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Academic literature on the topic 'Logarithmic decrement'

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Published: 4 June 2021
Last updated: 4 February 2022

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Journal articles on the topic "Logarithmic decrement"

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Savinov, A. M., G. M. Nigmetov, S. D. Kovaleva, and T. G. Nigmetov. "DEDETERMINATION OF THE LOGARITHMIC DECREMENT OF NATURAL VIBRATIONS OF BUILDINGS AND STRUCTURESTERMINATION OF THE LOGARITHMIC DECREMENT OF NATURAL VIBRATIONS OF BUILDINGS AND STRUCTURES." STRUCTURAL MECHANICS AND ANALYSIS OF CONSTRUCTIONS, no. 1 (February 25, 2021): 62–65. http://dx.doi.org/10.37538/0039-2383.2021.1.62.65.

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Abstract. For the passport of buildings and structures, it is required to determine the logarithmic damping decrement. The proposed expressions [1, 2] to determine the decrement use the value of the Q-factor, however, an expression is known in which the damping decrement is determined through the logarithm of the ratio of the amplitudes of the damped signal. Comparison of the formulas for calculating the logarithmic decrement of vibrations was carried out using the example of data obtained when testing a beam with reinforcement.
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Magalas, Leszek B. "Determination of the Logarithmic Decrement in Mechanical Spectroscopy." Solid State Phenomena 115 (August 2006): 7–14. http://dx.doi.org/10.4028/www.scientific.net/ssp.115.7.

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The comparison between the classical methods and a new algorithm OMI used to compute the logarithmic decrement is reported. The OMI algorithm is tested in the computation of the logarithmic decrement from exponentially damped harmonic oscillations. The OMI algorithm yields high precision in the computation of the logarithmic decrement and the resonant frequency, and the smallest dispersion of experimental points.
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Stanislawczyk, A. "Advanced Techniques for Determining High and Extreme High Damping: OMI - A New Algorithm to Compute the Logarithmic Decrement." Key Engineering Materials 319 (September 2006): 231–0. http://dx.doi.org/10.4028/www.scientific.net/kem.319.231.

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A new algorithm OMI (Optimization in Multiple Intervals) for the computation of the logarithmic decrement from exponentially damped harmonic oscillations is described. This method is shown to be effective and computationally compact for high damping materials. A comparison between the OMI algorithm and the four classical methods usually used in the computation of the logarithmic decrement is reported. The OMI algorithm yields high precision in the computation of the logarithmic decrement and the smallest dispersion of experimental points on the plots of mechanical loss spectra. The effect of the acquisition parameters and the experimental conditions on the results of computations of the logarithmic decrement and the relative error is discussed.
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Magalas, Leszek B., and T. Malinowski. "Measurement Techniques of the Logarithmic Decrement." Solid State Phenomena 89 (February 2003): 247–60. http://dx.doi.org/10.4028/www.scientific.net/ssp.89.247.

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Magalas, Leszek B., and M. Majewski. "Recent Advances in Determination of the Logarithmic Decrement and the Resonant Frequency in Low-Frequency Mechanical Spectroscopy." Solid State Phenomena 137 (March 2008): 15–20. http://dx.doi.org/10.4028/www.scientific.net/ssp.137.15.

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The advantages of the OMI algorithm to compute the logarithmic decrement and the resonant frequency from free decaying oscillations is reported. The OMI algorithm is proved to be the best solution in the computation of the logarithmic decrement and the resonant frequency for high damping levels.
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Mayama, Masakazu, and Masatoshi Harada. "Logarithmic Decrement and Dynamic Modulus of Coated Cement Concrete." Key Engineering Materials 302-303 (January 2006): 493–99. http://dx.doi.org/10.4028/www.scientific.net/kem.302-303.493.

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This report presents a research on vibration absorption properties of coated cement concrete, by discussing the logarithmic decrement and dynamic modulus obtained from bending vibration test at various temperatures. The effect of temperature and bitumen content on the vibration properties of materials was evaluated. As temperature and/or coating asphalt content increased, coated cement concrete increased logarithmic decrement and resulted in increasing vibration absorption than the conventional cement concrete. The vibration properties of coated cement concrete were similar to those of conventional cement concrete in the low temperature range. The dynamic modulus of coated cement concrete decreased at higher temperatures. The rate of decrease of dynamic modulus at higher temperatures was comparatively small in comparison with the rate of increase of logarithmic decrement.
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Little, Jared A., and Brian P. Mann. "Optimizing logarithmic decrement damping estimation through uncertainty propagation." Journal of Sound and Vibration 457 (September 2019): 368–76. http://dx.doi.org/10.1016/j.jsv.2019.05.040.

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Magalas, Leszek B., and M. Majewski. "Toward High-Resolution Mechanical Spectroscopy HRMS - Logarithmic Decrement." Solid State Phenomena 184 (January 2012): 467–72. http://dx.doi.org/10.4028/www.scientific.net/ssp.184.467.

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In this work, we present the comparison between different methods used to compute the logarithmic decrement,δ. The parametric OMI method and interpolated DFT (IpDFT) methods are used to compute theδfrom free decaying oscillations embedded in an experimental noise typical for low-frequency mechanical spectrometers. The results are reported forδ= 5×10-4, = 1.12345 Hz and different sampling frequencies, = 1 kHz and 4 kHz. A new YM algorithm yields the smallest dispersion in experimental points of the logarithmic decrement and the smallest relative errors among all investigated IpDFT methods. In general, however, the IpDFT methods suffer from spectral leakage and frequency resolution. Therefore it is demonstrated that the performance of different methods to compute theδcan be listed in the following order: (1) OMI, (2) YM, (3) YMC, and (4) the Yoshida method, Y. For short free decays the order of the best performers is different: (1) OMI and (2) YMC. It is important to emphasize that IpDFT methods (including the Yoshida method, Y) are discouraged for signals that are too short. In conclusion, the best methods to compute the logarithmic decrement are the OMI and the YM. These methods will pave the way toward high-resolution mechanical spectroscopy HRMS.
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El-Morsy, Abdel-Wahab, and Ahmed I. Z. Farahat. "Effect of Aging Treatment on the Damping Capacity and Mechanical Properties of Mg-6Al-1Zn Alloy." Scientific World Journal 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/170458.

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The damping capacity and mechanical properties of Mg-6Al-1Zn alloy after heat treatment were investigated. The damping characteristics of un-heat-treated, solution treated, and aged Mg-6Al-1Zn specimens were determined by measuring the damping ratio and the logarithmic decrement of free vibrations of a bending beam clamped at one side. The microstructural evaluations confirmed that theβ-Mg17Al12phase was reprecipitated after aging and increased with an increase in aging time. The peak level of damping ratio and logarithmic decrement was obtained after 34 hr of aging time, over which the damping capacity declined according to increasing amount of strong pining points.
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Magalas, L. B., and M. Majewski. "Hilbert-Twin – A Novel Hilbert Transform-Based Method To Compute Envelope Of Free Decaying Oscillations Embedded In Noise, And The Logarithmic Decrement In High-Resolution Mechanical Spectroscopy HRMS." Archives of Metallurgy and Materials 60, no. 2 (June 1, 2015): 1091–98. http://dx.doi.org/10.1515/amm-2015-0265.

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Abstract In this work, we present a novel Hilbert-twin method to compute an envelope and the logarithmic decrement, δ, from exponentially damped time-invariant harmonic strain signals embedded in noise. The results obtained from five computing methods: (1) the parametric OMI (Optimization in Multiple Intervals) method, two interpolated discrete Fourier transform-based (IpDFT) methods: (2) the Yoshida-Magalas (YM) method and (3) the classic Yoshida (Y) method, (4) the novel Hilbert-twin (H-twin) method based on the Hilbert transform, and (5) the conventional Hilbert transform (HT) method are analyzed and compared. The fundamental feature of the Hilbert-twin method is the efficient elimination of intrinsic asymmetrical oscillations of the envelope, aHT (t), obtained from the discrete Hilbert transform of analyzed signals. Excellent performance in estimation of the logarithmic decrement from the Hilbert-twin method is comparable to that of the OMI and YM for the low- and high-damping levels. The Hilbert-twin method proved to be robust and effective in computing the logarithmic decrement and the resonant frequency of exponentially damped free decaying signals embedded in experimental noise. The Hilbert-twin method is also appropriate to detect nonlinearities in mechanical loss measurements of metals and alloys.
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Dissertations / Theses on the topic "Logarithmic decrement"

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Savage, Nicholas James, and nicolasshu709@hotmail com. "Vibration absorption in the tennis grip and the effects on racquet dynamics." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080522.153134.

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The modern game of tennis has changed in recent years as a result of lightweight, stiffer racquets. The evolution of the tennis racquet, with respect to both design and materials, has increased the speed of the game but also the levels of stress placed on the player's bodies. Many believe that injuries such as lateral epicondylitis (tennis elbow) are caused and aggravated by the absorption of racquet energy by the player, in the form of shock and vibration. This thesis presents an experimental investigation into the absorption of racquet vibration to the player's hand and forearm. Quantification of the tennis grip has been achieved in this research using different experimental techniques to analyse different aspects of the tennis grip. Grip pressure distribution profiles during impact have been established using both pressure sensitive film and real-time data acquisition methods. Quantification of grip tightness during impact, together with gripping times, has also been quantified using a strain gauge cantilever system manufactured specifically for this research. The experimental data acquired in this research has provided the base for grip pressure distribution profiles to be established for three stroke types (e.g. Forehand, service and the problematic backhand). The profiles depict the distribution of pressure in the tennis grip in relation to the ball impact, in the time domain. Based on these grip profiles, the research hypothesises hand movements in an attempt to establish muscle contractions (and moreover locations of vibration absorption) specific to stroke types. The research investigates the absorption of racquet vibrations by the player's hand in the time domain. Filtering of accelerometer data allows for the isolation of specific frequencies of interest (i.e. below 200Hz). Logarithmic decrement of racquet vibration has been calculated and related to the grip pressure distributions in the time domain, and the relationship between grip pressure and vibration damping has been modelled. The correlation between grip pressure and the logarithmic decrement has been show to be significant (p less than 0.005) and non-linear. The relationship between the tennis grip and the damping of racquet vibrations has been found to be dependant on both grip pressure and the proximity of grip pressure application in proximity to the handle node. Grip pressure applied to the racquet close to the handle node has a greater damping effect than a similar pressure further away. In addition to these key research findings, the effectiveness of a piezoelectric racquet damping system is also investigated. A comprehensive modal analysis of two tennis racquets is given with further ball impact tests. The ball impact tests showed that the damping system has a 28% difference in racquet vibrations during freely suspended grip conditions. However, under hand-held grip conditions the inclusion of grip damping into the system provides a much greater damping entity (880% greater). Therefore, the effect of the piezoelectric system was deemed to be negligible.
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Book chapters on the topic "Logarithmic decrement"

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Gooch, Jan W. "Logarithmic Decrement." In Encyclopedic Dictionary of Polymers, 432. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_7000.

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Little, Jared A., and Brian P. Mann. "Optimizing Logarithmic Decrement Damping Estimation via Uncertainty Analysis." In Special Topics in Structural Dynamics & Experimental Techniques, Volume 5, 19–22. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-12243-0_3.

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Magalas, Leszek B. "Determination of the Logarithmic Decrement in Mechanical Spectroscopy." In Solid State Phenomena, 7–14. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/3-908451-24-8.7.

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Mayama, Masakazu, and Masatoshi Harada. "Logarithmic Decrement and Dynamic Modulus of Coated Cement Concrete." In Environmental Ecology and Technology of Concrete, 493–99. Stafa: Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/0-87849-983-0.493.

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Magalas, Leszek B., and M. Majewski. "Recent Advances in Determination of the Logarithmic Decrement and the Resonant Frequency in Low-Frequency Mechanical Spectroscopy." In Solid State Phenomena, 15–20. Stafa: Trans Tech Publications Ltd., 2008. http://dx.doi.org/10.4028/3-908451-53-1.15.

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"Logarithmic decrement." In Encyclopedic Dictionary of Polymers, 581. New York, NY: Springer New York, 2007. http://dx.doi.org/10.1007/978-0-387-30160-0_6890.

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Conference papers on the topic "Logarithmic decrement"

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Bulbik, Y. "Logarithmic decrement evaluation of damped oscillations by integral signal processing." In The 27th annual review of progress in quantitative nondestructive evaluation. AIP, 2001. http://dx.doi.org/10.1063/1.1373817.

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Lamarque, C. H., and S. Pernot. "A Wavelet-Logarithmic Decrement to Identify Damping in MDOF Systems: Theory and Applications." In ASME 2001 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/detc2001/vib-21008.

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Abstract A wavelet-based formula similar to the logarithmic decrement formula is introduced to estimate damping in multi-degree-of-freedom systems from time-domain responses. The new formula is then validated upon both numerical and in-situ experiments.
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Chandler, Cordelia K. "Methods of Determining a Damping Ratio From a Simple Impact Test." In ASME 2005 Pressure Vessels and Piping Conference. ASMEDC, 2005. http://dx.doi.org/10.1115/pvp2005-71041.

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Numerous tests have been performed in the nuclear industry to determine damping ratios for the analysis of steam generator tube bundles. Several methods have been used to analyze the response data, including the logarithmic decrement method, the half-power point method, and curve-fitting methods. Theoretically, the methods give the same damping results; however, in practice, the results may be appreciably different. Each of these methods presents certain difficulties in determining a damping ratio. For the half-power point method, the difficulties include selecting a sampling rate, setting a time span, and the use of a window to truncate the data. The difficulties associated with the logarithmic decrement method include selecting the initial and final peaks and selecting an appropriate frequency. In both cases, most of the difficulties arise from the need for subjective decisions by the engineer or technician. Blind curve-fitting methods have been shown to underestimate the actual damping. A practical comparison of these three methods was performed on damping data from a simple impact test. While the half-power point method and curve-fitting methods are useful tools to validate damping results, a logarithmic decrement method that averages the damping over a number of cycles appears to provide the most consistent and realistic damping results for SG tubes.
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Eldridge, Thom M., and Thomas A. Soulas. "Mechanism and Impact of Damper Seal Clearance Divergence on the Rotordynamics of Centrifugal Compressors." In ASME Turbo Expo 2005: Power for Land, Sea, and Air. ASMEDC, 2005. http://dx.doi.org/10.1115/gt2005-69104.

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Damper seals (such as honeycomb and hole pattern seals) have been widely used in the turbomachinery industry to counterbalance destabilizing aerodynamic forces acting on the rotor system and to provide the necessary amount of damping for stable operation of the machine. Recent experience and research developments have focused the interest of the turbomachinery community on the dynamic characteristics of the divergent-taper damper seal. In addition to offering a review of the current literature on the subject of interest (in order to provide a comprehensive vision of the overall phenomenon), this paper extends the discussion for a better understanding of the mechanism and impact of damper seal clearance divergence on the rotordynamics of a rotor-bearing-seal system (as applied to centrifugal compressors). The analysis of a damper seal alone is insufficient to assess the influence of this component on the rotordynamic stability of a turbocompressor. This paper will show the variation of a complete rotor-bearing-seal system’s logarithmic decrement as a function of the hole pattern seal clearance divergence for a sample centrifugal compressor application, as analyzed with the proprietary, state-of-the-art rotordynamic software suite from the author’s company. This divergence-based transition of system logarithmic decrement from positive to zero (thereby implying the onset of instability) leads to the definition of a “damper seal divergence stability threshold.” Divergence in a damper seal can originate from numerous sources, including taper produced during manufacture, and pressure or thermal-driven distortion of the seal under operation. While small damper seal divergence may first produce an increase of the system logarithmic decrement, additional seal divergence has a dramatic effect on the first forward whirling mode natural frequency, as well as on the logarithmic decrement of that mode. This paper describes the analytical methods used to derive the stability of the rotor-bearing-seal system. It also presents a practical experience that stresses the necessity for a sound approach to properly evaluate the impact of a divergent damper seal on the stability of centrifugal compressors.
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Lifson, Alexander, and Cecil R. Sparks. "Surge Model: Predicting Damping and Excitation Frequencies of Complex Pumping Systems." In ASME 1989 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1989. http://dx.doi.org/10.1115/89-gt-93.

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Frequency domain analysis is presented to define susceptibility of complex pumping systems to surge oscillations. In the analysis, piping spans are considered as distributed elements, compressors or pumps, orifices, valves, and junctions as lumped acoustic four pole elements. The piping elements are connected into one network through the use of appropriate matching boundary conditions. The analysis is most readily applicable to single stage units, typical of gas transmission stations. The surge model is based on predicting damping (logarithmic decrement values) and mode shapes for pressure and flow pulsations of the interactive dynamic system at its various natural acoustic frequencies. The system design is optimized by assuring that all operating points are sufficiently removed from surge, i.e., logarithmic decrements are above certain specified value. The effects of mean flow on acoustic wave propagation, pipe friction, viscothermal dissipation, and pressure losses at various piping locations (junctions, valves, orifices) are accounted for in the model. Results of the computational modeling of a complex centrifugal compressor system is presented. The analytical model is also verified by comparing the analytical results with experimental data.
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Li, Wei, Christopher Braman, Brian Hantz, Manish Thorat, and Brian Pettinato. "Squeeze Film Damper Bearing With Double-Ended Beam Springs: Part II — Experimental Validation." In ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/gt2020-15491.

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Abstract To validate a new squeeze film damper (SFD) bearing design introduced in [1], a pair of 3.5 inch SFD bearings were manufactured and tested. Static spring compression test was conducted to prove the spring design stiffness calculated through the geometry parametric spring model. High cycle loading fatigue testing of the spring was conducted to validate the design spring fatigue limit. The entire SFD bearing assembly was inspected and checked through a SFD centering bench test before the rotor dynamic test. Unbalance response correlation and logarithmic decrement (Log. Dec.) measurement using the operational modal analysis (OMA) method were employed for the rotor-dynamic tests. An agreement was seen between the analysis and the experimental measurement. It was seen that the SFD bearing provided the extra damping as expected to suppress the unbalance vibration when passing through the critical speed and also improve the stability (Log. Dec.) of the rotor. It was found that the measured SFD damping was closer to the full film damping model when the squeeze oil film was sealed with O-rings. The SFD improved the logarithmic decrement of the rotor-bearing system from 0.07 to more than 0.21 as compared to the system without SFD.
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Wang, Weimin, Qihang Li, Lifang Chen, Jinji Gao, and Paul Allaire. "Effect of Specific Load of Bearing on the Centrifugal Compressor Rotordynamic Stability." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-42977.

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With the ever increasing of the centrifugal compressor capability, such as large scale LNG and CO2 re-injection, the stability margin evaluation and instability control is crucial both for the centrifugal compressor OEM and end users. An industrial scale experimental test rig with two 5-pads tilting pad journal bearings and two active magnetic bearings was introduced. Tilting pad bearings were used to support the rotor, and active magnetic bearings were used to exert static load and sub-synchronous sine load to excite the rotor. The logarithmic decrement identification method of rotor-bearing system was presented. Here, weighted instrument variable and directional frequency response function were combined to improve anti-noise performance and separate forward/ backward whirl vibration. Thermoelastohydrodynamic bearing model was used to investigate the effect of hot clearance on the stability prediction of centrifugal compressor. Also, the contribution of bearing specific load on the stability was studied numerically. Also, experimental work was carried out to investigate the damping ratio of rotor under different rotating speed and bearing specific loads. The numerical results correlate with the test results very well. The results of the investigation indicate that: (i) Hot clearance is very important for centrifugal compressor rotordynamic instability prediction; (ii) The effect of pad mechanical deformation are smaller than that of thermal deformation; (iii) With the increase of bearing specific load, the logarithmic decrement is decreasing.
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Moran, Joaquin E., and David S. Weaver. "Damping Measurements in Tube Bundles Subjected to Two-Phase Cross Flow." In ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93431.

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An experimental study was conducted to investigate two-phase damping in tube arrays. The objective was to compare different measurement methodologies in order to obtain a more reliable damping estimate. This will allow for improved guidelines related to failures due to fluidelastic instability in tube bundles. The methods compared were the traditionally used half-power bandwidth, the logarithmic decrement and an exponential fitting to the tube decay response. The working fluid used was Refrigerant 11 (Freon), which better models the real steam-water problem, as it allows for phase change. The void fraction was measured using a gamma densitometer, introducing an improvement over the traditional Homogeneous Equilibrium Model (HEM) in terms of velocity and density predictions. The results obtained by using the half-power bandwidth method agree with data previously reported for two-phase flow. The experiments showed that the half-power bandwidth produces higher damping values than the other two, but only up to a certain void fraction. After that point, the results obtained from the three methods are very similar. The exponential fitting proved to be more consistent than the logarithmic decrement, and it is not as sensitive as the half-power bandwidth to the frequency shifting caused by the change in added mass around the tube. By plotting the damping ratio as a function of void fraction, pitch mass flux and flow regime, we were able to verify that damping is more dependent on void fraction and flow regime than on mass flux.
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Delgado, Adolfo, Mirko Librashi, and Giuseppe Vannini. "Dynamic Characterization of Tilting Pad Journal Bearings From Component and System Level Testing." In ASME Turbo Expo 2012: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/gt2012-69851.

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The dynamic response of a direct lube, 5-pad, rocker-back pivot tilting pad bearing is characterized in a controlled motion (component level) test rig, and in a spin bunker (full system level) using a dummy rotor mounted on two identical bearings. In the component level test, the force coefficients (stiffness, damping, mass) are identified from pseudorandom excitations using a 2-DOF model. N-DOF system including the pad motions has been shown to yield frequency dependent coefficients that warrant the use of asynchronous coefficients for stability analysis in centrifugal compressors. However, experimental results showed that the real part of the dynamic stiffness is well represented as a constant stiffness and mass coefficients while the imaginary part yields a constant damping coefficient (i.e. frequency independent). In the system level test, a dedicated dummy rotor (representative of a high speed centrifugal compressor rotor) is excited by a magnetic shaker throughout a frequency range covering the rotor modes of interest while spinning at constant speed. From the rotor harmonic response the damping of each mode is extracted using a curve-fitting method based on a 1-DOF model for a given set of speeds. The dummy rotor test provides reference values for system logarithmic decrement and further validates the component level test results. The logarithmic decrement prediction using identified bearing force coefficients are in good agreement with the experimental results. In addition, using for prediction identified coefficients in a classical K-C-M or synchronous K-C form yields similar results (within 15%). This indicates that for the given bearing geometry (clearance, offset and size) and operating conditions, synchronously reduced force coefficients are adequate for stability analysis. Comparison of the identified force coefficients with results from commercially available code yielded reasonable agreement on direct coefficients while some discrepancies are highlighted on the cross-coupled coefficients.
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Olunloyo, Vincent O. S., Charles A. Osheku, and Femi Agboola. "Vibration Damping and Active Noise Control in Ships and Floating Structures." In ASME 2007 26th International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2007. http://dx.doi.org/10.1115/omae2007-29015.

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Vibration and noise reduction in ships and floating structures can significantly enhance dynamic stability and improve hydrodynamic performance during navigation, exploration and exploitation of deep and ultra-deep offshore geo-resources. In this paper, slip damping with sandwich composite elastic beam-plate smart structures for dissipation of vibration and active noise control mechanism is investigated analytically. For this problem, a boundary value partial differential equation is formulated for linear and non-linear hydrodynamic wave loading. In particular the effect of interfacial pressure distribution variation at the interface of the layered smart structures on the energy dissipation, logarithmic damping decrement and spatial transfer function is analyzed and presented for design application and selection of stabilizers.
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