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Artykuły w czasopismach na temat "Elastohydrodynamic (EHD) coupling"
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Xing, Hui, Hui Zhang, Qili Wu i Shu Lin Duan. "Full Shafting-Based Elastohydrodynamic Lubrication Simulation for Main Bearings of Marine Diesel Engine". Advanced Materials Research 479-481 (luty 2012): 1119–23. http://dx.doi.org/10.4028/www.scientific.net/amr.479-481.1119.
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To predict and analyze accurately the lubrication characteristics and its influencing factors of main bearing for large low-speed two-stroke marine diesel engine, based on EHD lubrication model of dynamically loaded bearing, coupling simulation between EHD and MBD for main bearing of marine diesel engine was carried out. Systemic models were established separately considering the independent crankshaft of diesel engine and the full shafting of propulsion power plant. Main bearing load, peak oil film pressure, oil film pressure distribution, MOFT and orbital path in one working cycle under rated working conditions were investigated, and simulation results were compared based on both models. The results show that, if the impact of full shafting was considered, the lubrication characteristics of No.8 main bearing changed significantly, the lubrication characteristics of other main bearings were similar as the simulation results of the independent crankshaft model.
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Farah, Samatar Omar, Mohamed Guessasma i Emmanuel Bellenger. "Digital twin by DEM for ball bearing operating under EHD conditions". Mechanics & Industry 21, nr 5 (2020): 506. http://dx.doi.org/10.1051/meca/2020022.
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In this paper we investigate the elastohydrodynamic (EHD) lubrication in ball bearings by means of a digital twin. Based on an original description involving the discrete element method (DEM), the digital twin integrates all the components of ball bearings and enables realistic behavior under mechanical loading and kinematic conditions. In order to check the standard indicators recommended by most ball bearing manufactures, a stiffness model for elliptical Hertzian contact and an improved EHD formulation for lubricated contact are implemented in the numerical tool. In addition, we have introduced into the discrete modeling an electrical capacitance model correlated to the fluid film thickness and the contact pressure. The numerical predictions of lubricant film capacitance provided by digital twin are in good accordance, both qualitatively and quantitatively, with the experimental data available in the literature. The coupling of the discrete method with the electrical approach enables efficient solutions to be provided in terms of lubrication regime in relation to the lubricant properties to optimize the bearing lifetime.
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Wei, Lidui, Haijun Wei, Shulin Duan i Yu Zhang. "An EHD-mixed lubrication analysis of main bearings for diesel engine based on coupling between flexible whole engine block and crankshaft". Industrial Lubrication and Tribology 67, nr 2 (9.03.2015): 150–58. http://dx.doi.org/10.1108/ilt-08-2013-0088.
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Purpose – The purpose of this paper is to develop a good calculation model to accurately predict the lubrication characteristic of main bearings of diesel engine and improve the service life. Design/methodology/approach – Based on the coupling of the whole flexible engine block and the flexible crankshaft reduced by the Component Mode Synthesis (CMS) method, considering mass-conserving boundary conditions, the average flow model equation and Greenwood/Tripp asperity contact theory, an elastohydrodynamic (EHD)-mixed lubrication model of the main bearings for the diesel engine is developed and researched with the finite volume method and the finite element method. Findings – Obviously, the mixed lubrication of bearings is normal, while full hydrodynamic lubrication is transient. The results show that under the whole flexible block model, maximum oil film pressure, maximum asperity contact pressure and radial shell deformation decrease, while minimum oil film thickness increases. Oil flow over edge decreases, and so does friction loss. Therefore, coordination deformation ability of whole engine block is favorable to mean load. In the whole block model, friction contact happens on both upper shell and lower shell positions. In addition, average oil film fill ratio at the key position becomes smaller in the whole engine block model, and consequently increases the chances of cavitations erosion more. So, wearing resistance of both upper and lower shells and anti-cavitations erosion ability must be enhanced simultaneously. Originality/value – Based on the coupling of the whole flexible engine block and the flexible crankshaft reduced by the CMS method, considering mass-conserving boundary conditions, the average flow model equation and Greenwood/Tripp asperity contact theory, an EHD-mixed lubrication model of the main bearings for the diesel engine is built, which can predict the lubrication of journal bearings more accurately.
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Habchi, W. "Coupling Strategies for Finite Element Modeling of Thermal Elastohydrodynamic Lubrication Problems". Journal of Tribology 139, nr 4 (4.04.2017). http://dx.doi.org/10.1115/1.4034956.
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This paper investigates coupling strategies for finite element modeling (FEM) of thermal elastohydrodynamic lubrication (TEHL) problems. The TEHL problem involves a strong coupling between several physics: solid mechanics, fluid mechanics, and heat transfer. Customarily, this problem is split into two parts (elastohydrodynamic (EHD) and thermal) and the two problems are solved separately while an iterative procedure is established between their respective solutions. This weak coupling strategy involves a loss of information, as each problem is not made intimately aware of the evolution of the other problem's solution during the resolution procedure. This typically leads to slow convergence rates. The current work offers a full coupling strategy for the TEHL problem, i.e., both the EHD and thermal parts are solved simultaneously in a monolithic system. The system of equations is generated from a finite element discretization of the governing field variables: hydrodynamic pressure, solids elastic deformation, and temperature. The full coupling strategy prevents any loss of information during the resolution procedure leading to very fast convergence rates (solution is attained within a few iterations only). The performance of the full coupling strategy is compared to that of different weak coupling strategies. Out of simplicity, only steady-state line contacts are considered in this work. Nevertheless, the proposed methodology, results, and findings are of a general nature and may be extrapolated to circular or elliptical contacts under steady-state or transient conditions.
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Hassan, Mohammad Fuad, Sevki Cesmeci, Karthik Reddy Lyathakula i Hanping Xu. "DESIGN, MODELING, AND TESTING OF A NOVEL ELASTOHYDRODYNAMIC SEAL FOR SUPERCRITICAL CO2 POWER CYCLES". Journal of Tribology, 2.01.2025, 1–33. https://doi.org/10.1115/1.4067553.
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Abstract Effective sealing is a critical challenge in achieving the full potential of supercritical carbon dioxide (sCO2) power generation. Leakages from sCO2 cycles can reduce efficiency by up to 0.65%, underscoring the need for advanced sealing solutions. This study explores an elastohydrodynamic (EHD) seal as a promising option, designed to minimize leakage and wear under sCO2 conditions. A fluid-solid coupling model, based on finite element analysis and computational fluid dynamics, was developed and experimentally validated. Proof-of-concept tests were conducted on a 2-inch static shaft seal with pressures up to 1.2 MPa, using PTFE as the seal material. Both simulations and experiments revealed a quadratic leakage trend: leakage initially increased with pressure, peaked at about 6 g/s, and then declined to approximately 1.5 g/s at maximum pressure. The model proved efficient, converging in just 2 seconds, while providing insights into leakage rates, seal deformation, clearance pressure, and stress. In addition, a modified model was provided, which converged in less than 20 seconds with added accuracy. A parametric analysis further demonstrated the impact of key design factors on leakage, with results aligning with physical expectations. The proposed models could serve as a valuable design tool for EHD seals.
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Peterson, Wyatt, Thomas Russell, Farshid Sadeghi i Michael Tekletsion Berhan. "A Strongly Coupled Finite Difference Method–Finite Element Method Model for Two-Dimensional Elastohydrodynamically Lubricated Contact". Journal of Tribology 142, nr 5 (19.02.2020). http://dx.doi.org/10.1115/1.4045816.
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Abstract This paper presents a partitioned strongly coupled fluid–solid interaction (FSI) model to solve the 2D elastohydrodynamic (EHD) lubrication problem. The FSI model passes information between a control volume finite-difference discretized Reynolds equation and abaqus finite element (fe) software to solve for the fluid pressure and elastic deformation within heavily loaded lubricated contacts. Pressure and film thickness results obtained from the FSI model under a variety of load and speed conditions were corroborated with open published results. The results are in excellent agreement. Details of the model developed for this investigation are presented with a focus on the simultaneous solution of the Reynolds equation, load balance, and the coupling of the solid abaqus fe with the finite-difference fluid (Reynolds) model. The coupled FSI model developed for this investigation provides the critical venue needed to investigate many important tribological phenomena such as plasticity, subsurface stress, and damage. The current FSI model was used to explore and demonstrate the efficacy of the model to investigate the effects of microstructure inhomogeneity, material fatigue damage, and surface features on heavily loaded lubricated contacts as can be found in a wide range of industrial, automotive, and aeronautical drive systems.
Rozprawy doktorskie na temat "Elastohydrodynamic (EHD) coupling"
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Zhang, Hao. "Écoulement des fluides et déformation interfaciale : nano-rhéologie et force de portance". Electronic Thesis or Diss., Bordeaux, 2025. http://www.theses.fr/2025BORD0027.
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Cette thèse examine l'interaction entre l'écoulement des fluides et la déformation interfaciale à l'aide de la Microscopie à Force Atomique (AFM). Tout d'abord, l'AFM a été utilisé pour explorer les fluctuations capillaires thermiques résonantes (RTCF) des surfaces de bulles et de gouttes, permettant ainsi de mesurer l'élasticité de surface et la viscosité en volume «bulk » aux interfaces air/eau chargées en tensioactifs et dans les solutions polymères. Ces mesures ont élargi la plage de fréquence pour les investigations rhéologiques, surmontant les limitations des rhéomètres classiques. Ensuite, nous avons introduit une méthode sans contact pour évaluer les propriétés mécaniques des cellules vivantes, basée sur l'interaction élastohydrodynamique (EHD) entre les vibrations thermiques du levier AFM et les déformations des cellules. Cette méthode a permis de déterminer avec précision le module élastique d'une cellule vivante à différentes fréquences. Enfin, nous avons réalisé la première mesure directe et quantitative de la force de portance agissant sur une sphère se déplaçant le long d'une interface liquide-liquide. Cette force, résultant du couplage entre l'écoulement visqueux et la déformation capillaire de l'interface, a été mesurée en fonction de la distance entre la sphère et l'interface à l'aide de l'AFM. Nous avons étudié diverses interfaces liquides, fréquences de travail, vitesses de glissement et deux rayons de sphère différents. Ces résultats fournissent des informations précieuses sur les phénomènes interfaciaux et améliorent la compréhension des interactions entre l’écoulement des fluides et les interfaces mollesThis thesis investigates the interplay between fluid flow and interfacial deformation using Atomic Force Microscopy (AFM). First, AFM was employed to explore the resonant thermal capillary fluctuations (RTCF) of bubble and drop surfaces, enabling the measurement of surface elasticity and bulk viscosity in surfactant-laden air/water interfaces and polymer solutions. These measurements extended the frequency range for rheological investigations, effectively overcoming the limitations of classical rheometers.Next, we introduced a non-contact method to assess the mechanical properties of living cells based on the elastohydrodynamic (EHD) interaction between the thermal vibrations of the AFM cantilever and the cell deformations. This method enabled the precise determination of the elastic modulus of a living cell for different frequencies.Finally, we conducted the first direct and quantitative measurement of the lift force acting on a sphere moving along a liquid-liquid interface. This force, arising from the coupling between viscous flow and capillary deformation of the interface, was measured as a function of the distance between the sphere and the interface using an atomic force microscope (AFM). We investigated various liquid interfaces, working frequencies, sliding velocities, and two different sphere radii. The findings provide valuable insights into interfacial phenomena and enhance the understanding of interactions between fluid flow and soft interfaces
Streszczenia konferencji na temat "Elastohydrodynamic (EHD) coupling"
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Hayne, Cole, Ali Akbor Topu, Mohammad Fuad Hassan, George Sercer, Hanping Xu i Sevki Cesmeci. "Modeling of a Novel Elastohydrodynamic Seal for sCO2 Power Cycles With Experimental Verification". W ASME 2024 Power Conference. American Society of Mechanical Engineers, 2024. http://dx.doi.org/10.1115/power2024-138553.
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Abstract Effective sealing remains to be one of the technological challenges at the subcomponent level for supercritical carbon dioxide (sCO2) power generation to be practical. Leakages from sCO2 power cycles can lower cycle efficiencies by up to 0.65%. Therefore, to fully harness the benefits of sCO2 power generation; this leakage must be addressed through engineering of efficient sealing technology. To this end, we propose an elastohydrodynamic (EHD) seal as a potentially effective solution that can operate at sCO2 conditions with minimal leakage and wear. In this study, an FEA/CFD based fluid-solid coupling modeling approach was presented with experimental verification. For proof-of-concept purposes, the tests were performed on a 2” static shaft seal and with pressures up to 1.2 MPa using PTFE as the seal material. Both the test and simulation results exhibited a quadratic leakage trend. The leakage rate first increased with increasing pressures, then made its peak of about 6 g/s in mid-pressure range, then started to drop to lower values of about 1.5 g/s as the pressure reached the maximum operating pressure. The proposed model was demonstrated to be a quick and handy tool to determine the design space of the EHD seals with minimal computational time. The simulation was converged in only 2 s. Yet, the proposed model could provide data regarding the leakage rate, seal deformation, pressure in the clearance, and stress on the seal, and thus, could serve as a design guide for the EHD seals.
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Meunier, C., D. Mazuyer, P. Vergne, M. El Fassi i J. Obiols. "Correlation Between Film Forming Ability and Rheological Properties of New and Aged Lowsaps Automotive Lubricants". W ASME/STLE 2007 International Joint Tribology Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/ijtc2007-44277.
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The rheological behavior of fresh and aged diesel LowSaps 5W30 lubricant, is studied with both ElastoHydroDynamic tribometer, and low shear and high shear viscometers. The evolution of the film thickness in EHD contact, that varies between 1nm and 150 nm, displays two types of lubrication process according to rolling speed. On the one hand, a classical EHD behaviour, controlled by viscosity, may be observed beyond 35 nm with a significant shear thinning effect in the range of temperatures. On the other hand, below 35nm, a steep drop of film thickness indicates the unability of the viscosity improver polymer to form a thin film within the contact. These observations are closely related to rheological measurements carried out in a shear rate range from 10s−1 to 107s−1, and temperatures between 25°C and 150°C. Indeed, analysis of two rheological parameters, polymer relaxation time and hydrodynamic radius, may explain non newtonian and thin film effects in the EHD experiments. A rheological modelling based on the Cross model is developed to calculate these parameters. Then, the principle of time-temperature equivalence is used to map the characteristics of lubricants. Finally, the approach coupling EHD tribometer\Viscometer is applied to lubricants which have been degraded during a light duty diesel engine test.
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Glovnea, Romeo P., i Hugh A. Spikes. "EHD Contacts in Low-Amplitude Oscillatory Motion". W World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63226.
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In some practical applications such as spline couplings or constant velocity joints, the machine components are subjected to a low amplitude lateral motion, very often oscillatory, so that conditions for a full elastohydrodynamic film to form are not completely realized. The questions that arise are what mechanism of lubricating takes place in such contacts and what is the influence of working parameters and lubricant properties on such mechanism? In the present study, a EHD contact formed between a flat and a ball is subjected to oscillatory-motion of amplitude ranging between one half to one contact diameter. High speed ultra-thin film interferometry is used to monitor the gap between the two solid surfaces. The influence of parameters such as load, frequency and amplitude of motion are investigated.
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Barbieri, Marco, i Francesco Pellicano. "Coupling of Two EHL-Lubricated Contacts in Gear Dynamics". W STLE/ASME 2010 International Joint Tribology Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ijtc2010-41237.
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In this paper, the effect of vibrations on the elastohydrodynamical lubrication in spur gear pairs will be described. The relevance of inertial effects on film fluid lubrication is clarified by means of comparisons with static formulations. The multilevel technique is used to solve the transient EHL problem for elliptical contacts. Coupling with load balance equation and with different equations of motion is studied. A new model describing the dynamic behavior of two coupled transient EHL elliptical contacts is developed and applied to characterize the dynamics of a spur gear pair.
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Mastrandrea, Luca Nicolò, Matteo Giacopini, Daniele Dini i Enrico Bertocchi. "Elastohydrodynamic Analysis of the Conrod Small-End of a High Performance Motorbike Engine via a Mass Conserving Cavitation Algorithm". W ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51603.
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In this contribution a complementarity formulation for the solution of EHL problem in presence of cavitation is employed in order to investigate the tribological behavior of the conrod small-end of a high performance motorbike engine. The influence of different physical and geometrical parameters is discussed. In particular, the clearance between the conrod small-end and the piston pin, the lubricant physical properties, the surface roughness and the stiffness of the piston pin are investigated, thus providing preliminary guidelines for the correct design of the coupling. Due to the negligible influence of the transversal forces acting on the conrod small-end and of the relative sliding speed between the mating surfaces, a two symmetrical model of the assembly is prepared and results are compared with those obtained adopting a simply symmetrical model.
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Qasim, Syed Adnan, i M. Afzaal Malik. "Effects of High Initial Engine Start Up Speeds in Isothermal Fluid Flow and Piston Skirts EHL". W ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-62566.
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In the medium and high speed normal engine operating conditions a fully established elastohydrodynamic lubricating (EHL) film between the piston skirts and cylinder liner surfaces reduces friction and prevents adhesive wear. In the initial engine start up the absence of EHL film causes wear of piston skirts, especially at high speeds. In a few initial cold engine start up cycles, a highly efficient cooling system may not let the temperature to rise significantly and affect the viscosity and other characteristics of a lubricant. In view of the vulnerability of piston skirts to adhesive wear at high initial engine start up speeds, the hydrodynamic and EHL of piston skirts is modeled numerically. A 2-D Reynolds equation is solved by coupling the secondary piston motion and using a finite difference scheme. Transient hydrodynamic film thickness profiles are generated at a relatively high engine start up speed. In the EHL regime, the profiles of rising hydrodynamic pressures and film thicknesses are predicted by using the inverse solution technique in fully flooded conditions. The study is extended to a range of high engine start up speeds while using a fairly viscous engine lubricant. Numerical simulations show significant changes in the piston eccentricities and film thickness profiles in the hydrodynamic and EHL regimes at different start up speeds. Such variations alter the hydrodynamic and EHL pressures and visibly affect the load carrying capacity of the lubricant. This study suggests to optimize the high engine start up speed for the given viscosity grade engine lubricant when considering the vulnerability of skirts and liner surfaces to adhesive wear in the initial engine start up.