Academic literature on the topic 'Mode vibration cycle'
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Journal articles on the topic "Mode vibration cycle"
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Mroz, A., A. Orlowska, and J. Holnicki-Szulc. "Semi-Active Damping of Vibrations. Prestress Accumulation-Release Strategy Development." Shock and Vibration 17, no. 2 (2010): 123–36. http://dx.doi.org/10.1155/2010/126402.
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New method for semi-active control of vibrating structures is introduced. So-called Prestress Accumulation-Release (PAR) strategy aims at releasing of the strain energy accumulated in the structure during its deformation process. The strain energy is converted into kinetic energy of higher modes of vibration which is suppressed with structural damping or by means of a damping device. The adaptation process essentially affects the first mode vibrations by introducing an elastic force that opposes the movement. Numerical simulations as well as experimental results prove that the strategy can be very effective in mitigating of the fundamental mode of a free – vibrating structure. In a numerical example 95% of the vibration amplitude was mitigated after two cycles. An experimental demonstrator shows 85% reduction of the amplitude in a cantilever free- vibrations. In much more complex practical problems smaller portion of total energy can be released from the system in each cycle, nevertheless the strategy could be applied to mitigate the vibrations of, for example, pipeline systems or pedestrian walkways.
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Sun, Ying, and Yan Hong. "Analysis of Dynamic Performance of Air-Cooled Condenser Structure System." Applied Mechanics and Materials 170-173 (May 2012): 2675–80. http://dx.doi.org/10.4028/www.scientific.net/amm.170-173.2675.
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In situ measurements on two power plants designed air-cooled condenser structure were described in this paper. Operating condition was divided into three types to test the structure system, and then obtaining the data of time-domain waveform and spectrum analysis in each condition. Cycle, frequency and vibration mode of the structure system were obtained by analyzing the data. Meanwhile, the structure was theoretically calculated using finite element program, gaining the cycle, frequency and vibration mode of the structure system. It was concluded that basic vibration mode of the structure system was space torsional vibration by comparison between theoretical values and measured values.
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Feng, Yang, Xiao Diao Huang, Jie Chen, and Rong Jing Hong. "A Novel Denoising Method Based on Ensemble Empirical Mode Decomposition – Principle Component Analysis." Applied Mechanics and Materials 668-669 (October 2014): 1157–61. http://dx.doi.org/10.4028/www.scientific.net/amm.668-669.1157.
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Equipment performance degradation model is a key component in its diagnosis and prognosis models. As to slewing bearing, vibration signals are usually non-stationary and with strong white noise, which makes it very difficult to extract useful information from the signals. Therefore, an Ensemble Empirical Mode Decomposition – Principle Component Analysis (EEMD - PCA) based method was proposed to denoise the vibration signals and performance degradation model was established by PCA. To verify the proposed method, an experiment was conducted and the life cycle vibration signals were acquired. After denoising, performance degradation model was established to explain the denoising performance. Results show that the proposed method acquired a better denoising performance than EEMD-MSPCA, which provides a potential for further research.
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Gordon Kirk, R., and Ali A. Alsaeed. "Induced Unbalance as a Method for Improving the Dynamic Stability of High-Speed Turbochargers." International Journal of Rotating Machinery 2011 (2011): 1–9. http://dx.doi.org/10.1155/2011/952869.
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The high-speed diesel engine turbocharger is known to have subsynchronous vibrations for a wide speed range. The bearing fluid-film instability is the main source of the vibration. The nonlinear forces inside the bearings are causing the rotor to whirl in a limit cycle. This study presents a new method for improving the dynamic stability by inducing the turbocharger rotor unbalance in order to suppress the subsynchronous vibration. The finite-element model of the turbocharger with floating-ring bearings is numerically solved for the nonlinear time-transient response. Both compressor and turbine added unbalance are induced and the dynamic stability is computed. The turbocharger model with linearized floating-ring bearings is also solved for eigenvalues to predict the modes of instability. The linear analysis demonstrates that the forward whirling mode of the floating-ring at the compressor end also becomes unstable at the higher turbocharger speeds, in addition to the unstable forward conical and cylindrical modes. The numerical predictions are also compared to the former experimental results of a similar turbocharger. The results of the study show that the subsynchronous frequency amplitude of the dominant first mode is reduced when inducing either the compressor or the turbine unbalance at a certain level.
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Reeves, M., N. Taylor, C. Edwards, D. Williams, and C. H. Buckberry. "A study of brake disc modal behaviour during squeal generation using high-speed electronic speckle pattern interferometry and near-field sound pressure measurements." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 214, no. 3 (March 1, 2000): 285–96. http://dx.doi.org/10.1243/0954407001527420.
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The out-of-plane surface vibration of a brake disc during naturally excited squeal has been investigated using a combination of high-speed electronic speckle pattern interferometry (ESPI) and near-field sound pressure measurements. Both techniques provide visualization and quantification of the time-resolved surface velocity. A mathematical description of disc brake squeal modal behaviour is proposed that predicts accurately all of the experimentally observed interferometry and sound field measurements. The complex mode description proposed here is in agreement with that proposed by others for drum brake squeal. This assumes that two identical diametral modes are excited simultaneously, identical except for a spatial and temporal phase shift. The use of a near-field microphone array provided a convenient multipoint, non-contacting vibration probe which may find use in the study of other vibrations characterized by high surface amplitudes and efficient sound radiation. The high-speed ESPI provided a real-time visualization of surface deformation analogous to double- pulsed holographic interferometry, with the benefit of giving a true time series of the surface deformation during a single vibration cycle.
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Fraas, Arthur P. "Using Vibrations in Fluidized Beds." Mechanical Engineering 120, no. 01 (January 1, 1998): 76–79. http://dx.doi.org/10.1115/1.1998-jan-7.
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This article focuses on processes that do not require a high flow rate of sweep gas; the complex-mode vibration-fluidized bed offers lower power needs, attrition rates, and elutriation rates than gas-fluidized beds or rotary kilns. The fluidized solids are induced to flow horizontally by inclining the trough and/or axis of vibration downward in the direction of solids flow. When viewing the operating region through a window in the side wall, the particles in the bed move in unison, like a column of marching soldiers. In light of the complexities and uncertainties in the interaction of adjacent particles in the fluidized bed, the dynamics of a single particle falling on a horizontal plate vibrating along a vertical axis should be considered first. Because the complex-mode vibration-fluidized bed can be tailored for certain applications, a number of projects are currently in the early stages of development. Promising uses include coal pyrolysis to produce fuel for gas turbines in combined-cycle power plants, the manufacture of char for superior activated carbon, recycled synthetic fiber in carpeting, and counterflow heat exchangers.
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Datta, Nabanita. "Vortex-induced vibration of a tension leg platform tendon: Multi-mode limit cycle oscillations." Journal of Marine Science and Application 16, no. 4 (November 20, 2017): 458–64. http://dx.doi.org/10.1007/s11804-017-1440-8.
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Basaran, C., and R. Chandaroy. "Nonlinear Dynamic Analysis of Surface Mount Interconnects: Part I—Theory." Journal of Electronic Packaging 121, no. 1 (March 1, 1999): 8–11. http://dx.doi.org/10.1115/1.2792663.
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Solder joints are commonly used in surface mount technology microelectronics packaging. It is well known that the dominant failure mode for solder joints is thermal fatigue. When semiconductor devices are used in a vibrating environment, such as in automotive and military applications, dynamic stresses contribute to the failure mechanism and in certain circumstances they can become the dominant failure cause. In this paper a unified constitutive model for Pb40/Sn60 solder joints is developed and then implemented in a finite element dynamic analysis procedure. The purpose of the material model and the implementation is to study the contribution of vibration induced strains to the fatigue life of solder interconnects in low cycle and high cycle fatigue. The proposed material model, which is based on the disturbed state concept (DSC), is used for a dynamic analysis of a solder joint in the following paper, Part II, Basaran and Chandaroy (1998).
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Mathison, R. M., M. G. Dunn, M. M. Weaver, and A. Dushko. "Measurement of Air Film Damping Effectiveness." Journal of Turbomachinery 127, no. 3 (March 1, 2004): 557–63. http://dx.doi.org/10.1115/1.1928288.
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Air film damping systems have attracted considerable interest within the gas turbine industry because of their effectiveness at controlling modes of vibration without environmental limitations. Though still in the early stages of development, air film dampers have promise for improving the high cycle fatigue characteristics of solid gas turbine airfoils. This study used experimental methods to compare the vibrational response of a solid flat plate with the response of an identically sized plate that incorporated an air film damper. It also investigated the influence of elevated pressures on air film damping effectiveness, the impact of the damper on the various vibration modes, and the relative strain levels of the air film cover plate to the solid backing. The results show that the air film damper is very effective in controlling the two-stripe mode for which it was designed. Increasing the surrounding air pressure makes the damper more effective and shifts the resonant frequencies lower.
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Witek, Lucjan. "Experimental and Numerical Crack Initiation Analysis of the Compressor Blades Working in Resonance Conditions." Fatigue of Aircraft Structures 2011, no. 3 (August 1, 2011): 134–53. http://dx.doi.org/10.2478/v10164-010-0045-3.
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Experimental and Numerical Crack Initiation Analysis of the Compressor Blades Working in Resonance ConditionsThis paper presents the results of a complex experimental and numerical crack initiation analysis of the helicopter turbo-engine compressor blades subjected to vibrations. A nonlinear finite element method was utilized to determine the stress state of the blade during the first mode of transverse vibration. In this analysis, the numerical models without defects as well as those with V-notches were defined. The quality of the numerical solution was checked by the convergence analysis. The obtained results were next used as an input data into crack initiation (ε-N) analyses performed for the load time history equivalent to one cycle of the transverse vibration. In the fatigue analysis, the different methods such as: Neuber elastic-plastic strain correction, linear damage summation and Palmgreen-Miner rule were utilized. As a result of ε-N analysis, the number of load cycles to the first fatigue crack appearing in the compressor blades was obtained. Moreover, the influence of the blade vibration amplitude on the number of cycles to the crack initiation was analyzed. Values of the fatigue properties of the blade material were calculated using the Baumel-Seeger and Muralidharan methods. The influence of both the notch radius and values of the UTS of the blade material on the fatigue behavior of the structure was also considered. In the last part of the work, the finite element results were compared with the results of experimental vibration HCF tests performed for the compressor blades.
Dissertations / Theses on the topic "Mode vibration cycle"
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Elmaian, Alex. "Méthodologies de simulation des bruits automobiles induits par le frottement." Phd thesis, Université du Maine, 2013. http://tel.archives-ouvertes.fr/tel-00839253.
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Les bruits automobiles induits par le frottement sont à l'origine de nombreuses plaintes clients et occasionnent des coûts de garantie considérables pour les constructeurs automobiles. Les objectifs de la thèse consistent à comprendre la physique à l'origine de ces bruits et proposer des méthodologies de simulation afin de les éradiquer. Un système générique est tout d'abord étudié. Ce système discret met en jeu un contact entre deux masses et une loi de frottement de Coulomb présentant une discontinuité à vitesse relative nulle. Des calculs de valeurs propres complexes de ce système linéarisé autour de sa position d'équilibre glissant sont menés et montrent la présence d'instabilités par flottement voire par divergence. Les simulations temporelles montrent quant à elles que les non-linéarités de contact permettent de stabiliser les niveaux vibratoires en cas d'instabilité selon quatre régimes distincts. De plus, malgré ses trois degrés de liberté, ce système est capable de reproduire les mécanismes de stick-slip, sprag-slip et couplage modal ainsi que les bruits de crissement, grincement et craquement rencontrés sur les systèmes automobiles. Des études paramétriques sont également présentées et mettent en avant des bifurcations de Hopf ainsi que l'effet déstabilisant potentiellement induit par l'amortissement. Des méthodologies permettant de catégoriser les réponses en termes de bruit et de mécanisme sont par la suite proposées. Les occurrences et risques de ces derniers sont alors analysés et des tendances sont dégagées. Enfin, la relation entre les bruits et les mécanismes est établie. L'attention est ensuite portée sur un système automobile particulier. Afin d'étudier son comportement crissant, les analyses de stabilité et les simulations temporelles sont désormais menées sur des modèles éléments-finis. Les simulations temporelles permettent d'observer l'établissement de vibrations auto-entretenues et d'identifier, parmi tous les modes instables prédits lors des analyses de stabilité, celui qui est réellement à l'origine de l'instabilité. L'effet du coefficient de frottement sur les motifs de coalescence et les cycles limites est également investigué. Le risque de crissement est ensuite évalué pour des conditions d'utilisation variées du système. La méthodologie, basée sur des analyses de stabilité, permet de retrouver les principaux constats expérimentaux obtenus sur banc d'essai. Le rôle des géométries et des matériaux constituant le système est également discuté. Enfin, une solution permettant de réduire de façon significative le risque de crissement est proposée.
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Boulebnane, Hassane. "Étude conformationnelle et structurale des molécules hétéro-1 spiro (2. 5) octane par spectroscopie micro-onde." Nancy 1, 1988. http://www.theses.fr/1988NAN10091.
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L'étude des spectres de rotation de cinq isomères entre 12 et 26 GHZ permet la détermination des constantes de rotation dans l'approximation du rotateur rigide. La valeur du défaut d'inertie permet d'estimer la géométrie probable de chaque isomère et d'observer une déformation du cycle héxanique qui se manifeste surtout par un aplatissement
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Philippe, Jonathan. "Prédiction robuste du comportement vibratoire des redresseurs sectorisés désaccordés." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC020/document.
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Les différentes structures composant les moteurs aéronautiques requièrent des analyses dynamiques afin de prédire leur durée de vie. Pour des raisons d'allègement, les roues aubagées fixes de turbomachines, appelées redresseurs, sont conçus comme des ensembles de secteurs comportant plusieurs aubes. Cette architecture rompt la symétrie cyclique empêchant l'application des méthodes numériques l'exploitant. De plus, les dispersions géométriques et matériaux génèrent un désaccordage involontaire impliquant des zones de forte densité modale, dans lesquelles est observée une amplification de la réponse vibratoire, accrue par le caractère monobloc, et donc peu amorti, des secteurs. Une méthodologie statistique de prédiction du niveau vibratoire d'un secteur de redresseur désaccordé aléatoirement est développée ici. La modélisation des incertitudes est basée sur une approche paramétrique de la théorie probabiliste : des paramètres matériaux aléatoires suivant une loi uniforme sont associés à différentes parties du secteur. Une expansion de Karhunen-Loève permet de réduire le champ stochastique à un petit nombre de variables aléatoires et donc de diminuer les temps de calcul. Les modes stochastiques sont ensuite projetés sur ces espaces aléatoires par le biais de deux méthodes d'interpolation non-intrusives. La première est basée sur une projection sur une base du chaos polynomial tandis que la deuxième est une méthode de régression non-paramétrique (méthode MARS). Afin d'appliquer les deux méthodes de calcul à un modèle industriel, une méthode de double synthèse modale est appliquée permettant de diviser le temps de calcul des modes par un facteur d'environ 300. La sous-structuration adoptée s'adapte à la méthode de modélisation des incertitudes et s'avère robuste vis-à-vis du désaccordage. De plus, les deux méthodes permettent d'obtenir des résultats prédictifs en termes de moments statistiques tout en réduisant les temps de calculs. Enfin, la méthodologie est validée expérimentalement puisque l'enveloppe vibratoire numérique encadre la réponse fréquentielle expérimentale au niveau de la zone des modes d'intérêt. Une stratégie de positionnement des jauges de déformation est proposée à partir d'une distribution statistique des déplacements maximaux à mi-hauteur de veine sur une plage fréquentielle donnéeAircraft engine components necessitate extensive dynamical analyses in order to obtain life cycle prediction. In order to lighten the structure, turbomachinery stator bladed disks, called stator vanes, are designed as a set of multiple blades clusters. This architecture implies a loss of cyclic symmetry condition and prevents the use of numerical methods using it. Moreover, geometric dispersions and materials defaults generate an involuntary mistuning involving high modal density areas, in which is observed an amplification of the vibratory response, enhanced by the monobloc character - and hence low damped - of stator vanes. A statistical methodology for predicting the vibratory level of a randomly mistuned industrial stator vanes is developed here. Uncertainties modelization is based on a parametric approach of the probability theory : material random parameters following a uniform distribution are associated with different cluster's parts. A Karhunen-Loeve expansion reduces the stochastic field to a small number of random variables and therefore reduces the computation time. Stochastic modes are then projected on these random spaces through two non-intrusive methods of interpolation. The first is based on a projection on a polynomial chaos basis while the second is non-parametric regression method (MARS method). In order to implement both numerical methods to an industrial model, a double modal synthesis method is applied to divide the calculation time of modes by a factor around 300. The sub-structuring way adopted fits the uncertainties modelization method and is robust towards mistuning. Moreover, both methods yield predictive results in terms of statistical moments while reducing computation time. Finally, the methodology is experimentally validated because the numerical vibratory envelope frames the experimental frequency response at the area of the modes of interest. A positioning strategy of strain gauges is proposed based on a statistical distribution of the maximum displacements in vein halfway over a given frequency range
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Iranpour, Mohammad. "FATIGUE CHARACTERIZATION OF RISERS AND PIPELINES UNDER REALISTIC VARIABLE AMPLITUDE LOADING AND THE INFLUENCE OF COMPRESSIVE STRESS CYCLES." Thesis, 2013. http://hdl.handle.net/10222/50472.
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One of the most prominent factors affecting the performance and longevity of risers is vortex induced vibration (VIV), which can cause severe fatigue damage, especially in risers used in deep waters. The available approaches for analyzing VIV induced fatigue in risers mainly focus on the VIV aspect of the problem; indeed less attention has been paid on the effect of VIV on a riser’s fatigue life and in prediction of fatigue life using various models.
This dissertation first demonstrates how one can characterize fatigue of pipes and risers using an equivalent plate specimen as opposed to using a pipe specimen, thereby simplifying the task, yet obtaining good accuracy. Actual variable amplitude loadings (VAL) are used to study the fatigue crack growth in risers’ material with a focus on the various influencing parameters. Extensive experimental investigations are performed, followed by analytical and computational nonlinear finite element analyses. It is shown that the higher harmonics do cause significant fatigue damage, thus their influence should not be ignored. The influence of load interaction effects is also investigated, focusing on the fatigue crack growth retardation effects due to tension overloads, as well as the acceleration effects due to compression underloads. The crack closure concept is then used to explore into both the fatigue retardation and acceleration effects within a VAL scenario. An effective method for calculation of the stress intensity factor is proposed, which considers only the tensile portion of the stress range, while proposing another effective approach for accounting for the influence of compressive stress cycles.
Moreover, a two-parameter approach is used in this dissertation, relating the fatigue crack growth rate (FCGR) to the crack tip opening displacement (CTOD). It is shown that the CTOD provides adequate information for calculating the FCGR under VAL, and it can be effectively used to account for the influence of the compressive stress cycles. The experimental investigation also considers the retardation effect resulting from the applied peak tensile overload cycles (TOLC) and the influence of various so-called “clipping” levels, demonstrating the significant influence of the TOLC on crack growth retardation in VAL.
Book chapters on the topic "Mode vibration cycle"
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Pina Limongelli, Maria, Marco Domaneschi, and Luca Martinelli. "Vibration-based damage severity estimation basing on a non-model damage feature." In Life-Cycle of Engineering Systems, 347–54. CRC Press, 2016. http://dx.doi.org/10.1201/9781315375175-39.
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Klis, R., and E. Chatzi. "Model-based data compression for vibration monitoring using Wireless Sensor Networks." In Life-Cycle of Civil Engineering Systems, 138–45. CRC Press, 2014. http://dx.doi.org/10.1201/b17618-16.
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Fan, G., J. Li, and H. Hao. "Using deep learning technique for non-model based vibration response reconstruction." In Bridge Maintenance, Safety, Management, Life-Cycle Sustainability and Innovations, 2332–36. CRC Press, 2021. http://dx.doi.org/10.1201/9780429279119-318.
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Kim, S., K. Cho, and M. Choi. "A study on vibration performance estimation of footbridge using human body model." In Bridge Maintenance, Safety, Management and Life-Cycle Optimization, 530. CRC Press, 2010. http://dx.doi.org/10.1201/b10430-411.
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Manning, Jane. "PRIAULX RAINIER (1903–86)Cycle for Declamation (1954)." In Vocal Repertoire for the Twenty-First Century, Volume 1, 253–56. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780199391028.003.0070.
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This chapter looks at Priaulx Rainier’s piece for unaccompanied voice, Cycle for Declamation. Here, timeless, inspiring texts from John Donne’s Devotions (1624) receive music of the finest calibre. There are no flashy displays here, but a series of ringing phrases, not all of which lie easily in the voice at first. The work lies rather better for tenor than soprano, because of the tessitura, which often focuses around the top of the treble stave, where clear articulation could prove difficult with the higher vibrations. This is especially true of the first movement. The second exposes a potentially vulnerable, transitional area of the voice while requiring dynamic subtlety. The composer, ever-practical, suggests that the whole work can be transposed to make it more comfortable for other voices. This could, however, modify the gleaming colours resulting from the high pitches.
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"Numerical model for bridge-vehicle interaction and traffic-induced vibration investigation." In Advances in Bridge Maintenance, Safety Management, and Life-Cycle Performance, Set of Book & CD-ROM, 697–98. CRC Press, 2015. http://dx.doi.org/10.1201/b18175-277.
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Chilinski, Bogumil, and Anna Mackojc. "Proposal of the Coupled Thermomechanical Model of a Crank Mechanism." In Advances in Transdisciplinary Engineering. IOS Press, 2020. http://dx.doi.org/10.3233/atde200098.
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The aim of the paper is to propose analytical coupled thermomechanical model of the crankshaft system, which includes the mutual interaction between thermodynamic and mechanical phenomena occurring in engines. The most relevant dynamic effects observable in the crank system are connected with its kinematics. When the mechanism operates there are also additional effects corresponding with stress, strain and thermal fields. Elastic properties of the system parts and changeable stiffness of the fuel-air mixture cause different dynamics of the entire device. The authors assumed that rigid motion of the crank mechanism, parts deformation and thermodynamic effects and their mutual dependencies will be included in the modelling process. Elasticity of the crankshaft system components is the reason for the difference between a rigid ’ideal’ motion and the real movement of crankshaft elements. In most cases, it is enough to assume linear elastic material features based on the relatively high stiffness of the system preventing big deformations. This ensures small displacements and the correctness of the applied model. The performed investigations have shown an influence of the crank system flexibility on the overall device response. Moreover, the parameters that change due to thermodynamic and mechanical properties of the working medium were taken into account. The authors have applied simple engine cycles (Otto, Diesel or combined model) for determining engine load including the connection between mechanical and thermodynamic state variables. This caused another decrease of the total system stiffness. Further numerical testing proved a visible effect of the applied approach in the global system response. The main discrepancies are observable in natural frequencies and vibration modes. It can also be stated that the utilization of different engine cycles results in different engine features. The paper is concluded with an analysis of the existing systems and mutual reactions from the assumed phenomena. The authors have shown the necessity to take a transdisciplinary approach into account in order to model complex systems.
Conference papers on the topic "Mode vibration cycle"
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Sinha, P., N. Datta, and A. Kannamwar. "Vortex-Induced Vibration of a Tension Leg Platform Tendon: Multi-Mode Limit Cycle Oscillations." In ICSOT India 2015. RINA, 2015. http://dx.doi.org/10.3940/rina.icsotin15.2015.17.
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Kelley, Christopher R., and Jeffrey L. Kauffman. "Optimal Placement and Sizing of Piezoelectric Material for Multiple-Mode Vibration Reduction." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-77025.
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Modern turbomachinery blades have extremely low inherent damping, which can lead to high transient vibrations and failure through high-cycle fatigue. Recent research seeks methods to reduce vibration with minimal effect on the weight and aerodynamic efficiency of the blade. Smart materials present an interesting means to augment the mechanical characteristics of the blade while meeting the strict requirements of the turboma-chinery environment. In particular, piezoelectric-based vibration reduction offers the potential to semi-actively reduce vibration while simultaneously harvesting enough energy to power the implementation. The placement and size of the piezoelectric material is critical to the vibration reduction capabilities of the system. Furthermore, the implementation should target multiple vibration modes. This work develops a procedure to optimize electromechanical coupling across multiple vibration modes for a representative turbine blade with a surface-mounted piezoelectric patch.
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Golebiowski, Mateusz, Rainer Nordmann, and Eric Knopf. "Rotordynamic Investigation of Spiral Vibrations: Thermal Mode Equation Development and Implementation to Combined-Cycle Power Train." In ASME Turbo Expo 2014: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-25430.
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Rotation of vibration vector caused by thermally induced unbalance changes is a frequently observed phenomenon in large rotating machinery. The heat arising from the friction losses, which are generated at the interfaces between rotating and statoric components of the machine, is partly absorbed by the shaft. This heat input is typically not uniform around the shaft circumference and the resulting temperature difference causes the rotor to bow. The excitation resulting from the sum of mechanical unbalance and thermal bow will lead to a slowly rotating (in the synchronously rotating coordinates system) whirl vector, whose magnitude can decrease or increase in time. A generic understanding of this effect (B.L. Newkirk in 1926, [4]) had been followed by a number of physical models representing specific heat exchange mechanisms (W. Kellenberger [3], J. Schmied [6], P. Morton [11]). A hot spot on the shaft surface can be generated at various locations of a shaft-line. Typical components responsible for thermally induced modulation of vibration vector are journal bearings, seal rings, labyrinth seals (in case of a soft rubbing). Furthermore carbon brushes sliding on the slip ring, supplying the DC current to the field winding of the generator rotor, were identified as a source of nonuniform heat input that may excite spiral vibrations (L. Eckert and J. Schmied in [7], [8]). These local heat input phenomena affect consequently the vibration behavior of the overall shaft train. This paper provides a new approach to the quantitative description of a heat exchange mechanism which leads to the hot spot generation on the surface of a slip ring. A new thermal equation has been formulated, which determines the stability and frequency of the thermal mode. Characteristics of spiral vibration are discussed based on the analytical solution of the Jeffcott rotor model coupled with the proposed thermo-elastic equation. The implementation of the described method to a full shaft-line model of a combined cycle, single shaft power train was done using the Finite Element Method. The results of this calculation were validated against measurement data. The paper shows how the applied computational approach can be used to extend stability margin of the spiral vibration in turbo-generator shaft trains.
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Timusk, Markus A., Michael G. Lipsett, and Chris K. Mechefske. "Automated Duty Cycle Classification for Online Monitoring Systems." In ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/detc2007-34666.
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Transient operation of machinery can greatly complicate the task of vibration-based online condition monitoring. Because the operating mode of a machine affects the physical response and hence the diagnostic parameters, real-time information regarding the operating mode is likely to improve the performance of an online fault detection system. This paper proposes a method for automated duty cycle classification to augment the performance of vibration-based online condition monitoring systems for applications such as gearboxes, motors, and their constituent components. Experimental work is carried out on the swing machinery of an electromechanical excavator, which demonstrates how such a method might function on actual dynamic signals gathered from an operating machine. Several variations of the system are tested.
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Colding-Jørgensen, Jørgen. "Limit Cycle Vibration Analysis of a Long Rotating Cylinder Partially Filled With Liquid." In ASME 1990 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1990. http://dx.doi.org/10.1115/90-gt-040.
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The dynamics of a long, stiff cylinder, flexibly suspended at the ends, partially filled with liquid, is analyzed for varying rotating speed. It appears from the analysis that in the absence of external damping, two distinct speed ranges with unstable whirl are present, as opposed to one instability region for the short cylinder which has been analyzed by a number of authors (Kuipers, 1964), Wolf (1968). This is in agreement with field experience with centrifuges, where several regions of instability are often encountered, each corresponding to a particular vibration mode. The results should also apply to a jet engine with oil accidentally trapped in the rotor, or any hollow rotor with liquid trapped in the cavity. When external damping is applied, the linear theory predicts the rotor be unstable at all speeds (Kuipers, 1964). This is clearly not in accordance with field experience, and other authors have suggested different types of non-linear analysis which can give finite amplitude stable whirl or pulsating whirl (Berman et al., 1985). In the present analysis a simplified non-linear analysis known as the hydraulic jump approximation is applied in the two unstable speed ranges predicted by the linear theory, and a stable whirl finite amplitude, dependent on the external damping, follows. It is argued that the amplitudes found this way should always be higher than those predicted by a more sophisticated analysis, and also higher than the amplitudes measured by other authors, so that the procedure described should give a safe worst case prediction of rotor whirl amplitudes for a given external damping. Finally, an experimental setup which is intended to verify the analysis in a quantative way is presented.
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Lerche, Andrew H., J. Jeffrey Moore, and Timothy C. Allison. "Experimental Study of Blade Vibration in Centrifugal Compressors." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45928.
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Blade vibration in turbomachinery is a common problem that can lead to blade failure by high cycle fatigue. Although much research has been performed on axial flow turbomachinery, little has been published for radial flow machines such as centrifugal compressors and radial inflow turbines. This work develops a test rig that measures the resonant vibration of centrifugal compressor blades. The blade vibrations are caused by the wakes coming from the inlet guide vanes. These vibrations are measured using blade mounted strain gauges during a rotating test. The total damping of the blade response from the rotating test is compared to the damping from the modal testing performed on the impeller. The mode shapes of the response and possible effects of mistuning are also discussed. The results show that mistuning can affect the phase cancellation which one would expect to see on a system with perfect cyclic symmetry.
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Aziz, Imran, Sajjad Hussain, Wasim Tarar, and Imran Akhtar. "Experimental and Numerical Investigation of Vibration Damping Using a Thin Layer Coating." In ASME 2017 Power Conference Joint With ICOPE-17 collocated with the ASME 2017 11th International Conference on Energy Sustainability, the ASME 2017 15th International Conference on Fuel Cell Science, Engineering and Technology, and the ASME 2017 Nuclear Forum. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/power-icope2017-3723.
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High cycle fatigue (HCF) is the main cause of failure in rotating machinery especially in aircraft engines which results in the loss of human life as well as billions of dollars. More than 60 percent of aircraft accidents are related to High cycle fatigue. Major reason for HCF is vibratory stresses induced in the blades at resonance. Damping is needed to avoid vibratory stresses to reach the failure level. High speed rotating machinery has to pass through the resonance in order to reach the operational speed and chances of failure are high at resonance level. It is therefore required to suppress the vibrations at resonance level to avoid any damage to the structure. Application of coating to suppress vibrations is a current area of research. Various types of coatings have been studied recently. This includes plasma graded coatings, viscoelastic dampers, piezoelectric material damping, and magnetomechanical damping. In this research, the phenomenon of damping using a coating of nickel alloy on a steel beam is studied experimentally and numerically to reduce vibratory stresses by enhancing damping characteristics to avoid aircraft engine and rotating machinery failure. For this purpose, uncoated and nickel alloy coated steel beams are fabricated. The coating procedure was performed using plasma arc method. The beams were then mounted in a cantilevered position and bump and vibration shaker tests were conducted to determine the natural frequencies and mode shapes. One of the most important parameter to measure the damping of a system is the damping ratio. In order to determine the damping ratio, vibration analyzer mode was adjusted in time domain and beam was excited by using a hammer. The vibration analyzer showed the vibration decay as a function of time. Using that decay, damping ratio was calculated by using logarithmic decrement method. In order to investigate and compare the damping characteristics of un-coated and coated beams, forced response method was employed. In this method, beams were excited at 1st and 2nd bending mode natural frequencies using vibration shaker. Results were very encouraging and showed a significant improvement in damping characteristics. The experimental results were then endorsed by numerical results which were achieved by performing modal and forced response analysis using finite element analysis techniques.
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Jiazhe, Zhao, Wang Yanrong, Luo Yanbin, and Zhang Xiaojie. "A Vibration Damping Analysis Method of Turbine Blade Shroud Dampers Based on a Given Eigen-Mode." In ASME 2018 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/detc2018-85349.
Full textAbstract:
High cycle fatigue damage caused by resonance and forced vibration can significantly affect the life and reliability of turbine rotor blades in aero-engines. The friction damper has been widely used to reduce the resonant stress of blades, on which the turbine blade shroud dampers are highly used. In order to solve the problems of vibration damping analysis and design of shrouded blades dampers, an analytical method without complex and time-consuming nonlinear vibration response has been proposed based on a given eigen-mode in this paper. For the serrated shrouded damper, two typical friction models, namely macro-slip model, and micro-slip model, have been introduced. Additionally, a complete set of damping analysis method has been introduced by the energy method, based on the vibration dynamics principle and eigen-mode analyzed by finite element method. Combined with the analysis of the natural vibration characteristics of the shrouded turbine blade, the law of the damping ratio with the relevant design parameters, such as the vibration stress, the pre-twist angle, the friction coefficient and the nodal diameter, was obtained through a calculation example. The method can also provide an important reference for the parameterized design of dampers.
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Duong, Loc Q., Nagamany Thayalakhandan, and Charlene X. Hu. "Radial Inflow Turbine: Synchronous Vibration Failure." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-95651.
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Radial inflow turbine is frequently used in small gas turbine application where ruggedness and simplicity are prime requisites. For compactness, the radial turbine is mounted back to back with a radial compressor resulting in an overhung rotor in both compressor and turbine wheel. In such configuration the structural integrity of the radial turbine is crucial since due to its large inertia its failure could result in an uncontained egress of the engine. This paper presents one class of radial inflow turbine wheel failure due to high cycle fatigue of synchronous nature caused by two different excitation sources, namely mechanics and aerodynamics. While the first source of excitation is associated with the dynamics of the rotor, the second one is related to the dynamic of fluid flow and the thermal characteristics of the combustor, expressed in terms of hot streak. These sources of excitation can act individually or in combination. Two distinct types of failures were illustrated — blade mode — and disc-blade coupling mode. The failure phenomenon is characterized by fatigue crack originated at location corresponding to maximum dynamic stress for each type of failures, followed by the released of one portion of the blade. Analytical methods including finite element method, rotor dynamics analysis, and computational fluid dynamics are used to illustrate the root cause of such failure and also to its underlying solutions. Laser vibrometry and optical method were used to obtain the blade dynamic characteristics and to validate the solutions.
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Furuya, Hiroaki, Kiyotaka Yamashita, and Hiroshi Yabuno. "Nonlinear Stability of a Fluid-Conveying Cantilevered Pipe With End Mass in Case of Horizontal Excitation at the Upper End." In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-31239.
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Nonplanar vibrations of a cantilevered pipe with an end mass is studied. We have already clarified the nonplanar vibrations with a single frequency component when the pipe conveys fluid whose velocity is slightly over the critical value, above which the lateral vibration of the pipe is self-excited due to the internal flow. Moreover, for the case that the upper end of the pipe is excited periodically in the horizontal direction, we have shown in the previous paper that the nonplanar limit cycle motions start complex spatial transients and settle down to stationary planar forced-excited vibration when the excitation frequency is near the nonplanar limit cycle frequency. The purpose of this paper is to examine the stability of the nonplanar pipe vibrations when the nonplanar self-excited pipe vibrations are subjected to the excitation at the upper end. A set of ordinary differential equations, which govern the amplitudes and phases of unstable mode vibration and contain the effect of excitation at the upper end are derived. Stability analysis of these equations clarifies the nonlinear interactions between nonplanar self-excited pipe vibrations and the forced excitation. Second, the experiments are conducted with a silicon rubber pipe conveying water, confirming the dynamic features of pipe vibrations for the horizontal excitation.