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Durability and reliability have been studied for decades through intensive trial-error experimentation. However, there are numerous fields of application where the costs associated with this approach are not acceptable. In lubricated machines with severe dynamic loads, such as high-power-density engines, simulation tools offer clear advantages over intensive testing. Prototypes and multiple scenarios can be cost-effectively simulated to assess different lubricants and engine configurations. The work presented here details the study of wear based on a validated elastohydrodynamic (EHD) simulation model of the connecting rod journal bearing. This model accounts for elastic deformation through a connecting rod finite element model (FEM). In addition, multiple lubricant rheological and tribological dependences, determined by specific experimental tests, are applied in the model through their interaction with the simulation software. Correspondingly, a novel wear algorithm is proposed to predict wear depth over time evolution along a proposed wear cycle based on the typical working ranges of high-performance engines. A final assessment is presented to compare 4 different ultralow-viscosity lubricants in their protective performance under severe conditions. The results show the evolution of the wear load and wear depth over the wear cycle. This evaluation is key to describing a lubricant selection procedure for high-power-density engines. [ABSTRACT FROM AUTHOR]

Plastoelastohydrodynamic lubrication of rough surfaces (R-PEHL) is a cutting-edge area of research in interface fluid-structure coupling analysis. The existing R-PEHL model calculates the elastic-plastic deformation of rough surface by the Love equation in a semi-infinite space smooth surface, which deviates from the actual surface. Therefore, it is an innovative work to study the exact solution of elastic-plastic deformation of rough surface and its influence on the solution results of R-PEHL model. In this paper, a new contact calculation model of plastoelastohydrodynamic lubrication (PEHL) with three-dimensional (3D) rough surface is proposed by integrating numerical method of EHL and finite element method. The new model eliminates an original error introduced by the assumption of semi-infinite space in contact calculation, providing wide applicability and high accuracy. Under the given rough surfaces and working conditions, the study reveals that: (1) the oil film pressure calculated by the new model is lower than that of the smooth surface in semi-infinite space by 200–800 MPa; (2) the Mises stress of the new model is 2.5%–26.6% higher than that of the smooth surface in semi-infinite space; (3) compared with the semi-infinite space assumption, the rough surface plastic deformation of the new model is increased by 71%–173%, and the local plastic deformation singularity may appear under the semi-infinite space assumption; (4) the plastic deformation caused by the first contact cycle on the rough surface of the new model accounts for 66.7%–92.9% of the total plastic deformation, and the plastic deformation of the semi-infinite space accounts for 50%–83.3%. This study resolves the contradiction between the smooth surface assumption and the rough surface in the existing R-PEHL model, establishing a solid logic foundation for the accurate solution of R-PEHL model. [ABSTRACT FROM AUTHOR]

A spherical hinge structure is a key swivel bridge element that must be considered when evaluating friction characteristics and lubrication properties to meet the rotation requirement. Polytetrafluoroethylene (PTFE)-based spherical hinge sliders and lubrication coating have been employed for over 20 years, but with the growing tonnage of swivel bridge construction, their capacity to accommodate the required lubrication properties can be exceeded. In this manuscript, the optimal friction coefficient of the spherical hinge is obtained through the finite element analysis method. Four lubrication coatings and four spherical hinge sliders are prepared and tested through a self-developed rotation friction coefficient test, four-ball machine test, dynamic shear rheological test, and compression and shear performance test to evaluate the lubrication and friction properties of the spherical hinge structure. The results of the finite element analysis show that the optimum rotation friction coefficient of the spherical hinge structure is 0.031–1.131. The test results illustrate that the friction coefficient, wear scar diameter, maximum non-seize load, phase transition point, and thixotropic ring area of graphene lubrication coating are 0.065, 0.79 mm, 426 N, 14.6%, and 64,878 Pa/s. The graphene lubrication coating has different degrees of improvement compared with conventional polytetrafluoroethylene lubrication coating, showing more excellent lubrication properties, bearing capacity, thixotropy, and structural strength. Compressive and shear tests demonstrate that polyether ether ketone (PEEK) has good compressive and shear mechanical properties. The maximum compressive stress of PEEK is 87.7% higher than conventional PTFE, and the shear strength of PEEK is 6.07 times higher than that of PTFE. The research results can provide significantly greater wear resistance and a lower friction coefficient of the spherical hinge structure, leading to lower traction energy consumption and ensuring smooth and precise bridge rotation. [ABSTRACT FROM AUTHOR]

Lubricants are usually utilized to decrease wear, reduce friction, and release heat. Although the lubrication approximation originated from thin-film studies, it has limitations because of continuum mechanics assumptions. To overcome these limitations, for the first time, this article employs a hierarchical multiscale approach to study the frictional sliding contact considering elastohydrodynamic lubrication. This multiscale model consists of a molecular model of lubricant and a continuum model of sliding contact components. Specifically, the molecular dynamics method is used at the nanoscale to model the lubricant and analyze the friction coefficient in contacted surfaces. Through MD simulation, the effects of hydrocarbon chain lengths, temperature, and sliding velocity on a constant friction coefficient are studied in this article. The calculated friction coefficients from the molecular model are passed to the continuum model, in which the finite element method is employed to conduct stress and strain analysis of the sliding contact components. Although variations in the frictional sliding response are invariably coupled with the friction coefficients, the molecular-to-continuum hierarchical approach enables us to isolate the relative contributions from the chemical formulation of the lubricant and the temperature. This approach has further potential implications for the evaluation of tribological damage. The results demonstrate that an increase in temperature or the chain length of lubricant hydrocarbon molecules can significantly decrease the friction coefficient and, as a result, reduce contact shear stress, plastic deformation, and pile-up height. [ABSTRACT FROM AUTHOR]

This article discusses the importance of accurately simulating the contact force of clearance joints in deployable space structures. It proposes an enhanced hybrid theoretical and numerical contact force model to calculate the contact force of clearance joints. The proposed model is validated and shown to have an excellent correlation with finite element method (FEM) and a minor relative error. The article concludes that the proposed model provides a foundation for accurate impact models and is vital for the structural dynamic problems of high-precision space structures. The text also discusses various models and methods used to study contact force in engineering practice, acknowledging the limitations of the Finite Element Method (FEM) and the need for more accurate contact force models. The proposed model takes into account the effects of dimensionless hole radius and accurately calculates the contact force, maintaining a relative error within 10%. The study was funded by the National Natural Science Foundation of China. The document also includes a list of references for further research on the dynamics of mechanical systems and jointed structures. [Extracted from the article]

Purpose: The purpose of this study is to investigate the influence of surface texture on the subsurface characteristics of contact interfaces under elastohydrodynamic lubrication condition. As a typical contact form of gears and bearings, the optimization of friction characteristics at the elastohydrodynamic lubrication (EHL) interface has attracted the attention of scholars. Laser surface texturing is a feasible optimization solution, but there have been concerns about whether the surface texture of high-pair parts will affect their fatigue life. Design/methodology/approach: To examine the impact of texture preparation on the subsurface characteristics of high-pair interfaces under EHL conditions, a point contact EHL model is developed that takes into account the effect of textured surface topography. The pressure and thickness of the oil film are calculated as input parameters under different loads and entrainment velocities. The finite element method is used to simulate the impact of textures with varying diameters, densities and depths on the subsurface characteristics of the elastohydrodynamic interface. According to ISO 25178, analyze the relationship between 3D topography parameters and subsurface characteristics and study the trend of friction characteristics and subsurface characteristics based on the results of the ball on disc friction tests. Findings: The outcomes suggest that under different rotational velocity and load conditions, the textured surfaces exhibit improved friction reduction effects; however, the creation of textures can result in significant subsurface plastic deformation and local peeling. The existence of texture makes the larger stress zone in the subsurface layer closer to the surface, leading to fatigue failure near the surface. Reasonable design parameters can help enhance the attributes of the subsurface. A smaller Sa and a Str greater than 0.5 can achieve ideal subsurface properties on the textured surface. Originality/value: This paper investigates the influence of surface texture on the friction and subsurface characteristics of EHL interfaces and analyzes the impact of surface texture on interface contact performance while achieving lubrication improvement functional characteristics. The results provide theoretical support for the optimization design and functional regulation of surface texture in EHL interfaces. Peer review: The peer review history for this article is https://publons.com/publon/10.1108/ILT-10-2023-0324/ [ABSTRACT FROM AUTHOR]

The distribution of lubricant flow field inside the two‐stage transmission reducer is very complicated during splash lubrication, which is difficult to be visually simulated and analysed using traditional finite element methods (FEM). There are many problems in model processing, algorithm selection, mesh division, and computational workload. Through sufficient investigation and experimental validation based on literature, the moving particle semi‐implicit (MPS) method is proposed to study the splash lubrication characteristics of a rail vehicle reducer. Through this method, the visual simulation calculation of multiple working conditions of reducer with complex structure is realised, and the unreasonable structure of the gearbox body is optimised. The model of oil supply demand in the Hertz contact zone of gear transmission is established, and the time‐domain variation law of oil particles number in the contact zone and oil supply state are analysed. It is found that the optimised reducer model can meet the demand of oil supply under the four typical working conditions of the rail vehicle. The higher the initial oil volume is, the more sufficient the oil supply is. Compared with the working temperature conditions of 20 and 80 °C, the lubrication effect is better at 40 and 60 °C. By analysing the power loss proportion of each gear, it is found that the sum of power loss of gear 1 and gear 2 is dominant under different working conditions, reaching 76%–99.5% of the total churning power losses. [ABSTRACT FROM AUTHOR]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The anti-scuffing bearing capacity of gears is a significant issue for their service lives, especially for the cases with heavy loads or high speeds. Generally, the anti-scuffing bearing capacity is evaluated according to the surface contact temperature that can be calculated with either analytical methods or finite element analysis (FEA) methods. The analytical methods usually apply the theory of Blok to efficiently obtain the results by simplifying some actual physical conditions, which are well considered in the FEA methods with accurate results but more computation time. Conversely, a new efficient and accurate analytical method is proposed by introducing the actual lubricant film thickness and continuous heat transfer for the theory of Blok. These two physical conditions are the key issues for the calculation of the two parts of surface contact temperature, flash temperature and bulk temperature, respectively. For the calculation of flash temperature, elastohydrodynamic lubrication (EHL) is introduced to consider the lubricant film thickness for the theory of Blok, and the result is obtained by solving the Reynolds equation efficiently with the finite difference method. For the bulk temperature, the result for a contacting point on the gear tooth surface is directly obtained according the theory of Blok, and the continuous heat transfer among the adjacent contacting points is considered with Gaussian heat morphology, which can accurately construct the bulk temperature field distribution in the contact region. The proposed method is validated as in good agreement with the FEA method and with less computation time. [ABSTRACT FROM AUTHOR]

The paper mainly studied the temperature rise characteristics of under-race lubricated high-speed angular contact ball bearings under operational conditions from the perspective of dynamics. The steady-state calculation model of the bearing was established using a thermal network method in consideration of the influence factor of friction power consumption in bearing components based on a dynamic model. Following this, the steady-state change characteristics of the bearing were obtained by solving a thermal balance equation. Through this process, the influence laws of bearing rotation speed, oil supply, and environmental temperature on the friction temperature rise of the bearing were analyzed. Finally, the finite element analysis software ANSYS was employed to provide comparative verification. The results showed that the bearing temperature nonlinearly increased with the increase in inner ring rotation speed, and when it approached a certain critical value, the outer ring temperature exceeded the inner ring temperature. It had an obvious effect on controlling the temperature rise of the bearing inner ring by way of increasing the quantity and reducing the temperature of the lubricating oil supply. Comparative verification showed that the speed–temperature variation tendency from the dynamics-based thermal analysis well agrees with that of the finite element analysis. [ABSTRACT FROM AUTHOR]

The last decade has witnessed a surge of interest in artificial neural network in many different areas of scientific research. Despite the rapid expansion in the application of neural networks, few efforts have been carried out to introduce such a powerful tool into lubrication studies. Thus, this work aims to apply the physics-informed neural network (PINN) to the hydrodynamic lubrication analysis. The 2D Reynolds equation is solved. The PINN is a meshless method and does not require big data for network training compared with classical methods. Our results are consistent with those obtained by experiments and the finite element method. Hence, we envision that the PINN method will have great application potential in lubrication and bearing research. [ABSTRACT FROM AUTHOR]

The multi-lip combined seal has the advantages of multi-lip coupling, large supporting force, and can withstand high-pressure shocks. It is an irreplaceable structure for single-lip seals. However, most of the seal wear analysis focuses on the simulation method of the single-lip seal under the influence of macro factors, and very little involves the wear characteristics of multi-lip seals. In this paper, a micro numerical method is established, which combines the elastohydrodynamic lubrication theory with the modified Archard equation. The performance of a multi-lip combined seal under different working conditions is analyzed through simulation, including macro and micro factors. It is found that some of the characteristics of single-lip seals are also reflected in multi-lip seals, and there is a critical speed that makes the sealing behavior of each seal lip different. [ABSTRACT FROM AUTHOR]

In this study, we developed the electrical impedance method which simultaneously measures the thickness and breakdown ratio of oil films in elastohydrodynamic (EHD) line contacts within thrust needle roller bearings. Initially, we theoretically demonstrated that the oil film thickness and breakdown ratio can be simultaneously measured using the complex impedance that is produced when an AC voltage is applied to EHD line contacts. To verify the measurement accuracy of the electrical method, we monitored the oil film thickness of a thrust needle roller bearing and compared it with the theoretical value. The results revealed that the oil film thickness was thinner than the theoretical value immediately after starting the test, with the breakdown ratio being greater than 0 (indicating mixed lubrication); however, the breakdown ratio decreased over time, and the oil film thickness nearly matched the theoretical value one hour after starting the test, when it is believed that running-in wear is complete (i.e., breakdown ratio ≈ 0). Furthermore, following the test, after examining the race surface, we confirmed that running-in wear had indeed occurred. These results suggest that the developed method can monitor the lubrication conditions in EHD line contacts, such as those in thrust needle roller bearings, in detail. [ABSTRACT FROM AUTHOR]

Copyright of Bearing is the property of Bearing Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Due to its unique characteristic of non-contact torque transmission between its permanent magnetic rotor and conductor rotor, permanent magnet eddy current coupling (PMECC) is preferable in transmitting torque from the outside to the inside of a sealed container, which can effectively avoid the tricky problem of dynamic seals. To mix non-uniform liquid solutions or gas mixtures in sealed containers more effectively, a sinusoidal torque is also required. Thus, permanent magnet eddy current coupling with a slotted conductor is proposed in this paper, which can adaptively output sinusoidal torque under a real-time load when the input rotational speed is constant. Based on the equivalent magnetic circuit method, an analytical model for calculating torque is proposed. When establishing the equivalent magnetic circuit model of the PMECC, the radial magnetic flux leakage circuit is added to the equivalent magnetic circuit diagram, and the cross-sectional shape of the eddy current region is equivalent to an octagon, which simplifies the torque calculation process. The analytical model is verified by finite element method (FEM) simulation and experiments. According to a comparison, the peak and lowest values of output torque obtained by the experiments, the analytical model, and the FEM simulation are consistent. The output torque waveform obtained by the analytical model and FEM simulation are also consistent. [ABSTRACT FROM AUTHOR]

The tooth form is the most influential factor on the bearing capacity and operation performance of a gear drive. Tooth profiles of spur gears can be designed based on control of relative curvature of conjugate profiles, but how to conceive appropriate control strategies and appraise gear pairs accurately needs to be investigated in depth. This paper presents the control strategies through analysis of the effect mechanisms of relative curvature on the bearing capacity and lubrication performance. Evaluation approaches of the gear pairs are then proposed by establishing the analytical models (AMs). In case studies, gear pairs with optimal comprehensive performance are designed through five control strategies. The AMs for contact and bending capacity are validated with the finite element models. The effects of the control strategies are discussed through comparative analysis. Results reveal that the control strategies lead to remarkable enhancement of bearing capacity and lubrication performance. [ABSTRACT FROM AUTHOR]

Wear is one of the most common failures of hydrodynamic bearings. The main purpose of the present work was to investigate the effects of wear on lubrication performance and acquire efficient vibration signatures for fault diagnosis. In this paper, a finite element model (FEM) for a two-disk rotor supported on worn hydrodynamic bearings is presented in which the oil film force is evaluated by linear and nonlinear models. Numerical and experimental results indicate that the static and dynamic characteristics of the bearing are significantly changed by wear, leading to a drop in system critical speeds due to the deterioration of the constraint status provided by the bearings to the rotor. As the wear depth increases, the onset speed of oil whirl increases, while that of oil whip becomes lower, and large amplitudes of resonance and oil whip are more likely to be excited. More notably, all of the above vibration signatures in the y-direction are more sensitive to wear compared to those in the x-direction, which means that wear faults can be diagnosed by differences in vibration characteristics between the x- and y-directions. This research can provide a theoretical foundation and engineering guidance for the hydrodynamic bearing wear fault diagnosis. [ABSTRACT FROM AUTHOR]

A squeeze film damper (SFD) is a commonly used component in aeroengine support structures. However, eccentric SFDs are often employed in practical applications. Existing research in this field has mainly focused on simple rotor models and frequency-domain solution techniques. In this study, a rotor system tester with and without an eccentric SFD was built, and a simulation model based on the finite element method and fixed interface modal synthesis method was proposed. Then, the nonlinear dynamic response of the rotor system during run-up and run-down was studied based on the tester and simulation model. The results show that an eccentric SFD affords zero frequency and a series of double frequencies in the rotor system response. An eccentric SFD may cause the increase of the critical speed, amplitude jump, and displacement amplitude oscillation of the rotor system during run-up/run-down. Additionally, it may cause the acceleration response at the mounting bracket to significantly increase when the rotor system is suddenly accelerated. [ABSTRACT FROM AUTHOR]

In this study, the effects of surface roughness and thermal on slider bearings with turbulent fluid film were examined using the Streamline Upwind Petrov–Galerkin (SUPG)-Finite Element Method. Using the assumption that roughness is stochastic and has a Gaussian random distribution, one-dimensional transverse and longitudinal surface roughness models were taken into consideration. The texture of the surface's irregularity is changed into a regular domain for computational efficiency. To derive the modified Reynolds equation for turbulent lubrication, the Ng-Pan turbulent model is used. For all local Reynolds values, the pressure distribution of the combined effect is less than the thermal and surface roughness influences of the one-dimensional longitudinal surface roughness, which is a reduction of 16% in load-carrying capacity performance and 3% decrease in friction force, for non-parallel (w = 0.4) between the surface roughness effect and the combined effect condition, respectively. However, the pressure distribution of the thermal effect is smaller than the combined and surface roughness effects in the transverse, one-dimensional roughness model for all local Reynolds values, which is a reduction of 33% in load–carrying capacity performance and 13% decrease in friction force, for non-parallel (w = 0.4) between the surface roughness effect and the thermal effect condition, respectively. Moreover, the combined effects at various temperatures are examined. As a result, the load-carrying capacity performance is better in the case where the pad temperature is lower than the slider in both longitudinal and transverse models. The performance of a slider bearing will generally be improved by taking surface roughness and the coefficients of turbulent lubrication equations into account. Tables and figures were used to present the results. [ABSTRACT FROM AUTHOR]

As a severe plastic deformation process, equal-channel angular rolling (ECAR), which is based on equal-channel angular pressing (ECAP), can be used to develop fine-grain materials. With this in mind, in this study, the strain behavior of commercial AA-6061 aluminum alloy during the ECAR was investigated. Taguchi methodology and variance analysis were used to examine the effect of die channel angles, angular speed, and friction coefficient influence on the effective strain (ES) and standard deviation (SD) of the effective strain of ECAR. In this regard, the finite element method was exercised to determine the optimum parameters for ECAR processing to enhance the strain behavior. The results revealed that decreasing the die channel angles and increasing angular speed and friction coefficient result in better ES with 56, 23, and 17 percent effects, respectively. Based on the simulation results, the AA-6061 was exposed to the ECAR process with a low die angle, high angular speed, and no lubricant state. The microstructure results demonstrated significant grain size changes through the ECAR process, resulting in the decrease in grain size from 70 up to 20 µm. [ABSTRACT FROM AUTHOR]

Squeeze film damping is a dominant mechanism to examine the losses in the micro-opto-electro-mechanical systems. It plays an important role in understanding the dynamic performance of vertical-comb drive (VCD) microactuator. In the present paper, finite element method is used to estimate the Q factor and damping ratio at varying ambient pressures ranging from atmospheric (105 Pa) to vacuum (0.1 Pa) in COMSOL Multiphysics. The effect of ambient pressure on dynamic performance of the VCD is discussed in detail. Based on the applications, two different VCDs (VCD-L and VCD-SR) with extended micromirrors have been proposed in the current study for the manipulation of light. VCD-L having lower eigen frequency of 670 Hz can be used in laser and biomedical applications. VCD-SR with higher eigen frequency nearly 90 kHz has the potential use in a synchrotron radiation source. In addition, a parametric study is done to understand the performance of VCD for varying process parameters such as variable offset length among the comb fingers, spring dimensions, and orientation of single crystal silicon. For spring design, the von-Mises stress theory is preferred over maximum shear stress theory. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the performance improvement of journal bearing by applying the arc-shaped textures on various regions of bearing expressly full, second half and pressure increasing regions operating with and without nanoparticles in the lubricant. Design/methodology/approach: The Reynolds equation is solved numerically by using the finite element method to obtain static performance parameters such as load-carrying capacity (LCC) and coefficient of friction (COF), which are then compared with untextured bearing at eccentricity ratios of 0.2 to 0.8. Aluminum oxide (Al2O3) and copper oxide (CuO) nanoparticles additives are used, and viscosity variation due to the addition of additives in the base lubricant is computed for considering the range of temperatures 50 to 90°C at a weight fraction of 0.1 to 0.5% by using an experimentally validated regression model. Findings: The results indicate that the maximum LCC and the lower COF are found in the pressure-increasing region. A maximum increase of 34.42% is observed in the pressure-increasing region without nanoparticles, and furthermore, with the addition of Al2O3 and CuO nanoparticles in lubricants in the same region, the LCC increased to 21 and 24%, respectively. Originality/value: Designers should use optimal parameters from the present work to achieve high bearing performance. [ABSTRACT FROM AUTHOR]

Grinding residual stress (GRS) has been understood to have a great impact on the strength of gear fatigue life. However, there are lack of detailed studies on the influences in terms of mechanism and magnitude. To fill this gap, this study proposed a new method based on finite element analysis (FEA) to calculate the overall meshing stress on a gear tooth surface by including both the GRS and elastohydrodynamic lubrication (EHL) film pressure. Applying this method to a spiral bevel gear has resulted in a number of interesting results that GRS produced to reveal its mechanism of action through a full meshing cycle. The acquired understanding would be useful for development of manufacturing processes. [ABSTRACT FROM AUTHOR]

This work presents a high-fidelity lubricated transmission model, coupling Flexible MultiBody (FMB) dynamics with ElastoHydrodynamic Lubrication (EHL). The EHL model is discretised with a coupled finite element approach, in contrast with the more iteration-intensive finite difference approach using relaxation schemes. The finite element method yields nonlinear system matrices, requiring matrix reevaluation in each iteration. To mitigate computational overhead, tensorisation replaces integrals to compute the system matrices with tensor-vector multiplications. Furthermore, this work optimises the use of the discretised EHL model by scaling and reusing it across different contact conditions. Coupling of the contact force resulting from the EHL model with the rigid body displacement resulting from the FMB model enables the computation of steady-state equilibrium for a given torque applied to the gear pair. However, local deformations should be excluded from the FMB model to ensure proper coupling with the EHL model, which exclusively computes local deformation within the contact zone. Newly developed global line contact attachment modes allow the FMB model to exclusively calculate global tooth bending in response to a given contact force. • Elastohydrodynamic lubrication coupled with flexible multibody dynamics. • Finite element method to discretise all physical domains. • Global line contact attachment modes to exclude local deformation from gear pair. • Equivalent finite element model approximating local deformation from gear pair. • Scalable, tensorised finite element model discretising elastohydrodynamic lubrication. [ABSTRACT FROM AUTHOR]

The selection of appropriate geometrical characteristics of enclosure has salient influence on performance of different thermal engineering processes and devices like microelectronics, heat exchangers, power engines, boilers, solar collectors, nuclear reactors and so forth. Specifically, the triangular cavity of different aspect ratios are used to obtain multi-objective optimization and gaining excellence in thermal performance of micro channels. Subsequently, the installation of cold cylinder in a triangular enclosure are extensively used to remove high energy dissipation in micro heat sinks and heat exchangers. So, the purpose of current effort is to probe thermal characteristics of power-law liquid describing features of shear thinning and thickening materials containing applications in lubrication and polymer industry. Heat transfer is generated by the consideration of natural convection process generated due to consideration of cold walls and cylinder with provision of non-uniform heating at base wall. No-slip velocity conditions are supposed at all walls of isosceles triangle cavity. Solution of attained differential system is simulated by capitalizing finite element based COMSOL Multiphysics software (Version 5.6). Domain discretization by distributing into triangular and rectangular elements is conceded and equations at element levels are discretized by executing weak formulation. The validation of adopted numerical procedure is established by making agreement with formerly available works in both statistical and graphical approaches. Streamlines and isotherms are plotted and discussed against various parametric regimes. This study reveals noticeable influence of involved physical parameters on average and local heat flux coefficients, kinetic energy and cutlines against involved physical parameters are also evaluated. It is inferred thorough the analysis that with uplift in Rayleigh number (R a) produces enrichment in kinetic energy and local heat transfer coefficients whereas reverse pattern is depicted against power-law index. (n). [ABSTRACT FROM AUTHOR]

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

Copyright of Lubrication Engineering (0254-0150) is the property of Editorial Office of LUBRICATION ENGINEERING and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to predict the steady-state temperature of plastic gears under grease lubrication conditions, a finite element numerical model of plastic gear operating temperature field was established based on the temperature-modulus effect and the friction heat flux-hysteresis heat flux multi heat source effect. The distribution of plastic gear steady-state temperature field and the influences of load and speed levels on steady-state temperature were studied. The results show that the temperature of steady-state temperature field decreases gradually along the normal direction of the tooth profiles, and the temperature in the depth of 0.5 mm in the inner normal direction is about 90% of the surface temperature, and the steady-state temperature increases with the increasing of loads or speeds gradually. And the operating temperature tests of POM-POM gear pairs were carried out under grease lubrication conditions and the test results are in good agreement with the simulation ones. This study may pave way to the transmission design of heavy-loading plastic gears. [ABSTRACT FROM AUTHOR]

In this work, effects of sealing temperature, time, pressure, as well as sealant thickness and viscosity on squeeze out flow (SOF) in heat sealing were examined. A new image analysis approach is presented to quantify SOF in heat sealing. It was found that increasing temperature or pressure could improve SOF but only in thick 130 μm sealants and reducing the sealant thickness to 50 μm suppressed SOF. Reducing viscosity in 50 μm sealant films was also found to improve SOF only at high‐sealing pressure and long sealing times. Three approaches were used to model SOF: analytical one‐dimensional model, numerical one‐dimensional model using finite difference method (FDM), (iii) Numerical two‐dimensional model using finite element analysis. Heat transfer was modeled, and it was shown that heat transfer induces a delay in SOF. When the FDM and the heat transfer models were combined, a good agreement between experimental and model prediction could be obtained. In addition, modeling results showed that SOF occurred in shear rates within the transition region between the Newtonian and Power‐law regions. This indicates the importance of considering the Carreau‐Yasuda fluid behavior in modeling of SOF. [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 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]

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]

• A comprehensive stiffness model of intermediate bearing is presented. • A reduced model of dual rotor-bearing-casing coupling system is developed. • The effects of typical parameters on the vibration of the system are discussed. • The mechanism of the comprehensive stiffness and system vibration is revealed. This paper focuses on the vibrational properties of a dual rotor-casing coupled system with nonlinear clearance in the intermediate bearing, considering both the oil film stiffness and Hertzian contact stiffness between rolling elements and raceways. A comprehensive stiffness model for the intermediate bearing has been developed based on elastohydrodynamic lubrication (EHL) and Hertz contact theory. Subsequently, a dynamical model of the dual rotor-bearing-casing system is established using the finite element method, thereby verifying the feasibility of simulating the casing with beam elements. The dimensionality of the system equation is reduced using the fixed-interface component mode synthesis (CMS) method, and the resulting reduced-dimensionality equation is solved using the improved Newmark- β method. The effects of casing support, rotational speed, and radial clearance on the vibration characteristics of the system are investigated. Then, the comprehensive stiffness and coupled vibration characteristics of the system are analyzed to elucidate its intrinsic mechanism. Finally, the contact characteristics within the intermediate bearing under dynamic load are also studied. The results indicate that the support stiffness of the casing has a more significant impact on the second resonance caused by both the inner and outer rotors. The system is prone to experiencing varying compliance (VC) resonance at low rotational speeds. The excessive bearing clearance leads to complex vibrational characteristics of the system, making it challenging to predict its motion. The impact of minor changes in stiffness on system vibration is small when the comprehensive stiffness is large. At this time, the limited effect of oil film stiffness allows it to be disregarded in terms of comprehensive stiffness. Furthermore, the speed significantly influences the contact characteristics within the intermediate bearing under the unbalanced force of the rotor and gravity. [ABSTRACT FROM AUTHOR]

Design of new tooth shapes have been the focus of gear researchers aimed at overcoming the defects of involute gears. For the spur gear drive with curved path of contact, normal contact loads between engaged teeth vary in direction and magnitude, which makes it difficult to build the dynamics model of the gear drive. The current models treat the curved path of contact as an equivalent straight line without considering directional variation of normal tooth loads. This paper presents an efficient tribo-dynamics integrated model for this type of gear drive including effects of alternate meshing of single-double tooth pairs. Directional variation of normal tooth loads is considered by invoking geometric parameters of meshing points instantly. And the transient lubrication properties in mixed elastohydrodynamic lubrication are also taken into account without extensive numerical simulations. The dynamics model of a gear drive with constant relative curvature (CRC gear drive) is given as an example. The model is verified with the results of the finite element model. The results indicate that the CRC gear drive has advantages over the involute gear drive in terms of lubrication performance and mechanical efficiency. The proposed model can be used to analyze dynamics features of gear drives with curved path of contact comprehensively. [ABSTRACT FROM AUTHOR]

Calculating the flow of a film of lubricant between rough surfaces by solving the Reynolds equation requires a very fine mesh to capture the details of the topography and is thus very time consuming. In the present paper, a multiscale method is proposed. The domain is divided into an appropriate number of subdomains on which deterministic simulations are performed. The results of this microscale solution are coupled at the macroscale by employing a macromesh on which a mass flow balance is implemented. This method has already been successfully applied to liquid lubrication and is extended to gas lubrication. A significant reduction in computation time is obtained compared to a fully deterministic solution. The calculation of the load is also accurate. [ABSTRACT FROM AUTHOR]

The plasto‐elastohydrodynamic lubrication (PEHL) model of the greased ellipsoid contact is established and solved numerically. In doing so, the increment theory of the plastic surface is adopted to solve the residual deformation, and the fast Fourier transform (FFT) method is employed to accelerate the deformation and stress calculations. Meanwhile, the effeteness of the PEHL model is verified through the residual stress experiment and finite element method. It is found that the plastic behaviour results in a reduction in the maximum grease film pressure. Under heavy load conditions, the grease with large rheology index, large tangential modulus or high entrainment speed of the lubricant is helpful to reducing the maximum residual deformation and maximum residual stress of the greased ellipsoid contact. [ABSTRACT FROM AUTHOR]

Purpose: In this study, the dynamic characteristics of the water-lubricated rubber bearing considering asperity contact are numerically studied, including water-film stiffness and damping coefficients and plastic-elastic contact stiffness coefficient. Design/methodology/approach: The Kogut-Etsion elastic-plastic contact model is applied to calculate the contact stiffness coefficient at the bearing-bush interface and the perturbed method is used to calculate the stiffness and damping coefficients of water-film. In addition, the rubber deformation is determined by the finite element method (FEM) during the simulation. Parametric studies are conducted to assess the effects of the radial clearance, rubber thickness and elastic modulus on the dynamic characteristic of water-lubricated rubber bearing. Findings: Numerical results indicate that stiffness and damping coefficients of water film and the contact stiffness of asperity are increased with the decreasing of the radial clearance and the dynamic coefficients are less sensitive to the rubber thickness compared with the elastic modulus of rubber. Furthermore, due to the existed groove, a sudden change of the water film direct stiffness and damping coefficients is observed when the eccentricity ratio ranges from 0.6 to 1.0. Originality/value: It is expected this study can provide more information to establish a dynamic equation of water-lubricated rubber bearings exposed to mixed lubrication conditions. [ABSTRACT FROM AUTHOR]

In recent years, porous bearings have been increasingly used in various industrial applications because they are less noisy, have good precision, and are relatively maintenance free. In this article, the numerical analysis of a conical porous hybrid journal bearing system (CPHJBS) has been carried out. The interactive effects of permeability parameter, semi cone angle, and pseudoplastic (shear thinning) lubricant behavior on the performance of CPHJBS have been theoretically investigated. The governing Reynolds equation for a non-Newtonian lubricant in the bearing clearance space of CPHJBS is solved using a finite element model. Findings of this study indicate that the CPHJBS operating with a pseudoplastic lubricant offers a higher value of stability threshold speed margin ( ω ¯ t h ) for the lower value of semi cone angle (γ = 10 0 ) and lower value of permeability parameter (Ψ = 0.005). [ABSTRACT FROM AUTHOR]

In this paper, electret based vibration energy harvesters are designed and fabricated with perforated electrode based on MEMS technology. Through-holes are distributed on the fixed electrode in the device to optimize the energy harvesting process. The effect of the holes on the output power of the device are analyzed and discussed both in the finite element method (FEM) simulation and the experiments. It can be noticed that the through-holes can effectively lower the squeeze-film air damping force on the moveable proof mass at the atmosphere. Therefore, the energy loss due to the air damping could be reduced, and the output power of the device increases. The effects of the hole diameter and numbers on the output power of our device are also investigated in detail. By optimizing the configuration of the holes, the perforated device with the hole diameter of 400 μm and depth of 100 μm exhibits the highest power output at the low acceleration of 1.84 m/s2, which proves promising application for self-powered electronics in the future. [2020-0380] [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]

Based on the combination of elastohydrodynamic lubrication and contact deformation theory, i.e. fluid-solid coupling theory, and considering the surface roughness of stator and rotor, a three-degree-of-freedom vibration model of spherical bearings with spiral grooves is established. The finite difference method is used to calculate and analyze the distribution of lubricating film pressure, film thickness and the influence of eccentricity of rotor on film pressure. Combining the stiffness of lubricating oil film with the finite element method, the displacement, stator vibration speed, acceleration and displacement of lubricating oil film are calculated from the angle of elastic boundary, and compared with the slotless structure. The results show that the bearing capacity of lubricating oil film of spherical bearing is improved and the stability of continuous oil film is improved by adding spiral groove. Secondly, the vibration characteristics of stator and rotor with spiral groove structure are more in line with the viscoelastic periodic distribution law. The vibration stability of the system is improved. In order to further optimize the vibration stability of the motor, the theoretical basis is provided. [ABSTRACT FROM AUTHOR]

An effective way to improve the combined performance of mechanical seals is to optimize their surface textures using multi-objective optimization method. For compatibility with the multi-objective optimization algorithm, the theoretical performance of a mechanical seal is often determined using the finitedifference method (FDM). However, compared with the finite-volume method (FVM) and finite-element method (FEM), FDM is weaker for dealing with the issue of discontinuous film thickness for a textured surface. In the present study, the thermo-hydrodynamic lubrication model of a mechanical seal is modified by means of an equivalent-thickness treatment, and the accuracy of the modified lubrication model is assessed by comparing its predictions for film pressure and temperature with published FVM and FEM results, showing that the equivalent-thickness lubrication model is effective for addressing the issue of discontinuous film thickness. The present work is important in that it improves the simulation accuracy of multi-objective optimization for textured mechanical seals. [ABSTRACT FROM AUTHOR]

Hybrid steel-composite gears, which combine steel teeth with a fiber-reinforced polymer composite core, are a rapidly emerging technology for weight reduction in aerospace drivetrain systems. However, power transmission gears-and especially the requirement of rotorcraft gearboxes to operate under loss of lubrication-are a very challenging application for composite materials, due to the combination of mechanical and thermal loads. In this work, composite materials, including newly developed hybrid laminates featuring multiple grades of carbon fiber, are fabricated. Mechanical and thermal testing, along with ply-level finite element analysis, are employed to assess the suitability of these composite materials for hybrid aerospace gear applications. Particular focus is given to high-temperature epoxy and bismaleimide resins and to hybrid laminates reinforced by multiple grades of carbon fiber. This hybrid drivetrain technology would manifest significant weight reductions without compromising gear performance. [ABSTRACT FROM AUTHOR]

With the increasing challenges of climate change and scarce resources, the development of sustainable and energy-efficient technical systems is becoming increasingly important. In many applications, the friction losses occurring in contacts have a decisive influence on the overall efficiency. At this point, tribological contact optimization can make an important contribution to increasing the efficiency of technical systems. However, improvements are often associated with a considerable experimental effort. To reduce the development time, additional simulation models can be applied to predict the tribological behavior. This requires the closest possible approximation of the real contact within a numerical model. This paper presents a simulation approach for the time-dependent simulation of a cam–tappet contact. The simulation uses realistic operating conditions as they arise in the valve train of internal combustion engines. The influence of edge effects on the friction behavior is considered by a scaled calculation area and the influence of the surface roughness is investigated using stochastic asperity models. It is shown that the tribological behavior within the contact strongly depends on the surface properties and the load spectrum used. In addition, edge effects on the sides of the contact area have a clear influence on the pressure and film thickness distribution.

The actual contact point of a spiral bevel gear pair deviates from the theoretical contact point due to the gear deformation caused by the load. However, changes in meshing characteristics due to the migration of contact points are often ignored in previous studies on the elastohydrodynamic lubrication (EHL) analysis of spiral bevel gears. The purpose of this article is to analyze the impact of contact point migration on the results of EHL analysis. Loaded tooth contact analysis (LTCA) based on the finite element method is applied to determine the loaded contact point of the meshing tooth pair. Then, the osculating paraboloids at this point are extracted from the gear tooth surface geometry. The geometric and kinematic parameters for EHL simulation are determined according to the differential geometry theory. Numerical solutions to the Newtonian isothermal EHL of a spiral bevel gear pair at the migrated and theoretical contact points are compared to quantify the error involved in neglecting the contact point adjustment. The results show that under heavy-loaded conditions, the actual contact point of the deformed gear pair at a given pinion (gear) roll angle is different from the theoretical contact point considerably, and so do the meshing parameters. EHL analysis of spiral bevel gears under significant load using theoretical meshing parameters will result in obvious errors, especially in the prediction of film thickness. [ABSTRACT FROM AUTHOR]

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