real-time predictions of lubrication systems. • A neural network approach is demonstrated, using independent models to predict each variable. • Neural network models trained using an OpenFOAM numerical model display a mean error of < 0.4%. • Once trained, the neural network models are ∼ 10 000 x faster than traditional numerical models. [ABSTRACT FROM AUTHOR]

The role of friction in the forming of automotive parts composed of ultra-high-strength lightweight metals has become increasingly important as industry attempts to overcome inferior formability and springback against enhanced strength. At the tool-design stage, finite-element simulations should use more accurate and efficient friction models that account for complex friction behavior between the metal and tool surfaces. Complex friction behavior is commonly dependent on contact pressure, sliding velocity, microscale surface effects (or roughness), and lubrication, among other factors. This study presents a microscale, asperity-based friction model of mixed-boundary lubrication. The developed hydrodynamic friction model is based on the load-sharing concept, which considers the lubrication area and metal-to-metal contact separately. Lubricant film thickness is calculated to couple the existing boundary lubrication model, and film lubrication behavior is formulated using finite-element programming of the Reynolds equation to obtain the hydrodynamic pressure. The proposed computational framework is validated by simulating an in-line incremental die-forming process. The result shows that the predicted friction law with multi-scale, mixed-boundary lubrication can be efficiently applied to realistic sheet-metal-forming simulations with reasonable accuracy by accounting for complex frictional behavior. [Display omitted] • The asperity-based friction model of mixed boundary lubrication is presented. • The hydrodynamic pressure and file thickness can be calculated via new friction model. • The new friction model effectively integrates the concept of load-bearing. • Complex frictional behavior is accounted in the real sheet-metal-forming process. [ABSTRACT FROM AUTHOR]

In the framework of stochastic representation of surface roughness, a novel Reynolds-type Equation has been derived recently by the authors and utilized to calculate the average values of a bearing's operational parameters. To acquire an improved insight to the hydrodynamic lubrication phenomena in rough bearings, the stochasticity of the operational parameters should be described, by calculating their higher-order moments, such as the variation. The present work aims at deriving equations for calculation and quantification of these higher-order moments. More specifically, in the present paper equations for the variation of a slider bearing operational parameters (pressure, load carrying capacity, friction force and friction coefficient) are derived. The obtained results are validated against the deterministic Reynolds Equation solution, for a series of bearings with different random Gaussian surface roughness profiles, over a wide range of bearing design and operational parameters. • Stochastic implementation of the surface roughness profiles as Gaussian variables. • Hydrodynamically lubricated bearings with surface roughness on the bearing and slider. • Utilization of Stein's Lemma, novel stochastic calculus theorem of probability theory. • Mathematical derivation of novel equations for calculating the variance of critical bearing's operational parameters. • Validation of acquired equations via numerical simulations and with existing results found in literature. [ABSTRACT FROM AUTHOR]

A deterministic mixed lubrication model for parallel surfaces is proposed. The oil film force is solved by the Reynolds equation with a mass-conserving cavitation model. The contact force is predicted by using a neural network trained on a database, which was built by conducting finite element analysis on a single asperity. In addition, an extended Archard equation is introduced to predict the transient running-in wear. The contact model is proved to be suitable for Gaussian and non-Gaussian surfaces. The Stribeck curves calculated under the different wear coefficients and wear steps are compared with the experimental results. The influence of initial surface topography on the running-in behavior has also been studied. The contact database for GCr15 is provided. [ABSTRACT FROM AUTHOR]

Various anti-wear and anti-corrosion coatings are applied on the surface of journal and bearing to maximise service life of a bearing system. These coatings influence the wettability of surfaces consequently causes velocity slip phenomena in the bearing system. This article addresses a novel investigation to examine the influences of velocity slip and PVP (Piezo-viscous-polar) lubrication on multirecessed hybrid conical journal bearing (MHCJB). For various cases of velocity slip, novel forms of Reynolds equation are derived and solved numerically by using FEM. The results reveal that velocity slip severely affects the generation of oil film pressure. Consequently, it deteriorates the bearing characteristics viz. load carrying capacity, oil flow rate and rotordynamic coefficients. Further, PVP lubricant offers substantial enhancement in bearing characteristics. • Anti-wear/anti-corrosion coatings influence the wettability of surfaces consequently causes velocity slip in the bearing system. • Novel forms of Reynolds equation for various cases of velocity slip in conical journal bearing with PVP lubrication. • Velocity slip impacts oil film pressure distribution and thereby load carrying capacity, rotordynamic coefficients. • PVP lubricant offers valuable enhancement in load carrying capacity and stability characteristics of conical bearing. [ABSTRACT FROM AUTHOR]

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

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

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

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

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

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

Abstract A layered oil slip model considering the slip and thermal effect is proposed to explore the mechanism of film thickness behaviours at high speed. The modified Reynolds equation considering the interfacial slip is derived and the limiting shear stress of lubricant is utilised as the criteria for the occurrence of slip. The film thickness obtained from the proposed model matches the experimental results very well. The results indicate that both the interfacial slip and thermal effect contribute to the behaviours of film thickness at high speed. The interfacial slip may occur at both fast or/and slow surfaces depending on the speed conditions. Highlights • A layered slip model is built to explore the lubrication behaviors at high speeds. • Wall slip tends to become severe with increasing speed in tractive condition. • Slip occurs mainly at both contact surfaces at high speed conditions. • Slip will lead to the decrease of temperature rise. • Combination of slip and thermal effects induces the film behaviors at high speeds. [ABSTRACT FROM AUTHOR]

Abstract This paper presents an approach for modelling three-dimensional soft elastohydrodynamic lubrication (EHL) contact of heterogeneous materials. In this approach, a hydrodynamic interface element is developed to achieve the coupling of elastic deformation of heterogeneous contacting bodies and the steady-state hydrodynamic lubrication at the contact interface. The deformation behaviors are simulated by the finite element method, while the hydrodynamic lubrication is dealt with by solving the Reynolds equation. This approach can enable the simulation of soft EHL contact between bodies with heterogeneous materials and complicated geometric configurations. Predicted lubrication performances of soft EHL contacts show good agreement with the experimental measurements reported in literature. Analysis and discussion are also conducted on various cases of soft EHL contact between an elastic ball and a coating-substrate system with or without inhomogeneities. Highlights • An approach for modelling three-dimensional soft elastohydrodynamic lubrication contacts of heterogeneous materials is proposed. • A hydrodynamic interface element is developed to achieve the coupling of elastic deformations of heterogeneous contacting bodies and the steady-state hydrodynamic lubrication at the contact interface. • Various cases of soft EHL contact between an elastic ball and a coating-substrate system with heterogeneous materials are investigated. [ABSTRACT FROM AUTHOR]

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

Linear harmonic vibration during machining of a conical journal may produce micron order undulations on outer surface of journal. Further, a lubricant comprising of long chain polymer additives may attain polar effect due to couple stresses. At high pressure conditions, pressure viscosity interaction in oil may affect the actual viscosity of the lubricant. The flow behaviour of piezoviscous-polar lubricant in a conical bearing is modelled in cylindrical coordinates. FE analysis is utilized to solve the modified Reynolds equation. The results indicate that journal undulations offer relatively higher oil film pressure due to local convergence in oil film, consequently exhibit higher stiffness coefficients. Moreover, piezoviscous-polar lubricant may raise the values of S ¯ z z upto 18% and C ¯ z z upto 32% than Newtonian lubricant. • Micron order undulation on conical journal due to linear harmonic vibration in tool during machining. • Cumulative effect of piezoviscosity and polarity in long chain polymer additives based oils. • Finite element modeling of modified form of Reynold Equation. • Higher values of stiffness coefficients due to journal undulations. • Piezoviscous-polar lubricant reduces oil flow rate and frictional torque and raises the stiffness and damping coefficient. [ABSTRACT FROM AUTHOR]

Effective lubrication under zero entrainment velocity (ZEV) conditions has been experimentally demonstrated by using lubricated conjunction of oleophilic and oleophobic surfaces. It is hypothesized that the phenomenon is attributed to the boundary slip effect. The isothermal elastohydrodynamic lubrication (EHL) of a non-conformal contact of slip and non-slip surfaces under ZEV conditions is analyzed numerically. A modified Reynolds equation that incorporates the slip length model is used. A method of measuring the slip velocity of lubricant on a surface is devised and implemented in ZEV tests with contact surfaces of different affinities to the lubricant. The slip velocity that is extracted using the new method is compared with the speed of the contact surfaces to derive their relationship. [ABSTRACT FROM AUTHOR]

The EHL model of tapered roller bearing considering free ends is established and the effect of force on the large end is also considered. The free ends are constructed through the overlapping method, and the distribution of pressure and film thickness are obtained with the unified Reynolds equation. The effect of force and distance between two neighboring free ends are investigated, based on which the proper contact case is selected. The EHL of tapered roller bearing with different fillets and Lundberg profile are discussed. The results show the length and radius of roller fillet and the modification of Lundberg profile roller should be carefully selected to improve lubrication performance with low pressure, large minimal film thickness and low stress concentration. • The EHL model of tapered roller bearing considering free ends is established. • Lower load and larger distance from ends reduce the effect of roller free ends. • The force on large end only slightly influences the EHL of roller. • A moderate modification factor δ is suggested for Lundberg profile roller. [ABSTRACT FROM AUTHOR]

The time lag of bearing deformation caused by viscoelasticity cannot be ignored under time-varying load. This paper proposes a new temporal correlation micro visco-elastohydrodynamic lubrication (T-MVEHD) model. It corrects the calculation method of deformation for dynamically loaded bearings based on the finite element method and viscoelastic constitutive equation and improves the efficiency by uncoupling the stiffness and Reynolds equations. Further, it is applied to the lubrication analysis of internal combustion engine bearing. The simulation results show that the discernment of the new model to the impact is increased by 29.6% than the micro elastohydrodynamic lubrication model. It has better continuity and compatibility when the lubrication state changes and captures the asperity contact of connecting rod bearing 12° in advance. [ABSTRACT FROM AUTHOR]

This study deal with the numerical simulation of a hybrid double layer conical porous bearing (DCPB) considering the synergistic effects of a double layer porous matrix and non-Newtonian lubricant (cubic law model) behaviour. The present study investigates the interactive effects of the non-linear factor of lubricant, permeability parameter and semi cone angle on the performance of a hybrid DCPB. The modified Reynolds equation is solved using the finite element technique for a hybrid DCPB. Findings of this study indicate that the DCPB improve the performance parameters as compared to hybrid single layer conical porous bearing (SCPB). Further, the use of non-Newtonian lubricant improves the stability threshold speed margin ω ̅ th and reduces the frictional power loss ( p ̅ fric). • DCPB with synergistic effect of double layer porous matrix and non-Newtonian lubricant (cubic law model) is computed. • Finite element analysis of double layer conical porous hybrid journal bearing is performed. • The interactive effects of semi cone angle, non-linear factor of lubricant and permeability parameter has been studied. • Performance of bearing in terms of static and dynamic characteristics for different values of radial load W ̅ r . [ABSTRACT FROM AUTHOR]

New kite-shaped textures are designed in this paper to improve the lubrication performance of tribological systems under hydrodynamic lubrication. Moreover, pressure distribution and load-carrying capacity of the kite-shaped textures under fixed working conditions are solved using Reynolds' equation based on the form of mass conservation. Lastly, the influence of kite-shaped textures on the friction coefficient under different geometric parameters is investigated. Moreover, a double-layer composite kite-shaped texture is designed, and the influence of parameters on lubrication performance is investigated. Numerical simulations and experiments are used to find the optimal parameters and effectively reduce the friction coefficient, thus providing a reference for reducing frictional wear in mechanical systems under full-film oil lubrication conditions. [ABSTRACT FROM AUTHOR]

Recent advances in computational methods and resources have fuelled numerical studies to explore novel techniques for solving thermal elasto-hydrodynamic lubrication (TEHL) problems. Commercial codes such as those that feature the Computational Fluid Dynamics (CFD) approach have gained much attention in the field of tribology due to the ability to tackle the limitations imposed by Reynolds equation assumptions and aptness in modelling complex geometries. However, the computational cost incurred by CFD software is significantly high due to the governing equations involved when solving the most general problem. The present contribution proposes an integrated finite-volume framework to solve TEHL problems to predict the lubrication performance of non-conformal contacts. Fluid flow effects are considered through the generalized Reynolds equation with the p − θ Elrod–Adams mass-conserving cavitation model to ensure the mass flow-rate conservation throughout the lubricated domain. The thermal behaviour of the lubricant film is predicted via the solution of the conservation of energy equation with appropriate boundary conditions for the fluid–solid interfaces. Novel partitioned iterative solution methods are integrated into the framework to handle the strong nonlinearities and improve the convergence of the coupled system of equations. Thermal and isothermal cases are presented and compared to results generated by existing CFD solvers and other experimental data to validate the proposed framework. [ABSTRACT FROM AUTHOR]

The non-Newtonian phenomenon is significant in hydrodynamic lubrication of some special lubricants, or elastohydrodynamic lubrication (EHL). However, the conventional methods to solve the non-Newtonian lubrication problem are either too complicated or inaccurate. This paper puts forward a Reynolds equation for general lubrication problem of the non-Newtonian fluid by treating the lubricant flow as the superposition of the Poiseuille flow and Couette flow. Then, as examples, a set of simulations for EHL in the line contact are presented to investigate the feasibility of the method. Finally, comparisons with the conventional methods establish the validity and simplicity of the method. [ABSTRACT FROM AUTHOR]

This study concerns with the numerical simulation of a conical porous hybrid journal bearing (CPHJB S) considering the synergistic effect of three-dimensional (3D) surface irregularities and magnetohydrodynamic (MHD) lubricant. The study analyzes the interactive effects of permeability parameter, MHD lubricant behaviour, semi cone angle and 3D surface irregularities on the performance of CPHJB S. FEM is used to solve the governing Reynolds equation for an irregular surfaced CPHJB S configuration lubricated with MHD lubricant. The findings of the study shows that the CPHJB S operating with MHD lubricant provide enhanced values of fluid film thickness and damping coefficients. • Conical porous hybrid journal bearing with synergistic effect of 3D surface irregularities and MHD lubricant is computed. • Finite element analysis of conical porous hybrid journal bearing is performed. • The interactive effect of permeability parameter and semi cone angle has been studied. • The static and dynamic characteristics for different values of radial load W ̅ r and Hartmann number H m . [ABSTRACT FROM AUTHOR]

This paper presents an experimental and analytical investigation into the lubrication of deep groove ball bearing (DGBB) cage pockets. A custom acrylic replica of a cage segment was designed, developed, and installed on a cage friction test rig for the simultaneous measurement of frictional torque and visualization of oil flow inside of the cage pocket. A broad set of experiments was conducted with different lubrication methods, oil viscosities, cage positions, and ball speeds to characterize the state of lubrication inside of the cage pocket. The quantity of oil inside of the pocket was found to correlate closely with the measured frictional torque. Videos of oil flow were subsequently analyzed to estimate the volume of oil present within the cage pocket at each operating condition. This oil volume information was then used to define an equivalent fluid to be used in a numerical cage pocket lubrication model. The model solves the Reynolds equation over a spherically defined cage pocket domain and produces estimates of frictional torque. Predictions from the model agree well with experimental friction measurements. The cage pocket friction results exhibit a dichotomous relationship – first increasing with speed then decreasing due to the dominating evacuation of lubricant from the cage pocket. Curve fit equations are presented to describe both behaviors, allowing for the prediction of cage pocket friction spanning a range of Reynolds numbers from 2 to 5000. [ABSTRACT FROM AUTHOR]

The effect of aerated oil, containing air bubbles, on the steadily and dynamically loaded journal bearing is investigated. The study is based on the thermohydrodynamic (THD) lubrication theory, which fully couples the Reynolds equation with the energy for the oil and heat conduction equations for solids through the oil viscosity. The oil's effective viscosity is influenced by the presence of bubbles via the surface tension and/or the volume fraction. The Reynolds equation is solved using the mass conservation algorithm and the two-dimensional equations for the temperature fields both in oil and solids are solved simultaneously to save computational time. The bubble radius, density, and viscosity are directly influenced by the pressure and temperature fields, requiring updating their values at each pressure and temperature. The simulations show that with a realistic viscosity model, the effect of the air bubbles in the lubricating oil on the pressure and temperature fields is small at normal operating speeds, while the density and the effective viscosity are reduced noticeably due to bubbles. [ABSTRACT FROM AUTHOR]

This article presents a film thickness prediction, using a new analytical form of the one-dimensional Reynolds equation, for lubricants whose rheological behaviour follows a modified Carreau model proposed by Bair. The development of the new equation was presented in New Reynolds equation for line contact based on the Carreau model modification by Bair, Tribol Int 55 (2012) 141–147. Hereby the numerical calculation process is presented and the ensuing results of film thickness, mid-plane shear stress and shear rate are compared with those published by other researchers for line contact in elastohydrodynamic lubrication. [ABSTRACT FROM AUTHOR]

The present work is aimed to numerically analyze the synergistic effect of the geometric shapes of recess and non-linear behavior of the lubricant on 4-pocket hybrid multi-recess spherical journal bearings. Recesses with square, circular, triangular, and elliptical shapes have been investigated. The influence of non-Newtonian lubricant has been considered using cubic shear stress law model. The performance parameters have been calculated for typically chosen values of non-linear factor. The finite element technique is used to solve the modified Reynolds equation. The results demonstrate that effect of recess shapes and non-linear factor significantly affects bearing performance. The proper selection of recess shapes and non-linear factor is needed to obtain an enhanced performance of hybrid multi-recess spherical journal bearings. • Finite element modeling has been carried out for hybrid multi-recess spherical journal bearings. • The non-linear behavior of the lubricants has been investigated using the cubic stress law model. • The influence of various geometric shapes of recess has been studied. • The interactive effect of recess shapes and non-linear factors significantly affects bearing performance. [ABSTRACT FROM AUTHOR]

Abstract: The elastohydrodynamic lubrication (EHL) characteristics of transversely isotropic materials are investigated. A finite element method (FEM) is utilized to solve the Reynolds equation, elastic equation, and load balance equation simultaneously on a ball-on-plane equivalent model. A simplified problem related to cornea and contact lens during blinking is studied. The pressure and oil film thickness distributions, surface deformation, and friction coefficient are discussed for various material properties (Young's modulus) and operating conditions (sliding velocity and load). Results reveal that the effects of soft transversely isotropic materials on lubricating performances are significant, which are helpful to further investigate the biomechanical interactions between a keratoconic cornea and a lens during blinking. [Copyright &y& Elsevier]

Abstract: The effect of couple stress fluid on the elastohydrodynamically lubricated finite line contact is studied. Modified Reynolds equation is derived from Stokes microcontinuum theory and solved numerically using finite difference method. Owing to the finite contact analysis, the effect of couple stress fluid at the edges of the roller is examined. The study reveals that overall film thickness increases significantly with couple stress parameter. This suggests less wear as there may be a chance of getting direct metal-to-metal contact. The coefficient of friction, which is of greater importance in lubrication, also decreases with increase in the couple-stress parameter. Based on the numerically evaluated results, empirical formulae for central and central minimum film thickness are developed. [Copyright &y& Elsevier]

Abstract: This paper presents a new form of the one-dimensional Reynolds equation for lubricants whose rheological behaviour follows a modified Carreau rheological model proposed by Bair. The results of the shear stress and flow rate obtained through a new Reynolds–Carreau equation are shown and compared with the results obtained by other researchers. [Copyright &y& Elsevier]

Abstract: A computational framework has been developed for a fully coupled analysis of elastohydrodynamic lubrication and finite deformations of elastomeric reciprocating seals in hydraulic actuators. The relevant formulation is provided, which consistently treats finite configuration changes of the seal modelled as a hyperelastic (Mooney-Rivlin) solid. The steady-state hydrodynamic lubrication is modelled using the classical Reynolds equation. Coupling of the solid and fluid parts is fully accounted for, including friction due to shear stresses in the lubricant film. Detailed results of finite element simulations are provided for two benchmark problems of O-ring and rectangular rod seals in a wide range of process parameters. [Copyright &y& Elsevier]

In this paper, a new tribodynamic model for the translational joints with clearance is proposed by coupling the mixed lubrication model and the rigid-flexible multibody system dynamic model. The lubrication behavior is described by the average Reynolds equation and the Greenwood-Tripp asperity contact theory. Under a unified framework of the absolute nodal coordinate formulation (ANCF), motion equations of the rigid-flexible multibody system are established. The assembled equations of tribodynamic model are solved by a stable and effective algorithm. An application example of a two-stroke marine diesel engine is then used to study the tribological and dynamic behaviors of the crosshead-guide translational joint with clearance. The results show that considering the elastic deformation of components will lead to more intense secondary motion and smaller local clearance, resulting in an oil film pressure distribution with great difference from the rigid body modeling. • A new tribodynamic model for the translational joints with clearance is proposed. • Tribological and dynamic behaviors of crosshead-guide kinematic pairs of two-stroke marine diesel engines are studied. • The influence of flexible body modeling of joint components on lubrication and dynamics performance is analyzed. [ABSTRACT FROM AUTHOR]

Total knee replacements are an effective surgical treatment to restore the function of the knee. For an adequate design, knowledge about stresses and lubrication conditions is vital. Part II proposes a fully-coupled transient 3D model for the soft elastohydrodynamically lubricated contact based upon the generalized Reynolds equation and Finite Element Method while Part I of this study focused on experimental observations. Within the scope of this contribution, a numerical model is presented and validated with experimental data. Good agreement between model predictions and experimental data was found. A strong influence of fluid and geometry assumptions and transient effects were found. Besides, it was demonstrated that the rheological synovial fluid properties have a decisive role in the tribological behavior. Image 1 • Combination of experimental investigations with FEM-based numerical modeling. • Good agreement when all relevant influencing factors are considered. • Load and geometry dominated the pressure and film formation in the stance phase. • The swing phase was largely influenced by the kinematics. • The fluid film formation was largely affected by reversal points of motion. [ABSTRACT FROM AUTHOR]

In elastohydrodynamic lubrication (EHL) contact, the film thickness strongly depends on boundary slips, including velocity slip and thermal slip at the solid–lubricant interface. In the EHL studies published thus far, velocity slip at the solid–lubricant interface has been investigated individually without considering thermal slip. In this study, the effects of both types of boundary slip on film thickness were investigated simultaneously in rolling/sliding contact. Numerical simulations were conducted based on the modified Reynolds equation and energy equation by considering boundary slips on the sliding surface. The results indicate that the velocity slip causes a reduction in film thickness under pure rolling contact, while a shifted surface dimple is formed along the sliding direction due to both velocity slip and thermal slip under zero entrainment velocity (ZEV) contact. Image 1 • This study, for the first time, reveales the effect of thermal slip at the solid–lubricant interface on EHL lubrication. • Under the pure rolling contact, velocity slip induces a general reduction in film thickness. • Under the ZEV contact, velocity and thermal slip cause shifted surface dimple oppositely along the sliding direction. [ABSTRACT FROM AUTHOR]

The research work undertaken in this article addresses the use of electro-rheological (ER) lubricant for controlling the performance of spherical thrust bearing system. In the present work numerical investigation of a circular recessed spherical thrust bearing system with a capillary restrictor lubricated with ER lubricant has been described. The governing Reynolds equation for spherical thrust bearing has been solved by FEM technique. The influence of axial eccentricity ratio and various value of imposed electric field on the bearing performance has been investigated. The findings of study indicates that a bearing operating with negative axial eccentricity provides improved performance with ER lubricant. A designer can harness this effect by using a fitted type of spherical thrust bearing system. • Modelling of recessed hydrostatic spherical thrust bearing lubricated with ER lubricant. • Studied the influence of ER lubricant on the performance of recessed hydrostatic spherical thrust bearing. • The bearing characteristics have been widely studied for various values of eccentricity ratio and electric field. • ER lubricant enhance the performance of the recessed hydrostatic spherical thrust bearing system. [ABSTRACT FROM AUTHOR]

A thermo-elastohydrodynamic lubrication transient simulation model for reciprocating rod seals was developed. In the model, the viscoelastic response of rubber materials under transient operating conditions was considered, and the transient Reynolds equation was solved. The stiffness matrix method, which is more stable and effective than the traditional influence coefficient method, was used to solve the problem of fluid - solid coupling in reciprocating sealing. The transient temperature distribution of the sealing system was calculated, and the viscosity of the fluid film was corrected according to the calculation result. • The model considers viscoelasticity, squeeze film and other transient effects. • The thermal-fluid-solid coupling calculation under transient conditions is realized. • A special contact pressure peak is generated due to the viscoelasticity of rubber. • The simulated sealing performance under transient conditions is worse. [ABSTRACT FROM AUTHOR]

This paper presents a modified Reynolds equation used for the analysis of thin film lubrication with high viscosity surface layers. The enhanced viscosity surface layers are considered on both sides of the bearing surfaces. The modified factors in the Reynolds equation are expressed as closed form functions for a surface layer viscosity function whose parameters values can be determined from the effective viscosity measured for a uniform lubricant film. To understand the mechanism of high load capacity and super-low friction coefficients in micro-texture lubrication through running-in, load capacity, friction force, and friction coefficient of micro-tapered bearing models are calculated comparing two and one-side surface layer models. • New Reynolds equation was developed for thin film lubrication analysis with an enhanced viscosity layer. [ABSTRACT FROM AUTHOR]

This study provides a new insight on the EHL regime in time-varying conditions. A full-analytical resolution of the Reynolds equation was proposed considering forced oscillations. Confronted to experimental validation, the analytical film thickness equations provide perfect modeling of the film forming mechanisms: squeeze induced by the transient evolution of the film thickness with time, asymmetry and hysteresis in the film distribution resulting from the change in direction and the transport effect. Furthermore, the analytical equations combined with a modulation of the inlet flow give an accurate prediction of the effects induced by the starvation resulting from the change in direction, i.e. as the original outlet zone becomes the next inlet zone. • An analytical of the Reynold's equation by considering the time dependence. • The measured and calculated lubricant film thickness time evolution is hysteretic. • The squeeze and the residence time influence is retrieved in the calculation. • A starvation effect is produced by the cavitation wake crossover during sliding. • The starvation is calculated with an adaptation of Chevalier's reduction parameter. [ABSTRACT FROM AUTHOR]

The impact of reducing friction losses on the fuel consumption and CO 2 emissions was investigated through computational simulation of piston ring dynamics. Experimentally determined cylinder bore surface finishes, low viscosity oil and ring coatings response to oil additives were used as simulation inputs. Oil viscosity grades from SAE10W-40 to SAE0W-4 were considered. 3D roughness measurements of regular and "mirror-like" cylinder bores were used to estimate the flow factors coefficients for the average Reynolds equation and asperity contact stiffness. The combination of smooth cylinder bores, low viscosity oils with appropriate additives promoted ring pack FMEP reductions of up to 66% at part load and WOT with consequent CO 2 reductions of up to 10% at part load and 1.5% at WOT. • Regular grey cast iron and mirror like coated bores actual measurements were used to calculate asperity and hydrodynamic pressures. • Ring friction losses etc. were calculated for 2000 and 4000 rpm, 20 and 100% engine loads, using a computational model. • The smoother bore surfaces generated much lower oil film thickness without increase of the asperity pressures. • The use of smooth cylinder bores, low viscosity oils brought reductions of: Ring pack FMEP up to 66% at part load and WOT. • CO 2 was reduced up to 10% at part load and 1.5% at WOT with the optimal combination. [ABSTRACT FROM AUTHOR]

This paper investigated the performance characteristics of misaligned journal bearing lubricated using couple stress fluids. Based on micro-continuum theory, the modified Reynolds equation for couple stress lubricants was developed, in which viscosity-pressure effect was considered. By setting the critical oil film thickness, the region with couple stress effect can be recognized. The ratio of the critical oil film thickness to couple stress parameter was referred to as film thickness coefficient. It was found from results that increase of film thickness coefficient can significantly improve the maximum film pressure and high-pressure area, when film thickness coefficient was smaller than 4. Viscosity-pressure effect was capable of enhancing viscosity, friction coefficient and the maximum film pressure, and reducing couple stress parameter, especially for large misalignment angle. • The critical oil film thickness was proposed to discriminate couple stress fluid from Newtonian fluid. • The film thickness coefficient signified an improvement in the maximum film pressure and high-pressure area. • Viscosity-pressure effect was applied to develop a modified Reynolds equation for couple stress fluids. • Viscosity-pressure effect provided a reduction in couple stress parameter, especially at high values of misalignment angle. [ABSTRACT FROM AUTHOR]

The commonly existed imperfect coatings may cause the displacements and forces transmitting discontinuously at the coating-substrate interface. This paper reports an elastohydrodynamic lubrication (EHL) model of ball-coated half space with coupled dislocation-like and force-like coating-substrate interface. Reynolds equation is solved to obtain the pressure. The surface elastic deformation and subsurface stress are calculated with the discrete convolution and fast Fourier transform (DC-FFT) method with the influence coefficients (ICs) obtained through corresponding frequency response functions (FRFs). The model is validated by the available data, and then implemented to study the pressure, film thickness, and subsurface stress distributions under imperfect coating-substrate interfaces of dislocation-like, force-like, and the coupled conditions, with various displacements and stresses jumping coefficients. • An elastohydrodynamic lubrication (EHL) model of ball-coated half space with imperfect coating is developed. • The frequency response functions (FRFs) for dislocation-like and force-like coating-substrate interfaces are derived. • The discrete convolution and fast Fourier transform (DC-FFT) method is used for displacement and stress calculations. • The pressure, film thickness, and subsurface stress affected by displacement and stress jumping coefficients are studied. • Lubrication performance with the coupled dislocation-like and force-like coating-substrate interface is studied. [ABSTRACT FROM AUTHOR]

In this study, a quasi-dynamic lubrication model of a thrust bearing is developed to identify the behaviors of scroll compressors. The present model is comprehensive and accurate with fewer assumptions. It is composed of the Reynolds equation for a lubrication film, an energy equation for temperature distribution, and a stress–strain equation for deformation owing to fluid pressure, forces, moments, and thermal stress. For model validation, the film thickness of the thrust bearing was compared with the results of numerical simulation and experiment at two operating conditions. The numerical simulation is consistent with the experiment, showing an error within 5%. • A quasi-dynamic model of a thrust bearing in a scroll compressor is developed. • Including refrigerant pressure, lubrication, and structural-thermal deformation. • Calculated gas force, film thickness, attitude angle, pressure, and deformation. • Accuracy is validated with experiment by measuring film thickness. • Thermal deformation model provides the most precise result. [ABSTRACT FROM AUTHOR]

In this paper, a composite model of average flow Reynolds equation with considering electrical double layer (EDL) effect in roughness surface is proposed to analysis aqueous solution lubrication performance. The numerical simulations are conducted to explain the phenomena of water-based lubrication with ultra-low friction coefficient. The results have showed that: The EDL hydrodynamic and asperity contact will work together to balance the out applied load. The EDL effect has greatly benefited for enhancing film formation and decreasing the friction to obtain the ultralow friction coefficient. To achieve the liquid superlubricity, the sliding velocity, liquid viscosity, surface roughness and EDL effect should be comprehensively considered. The proposed numerical model could be provided a better understanding and design thin film lubrication behavior. • The model of water-based liquid lubrication is proposed to prediction of its friction behavior. • EDL effect has significantly benefited for achieving ultra-low friction coefficient. • Effect of surface roughness, sliding velocity and liquid viscosity on the friction behavior is investigated and discussed. [ABSTRACT FROM AUTHOR]

In the field of elastohydrodynamic lubrication (EHL) simulations, the importance of considering non-linearities in the structure increases constantly. In most cases, the finite element method is used to discretize the non-linear continuum equations. Apart from this, model order reduction techniques are used in EHL simulations to decrease the number of unknowns and the computational time. However, the reduction methods typically used are limited to linear problems. The aim of this paper is to introduce a model order reduction technique to EHL simulations, that captures non-linear behavior. As an example, a hyperelastic 2D axially symmetric seal is reduced and coupled to the Reynolds equation. The simulation is accelerated by a factor of 10 and beyond while the non-linear properties are preserved. • Introduction of a non-linear model order reduction to EHL simulations with reduction of structural part and fluid coupling. • Comparison of reduced model with full order FEM discretization for a lubricated polymer seal in large areas of non-linearity. • Efficient generation of the reduced model by using uncoupled structural mechanical precomputations in a commercial FEM tool. • Computational speed-up of a factor of 10 and beyond due to the reduction. [ABSTRACT FROM AUTHOR]

Surface micro-texturing with slip boundary has attracted extensive attention. To accurately investigate the coupling influences of slip and micro-texturing on piston skirt lubrication performance, a comprehensive method called Reynolds-Stokes Galerkin finite element method (R-SGFEM) is proposed. Modified Reynolds equation is employed to calculate slip velocity by Navier slip model, and lubrication flow is solved by Stokes systems using the Galerkin finite element method. This method treats the slip boundary and recirculation in micro-textures skillfully, and is confirmed correct by designed experiments. The effects of slip length and geometric parameters are investigated and discussed. Results show that slip length and texture depth can reverse adjust pressure fluctuation of lubricant. The computing method of no-slip state of internal axial boundary is expressed. • R-SGFEM is proposed to handle coupling influences of slip and textured surface. • Modified Reynolds and Stokes systems calculated by GFEM are employed. • The influences of slip length and texture parameters on flowing are investigated. • A friction experiment is designed to verify that the R-SGFEM is correct. [ABSTRACT FROM AUTHOR]