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Relevant bibliographies by topics / Stiffness and damping coefficients

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Academic literature on the topic 'Stiffness and damping coefficients'

Author: Grafiati

Published: 4 June 2021

Last updated: 16 February 2022

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Journal articles on the topic "Stiffness and damping coefficients"

1

Iasa Abdulhadi, M. "Stiffness and Damping Coefficients of *Rubber." Shock and Vibration Digest 17, no. 5 (May 1, 1985): 3–9. http://dx.doi.org/10.1177/058310248501700502.

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Abdulhadi, M. "Stiffness and damping coefficients of rubber." Ingenieur-Archiv 55, no. 6 (1985): 421–27. http://dx.doi.org/10.1007/bf00537649.

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Ghosh, M. K., and N. S. Viswanath. "Recess Volume Fluid Compressibility Effect on the Dynamic Characteristics of Multirecess Hydrostatic Journal Bearings With Journal Rotation." Journal of Tribology 109, no. 3 (July 1, 1987): 417–26. http://dx.doi.org/10.1115/1.3261462.

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An analysis using finite difference method and small amplitude perturbation technique has been presented to evaluate the frequency dependent stiffness and damping coefficients of multirecess hydrostatic journal bearings including the effect of shaft rotation that results in hybrid operation. Recess volume fluid compressibility effect that results in the frequency dependent dynamic coefficients have been taken into account. Results for direct and cross stiffness coefficients, direct and cross damping coefficients are presented for a capillary compensated bearing with deep recesses. Frequency effects are shown in terms of dimensionless squeeze number (σ) for various recess volume parameters (γ) for different eccentricity ratios (ε0) and dimensionless speed parameter (Λ). It has been found that the dynamic coefficients are very drastically altered within a very useful range of frequency parameter (σ) and recess volume parameter (γ) resulting in increased direct stiffness coefficient and a substantially decreased direct damping coefficients. Journal speed parameter (Λ) results in substantial magnitude of cross stiffness and cross damping parameters. However, the cross damping coefficient is usually small in comparison to direct damping coefficient.

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Xu, Chun Dong, Hui Hui Feng, and Feng Feng Wang. "Analysis of the Dynamic Characteristics of the Aerostatic Journal Bearings." Applied Mechanics and Materials 607 (July 2014): 600–603. http://dx.doi.org/10.4028/www.scientific.net/amm.607.600.

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This paper investigates the dynamic characteristics of the aerostatic journal bearing, the rotation center of which is not the center of the journal length. The Finite Difference Method (FDM) and the perturbation method are employed to calculate the stiffness and damping coefficients. Results show that the coupled stiffness and damping coefficients cannot be neglected due to the rotation center being not the center of the journal length. Furthermore, with the increase of the distance between the rotation center and the center of the journal length, the coupled stiffness and damping coefficients increase.

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Xiang, Guo, Yijia Wang, Cheng Wang, and Zhongliang Lv. "Numerical study on the dynamic characteristics of water-lubricated rubber bearing under asperity contact." Industrial Lubrication and Tribology 73, no. 4 (April 2, 2021): 572–80. http://dx.doi.org/10.1108/ilt-12-2020-0453.

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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.

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Al-Bender, Farid, Federico Colombo, Dominiek Reynaerts, Rodrigo Villavicencio, and Tobias Waumans. "Dynamic Characterization of Rubber O-Rings: Squeeze and Size Effects." Advances in Tribology 2017 (2017): 1–12. http://dx.doi.org/10.1155/2017/2509879.

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This paper concerns the dynamic characterization of rubber O-rings used to introduce damping in high speed gas bearing systems. O-shaped rubber rings composed of high temperature rubber compounds are characterized in terms of stiffness and damping coefficients in the frequency range 100–800 Hz. Simple formulas with frequency independent coefficients were identified to express the viscoelastic properties of the O-rings. The formulas proposed approximate the stiffness and damping coefficients of O-rings of general size.

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Jagadish, H. P., and L. Ravikumar. "Calibration of the Stiffness and Damping Characteristics of a Magnetorheological Fluid Long Squeeze Film Damper in Terms of Reynolds Number." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, no. 10 (April 22, 2010): 2121–28. http://dx.doi.org/10.1243/09544062jmes2031.

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Magnetorheological (MR) fluids are suspensions of fine micron-sized magnetizable particles in a suitable carrier liquid. The rheological properties of the fluid can be controlled by application of a suitable magnetic field and can be used in a variety of applications where variable damping and stiffness characteristics are required, based on the requirements of the rotor dynamic system. In this work, the stiffness and damping characteristics of MR fluid long squeeze film damper operating at low eccentricity ratios are calibrated in terms of Reynolds number of the squeeze film for different clearance and L/D ratios. A theoretical constant magnetic field viscosity model is developed, based on the literature, and is subsequently used to evaluate the theoretical stiffness and damping coefficients, at a particular excitation frequency. The results indicate that the stiffness and damping coefficients decrease with increasing Reynolds number of the squeeze film and is found to be abysmally low, indicating that the flow has ceased and the film has solidified. This is in accordance with the literature that predicts the formation of chain-like semi-solid structures, restricting the flow, and consequently increasing the viscosity, under the influence of the magnetic field. This change in viscosity, in turn, influences the stiffness and damping coefficients and the Reynolds number of the squeeze film. The stiffness and damping coefficients are found to increase with decreasing clearance, increasing L/D ratio, and eccentricity ratio. The results of the investigation assist the designer in obtaining the stiffness and damping characteristics of the squeeze film damper based on the Reynolds number of the squeeze film. Conversely, the stiffness and damping characteristics of the squeeze film damper are calibrated in terms of the Reynolds number of the squeeze film for different damper configurations.

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Peng, J. P., and M. Carpino. "Finite Element Approach to the Prediction of Foil Bearing Rotor Dynamic Coefficients." Journal of Tribology 119, no. 1 (January 1, 1997): 85–90. http://dx.doi.org/10.1115/1.2832484.

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A finite element perturbation approach to the prediction of foil bearing stiffness and damping coefficients is presented. The fluid lubricant is modeled as a simple barotropic fluid which is described by the Reynolds equation. The structural model includes membrane, bending, and elastic foundation effects in a general geometry. The equivalent viscous damping of the Coulomb friction caused by the foil relative motion is included in the structural calculation. Bearing stiffness and damping coefficients are predicted for an air-lubricated foil bearing with a corrugated sub-foil. The effects of the bearing number, bearing compliance, sub-foil Coulomb friction, and foil membrane stiffness on the bearing dynamic coefficients are discussed.

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Ku, C. P. Roger, J. F. Walton, and J. W. Lund. "Dynamic Coefficients of Axial Spline Couplings in High-Speed Rotating Machinery." Journal of Vibration and Acoustics 116, no. 3 (July 1, 1994): 250–56. http://dx.doi.org/10.1115/1.2930421.

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This paper provided the first opportunity to quantify the angular stiffness and equivalent viscous damping coefficients of an axial spline coupling used in highspeed turbomachinery. The bending moments and angular deflections transmitted across an axial spline coupling were measured while a nonrotating shaft was excited by an external shaker. A rotordynamics computer program was used to simulate the test conditions and to correlate the angular stiffness and damping coefficients. The effects of external force and frequency were also investigated. The angular stiffness and damping coefficients were used to perform a linear steady-state rotordynamics stability analysis, and the unstable natural frequency was calculated and compared to the experimental measurements.

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Marcinkevičius, Andrejus Henrikas. "Theoretical Analysis of Vibrations of a Mass Connected with a Support through a Chain of Elastic Elements." Solid State Phenomena 164 (June 2010): 303–7. http://dx.doi.org/10.4028/www.scientific.net/ssp.164.303.

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Vibrations of a mass are analyzed when the mass is connected with the support in succession of two elastic elements characterized by stiffness and damping coefficients. It is demonstrated that upon harmonic excitation of the mass and considering different values of stiffness and damping coefficients the system can respond differently in comparison to the case when the mass is connected to the support by means of single elastic element. Reduction of stiffness and damping coefficients of a pair of elements to a single one (as it is proposed in calculations of considered systems) can lead to incorrect results. This is confirmed by presented calculations and dependences.

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Dissertations / Theses on the topic "Stiffness and damping coefficients"

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Mohammad, Zakariya Yahya. "The determination of a journal bearing's stiffness and damping coefficients using an extended Kalman filter." Thesis, University of Newcastle Upon Tyne, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.315588.

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Fang, Yuefa. "Calculation and measurement of the eight oil film stiffness and damping coefficients for a variable impedance hydrodynamic bearing." Thesis, Staffordshire University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359621.

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Hoa, Pham Trong, and Nguyen Manh Hung. "Numerical calculation of dynamic stiffness and damping coefficients of oil lubrication film in internal gear motors and pumps." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71107.

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Oil lubrication film plays an important role in analysis of dynamic behavior of the internal gear motors and pumps. During operation, the oil film is considered as the spring and damping system. Therefore, calculation of the dynamic stiffness and damping coefficients is necessary to build the mathematical model for studying of dynamic problem. In order to calculate these coefficients, the dynamic pressure and perturbing pressure distribution must be determined firstly. In this paper, the infinitesimal perturbation method (IFP) is used to calculate the dynamic pressure distribution. Based on that the dynamic stiffness and damping coefficients can be computed. The calculation results point out that the dynamic stiffness and damping coefficients are much dependent on the eccentricity ratio.

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Breedlove, Anthony Wayne. "Experimental identification of structural force coefficients in a bump-type foil bearing." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1936.

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Punna, Harshitha. "Impact of stiffness and damping capacity using two different rubbers on friction coefficient and noise levels of brake materials." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2773.

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Friction contact with both external and internal environments can significantly influence its efficiency, which could cause friction instabilities, vibration, and noise. Focusing on the effects that troubles brake pad, rotor, and friction-induced NVH, the main motivation for this study is to understand its drawbacks for some extent in a braking system. By proper study on applied statistics, an experimental design is planned. The design has friction tests that are performed by scaling down real test properties used in dynamometer to scaled-down properties in a subscale tester by using scaling law of physics. The test has two different types of rubbers with different humidity conditions with respect to two different brake pads in a small-scale tester, the Universal Mechanical Tester (UMT). This friction experiment helps in determining how different rubbers impact its stiffness on the coefficient of friction and noise levels, also to evaluate which scenario has the better damping capacity. The effect on the coefficient of friction and noise levels with and without rubbers is also compared. The results are subjected to the Design of Experiments analyses test know the statistical relationship between factors affecting the process and output of that process at different controllable variables namely humidity and temperature.

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Harris, Joel Mark. "Static characteristics and rotordynamic coefficients of a four-pad tilting-pad journal bearing with ball-in-socket pivots in load-between-pad configuration." [College Station, Tex. : Texas A&M University, 2008. http://hdl.handle.net/1969.1/ETD-TAMU-3194.

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Erickson, Darren Andrew. "Contact stiffness and damping estimation for constrained robotic systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq53042.pdf.

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Kim, Sung-June 1972. "A simulation scheme for strategic distribution of damping coefficients." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/80948.

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Hyung, Sang Su. "Nondestrutive damage detection by simultaneous identification of stiffness and damping." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2472.

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Le, Guen Marie Joo. "Damping behaviour of plant-fibre composite materials." Thesis, University of Canterbury. Mechanical Engineering, 2014. http://hdl.handle.net/10092/9978.

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The vibration damping property of plant fibres composites is of practical interest for commercial applications of biobased and eco-composites. Damping behaviour has been observed by experimentation and exploited in the marketing of sporting equipment but the origins of this behaviour have so far been only based on conjectures. In this thesis, the damping capacity of plant fibre composites was attributed to their chemical composition and the reversible interactions enabled by the breaking and reforming of hydrogen bonds under stress. The approach to explaining the mechanisms started with the characterisation of different plant fibre types to search for correlations between their physical and chemical structure. The investigation continued with quantifying the effect of hydrogen bonding compounds such as water, glycerol and polyglycerol on the damping coefficient of fibres and reinforced composites. The results of the polyol impregnation indicated that applying a pretreatment enhanced the vibration damping performance of flax reinforced composites, validating the hypothesis of the essential role played by hydrogen bonds in the fibres. The improvement in the damping coefficient of the composites was shown to be to the detriment of their stiffness. The compromised between the two properties was investigated in the final part of this thesis by using hybrid flax-carbon fibre reinforced composites.

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Books on the topic "Stiffness and damping coefficients"

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Rivin, Eugene I. Stiffness and damping in mechanical design. New York: Marcel Dekker, 1999.

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Stiffness and damping in mechanical design. New York: Marcel Dekker, 1999.

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3

Banks, H. Thomas. Methods for the identification of material parameters in distributed models for flexible structures. Hampton, Va: ICASE, 1986.

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Rivin, Eugene I. Handbook of stiffness & damping in mechanical design. New York: ASME Press, 2010.

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Handbook on stiffness & damping in mechanical design. New York: ASME Press, 2010.

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Banks, H. Thomas. Computational methods for the identification of spatially varying stiffness and damping in beams. Hampton, Va: ICASE, 1986.

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Smith, Ralph C. A fully Galerkin method for the recovery of stiffness and damping parameters in Euler-Bernoulli beam models. Hampton, Va: Institute for Computer Applications in Science and Engineering, 1991.

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8

K, Ghosh A. Evaluation of dynamic stiffness and damping factor of a hydraulic damper. Mumbai: Bhabha Atomic Research Centre, 2000.

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9

Morales, Wilfredo. Permanent magnetic bearing for spacecraft applications. [Cleveland, Ohio]: National Aeronautics and Space Administration, Glenn Research Center, 2003.

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10

Ebrahim, A. M. Mohamed. Effect of rotor wedges on the stiffness, damping and parameters of turbine generators. Manchester: UMIST, 1993.

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Book chapters on the topic "Stiffness and damping coefficients"

1

Czolczynski, Krzysztof. "Identification of Stiffness and Damping Coefficients." In Mechanical Engineering Series, 25–48. New York, NY: Springer New York, 1999. http://dx.doi.org/10.1007/978-1-4612-1518-9_3.

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Nordmann, R. "Identification of Stiffness, Damping and Inertia Coefficients of Annular Turbulent Seals." In Application of System Identification in Engineering, 543–63. Vienna: Springer Vienna, 1988. http://dx.doi.org/10.1007/978-3-7091-2628-8_17.

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Nordmann, R. "Identification of Stiffness, Damping and Inertia Coefficients of Annular Turbulent Seals." In Vibration and Wear in High Speed Rotating Machinery, 507–26. Dordrecht: Springer Netherlands, 1990. http://dx.doi.org/10.1007/978-94-009-1914-3_29.

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Fukuyama, H., T. Takizawa, N. Sakai, and M. Murakami. "Stiffness and Damping Coefficients for Superconducting Magnetic Bearings Using MPMG2-YBaCuO." In Advances in Superconductivity VII, 1297–300. Tokyo: Springer Japan, 1995. http://dx.doi.org/10.1007/978-4-431-68535-7_295.

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Bouaziz, Amel, Maher Barkallah, Slim Bouaziz, Jean-Yves Cholley, and Mohamed Haddar. "Non-linear Stiffness and Damping Coefficients Effect on a High Speed AMB Spindle in Peripheral Milling." In Mechatronic Systems: Theory and Applications, 99–110. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-07170-1_10.

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Connor, Jerome, and Simon Laflamme. "Optimal Stiffness/Damping for Dynamic Loading." In Structural Motion Engineering, 75–140. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-06281-5_3.

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de Carvalho, Áquila Chagas, Fabio Mazzariol Santiciolli, Samuel Filgueira da Silva, Jony J. Eckert, Ludmila C. A. Silva, and Franco G. Dedini. "Gear Mesh Stiffness and Damping Co-simulation." In Multibody Mechatronic Systems, 177–84. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-60372-4_20.

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Vain, A. "Influence of Stiffness and Damping on Muscular Performance." In Biomechanics: Current Interdisciplinary Research, 639–41. Dordrecht: Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-011-7432-9_96.

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Lumori, Mikaya LD, Johan Schoukens, and John Lataire. "Identification of Stiffness and Damping in Nonlinear Systems." In Structural Dynamics, Volume 3, 341–48. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-9834-7_32.

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Bukhgeim, A. L., J. Cheng, V. Isakov, and M. Yamamoto. "Uniqueness in Determining Damping Coefficients in Hyperbolic Equations." In Analytic Extension Formulas and their Applications, 27–46. Boston, MA: Springer US, 2001. http://dx.doi.org/10.1007/978-1-4757-3298-6_3.

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Conference papers on the topic "Stiffness and damping coefficients"

1

Sawicki, Jerzy T., and T. V. V. L. N. Rao. "Limiting Stiffness and Damping Coefficients of Foil Bearing." In ASME 2005 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/detc2005-84550.

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The limiting values of load capacity, stiffness and damping coefficients for a foil bearing are presented. The necessary conditions for high bearing numbers (journal operating at high speed) are obtained by simplifying the compressible Reynolds equation. Linearized stiffness and damping coefficients are obtained using infinitesimal perturbation method. Results of load capacity, stiffness and damping coefficients, for foil bearing are compared with those obtained for a rigid gas journal bearing. The limiting values of dynamic characteristics for a foil bearing are constant for all eccentricity ratios.

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Jáuregui, Juan C., Luis San Andrés, and Oscar De Santiago. "Identification of Bearing Stiffness and Damping Coefficients Using Phase-Plane Diagrams." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-69980.

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The reliable identification of dynamic parameters in mechanical systems remains a big challenge, in particular for nonlinear systems. There is not a single mathematical model encompassing the universe of most systems. From a practical point of view, the identification of system parameters depends on the measurement data as well as on the reference model. This paper presents a novel method for identifying the dynamic parameters of a gas bearing, whose force coefficients are strong functions of frequency. The method is based on the analysis of the phase diagram with the model assuming a mass-damper-spring system with time-dependent force coefficients. The phase diagram could be implemented electronically for on line monitoring and ready fault detection.

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Matsumura, Yoshiki, Toshihiko Shiraishi, and Shin Morishita. "Stiffness and Damping Coefficients of Liquid Crystal Film Under Electric Field." In STLE/ASME 2006 International Joint Tribology Conference. ASME, 2006. http://dx.doi.org/10.1115/ijtc2006-12124.

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Delgado, Adolfo, and Luis San Andre´s. "Identification of Structural Stiffness and Damping Coefficients of a Shoed Brush Seal." In ASME 2005 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/detc2005-84159.

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The multiple-shoe brush seal, a variation of a standard brush seal, accommodates arcuate pads at the bristles free ends. This novel design allows reverse shaft rotation operation, and reduces and even eliminates bristle wear, since the pads lift off due to the generation of a hydrodynamic film during rotor spinning. This type of seal, able to work at both cold and high temperatures, not only restricts secondary leakage but also acts as an effective vibration damper. The dynamic operation of the shoed-brush seals, along with the validation of reliable predictive tools, relies on the appropriate estimation of the seal structural stiffness and energy dissipation features. Single frequency external load tests conducted on a controlled motion test rig and without shaft rotation allow the identification of the structural stiffness and equivalent damping of a 20-pad brush seal, 153 mm in diameter. The seal energy dissipation mechanism, represented by a structural loss factor and a dry friction coefficient, characterizes the energy dissipated by the bristles and the dry friction interaction of the brush seal bristles rubbing against each other. The physical model used reproduces well the measured system motions, even for frequencies well above the identification range.

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San Andre´s, Luis, Thomas Abraham Chirathadam, and Tae-Ho Kim. "Measurement of Structural Stiffness and Damping Coefficients in a Metal Mesh Foil Bearing." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59315.

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Engineered Metal Mesh Foil Bearings (MMFB) are a promising low cost bearing technology for oil-free microturbomachinery. In a MMFB, a ring shaped metal mesh (MM) provides a soft elastic support to a smooth arcuate foil wrapped around a rotating shaft. The paper details the construction of a MMFB and the static and dynamic load tests conducted on the bearing for estimation of its structural stiffness and equivalent viscous damping. The 28.00 mm diameter, 28.05 mm long bearing, with a metal mesh ring made of 0.3 mm Copper wire and compactness of 20%, is installed on a test shaft with a slight preload. Static load versus bearing deflection measurements display a cubic nonlinearity with large hysteresis. The bearing deflection varies linearly during loading, but nonlinearly during the unloading process. An electromagnetic shaker applies on the test bearing loads of controlled amplitude over a frequency range. In the frequency domain, the ratio of applied force to bearing deflection gives the bearing mechanical impedance, whose real part and imaginary part give the structural stiffness and damping coefficients, respectively. As with prior art published in the literature, the bearing stiffness decreases significantly with the amplitude of motion and shows a gradual increasing trend with frequency. The bearing equivalent viscous damping is inversely proportional to the excitation frequency and motion amplitude. Hence, it is best to describe the mechanical energy dissipation characteristics of the MMFB with a structural loss factor (material damping). The experimental results show a loss factor as high as 0.7 though dependent on the amplitude of motion. Empirically based formulas, originally developed for metal mesh rings, predict bearing structural stiffness and damping coefficients agreeing well with the experimentally estimated parameters. Note, however, that the metal mesh ring, after continuous operation and various dismantling and reassembly processes, showed significant creep or sag that resulted in a gradual decrease of its structural force coefficients.

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San Andre´s, Luis, Adolfo Delgado, and Jose´ Baker. "Rotordynamic Force Coefficients of a Hybrid Brush Seal: Measurements and Predictions." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59072.

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Brush seals effectively control leakage in air breathing engines, albeit only applied for relatively low-pressure differentials. Hybrid brush seals (HBS) are an alternative to resolve poor reliability resulting from bristle tip wear while also allowing for reverse shaft rotation operation. A HBS incorporates pads contacting the shaft on assembly; and which under rotor spinning, lift off due to the generation of a hydrodynamic pressure. The ensuing gas film prevents intermittent contact, reducing wear and thermal distortions. The paper presents rotordynamic measurements conducted on a test rig for evaluation of HBS technology. Single frequency shaker loads are exerted on a test rotor holding a hybrid brush seal and measurements of rotor displacements follow for operating conditions with increasing gas supply pressures and two rotor speeds. A frequency domain identification method delivers the test system stiffness and damping coefficients. The HBS stiffness coefficients are not affected by rotor speed though the seal viscous damping shows a strong frequency dependency. The identified HBS direct stiffness decreases ∼15% as the supply/discharge pressure increases Pr = 1.7 to 2.4. The HBS cross-coupled stiffnesses are insignificant, at least one order of magnitude smaller than the direct stiffnesses. A structural loss factor (γ) and dry friction coefficient (μ) represent the energy dissipated in a HBS by the bristle-to-bristle and bristle-to-pads interactions. Predictions of HBS stiffness and damping coefficients correlate well with the test derived parameters. Both model predictions and test results show the dramatic reduction of the seal equivalent viscous damping coefficients as the excitation whirl frequency increases.

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Pugachev, Alexander O., and Martin Deckner. "CFD Prediction and Test Results of Stiffness and Damping Coefficients for Brush-Labyrinth Gas Seals." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22667.

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This paper presents ongoing investigations on calculation and measurement of rotordynamic coefficients for brush-labyrinth gas seals. The seals are tested on static and dynamic test rigs to measure leakage, pressure distribution, and seal specific forces. To predict seal performance a full three-dimensional eccentric CFD model is considered. Rotordynamic coefficients are calculated using the whirling rotor method. The bristle pack of the brush seal is modeled using the porous medium approach. The prediction results show some deviations in absolute values of stiffness and damping coefficients in comparison with the experimental values, but the trends are similar. Comparing with a staggered labyrinth seal, the brush seal improves rotordynamic characteristics in most cases. Position of the brush seal in sealing configuration has a great influence on the stiffness and damping coefficients, while leakage performance remains relatively unaffected. The capability of the brush seal model based on the porous medium approach to predict rotordynamic coefficients is discussed.

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Agnew, Jeff, and Dara Childs. "Rotordynamic Characteristics of a Flexure Pivot Pad Bearing With an Active and Locked Integral Squeeze Film Damper." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-68564.

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Measured rotordynamic coefficients are presented for a flexure-pivot-pad journal bearing (FPJB) in a load-between-pad configuration with: (1) an active, and (2) locked integral squeeze film damper (ISFD). Prior rotordynamic-coefficient test results have been presented for FPJBs (alone), and rotor-response results have been presented for rotors supported by FPJBS with ISFDs; however, these are the first rotordynamic-coefficient test results for FPJBs with ISFDs. A multi-frequency dynamic testing regime is employed. For both bearing configurations, quadratic curve fits provide good representation of the real portions of the dynamic-stiffness coefficients yielding a direct stiffness and a direct added-mass coefficient. The imaginary portions are well represented by linear curve fits, implying constant, frequency-independent direct-damping coefficients. Direct stiffness coefficients are ∼50% lower for the active-damper configuration, and direct damping coefficients are only modestly lower. The combination of ∼50% reduction in direct stiffness with a modest drop in direct damping indicates a very effective squeeze-film damper application. Added-mass coefficients are normally lower for the active-damper configuration, and all coefficient trends (for changes in loading and shaft speed) are “flatter” for the active flexure pivot-pad damper bearing. The measured rotordynamic coefficients are used to calculate the whirl frequency ratio and indicate high stability for both bearing configurations.

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Wilkes, Jason, and Steve White. "Influence of Ambient Pressure on Measured Stiffness and Damping of Radial Gas Foil Bearings." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-02669.

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Abstract As gas bearings have gained popularity, they have been used in a diverse range of applications. In many cases these bearings are used in various process gases at a range of pressures. Although numerous analytical tools exist to predict the behavior of gas bearings in these environments, these tools are challenging to validate. The current work describes a test loop that is capable of measuring rotordynamic force coefficients in a hermetically sealed environment. To the author’s knowledge, this capability is the first of its kind. To illustrate operation of the test rig, an industrial 3-lobe gas-foil bearing was installed in the test fixture, and operated at pressures from .5–3.5 bara at speeds ranging from 25–65 krpm. The tests show that dynamic coefficients increase with speed and pressure; however, a slight reduction in coefficients were observed at the highest speed under ambient conditions. In addition, sub ambient pressure tests showed higher than ambient stiffness, but comparably low damping in comparison to the other test cases. It is believed that this is the first publication of gas foil bearing coefficients at sub-ambient pressure.

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Brassart, François P., and Malcolm E. Wright. "A Machine to Study Vertical Tire Stiffness and Damping Coefficient." In International Off-Highway & Powerplant Congress & Exposition. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International, 1993. http://dx.doi.org/10.4271/932391.

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Reports on the topic "Stiffness and damping coefficients"

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Radhakrishnan, R., S. Kotha, and K. Sylvester. High Stiffness High Damping Structure. Fort Belvoir, VA: Defense Technical Information Center, February 2002. http://dx.doi.org/10.21236/ada407965.

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2

Smith, H. A. Adaptive Control of Smart Structures with Time Variant Stiffness and Damping. Fort Belvoir, VA: Defense Technical Information Center, March 1997. http://dx.doi.org/10.21236/ada326843.

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Creasy, Terry S., Gary Hawkins, Ching-Yao Tang, Brain W. Gore, Juliet N. Schurr, Aaron L. Cheung, and Gene Cha. FFATA: Mechine Augmented Composites for Structures with High Damping with High Stiffness. Fort Belvoir, VA: Defense Technical Information Center, December 2012. http://dx.doi.org/10.21236/ada586575.

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4

Griffin, Jerry H. Friction Test Specimens That Will Be Used to Measure Nonlinear Damping and Stiffness. Fort Belvoir, VA: Defense Technical Information Center, September 2004. http://dx.doi.org/10.21236/ada427102.

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5

Weinacht, Paul, and James E. Danberg. Prediction of the Pitch-Damping Coefficients Using Sacks Relations. Fort Belvoir, VA: Defense Technical Information Center, June 2004. http://dx.doi.org/10.21236/ada425202.

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6

Paden, Brad, and Thomas A. Trautt. Characterization of Joint Nonlinear Stiffness and Damping Behavior for Inverse Dynamics of Flexible Articulated Structures. Fort Belvoir, VA: Defense Technical Information Center, August 1996. http://dx.doi.org/10.21236/ada330608.

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EXPERIMENTAL STUDY ON SEISMIC PERFORMANCE OF PEC COMPOSITE COLUMN-STEEL BEAM FRAME WITH WELDED T-STUB STRENGTHENED CONNECTIONS. The Hong Kong Institute of Steel Construction, September 2021. http://dx.doi.org/10.18057/ijasc.2021.17.3.5.

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Seismic performance of innovative Partially Encased Composite (PEC) column-steel beam composite frame was investigated, where the connection was strengthened by the welded T-stub. A ½ scale, two-storey, and one bay composite frame specimen was designed and fabricated for the quasi-static test. Through the experimental observation and measurements, the seismic performance were evaluated, including hysteretic characteristic, lateral stiffness, seismic energy dissipation, and ductility. The plastic damage evolution process and ductile failure mode were clarified. The results indicated that the welded T-stud strengthened connection enhanced the integrity of the frame and led to higher seismic strength and larger lateral stiffness. The plastic hinge was observed away from the beam end due to the welded T-stud and the specimen exhibited an approximately completed hysteretic loop. Without significant decreasing of the ultimate bearing capacity, its overall drift, ductility efficient and equivalent viscous damping ratio were 3.63% (push) / 4.07% (pull), 3.21 (push) / 3.70 (pull) and 0.261 respectively. The proposed structure possesses sound deformation, ductility, and energy-dissipation capacity with the desired plastic failure mode induced by the plastic hinges formed in all beam sections near the T-stud end and column section at the bottom, successively. It was demonstrated an ideal ductile energy-dissipation mode of the frame structure.

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