Relevant bibliographies by topics / Isoviscose

Contents

  1. Journal articles
  2. Dissertations / Theses
  3. Book chapters
  4. Conference papers

Academic literature on the topic 'Isoviscose'

Author: Grafiati
Published: 4 June 2021
Last updated: 1 February 2022

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Journal articles on the topic "Isoviscose"

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Rajagopalan, V., P. S. Goyal, B. S. Valaulikar, and B. A. Dasannacharya. "SANS by isoviscous micellar solutions." Physica B: Condensed Matter 180-181 (June 1992): 525–27. http://dx.doi.org/10.1016/0921-4526(92)90812-7.

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Thorey, Clement, and Chloé Michaut. "Elastic-plated gravity currents with a temperature-dependent viscosity." Journal of Fluid Mechanics 805 (September 16, 2016): 88–117. http://dx.doi.org/10.1017/jfm.2016.538.

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We develop a set of equations to explore the behaviour of cooling elastic-plated gravity currents for constant influx conditions. In particular, we introduce a temperature-dependent viscosity to couple the flow thermal structure with the velocity field. We show that this coupling results in important deviations from the isoviscous case. In particular, the bending and gravity asymptotic regimes, characteristic of the isoviscous case, both split into three different thermal phases: a first ‘hot’ isoviscous phase, a second phase where the spreading rate drastically decreases and the flow thickens and a third ‘cold’ isoviscous phase. The viscosity that controls the spreading rate differs in both asymptotic regimes; it is the average viscosity of a small peeling region at the current tip in the bending regime and the average flow viscosity in the gravity regime. In both regimes, we characterize the evolution of the thermal anomaly and determine the time scale of the phase changes in terms of the Péclet number and of the viscosity contrast. Finally, we show that the evolution with bending and gravity can result in six different evolution scenarios depending on the combination of dimensionless numbers considered. We provide a phase diagram which summarizes them as a function of the flow Péclet number and viscosity contrast.
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Shahrivar, K., E. M. Ortigosa-Moya, R. Hidalgo-Alvarez, and J. de Vicente. "Isoviscous elastohydrodynamic lubrication of inelastic Non-Newtonian fluids." Tribology International 140 (December 2019): 105707. http://dx.doi.org/10.1016/j.triboint.2019.03.065.

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Hooke, C. J. "The Minimum Film Thickness in Lubricated Line Contacts during a Reversal of Entrainment—Isoviscous Behaviour." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 206, no. 5 (September 1992): 337–45. http://dx.doi.org/10.1243/pime_proc_1992_206_136_02.

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In most line contacts, the film thickness can be adequately determined using a quasi-static analysis. The one exception appears to occur when the direction of entrainment changes. Here, the quasi-static approach predicts that the film will fall to zero while, in practice, there will always be a finite clearance between the surfaces. It was shown in a previous paper that this minimum clearance depends upon the rate of change of entrainment velocity, and limit expressions for the film thicknesses in the four regimes of lubrication were developed. The present paper examines the transition between the rigid-isoviscous and the elastic-isoviscous regimes and determines how the minimum film thickness behaves in this transition zone.
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Jang, Siyoul, and John Tichy. "Rheological Models for Thin Film EHL Contacts." Journal of Tribology 117, no. 1 (January 1, 1995): 22–28. http://dx.doi.org/10.1115/1.2830602.

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Rheological behavior in concentrated contacts has been studied extensively. In certain conditions such as a rough concentrated contact or sliding of nominally flat surfaces, films may be of molecular (nanometer) scale. The question arises as to whether the application of any viscous fluid model is appropriate. In this study, elastohydrodynamic lubrication analysis is performed on three candidate rheological models: (1) the classical case of viscosity variation with pressure, (2) an isoviscous model which idealizes porous layers on the solid surfaces representing the molecular microstructure, and (3) an isoviscous model which includes van der Waals and solvation surface forces. The latter two models predict behavior similar to classical behavior. The study is not sufficiently sensitive to determine which model best predicts experimental results, but some credence must be given to the latter two because experimental evidence suggests that Reynolds’ equation is not valid for molecularly thin films.
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Zhong, Shijie. "Dynamics of thermal plumes in three-dimensional isoviscous thermal convection." Geophysical Journal International 162, no. 1 (July 2005): 289–300. http://dx.doi.org/10.1111/j.1365-246x.2005.02633.x.

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Mahdavian, S. M., and Z. M. Shao. "Isoviscous Hydrodynamic Lubrication of Deep Drawing and Its Comparison With Experiment." Journal of Tribology 115, no. 1 (January 1, 1993): 111–18. http://dx.doi.org/10.1115/1.2920963.

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An analytical model for the isoviscous hydrodynamic lubrication of deep drawing is developed. The model covers the complete drawing stages from sheet metal blank to the drawn cup-shaped product. Equations to calculate the film thickness, radial, and drawing stresses related to the blank holder squeezing action are presented. Theoretical predictions of both film thickness and drawing force ratio for lubricated, low carbon steel are compared with experimental measurements.
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Hooke, C. J. "Calculation of Clearances in Soft Point Contacts." Journal of Tribology 110, no. 1 (January 1, 1988): 167–73. http://dx.doi.org/10.1115/1.3261558.

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The clearances in highly deformed contacts are formed in a narrow region on the upstream side, are convected through the contact with little change and emerge downstream where a restriction forms in a narrow exit zone. The paper describes how this behavior simplifies the lubrication analysis. Expressions for the minimum film thickness under point contacts are obtained for the elastic isoviscous regime.
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Hooke, C. J. "The Minimum Film Thickness in Lubricated Line Contacts during a Reversal of Entrainment—General Solution and the Development of a Design Chart." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 208, no. 1 (March 1994): 53–64. http://dx.doi.org/10.1243/pime_proc_1994_208_349_02.

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In most line contacts the load, effective radius of curvature and entraining velocity change with time. Generally this is ignored when calculating the film thickness and a quasi-steady solution is obtained. Under most conditions the errors introduced by this are either small or are not critical. However, when the entraining velocity reverses, as, for example, in some designs of cams, the quasi-steady approach predicts that the film thickness will be zero. In practice a residual film persists and can provide adequate surface separation. Previous papers by the author have shown that the minimum film thickness at entrainment reversal depends on the rate of change of the entraining velocity. Expressions for the film thickness in the four regimes of lubrication—rigid isoviscous, rigid piezoviscous, elastic isoviscous and elastic piezoviscous—were obtained and the variations of the film thickness in the transitions between adjacent regimes examined. The present paper examines the region where more than two regimes overlap. The values of film thickness obtained are then used to develop an interpolation procedure for the accurate calculation of the minimumfilm thickness under all operating conditions.
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Hooke, C. J. "The Elastohydrodynamic Lubrication of Elliptical Point Contacts Operating in the Isoviscous Region." Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology 209, no. 4 (December 1995): 225–34. http://dx.doi.org/10.1243/pime_proc_1995_209_433_02.

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The elastohydrodynamic lubrication of point contacts is examined and results for the minimum film thickness are presented for a wide range of radius ratios and operating conditions. The results are compared with the predictions of the appropriate regime formulae. Although these formulae give a reasonable estimate of the contact's behaviour, the actual clearances are often substantially different, particularly close to the regime boundaries. Interpolation equations for seven values of radius ratio are given and these should be sufficient to allow the minimum clearance to be estimated for most isoviscous point contacts.
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Dissertations / Theses on the topic "Isoviscose"

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Dočkal, Kryštof. "Analýza mazaného kontaktu poddajných těles." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231789.

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This diploma thesis deals with the proposal of methodology for film thickness eva- luation within compliant contacts. With respect to characteristics of such contact pairs, like variable film thickness, high surface roughness, or poor conductivity and reflectivity, the usage of conventional experimental methods is particularly complicated. In present study, an optical method based on the principle of fluo- rescent microscopy was employed in present thesis. An evaluation algorithm in- volving background normalization and calibration of fluorescent intensity to film thickness was created in a form of experimental software. The proposed algori- thm was validated by using elastohydrodynamic contact formed between ceramic ball and glass disc. The measured film thickness was compared with theoretical prediction, while very good agreement of obtained data was observed. Further, a series of experiments with compliant samples was conducted, while the central film thickness was evaluated as a function of mean speed, applied lubricant, ap- plied load and slide-to-roll ratio. The last part of the thesis is focused on results analysis and discussion considering the previously published literature.
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Cha, Matthew. "Nonlinear Isoviscous Behaviour of Compliant Journal Bearings." Licentiate thesis, KTH, Maskinkonstruktion (Avd.), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91490.

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Plans to shut down nuclear power plants in some European countries as well as increased electricity production by wind and solar power will increase the work load on hydroelectric power plants in the future. Also, due to the power grid regulations, hydroelectric power plants undergo more frequent start-ups and shut-downs. During such transient periods, a large amplitude shaft motion can occur, especially in the power plants with vertical shafts. Large shaft motion is not desirable because it can lead to a machine failure. Furthermore, performance limitations of conventional white metal or babbitted bearings call for the development of new bearing designs. An outstanding tribological performance can be achieved by introducing compliant polymer liners. At the same time, bearings with compliant liners may alter rotor-bearing system dynamic behaviour compared to the systems with conventional white metal bearings. The research approach of this thesis is to employ nonlinear analysis to provide further understanding of the compliant bearing dynamic response to synchronous shaft excitation. Plain cylindrical journal bearings with different compliant liner thicknesses were analysed using a nonlinear approach. The numerical model was verified with an in-house developed code at steady state conditions. Results obtained by the numerical models showed good agreement. After verification of the numerical model for fixed geometry journal bearings, models for tilting pad journal bearings were developed. Results for the tilting pad journal bearing with three pads with line pivot geometry were compared with published data in dynamic conditions. A good agreement was obtained between the two numerical models. The effect of pad pivot geometry on bearing dynamic response was investigated. Vertical and horizontal shaft configurations were compared in terms of the effect of preload factor, pivot offset, tapers and pad inclination angles. Influence of the viscoelastic properties of compliant liners was also studied. All these factors significantly affect bearing dynamic response. It is shown how these factors should be selected to control the journal orbit sizes. It was also shown that the compliant liner provides lower maximum oil film pressure and thicker minimum oil film thickness in the bearing mid-plane in both static and dynamic operating conditions.

QC 20120319


Swedish Hydropower Centre
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Hall, R. W. "Two dimensional isoviscous EHL and associated contact problems in linear elasticity." Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374172.

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Jaroš, Tomáš. "Utváření mazacího filmu v poddajném kontaktu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318376.

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This diploma thesis deals with the study of film formation in compliant contact. Primary attention is dedicated to the influence of the entrainment speed and slide-to-roll ratio (SRR) on the central film thickness. Based on a research study of the available experimental methods, the fluorescence microscopy was used to achieve the aim of the work. Experiments were realized in ball-on-disk configuration. Firstly, a validation of the method was performed where the solid contact of the ceramic ball and the glass disk was analyzed. Since the measured values were in a good agreement with the theoretical prediction, a ball of NBR rubber material, which is commonly used for production of lip seals and o-rings, was subsequently used. The experimental measurements were performed under pure rolling and rolling/sliding conditions when the entrainment speeds varied in the range from 10 to 400 mm / s. A constant load of 0.2 N was applied. The measured data were then compared to the theoretical predictions for compliant contacts. The results showed that the thickness of the lubricating film gradually increases with increasing entrainment speed, which corresponds to theoretical assumption. Against expectations, evident influence of SRR on the film formation has been observed. In the last part of the thesis the measured data are confronted with previously published studies. Finally, some limitations of this study are discussed and recommendations for further improvement of the used experimental method are suggested.
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Poledník, Radim. "Mazání plastových převodů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-379038.

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The purpose of this diploma thesis is to describe the influence of input parameters (rolling speed, load, temperature, dynamic viscosity and pressure coefficient of the lubricant) on film thickness in point and elliptical contacts using optical interferometry. Regression based film thickness formula has been obtained using universal form of non-dimensional parameters of entrainment speed U, load W and material G. Equations were also complemented by the function of ellipticity k. New regression formulas for central and minimum film thickness have been compared with existing EHL thickness equations. These film thickness measurement and new regression formulas have applicability to our understanding of the performance and more effective design of lubricated gears from polymeric materials.
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Book chapters on the topic "Isoviscose"

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Lliboutry, Louis A. "Thermal convection in an isoviscous layer and in the Earth’s mantle." In Mechanics of Fluids and Transport Processes, 229–59. Dordrecht: Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-3563-1_9.

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Shigetoshi, Kenji, Tadao Isaka, and Sadao Kawamura. "A New Evaluation System for Dynamic Muscular Strength Characteristics using Isoviscous Loading (P231)." In The Engineering of Sport 7, 419–28. Paris: Springer Paris, 2008. http://dx.doi.org/10.1007/978-2-287-09413-2_52.

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Noutary, M. P., and A. A. Lubrecht. "Starved lubrication of isoviscous rigid elliptical contacts." In Tribology Series, 573–78. Elsevier, 2003. http://dx.doi.org/10.1016/s0167-8922(03)80085-8.

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Noutary, M. P., and A. A. Lubrecht. "Starved lubrication of isoviscous rigid circular contacts." In Tribology Series, 713–18. Elsevier, 2003. http://dx.doi.org/10.1016/s0167-8922(03)80184-0.

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Nakamura, T., T. Matsubara, and F. Itoigawa. "Isoviscous-EHL and mixed lubrication mechanism of parallel slide-way with oil groove." In Tribology Series, 223–29. Elsevier, 1999. http://dx.doi.org/10.1016/s0167-8922(99)80044-3.

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Hall, R., and M. D. Savage. "Paper VI(iii) Solutions for isoviscous line contacts using a closed form analytic solution." In Tribology Series, 191–95. Elsevier, 1987. http://dx.doi.org/10.1016/s0167-8922(08)70945-3.

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Conference papers on the topic "Isoviscose"

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Dobrica, Mihai B., and Michel Fillon. "Thermohydrodynamic Behavior of a Slider Pocket Bearing." In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63479.

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Pocket-pads or steps are often used in journal or thrust bearings, as a source for hydrodynamic pressure and dynamic stability. A literature review shows that, to date, only isoviscous and adiabatic studies of such geometries, involving film thickness discontinuities, were performed. This paper presents a full thermohydrodynamic (THD) numerical model, applied to the case of a slider pocket bearing.
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Lee, S., and N. D. Spencer. "Influence of Surface Modification on Aqueous Lubrication of Elastomers." In World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63234.

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Water is generally not an efficient lubricant for most tribosystems due to its extremely low pressure-coefficient of viscosity. This barrier is less important, however, when elastomers are employed as tribopairs, since a low-pressure, conformal contact is readily achieved under these conditions, and thus the isoviscous-elastic lubrication (or soft elastohydrodynamic lubrication, “soft EHL”) mechanism can be activated. Isoviscous-elastic lubrication does not necessitate the increase of viscosity under pressure. The aqueous lubrication of elastomers, however, requires a careful control of surface properties of tribopairs since hydrophobic interactions between the sliding surfaces in water can result in the failure of lubricating films to form at low sliding speeds. In this context, we have investigated the influence of surface modification of an elastomer, poly(dimethylsiloxane) (PDMS), on its aqueous lubrication properties. A dramatic reduction in frictional forces has been observed upon hydrophilization by oxygen-plasma treatment when PDMS was slid against PDMS in an aqueous environment. A similar effect was also observed when the PDMS surface was coated with a variety of copolymers that possess amphiphilic characteristics. This effect is attributed to the removal of the strong hydrophobic interaction between PDMS surfaces in water, thereby enabling the soft EHL mechanism to predominate. This study demonstrates the significance of surface modification in allowing effective soft EHL of an elastomer to take place.
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Bonner, Thomas, and John H. Vohr. "Measurement of Static and Dynamic Properties of a Tilting Pad Bearing and Comparison With Theory." In ASME 1993 Design Technical Conferences. American Society of Mechanical Engineers, 1993. http://dx.doi.org/10.1115/detc1993-0269.

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Abstract Measurements were made of the static and dynamic properties of a seven inch diameter, four-pad, tilting pad bearing with both centrally pivoted and 60% offset pads. Data was recorded at 1500, 1800 and 3000 RPM and covered a range of Sommerfeld numbers from .055 to .625. Dynamic properties were measured by applying unbalance weights of various magnitudes to the rotor and measuring the synchronous response amplitudes and phase angles. Good agreement was obtained between measured properties and those predicted using linearized stiffness and damping coefficients obtained from isoviscous lubrication theory.
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Li, Wei, and Manish Thorat. "Fixed Geometry Bearing Analysis Using 2 Dimensional Pad Data." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43386.

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A fast and efficient method for evaluating bearing coefficients of the fixed geometry bearings is presented. In a typical industrial application, where the accuracy of the solution is desired, this paper presents a method whose accuracy is verified to be good by the benchmark study. Reynolds equation is solved to obtain non-dimensionalised static and rotor-dynamic characteristics for a pre-defined bearing pad geometry. The solution in the form of non-dimensional functions is obtained for a 2 dimensional space representing all possible journal loci for any load vector orientation. Laminar flow is considered in the analysis, although the method of analysis can be extended to Turbulent flow regime. The analysis method is most efficient for isoviscous boundary condition. A pad assembly method for the fixed pad journal bearings is presented. Any fixed pad bearing geometry including multi-pad bearings, preload with any load vector orientation can be evaluated using this method. In this paper, demonstrating cases for a four-pad bearing are presented.
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Nair, K. Prabhakaran, P. K. Rajendra Kumar, and K. Sreedhar Babu. "Thermohydrodynamic Analysis of Journal Bearing Operating Under Nanolubricants." In ASME/STLE 2011 International Joint Tribology Conference. ASMEDC, 2011. http://dx.doi.org/10.1115/ijtc2011-61244.

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The static performance characteristics of thermo hydrodynamic journal bearing operating under lubricant Veedol SAE 15W 40 multi grade engine oil with CuO, CeO2 and Al2O3 nanoparticles are presented. These static performance characteristics mainly depend on the viscosity of the lubricant. The addition of nano particles on commercially available lubricant may enhance the viscosity of lubricant and in turn changes the performance characteristics. In the proposed work CuO, CeO2 and Al2O3 nano particles are used with commercial lubricant Veedol SAE 15W 40 multi grade engine oil. To obtain pressure and temperature distribution, modified Reynolds and energy equations are used and these equations are solved by using the powerful numerical technique, Finite Element Method. An iterative procedure is used to establish the film extent. The static performance characteristics in terms of load capacity, attitude angle, end leakage and friction force are evaluated when the bearing operates under nanolubricants for the following cases. 1. Isoviscous; 2. Thermoviscous.
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Cook, Jason T. "Estimated Fluid Force and Damping Characteristics of a Thin Film Damper Comparison Between Closed-Form Solutions and Numerical Analysis." In ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-10171.

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Abstract Analytical solutions of thin film dampers are useful for determining critical speeds and stability of rotor systems. Most thin film dampers in use are of short axial length, and closed-form solutions to the Reynolds equations exist for estimating pressure, forces, and damping for these types of dampers. This article compares the fluid film forces and damping estimated by the short film bearing model form of the Reynolds equations to the calculated forces and damping of a transient computational fluid dynamic simulation. For this comparison, the fluid was assumed to be incompressible, laminar, and isoviscous. The fluid film forces and damping are calculated from integrating the pressure distribution over the surface of the damper due to small amplitude motions about a steady state static off-center circular orbit. In this case, no cavitation is assumed, and the journal has no angular velocity, so direct stiffness cannot be calculated from the closed-form solution. Radial clearance, journal length, and journal eccentricity have a significant effect on fluid force and damping within a thin film damper. Fluid density does not affect fluid force or damping substantially, while fluid viscosity does. Both the closed-form solutions and computational fluid dynamics simulation compare well with each other and reflect these trends.
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De la Cruz, Miguel, Stephanos Theodossiades, Homer Rahnejat, and Patrick Kelly. "The Effect of Thermo-Hydrodynamics on Manual Automotive Transmissions Gear Rattle." In ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/detc2009-87226.

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Manual transmission gear rattle is the result of repetitive impacts of gear meshing teeth within their backlash. This NVH phenomenon is a major industrial concern and can occur under various loaded or unloaded conditions. It fundamentally differs from other transient NVH phenomena, such as clonk or thud, which are due to impulsive actions. However, they all have their lowest common denominator in the action of contact/impact forces through lubricated contacts. Various forms of rattle have, therefore, been defined: idle rattle, drive rattle, creep rattle and over-run rattle. This paper presents a dynamic transmission model for creep rattle conditions (engaged gear at low engine RPM). The model takes into account the lubricated impact force between a gear teeth pair during a meshing cycle as well as the friction between their flanks. Hertzian contact conditions are applied to the gear pair along the torque path. Additionally, isoviscous hydrodynamic regime of lubrication is assumed for unselected (loose gear pairs) with lightly loaded impact conditions. The highly non-linear impacts induce a range of system response frequencies. These include engine order harmonics, harmonics of meshing frequency and natural frequencies related to contact stiffness. The last of these are dependent on the contact geometry and lubricant rheology. The analysis includes lubricant viscosity variation due to generated contact pressures as well as temperature. For loose gears, subject to oscillations on their retaining bearings, bearing friction is also considered.
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Al-Jughaiman, Bader, and Dara Childs. "Static and Dynamic Characteristics for a Pressure-Dam Bearing." In ASME Turbo Expo 2007: Power for Land, Sea, and Air. ASMEDC, 2007. http://dx.doi.org/10.1115/gt2007-27577.

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Measured rotordynamic force coefficients (stiffness, damping, and added-mass) and static characteristics (eccentricity and attitude angle) of a pressure-dam bearing are presented and compared to predictions from a Reynolds-equation model, using an isothermal and isoviscous laminar analysis. The bearing’s groove dimensions are close to the optimum predictions of Nicholas and Allaire (1980) and are consistent with current field applications. The bearing has a diameter of 117.1 mm (4.61 in), a length-to-diameter ratio of 0.655 and, a nominal radial clearance of 0.133 mm (5.25 mils). The upper pad of the bearing has a step located at 130° and a 0.620 mm (15.75 mils) deep dam. The bottom pad has a deep, centered relief track over 25% of the pad’s axial length. Test conditions include four shaft speeds (4000, 6000, 8000 and 10000 rpm) and bearing unit loads from 0 to 1034 kPa (150 psi). Laminar flow was produced for all test conditions. A finite-element algorithm was used to generate solutions to the Reynolds equation model. Excellent agreement was found between predictions and measurements for the eccentricity ratio and attitude angles. Predictions of stiffness and damping coefficients are in reasonable agreement with measurements. However, experimental results show that the bearing has significant added mass of about 60 kg at no-load conditions, versus zero mass for predictions from the Reynolds-equation model and 40 kg using Reinhardt and Lund’s extended Reynolds equation model. The added mass drops quickly to zero as the load increases. Measured results also show a whirl frequency ratio near 0.36 at no-load conditions; however, a zero whirl frequency ratio was obtained at all loaded conditions, indicating an inherently stable bearing from a rotordynamics viewpoint.
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Deng, Xin, Cori Watson, Minhui He, Houston Wood, and Roger Fittro. "Comparison of Experimental, Thermoelastohydrodynamic (TEHD) and Isothermal, Non-Deforming Computational Fluid Dynamics (CFD) Results for Thrust Bearings." In ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/fedsm2018-83177.

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Bearings are machine elements that allow components to move with respect to each other. A thrust bearing is a particular type of rotary bearing permitting rotation between parts but designed to support a predominately axial load. Oil-lubricated bearings are widely used in high speed rotating machines such as those found in the aerospace and automotive industries. With the increase of velocity, the lubrication regime will go through boundary lubrication, mixed lubrication, and hydrodynamic lubrication (full film). In this paper, the analysis was in the hydrodynamic lubrication region. THRUST is used to predict the steady-state operating characteristics of oil-lubricated thrust bearings. As a thermoelastohydrodynamic prediction tool, THRUST assumes a 3D turbulence model, 3D energy equation, and 2D Reynolds equation. Turbulence is included by obtaining average values of eddy momentum flux (Reynolds stress) and averaging the influence down to a 2D Reynolds equation. Convergence is achieved by iterating on the pad tilt angles and pivot film thickness until the integrated pressure matches the load applied to the pad. Despite the multiple experimental, CFD, and TEHD studies of thrust bearings that have been performed to date, no validation has yet been performed to confirm the accuracy of TEHD methods in modeling the performance of thrust bearings by both experimental and advanced computational means simultaneously. This study addresses this need by comparing TEHD and CFD simulation results of film thickness, temperature, power loss, and pressure in thrust bearings taken from the literature at multiple speeds and loads with results from experimental data. Starting from the case of the lowest speed and load, it was verified that this case is indeed laminar and with negligible thermal and elastic effects. Four cases were run in THRUST, a TEHD solver, combining thermal and deformation in each rotational speed and load combination. Additionally, a CFD study was performed in ANSYS CFX with the assumptions of isothermal, non-deforming. The average viscosity from THRUST was used in CFD to follow the effects of the isoviscous assumption. Then, the experimental, TEHD and CFD results were compared at each case. Experimental, TEHD, and CFD results show acceptable agreement when turbulence is negligible.
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Kim, Tae Ho, and Tae Won Lee. "Design Optimization of Gas Foil Thrust Bearings for Maximum Load Capacity." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43999.

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Improvement of the load capacity of gas foil thrust bearings (GFTBs) is important to broadening their application in oil-free microturbomachinery (<250 kW) with high power density. Although GFTBs have the significant advantage of low friction without the use of lubrication systems compared to oil film thrust bearings, their inherently low load capacity has limited their application. The aim of the present study was to develop a design guideline for increasing the load capacity of GFTBs. The Reynolds equation for an isothermal isoviscous ideal gas was used to calculate the gas film pressure. To predict the ultimate load capacity of the GFTB, the pressure was averaged in the radial direction of the gas flow field used to deflect the foil structure. The load capacity, film pressure profile, and film thickness profile were predicted for a GFTB with an outer radius of 55 mm, inner radius of 30 mm, and eight foils each of arc length 45°. The predictions showed that the load capacity of the GFTB increased with increasing rotor speed and decreasing minimum film thickness, and was always lower than the analytically determined limit value for infinite rotor speed (obtained by simple algebraic equations). A parametric study in which the ramp extent (or inclined angle) was increased from 5° to 40°, and the ramp height from 0 to 0.320 mm, revealed that the GFTB had an optimal ramp extent of ∼22.5° and ramp height of ∼0.030 mm for maximum load capacity. Interestingly, the optimal values were also valid for a rigid-surface bearing. The predicted load capacities for a ramp extent of ∼22.5° and increasing ramp height from 0.030 to 0.320 mm were compared with experimental data obtained from a previous work. The predictions for a ramp height of 0.155 mm were in good agreement with the experimental data for all three test GFTBs with outer radii of 45, 50, and 55 mm, respectively. In addition, this paper shows that the predicted drag torque increases linearly with increasing rotor speed and decreasing minimum film thickness, and nonlinearly with decreasing ramp height. The drag torque significantly increased only for ramp heights below the optimal value. The predictions imply that the optimal ramp height improves the load capacity of the GFTB with little change in the drag torque.
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