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Troeng, Tor. "Frequency Response Analysis using Component Mode Synthesis." Thesis, Umeå universitet, Institutionen för matematik och matematisk statistik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-37809.
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Solutions to physical problems described by Differential Equationson complex domains are in except for special cases almost impossibleto find. This turns our interest toward numerical approaches. Sincethe size of the numerical models tends to be very large when handlingcomplex problems, the area of model reduction is always a hot topic. Inthis report we look into a model reduction method called ComponentMode Synthesis. This can be described as dividing a large and complexdomain into smaller and more manageable ones. On each of thesesubdomains, we solve an eigenvalue problem and use the eigenvectorsas a reduced basis. Depending on the required accuracy we mightwant to use many or few modes in each subdomain, this opens for anadaptive selection of which subdomains that affects the solution most.We cover two numerical examples where we solve Helmholtz equationin a linear elastic problem. The first example is a truss and the othera gear wheel. In both examples we use an adaptive algorithm to refinethe reduced basis and compare the results with a uniform refinementand with a classic model reduction method called Modal Analysis. Wealso introduce a new approach when computing the coupling modesonly on the adjacent subdomains.
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Soucy, Yvan. "Test-based hybrid component mode synthesis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0014/NQ37056.pdf.
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Blackwood, Gary H. (Gary Howard). "Experimental component mode synthesis of structures with joint freeplay." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/37486.
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Petersen, Lynn James. "Mast-antenna survivability : structural dynamic design analysis by component mode synthesis." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA280669.
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Zoet, Petrus Gosse. "Component mode synthesis for ship structures : investigation into an alternative approach." Thesis, University of Strathclyde, 2013. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=24881.
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The main aim of this work is to help the shipbuilder to effectively assess a ships' structural design for its vibratory behaviour. For that purpose state of the art structural modelling techniques are reviewed for the validity of their basic principles, accuracy, practicality and required computation time when applied on typical marine structures. Full finite element modelling has been applied on a part of the structure of an LNG carrier on board which the author has taken vibration and noise measurements. Also fixed interface (Craig-Bampton) and free interface (Rubin's method) component mode synthesis sub structuring techniques have been applied. The aim of the analysis is to evaluate the effectiveness of finite element modelling through evaluation with measurement results, evaluate the accuracy of the sub structuring modelling techniques and to identify short comings of any of the tested methods. Two alternative component synthesis modelling sub structuring techniques are proposed in order to reduce required computation time; Zoet's method and the Rubin Zoet method. The Zoet method is tested using a section of the LNG carrier's structural model. The method is evaluated for accuracy (comparing obtained results with the results obtained through the full harmonic finite element analysis) and required computation time through comparison with the required computation time for: - full harmonic analysis - the classical modal reduction and mode superposition technique - the classical Rubin free interface component mode synthesis - and Rubin's method with interface reduction according to the IRS method (see section 6.5.3) - the Rubin-Zoet technique.
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Abdallah, Ayman Ahmed. "Dynamic substructuring by the boundary flexibility vector method of component mode synthesis." Case Western Reserve University School of Graduate Studies / OhioLINK, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=case1054567783.
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Ramani, Anand. "Two-step Component Mode Synthesis with convergence for the eigensolution of large-degree-of-freedom systems." Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/39162.
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Beck, Joseph A. "Stochastic Mistuning Simulation of Integrally Bladed Rotors using Nominal and Non-Nominal Component Mode Synthesis Methods." Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1278600105.
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Lindberg, Eskil. "A Vibro-Acoustic Study of Vehicle Suspension Systems : Experimental and Mathematical Component Approaches." Doctoral thesis, KTH, MWL Strukturakustik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-121575.
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The objective of the present work is to study the vehicle suspension as a vibro-acoustic system of high complexity, consisting of many sub-systems with fundamentally different acoustical properties. In a parallel numerical and experimental modelling effort, important contributions to the understanding of its behaviour have been achieved. These findings are based on a balance between component investigations and global modelling of the complete system; they have been formulated for the transmission of both tyre-road excitation and friction-induced vibrations in the brake system. Initially an experimental study was conducted on a full vehicle test rig studying the broadband interior brake noise problem of, here named, roughness noise. The purpose of the study was twofold: first, to determine if the transmission from the source to the interior of the vehicle was structure-borne; second, to study the complexity of the suspension as a vibro-acoustic system. Parameters a_ecting the vibro-acoustic source were varied to gain understanding of the source mechanisms. This experimental study laid the foundation of the first part of this thesis (paper A) and provided the directions for the second part, the development of a mathematical modelling approach (paper B and C). In these two papers, methods for analysing the complex vibro-acoustic transfer of structure-borne sound in a vehicle suspension system were developed. The last part was then focussed on the wheel rim influence on the vibro-acoustic behaviour (paper D) of the suspension system. As a whole, the work clearly demonstrates that it is possible to conduct component studies of subsystems in the vehicle suspension system; and from these component studies it is possible draw conclusions that very well may avoid severe degradations in the interior noise of future vehicle generations.QC 20130503
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Zhou, Changwei. "Approche couplée propagative et modale pour l'analyse multi-échelle des structures périodiques." Thesis, Ecully, Ecole centrale de Lyon, 2014. http://www.theses.fr/2014ECDL0040/document.
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La dynamique d’une structure peut être vue aussi bien en termes de modes (ondes stationnaires) qu’en termes d’ondes élastiques libres. Les approches modales sont largement utilisées en mécanique et de nombreuses techniques de réduction de modèles (Model Order Reduction - MOR) ont été développées dans ce cadre. Quant à la dynamique des structures périodiques, les approches propagatives sont majoritairement utilisées, où la périodicité est exploitée en utilisant la théorie de Bloch. Pour les structures périodiques complexes, plusieurs techniques MOR sur la base d’onde ont été proposées dans la littérature. Dans ce travail, une approche couplée propagative et modale a été développée pour étudier la propagation des ondes dans les structures périodiques. Cette approche commence par la description modale d’une cellule unitaire (échelle mésoscopique) en utilisant la synthèse modale (Component Mode Synthesis - CMS). Par la suite, la méthode propagative - Wave Finite Element Method (WFEM) est appliquée sur la structure (échelle macroscopique). Cette méthode est nommée “CWFEM” pour CondensedWave Finite Element Method. Elle combine les avantages de la CMS et WFEM. La CMS permet d’analyser le comportement local d’en extraire une base réduite. La WFEM exploite la périodicité de la structure d’en extraire les paramètres de propagation. Ainsi, l’analyse de la propagation des ondes dans la structure à l’échelle macroscopique peut être réalisée en prenant en compte l’échelle mésoscopique. L’efficacité de la CWFEM est illustrée par de nombreuse applications aux structures périodiques monodimensionnelle (1D) et bidimensionnelle (2D). Le critère de réduction optimale assurant la convergence est discuté. Les caractéristiques de propagation dans les structures périodiques sont identifiées: bande passante, bande interdite, la directivité marquée (wave beaming effects), courbe de dispersion, band structure, surface des lenteurs... Ces propriétés peuvent répondre au besoin de conception des barrières vibroacoustiques, pièges à ondes. La CWFEM est ensuite appliquée pour étudier la propagation des ondes dans des plaques perforées et plaques raidies. Une méthode d’homogénéisation pour déterminer le modèle équivalent de la plaque perforée est proposée. Les comportements à haute fréquence tels que la directivité marquée sont également prédits par CWFEM. Trois modèles de plaques avec perforations différentes sont étudiées dans ce travail. Une validation expérimentale est effectuée sur deux plaques. Pour la plaque raidie, l’influence des modes internes sur la propagation globale est discutée. La densité modale est estimée, en moyenne et haute fréquences, pour une plaque raidie finie, où une bonne corrélation est obtenue en comparant les résultats à l’issue des analyses modalesStructural dynamics can be described in terms of structural modes as well as elastic wave motions. The mode-based methods are widely applied in mechanical engineering and numerous model order reduction (MOR) techniques have been developed. When it comes to the study of periodic structures, wave description is mostly adopted where periodicity is fully exploited based on the Bloch theory. For complex periodic structures, several MOR techniques conducted on wave basis have been proposed in the literature. In this work, a wave and modal coupled approach is developed to study the wave propagation in periodic structures. The approach begins with the modal description of a unit cell (mesoscopic scale) using Component Mode Synthesis (CMS). Subsequently, the wave-based method -Wave Finite Element Method (WFEM) is applied to the structure (macroscopic scale). The method is referred as “CWFEM” for Condensed Wave Finite Element Method. It combines the advantages of CMS and WFEM. CMS enables to analyse the local behaviour of the unit cell using a reduced modal basis. On the other hand, WFEM exploits fully the periodic propriety of the structure and extracts directly the propagation parameters. Thus the analysis of the wave propagation in the macroscopic scale waveguides can be carried out considering the mesoscopic scale behaviour. The effectiveness of CWFEM is illustrated via several one-dimensional (1D) periodic structures and two-dimensional (2D) periodic structures. The criterion of the optimal reduction to ensure the convergence is discussed. Typical wave propagation characteristics in periodic structures are identified, such as pass bands, stop bands, wave beaming effects, dispersion relation, band structure and slowness surfaces...Their proprieties can be applied as vibroacoustics barriers, wave filters. CWFEM is subsequently applied to study wave propagation characteristics in perforated plates and stiffened plate. A homogenization method to find the equivalent model of perforated plate is proposed. The high frequency behaviours such as wave beaming effect are also predicted by CWFEM. Three plate models with different perforations are studied. Experimental validation is conducted on two plates. For the stiffened plate, the influence of internal modes on propagation is discussed. The modal density in the mid- and high- frequency range is estimated for a finite stiffened plate, where good correlation is obtained compared to the mode count from modal analysis
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Lindberg, Eskil. "Vehicle Disc Brake Roughness Noise : Experimental Study of the Interior Noise andVibro-Acoustic Modelling of Suspension Systems." Licentiate thesis, KTH, MWL Strukturakustik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-39554.
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Prediction of vehicle disc brake roughness noise is a non-trivial challenge. In fact, neither the source mechanisms, nor the transfer paths are so far well understood. Traditionally, disc brake noise problems are studied as part of the friction-induced noise field, where the source is considered to be a more or less local phenomenon related to the brake disc and brake pad. However, for the roughness noise of interest here this viewpoint is not adequate when attempting to solve the interior noise problem since the transfer of vibro-energy from the brake into the vehicle body is a crucial aspect and plays an important role in the understanding and solution to the problem. The vibroacoustic energy transfer associated with the brake roughness noise is a problem where geometrical complexity and material combinations, including rubber bushings, pose an intricate modelling problem. Additionally, system altering effects from moving parts and loadings are important, e.g. due to the steering or brake systems. In addition, the source mechanisms themselves must also be understood to be able to solve the problem. The current work constitutes a combined experimental and theoretical investigation, aiming at an increased understanding of the source, the transfer paths and how they are a affected by change in the operational state. The experimental study of the vehicle disc brake roughness noise, is based on measurements conducted in a laboratory using a complete passenger car. It is found that the interior noise is a structural-borne broadband noise event well correlated to vehicle speed and brake pressure. The results suggest that the friction source may be divided into vibrations created in the sliding direction and vibrations created normal to the contact plane, where the sliding direction levels appear to be proportional to brake pressure according to Coulomb’s friction law; the vibration level in the normal direction of the contact plane on the other hand has behaviour proportional to Hertz contact theory. The measurements also indicate that the brake force created carried by the suspension system when braking will also alter the vibro-acoustic response of the system. To facilitate the theoretical simulations, an approach for modelling of the suspension system is developed. The vibro-acoustic transfer path model developed is using a modal based on the Craig-Bampton method where a restriction on the coupling modes is suggested. The approach suggested uses undeformed coupling interfaces, to couple structures of fundamentally different stiffness such as may be the case in a vehicle suspension system where for instance rubber bushings are combined with steel linking arms. The approach show great potential inreducing computational cost compared to the classical Craig-Bampton method.QC 20110913
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Joannin, Colas. "Réduction de modèle par sous-structuration et modes non-linéaires : Application à la dynamique des roues aubagées." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEC014/document.
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Le désaccordage des roues aubagées est une thématique de recherche d’un intérêt tout particulier pour l’industrie aéronautique, en recherche constante d’outils de calcul toujours plus prédictifs et performants pour répondre aux exigences croissantes des organismes de certification. Si le phénomène est aujourd’hui relativement bien maîtrisé dans un cadre linéaire, la prise en compte des non-linéarités dans l’étude du désaccordage reste encore problématique, notamment en raison du manque de méthode adaptée pour mener ce type d’analyses sur des modèles industriels. L’objectif principal de ce travail de thèse est de proposer une nouvelle méthode de calcul permettant de déterminer efficacement la réponse forcée d’une roue aubagée désaccordée, en tenant compte de l’impact des non-linéarités sur la dynamique de la structure à l’échelle macroscopique. La méthode développée repose sur le concept de sous-structuration, et exploite la notion de mode complexe non-linéaire pour capturer les non-linéarités dans l’espace de réduction de chaque sous-structure. En adoptant une approche fréquentielle, les sous-structures sont représentées par des super-éléments non-linéaires, dont l’assemblage conduit au modèle réduit de la roue désaccordée. La résolution du système mathématique obtenu est ensuite réalisée numériquement par des techniques itératives. La méthode développée a pu être testée et validée sur différents systèmes soumis à des non-linéarités de frottement, allant du simple modèle phénoménologique à un modèle éléments finis de roue aubagée industrielle. Sur des modèles à paramètres concentrés de taille relativement faible, les performances très intéressantes de cette méthode permettent de conduire des études statistiques quantitatives sur l’impact du désaccordage en présence de non-linéarités. Les résultats obtenus suggèrent que le comportement du système non-linéaire face au désaccordage est susceptible d’être significativement différent du comportement de son homologue linéaire, d’où l’intérêt de mener ce type d’investigations. Les performances de cette méthode ont également pu être confirmées sur des modèles éléments finis de grande taille, en permettant de réaliser à un coût raisonnable des simulations de réponse forcée non-linéaire sur une roue industrielle désaccordéeMistuning of bladed disks has been a key topic of research for the aeronautics industry. To get accreditation for their engines, manufacturers must comply with evermore stringent requirements, and thus constantly seek for better simulation tools. Even though the phenomenon is well understood nowadays for linear systems, nonlinearities are still seldom taken into account when dealing with the mistuning of industrial structures, partly due to the lack of a dedicated method to tackle such a complex problematic. The main objective of this work is to develop a novel method allowing to compute efficiently the forced response of a mistuned bladed disk, while taking into account the impact of nonlinearities on the vibrations at a macroscopic scale. The method derived relies on a substructuring approach, and uses the concept of nonlinear complex modes to capture the nonlinearities in the reduction basis of each substructure. In the frequency domain, the substructures take the form of nonlinear superelements, which once assembled lead to the reduced-order model of the mistuned bladed disk. The resulting mathematical system is then solved by means of iterative solvers. This new method is tested and validated on different systems subjected to dry friction nonlinearities, from basic phenomenological models to large-scale finite element models of industrial structures. On lumped-parameter models, the performance of this method allows to investigate the statistical impact of mistuning in the presence of nonlinearities, by performing thousands of simulations. The results suggest that the behaviour of the nonlinear model can be significantly different from that of the linear one, hence the importance to carry out such investigations. The capabilities of the method have also been confirmed on large-scale models, by performing several forced response computations on a nonlinear and mistuned finite element model, at a reasonable cost
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Ribaric, Adrijan Petar. "Orientation Invariant Characteristics of Deformable Bodies in Multibody Dynamics." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/238644.
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In multibody systems, mechanical components (bodies) can be assumed rigid (non-deformable), if their deformation is negligible. For components with non-negligible deformations several methods were developed to represent their deformation. The most widely used method is the floating frame of reference. In this formulation the deformable body is represented by a finite element model whose deformation is described with respect to a local body-fixed frame. Unfortunately, finite element models can include many degrees-of-freedom, which stand in contradiction to the requirements of multibody dynamics. System truncation is therefore inevitable to support computational efficiency. The use of modal data in representing a deformable body is well understood in the multibody community. By truncating modes associated with higher frequencies, the total degrees-of-freedom of the deformable body can be reduced while preserving its dynamic eigen-properties. However, since the finite element model may be in contact with other moving bodies, the reduction technique needs to address the issue of moving boundary conditions. The component mode synthesis reduction methods are such techniques that describe the deflection of all the nodes as a superposition of different types of modes. However, it is limited in the fact that the nodes in contact need to remain in contact throughout a simulation. In some applications these nodes may change, i.e. a node that is in contact with another body or the ground at one instant may become free at the next instant. The present methodologies in multibody modeling of a deformable body with modal data have not yet addressed the issue of changing contact nodes. This research highlights the usefulness of orientation invariant characteristics of some deformable bodies. It proposes to define orientation invariant degrees-of-freedom of the reduced model in Eulerian space, while the remaining degrees-of-freedom are defined in Lagrangian space. In some circumstances, this approach can resolve the issue of changing contact nodes. The combination of Eulerian and Lagrangian formulation for component mode synthesis reduced finite element models is a new concept in deformable multibody dynamics.
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Orbay, Gunay. "Nonlinear Vibration Of Mistuned Bladed Disk Assemblies." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609740/index.pdf.
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High cycle fatigue (HCF) failure has been studied extensively over the last two decades. Its impact on jet engines is severe enough that may result in engine losses and even life losses. The main requirement for fatigue life predictions is the stress caused by mechanical vibrations. One of the factors which have major impact on the vibratory stresses of bladed disk
assemblies is a phenomenon called &ldquomistuning&rdquo
which is defined as the vibration localization caused by the loss of cyclic periodicity which is a consequence of inter&
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blade variations in structural properties. In this thesis, component mode synthesis method (CMSM) is combined with nonlinear forced response analysis in modal domain. Newton&
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Raphson and arc length continuation procedures are implemented for the solution. The component mode synthesis method introduces the capability of imposing mistuning on the modal properties of each blade in the assembly. Forced response analysis in modal domain reduces the problem size via mode truncation. The main advantage of the proposed method is that it is capable of calculating nonlinear forced response for all the degrees&
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of&
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freedom at each blade with less computational effort. This makes it possible to make a stress analysis at resonance conditions. The case studies presented in this thesis emphasize the importance of number of modes retained in the reduced order model for both CMSM and nonlinear forced response analysis. Furthermore, the results of the case studies have shown that both nonlinearity and mistuning can cause shifts in resonance frequencies and changes in resonance amplitudes. Despite the changes in resonance conditions, the shape of the blade motion may not be affected.
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Rumpler, Romain. "Efficient finite element approach for structural-acoustic applicationns including 3D modelling of sound absorbing porous materials." Phd thesis, Conservatoire national des arts et metiers - CNAM, 2012. http://tel.archives-ouvertes.fr/tel-00726915.
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In the context of interior noise reduction, the present work aims at proposing Finite Element (FE) solution strategies for interior structural-acoustic applications including 3D modelling of homogeneous and isotropic poroelastic materials, under timeharmonic excitations, and in the low frequency range. A model based on the Biot-Allard theory is used for the poroelastic materials, which is known to be very costly in terms of computational resources. Reduced models offer the possibility to enhance the resolution of such complex problems. However, their applicability to porous materials remained to be demonstrated.First, this thesis presents FE resolutions of poro-elasto-acoustic coupled problems using modal-based approaches both for the acoustic and porous domains. The original modal approach proposed for porous media, together with a dedicated mode selection and truncation procedure, are validated on 1D to 3D applications.In a second part, modal-reduced models are combined with a Padé approximants reconstruction scheme in order to further improve the efficiency.A concluding chapter presents a comparison and a combination of the proposed methods on a 3D academic application, showing promising performances. Conclusions are then drawn to provide indications for future research and tests to be conducted in order to further enhance the methodologies proposed in this thesis.
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Beck, Joseph A. "Fundamental Understanding of Blisk Analytical Response." Wright State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=wright1367848915.
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Rumpler, Romain. "Efficient Finite Element Approach for Structural-Acoustic Applications including 3D modelling of Sound Absorbing Porous Materials." Doctoral thesis, KTH, MWL Numerisk akustik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-90335.
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In the context of interior noise reduction, the present work aims at proposing Finite Element (FE) solution strategies for interior structural-acoustic applications including 3D modelling of homogeneous and isotropic poroelastic materials, under timeharmonic excitations, and in the low frequency range. A model based on the Biot-Allard theory is used for the poroelastic materials, which is known to be very costly in terms of computational resources. Reduced models offer the possibility to enhance the resolution of such complex problems. However, their applicability to porous materials remained to be demonstrated.First, this thesis presents FE resolutions of poro-elasto-acoustic coupled problems using modal-based approaches both for the acoustic and porous domains. The original modal approach proposed for porous media, together with a dedicated mode selection and truncation procedure, are validated on 1D to 3D applications.In a second part, modal-reduced models are combined with a Padé approximants reconstruction scheme in order to further improve the efficiency.A concluding chapter presents a comparison and a combination of the proposed methods on a 3D academic application, showing promising performances. Conclusions are then drawn to provide indications for future research and tests to be conducted in order to further enhance the methodologies proposed in this thesis.Dans le contexte de lutte contre les nuisances sonores, cette thèse porte sur le développement de méthodes de résolution efficaces par éléments finis, pour des problèmes de vibroacoustique interne avec interfaces dissipatives, dans le domaine des basses fréquences. L’étude se limite à l’utilisation de solutions passives telles que l’intégration de matériaux poreux homogènes et isotropes, modélisés par une approche fondée sur la théorie de Biot-Allard. Ces modèles étant coûteux en terme de résolution, un des objectifs de cette thèse est de proposer une approche modale pour la réduction du problème poroélastique, bien que l’adéquation d’une telle approche avec le comportement dynamique des matériaux poreux soit à démontrer.Dans un premier temps, la résolution de problèmes couplés élasto-poro-acoustiques par sous-structuration dynamique des domaines acoustiques et poreux est établie. L’approche modale originale proposée pour les milieux poroélastiques, ainsi qu’une procédure de sélection des modes significatifs, sont validées sur des exemples 1D à 3D.Une deuxième partie présente une méthode combinant l’utilisation des modèles réduits précédemment établis avec une procédure d’approximation de solution par approximants de Padé. Il est montré qu’une telle combinaison offre la possibilité d’accroître les performances de la résolution (allocation mémoire et ressources en temps de calcul).Un chapitre dédié aux applications permet d’évaluer et comparer les approches sur un problème académique 3D, mettant en valeur leurs performances encourageantes. Afin d’améliorer les méthodes établies dans cette thèse, des perspectives à ces travaux de recherche sont apportées en conclusion.
QC 20120224
FP6 Marie-Curie Smart Structures
FP7 Marie-Curie Mid-Frequency
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Menday, M. T. "Multi-body dynamics analysis and experimental investigations for the determination of the physics of drive train vibro-impact induced elasto-acoustic coupling." Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/20789.
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A very short and disagreeable audible and tactile response from a vehicle driveline may be excited when the throttle is abruptly applied or released, or when the clutch is rapidly engaged. The condition is most noticeable in low gear and in slow moving traffic, when other background engine and road noise levels are low. This phenomenon is known as clonk and is often associated with the first cycle of shuffle response, which is a low frequency longitudinal vehicle movement excited by throttle demand. It is often reported that clonk may coincide with each cycle of the shuffle response, and multiple clonks may then occur. The problem is aggravated by backlash and wear in the drivetrain, and it conveys a perception of low quality to the customer. Hitherto, reported investigations do not reveal or discuss the mechanism and causal factors of clonk in a quantitative manner, which would relate the engine impulsive torque to the elastic response of the driveline components, and in particular to the noise radiating surfaces. Crucially, neither have the issues of sensitivity, variability and non-linearity been addressed and published. It is also of fundamental importance that clonk is seen as a total system response to impulsive torque, in the presence of distributed lash at the vibro-elastic impact sites. In this thesis, the drivetrain is defined as the torque path from the engine flywheel to the road wheels. The drivetrain is a lightly damped and highly non-linear dynamic system. There are many impact and noise emitting locations in the driveline that contribute to clonk, when the system is subjected to shock torque loading. This thesis examines the clonk energy paths, from the initial impact to many driveline lash locations, and to the various noise radiating surfaces. Both experimental and theoretical methods are applied to this complex system. Structural and acoustic dynamics are considered, as well as the very important frequency couplings between elastic structures and acoustic volumes. Preliminary road tests had indicated that the clonk phenomenon was a, very short transient impact event between lubricated contacts and having a high frequency characteristic. This indicated that a multi-body dynamics simulation of the driveline, in conjunction with a high frequency elasto-acoustic coupling analysis, would be required. In addition, advanced methods of signal analysis would be required to handle the frequency content of the very short clonk time histories. These are the main novelties of this thesis. There were many successful outcomes from the investigation, including quantitative agreement between the numerical and experimental investigations. From the experimental work, it was established that vehicle clonk could be accurately reproduced on a driveline rig and also on a vehicle chassis dynamometer, under controlled test conditions. It then enabled Design of Experiments to be conducted and the principal causal factors to be identified. The experimental input and output data was also used to verify the mathematical simulation. The high frequency FE analysis of the structures and acoustic cavities were used to predict the dynamic modal response to a shock input. The excellent correlation between model and empirical data that was achieved, clearly established the clonk mechanism in mathematical physics terms. Localised impact of meshing gears under impulsive loads were found to be responsible for high frequency structural wave propagation, some of which coupled with the acoustics modes of cavities, when the speed of wave propagation reached supersonic levels. This finding, although previously surmised, has been shown in the thesis and constitutes a major contribution to knowledge.
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Brown, Jeffrey M. "Reduced Order Modeling Methods for Turbomachinery Design." Wright State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=wright1229962254.
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Bourmich, Sophie. "Optimisation de la qualité vibro-acoustique des structures d'automobiles pour les basses fréquences." Thesis, Ecully, Ecole centrale de Lyon, 2012. http://www.theses.fr/2012ECDL0026/document.
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Les modèles d'éléments finis des automobiles donnent des grandes tailles de problèmes matriciels, ce qui demeure coûteux en ressources numériques pour une procédure d'optimisation. La multiplicité des phénomènes couplés du problème d'interaction de l'air de l'habitacle et de la superstructure rend plus sensible, à des variations mineures des paramètres, une optimisation directe du véhicule. Pour réduire les temps de calculs et l'espace mémoire liés à la simulation numérique en éléments finis, une méthode de double synthèse modale est appliquée sur la structure et le fluide. Ceci permet de diminuer le nombre de degrés de liberté de frontière. Egalement, un algorithme a été développé pour minimiser le nombre d'évaluations de fonction au cours des itérations d'optimisation. L'approche modale permet également de décomposer le problème d'optimisation de la réponse vibro-acoustique par des sous-problèmes couplés d'optimisation de critères modaux. Ces critères modaux explicitent les couplages fréquentiels par des termes d'amplification et les couplages spatiaux par des paramètres effectifs modaux. Ils favorisent ainsi le développement d'une stratégie d'optimisation robuste par le contrôle modal des effets prépondérants sur la qualité vibro-acoustique des véhiculesFinite element models and the complexity of vehicle passenger compartments make it harder the optimization, mainly because of expensive computing resources and multiple coupled phenomena of fluid-structure problems. Strategies to improve time and memory performance consist in the use of reduction methods, and combined with efficient optimization techniques, vibro-acoustic solutions of better quality can be performed. The complexity of the system is taken into account thanks to a hierarchical optimization process. Both reduction method and gradient-based optimization algorithm are investigated. Based on modal synthesis, special criteria help to determine critical vibration propagation paths. A modified SQP (Sequential Quadratic Programming) algorithm is also developed in order to provide a faster convergence speed. Such process is to be applied on an academic example and hollow parts and panels of a whole passenger compartments. It allows to find relevant and non obvious solutions by minimizing noise and vibration transfer functions in a relatively wide range of frequencies
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Mahieux, Bruno. "Contribution à l'optimisation en masse de structures complexes sous contraintes vibratoires : application à la conception des planches de bord en phase d'études préliminaires." Valenciennes, 1996. http://www.theses.fr/1996VALE0031.
Full textAbstract:
Dans le cadre de la conception des planches de bord en phase d'études préliminaires, nous proposons une stratégie d'optimisation permettant de réaliser des gains en masse rapidement à partir d'un cahier des charges. Ce cahier des charges comprend en particulier des critères vibratoires. En fonction des besoins d'études ainsi que des caractéristiques d'une planche de bord, la stratégie développée fait appel à une utilisation conjointe des techniques de sous-structuration et d'optimisation. Elle consiste à optimiser séparément les éléments (ou sous-structures) modifiables. Pour cela, nous étudions les possibilités offertes par les techniques de synthèse modale, puis nous examinons les principaux concepts nécessaires à la mise en forme d'un problème d'optimisation. À partir de cette dernière, nous proposons un développement particulier du calcul des sensibilités paramétriques basé sur la dérivation d'une équation de synthèse modale. Nous confrontons cette nouvelle approche à des techniques usuelles a partir d'un cas test élémentaire. Nous définissons ensuite les hypothèses de passage d'une optimisation de l'ensemble de la planche de bord, vers une optimisation séparée des éléments modifiables. Nous spécifions alors une modélisation des restrictions locales relatives aux problèmes d'optimisation des éléments modifiables. Nous abordons ensuite la validation expérimentale de la stratégie d'optimisation proposée, sur la base d'une structure minimale représentative du comportement vibratoire d'une planche de bord réelle. En conclusion, nous présentons l'optimisation de la planche de bord du véhicule zx, qui constitue l'aboutissement de la stratégie d'optimisation sur des planches de bord réelles.
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Kšica, Filip. "Modelování dynamických vlastností a chování technických soustav." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-241945.
Full textAbstract:
The aim of this diploma thesis is to evaluate the potential of available methods for simplification and reduction of complex models of technical systems and their integration with experimental models. Finding methods, which would allow us to create models and run simulations in shorter periods of time, is key in design process of modern technical systems. In the beginning of this thesis, a theory necessary for understanding and application of presented methods is given. These methods can be separated into two groups, first as experiment related, second as simulation related. The first group contains methods for experimental evaluation of response and its use for dynamic system identification. The second group contains methods of finite element model creation, with the usage of standard structural elements as well as Component Mode Synthesis substructures, and these models are in the following step reduced into state space models. In the next step, all presented methods are applied on simple experimental structure. In conclusion, the results of simulations are the subject for comparison not only from quantitative point of view, but also, for the purpose of practical application, in terms of time, feasibility, versatility and accuracy. The system identification method along with state space method proved to be very suitable. The results presented in this thesis might help, by selecting the appropriate method, in simpler evaluation of dynamic properties of technical structures.
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Covi, Patrick. "Multi-hazard analysis of steel structures subjected to fire following earthquake." Doctoral thesis, Università degli studi di Trento, 2021. http://hdl.handle.net/11572/313383.
Full textAbstract:
Fires following earthquake (FFE) have historically produced enormous post-earthquake damage and losses in terms of lives, buildings and economic costs, like the San Francisco earthquake (1906), the Kobe earthquake (1995), the Turkey earthquake (2011), the Tohoku earthquake (2011) and the Christchurch earthquakes (2011). The structural fire performance can worsen significantly because the fire acts on a structure damaged by the seismic event. On these premises, the purpose of this work is the investigation of the experimental and numerical response of structural and non-structural components of steel structures subjected to fire following earthquake (FFE) to increase the knowledge and provide a robust framework for hybrid fire testing and hybrid fire following earthquake testing. A partitioned algorithm to test a real case study with substructuring techniques was developed. The framework is developed in MATLAB and it is also based on the implementation of nonlinear finite elements to model the effects of earthquake forces and post-earthquake effects such as fire and thermal loads on structures. These elements should be able to capture geometrical and mechanical non-linearities to deal with large displacements. Two numerical validation procedures of the partitioned algorithm simulating two virtual hybrid fire testing and one virtual hybrid seismic testing were carried out. Two sets of experimental tests in two different laboratories were performed to provide valuable data for the calibration and comparison of numerical finite element case studies reproducing the conditions used in the tests. Another goal of this thesis is to develop a fire following earthquake numerical framework based on a modified version of the OpenSees software and several scripts developed in MATLAB to perform probabilistic analyses of structures subjected to FFE. A new material class, namely SteelFFEThermal, was implemented to simulate the steel behaviour subjected to FFE events.
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Simone, Panconi. "Ottimizzazione della dinamica e del comfort di sistemi ferroviari e metropolitani di nuova generazione." Doctoral thesis, 2018. http://hdl.handle.net/2158/1127170.
Full textAbstract:
Il comfort di marcia è una delle caratteristiche dinamiche più importanti per un veicolo ferroviario poiché è direttamente collegato alla percezione di benessere dei passeggeri. Esso dipende da innumerevoli fattori come odori, temperatura e umidità, ma le vibrazioni, che si trasmettono al passeggero attraverso le sospensioni e la cassa, sono riconosciute come le maggiori responsabili di un suo peggioramento e per questo motivo sono considerate come causa principale nel presente lavoro di tesi.
Per stimare in maniera precisa gli indici di comfort si utilizza un modello multibody rappresentante il veicolo ferroviario di riferimento.
Poiché la cassa ha un impatto notevole sul calcolo del comfort si presenta una procedura validata tramite un confronto con dati sperimentali; tale procedura permette di inserire all'interno del modello del veicolo i modi propri di vibrare che caratterizzano il suo comportamento dinamico, senza gravare eccessivamente sullo sforzo computazionale richiesto dalle simulazioni flexible multibody. La cassa è descritta, infatti, tramite un numero ridotto di gradi di libertà ottenuti con tecniche di riduzione modale, raggiungendo un buon compromesso tra efficienza computazionale e accuratezza dei risultati. Disponendo quindi di un modello validato, per ottimizzare il comfort di marcia del veicolo si sostituisce lo smorzatore passivo della sospensione secondaria con uno smorzatore magneto-reologico: quest'ultimo è comandato da due differenti tipologie di algoritmo basate entrambe sulla logica skyhook, così da controllare, sfruttando le caratteristiche reologiche, la viscosità del fluido magneto-reologico per diminuire le vibrazioni non desiderate della cassa. È infine mostrato un confronto tra i risultati ottenuti utilizzando la sospensione passiva e quelli ottenuti con quella magneto-reologica, così da mostrare l'influenza del controllo sul comfort di marcia.
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Tzu-ChiChiu and 邱子齊. "Application of ANSYS in Component Mode Synthesis." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/72631277124771399032.
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Du-ChingTsai and 蔡篤慶. "Dynamic Analysis of Structures Using Component Mode Synthesis." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/91706828919329978917.
Full textAbstract:
碩士國立成功大學
航空太空工程學系碩博士班
98
Conventional finite-element analysis may encounter the problem of insufficient computational resources especially when the structure system under consideration is very large and complex. This paper discusses the application of component mode synthesis for the dynamic analysis of structures. This method is that divides the structure into several components, reduces the component mode, keeps the important modes and compensation modes, and then assembles a reduced-order model of the entire structure. The critical problems lie in how to appropriately select the compensation modes to increase the precision of model. This paper improves the conventional fixed-interface component modes synthesis by introducing the concept of residual-stiffness into the solving process of conventional constraint mode, and then dealing with the problem which the constraint mode can’t be solved due to component’s constraint conditions may be insufficient. Simultaneously, this paper also discusses how to analyze the flexibility of interconnection structures by component mode synthesis. Through numerical simulation, component mode synthesis can effectively reduce model order of the large structure, and then increase analyzed effectiveness.
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Liu, Pin-Cheng, and 劉品呈. "A Generic Component-Based Model Synthesis Technique." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/07331327362045563372.
Full textAbstract:
碩士國立勤益科技大學
電子工程系
103
In this paper, we have proposed a component-based 3D model synthesis system. In the new system, the user is able to design a new model by assembling available mesh components from two or more models. Such technique is often applied to increase the variation of a type of object for a large population. With our technique, we may create characters such as the legendary Minotaur, centaur, mermaid, as well as some illusionary figures in science fictions, movies, or computer games.
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Yu-ChengTang and 湯育澄. "Application of the Method of Pseudo Mode Shape in Component Mode Synthesis." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/d4j8t9.
Full textAbstract:
碩士國立成功大學
航空太空工程學系
107
Conventional finite-element analysis may encounter the problem of insufficient computational resources especially when the structure system under consideration is large and complex. In order to reduce the model order of a system, Component Mode Synthesis is one of the reduction methods, which can make the structure system be divided into several components according to the features. Further finite element modeling or modal test analysis is performed on each component, and then these components are integrated into an approximate overall structural model. However, in the above synthesize process, it may face the combination of the two different types of information between the finite element model and the frequency response function obtained by the modal test, which makes it difficult to obtain the dynamic characteristics of the overall structural model. This thesis discusses how to apply the pseudo mode shape method to the component modal synthesis method. When the corresponding frequency response function of the component in the defined degree of freedom is measured, the pseudo mode shape matrix of the method converts the frequency response function of the component to obtain the substitute model matrix of the component at the physical coordinate. The surrogate model of this component is integrated with the finite element model into an approximate overall model, and the dynamic characteristics of the overall model can be appropriately described. The focus of this thesis is on how to use pseudo mode shapes to improve the accuracy of modal synthesis analysis. We improved the pseudo mode shape method proposed in the past, and used the full pseudo mode matrix to derive the equivalent analysis model, which can save the calculation programs of the vibration mode information at the joint. The equivalent analysis model still maintain the important dynamic characteristics of the original system. In this paper, a two-dimensional beam is taken as an example to verify the feasibility of the method.
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Amini, Aliakbar A. "Parametric study of rotor-bearing-pedestal system using component mode synthesis." Thesis, 1990. http://spectrum.library.concordia.ca/3867/1/ML56076.pdf.
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Muravyov, Alexander. "Analysis of damped linear dynamic systems and application of component mode synthesis." Thesis, 1994. http://hdl.handle.net/2429/5087.
Full textAbstract:
The analysis of nongyroscopic damped (viscous) linear dynamic systems is presented.
Discrete systems having symmetric mass, stiffness and damping matrices are considered.
Discretization of the systems is accomplished by application of the finite element proce
dure.
The general case of classically damped systems is considered, and the necessary and
sufficient condition for classical damping is given. For a system of this type, it is possible
to specify the damping matrix that will result in each mode having either a prescribed
decay factor or a damped eigenfrequency. This may be accomplished with only a knowl
edge of the undamped eigenfrequencies. The equations required to accomplish this task
are presented. Graphical results are presented that illustrate the effect of damping for
mass-proportional, stiffness-proportional and for Rayleigh damping.
Nonclassically damped systems are considered and the formulation of a component
mode synthesis (CMS) method for the solution of the free vibration problem is described.
The component mode synthesis method is a procedure in which the exact solution
is approximated by one constructed from some basis vectors (e.g., mode shapes) of sub
systems (components of the original system). This method allows significant reduction
of the eigenvalue equation size due to the use of a limited number of basis vectors. The
approximate solution found for the lower eigenvalues and eigenvectors is very close to
the exact one due to the proper selection of the basis vectors and the procedure followed
(e.g., Galerkin’s method) that determines the best approximation. The use of CMS
methods is especially advantageous in the case of large systems, subjected to numerous
modifications. In this work the formulation of the CMS method was developed for the general case of
nonclassically damped systems. It was tested for different cases of noriclassically damped
systems and the excellent agreement with the exact results derived from nonsubdivided
systems was found. Also a new method to treat an unconstrained component for the
purpose of stiffness matrix inversion is presented. The selection procedure of component
modes is generalized from the undamped system case to the damped one.
Some examples of forced responses are considered, particularly, the case of sinusoidal
excitation and the influence of the damping factor is analyzed.
The experimental part of this study consists of the designing and testing of a vibration
rig designed to simulate the behaviour of a rigid engine resting on isolators that in turn are
supported on flexible beams. Free and steady-state responses of the rig are experimentally
determined.
Comparison of analytical results with experimental ones show good agreement for
eigenquantities and steady-state forced response.
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Chen, Hong-kai, and 陳弘凱. "Component Mode Synthesis Method on the Dynamic Characteristics of Shrouded Turbo Blades." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/32319900613054458175.
Full textAbstract:
碩士國立中山大學
機械與機電工程學系研究所
99
The dynamic characteristics of shroud blade group played a significant role in steam turbine design. However, the complex shape and periodical structure of shroud blades make it so hard to find its dynamic characteristics under high speed operation. The complicate shape, periodic structure, and tedious computation limit the application of finite element method in the design analysis of shroud group blades. In order to design the shroud blade group, the component mode synthesis method was employed to derive the system dynamic equation of the grouped periodical blades. For simplicity, a pre-twisted and tapered cantilever beam is used to derive the approximate analytic solution of a rotating turbo blade. Then the approximated eigen solution of single blade is synthesized in company with the constrain condition by using the component mode synthesis method. In order to confirm the feasibility of the proposed simulation method, a real size turbine blade is used to discuss in the study. Through a comparison between the results solved from the proposed method and finite element method of single blade and shroud blade group to prove the reliability of the proposed method. The effect of blade parameters on the dynamic characteristic of shroud blade group has investigated in this work. Numerical results indicate the proposed method is feasible and effective in dynamic design analyses of the shroud blade group.
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Smith, Malcolm J. "An evaluation of component mode synthesis for modal analysis of finite element models." Thesis, 1993. http://hdl.handle.net/2429/2256.
Full textAbstract:
Component mode synthesis (CMS) is a condensation method for vibration analysis which preserves the low frequency vibrational characteristics of a structure. In this method, the structure is treated as an assemblage of components whose displacements are described in terms of component modes. These modes may be some combination of static response, free vibration, or rigid body displacements of a component. In this thesis, the component mode sets used by other researchers are reviewed with a view to establishing which is most suitable for large-order finite element models. Two component mode sets are identified as ideally satisfying the basic requirements for inter-component compatibility, high convergence rate, linear independence and completeness. Fixed-interface and free-interface CMS formulations in the form of matrix eigen value equations are derived from these mode sets and describe approximately the low-frequency free vibration modes of the structure. They are improvements over previous formulations in that they can be systematically and efficiently applied to linear, undamped, discrete systems of an arbitrarily complex geometry. The free-interface formulation is derived both with and without an approximation of the high-frequency component inertia, and this results in two different structural mass matrices. Two new developments of the free-interface formulation are presented: (1) a method for calculating upper and lower bounds to the exact natural frequencies is given, providing a measure of the absolute accuracy of the structural frequencies; (2) the convergence and interlacing properties of the free-interface method are explored through the analysis of a two-component vibrating rod. Both the fixed- and free-interface methods have been implemented in the general-purpose finite element program VAST. Three finite element models are analyzed and a comprehensive comparison of the frequency and mode shape results obtained with CMS, direct finite element analysis, and Guyan reduction is presented. The complexity of the test cases is sufficient to infer general performance characteristics of the CMS methods. It is shown that with CMS, accuracy equal to a direct analysis is readily obtained in the low frequency modes, and that by using a frequency cutoff criterion to select dynamic modes, the natural frequencies converge in a fairly uniform manner. It is also shown that in terms of computational cost and order-reduction, the relative advantages of using CMS increase with the size of the model and with the stringency of the accuracy requirements. The free-interface method with second-order mass approximation gives the best overall performance because of its high convergence rate and superior condensation in complex two and three dimensional models. Application of CMS to structural dynamic modification and inverse modification is also studied. These techniques use a baseline modal analysis as a reference point for the modified system dynamics. A generalized CMS formulation for the baseline system is used to derive a linear-equivalent perturbation equation from which modified modes can be efficiently determined without recalculating the component modes. Also, two new methods are presented for predicting design changes which satisfy prescribed frequency constraints. An iterative scheme is proposed in which the energy-balance perturbation equations are solved with a full account of the nonlinear coupling terms; and a Newton's method algorithm using inverse iteration eigenvector updating is applied to the linear-equivalent equation. Numerical results using a finite element model are presented which show that for large structural changes, the two new methods give similar or better results than an established method.
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HE, CHUAN-REN, and 何傳仁. "A study on the dynamic characteristics of heat exchanger tube by component mode synthesis method." Thesis, 1989. http://ndltd.ncl.edu.tw/handle/46164086545783619291.
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Bukar, Ali M., Hassan Ugail, and Nosheen Hussain. "On facial age progression based on modified active appearance models with face texture." 2016. http://hdl.handle.net/10454/9481.
Full textAbstract:
NoAge progression that involves the reconstruction of facial appearance with a natural ageing effect has several applications. These include the search for missing people and identification of fugitives. The majority of age progression methods reported in the literature are data driven. Hence, such methods learn from training data and utilise statistical models such as 3D morphable models and active appearance models (AAM). Principal component analysis (PCA) which is a vital part of these models has an unfortunate drawback of averaging out texture details. Therefore, they work as a low pass filter and as such many of the face skin deformations and minor details become faded. Interestingly, recent work in 2D and 3D animation has shown that patches of the human face are somewhat similar when compared in isolation. Thus, researchers have proposed generating novel faces by compositing small face patches, usually from large image databases. Following these ideas, we propose a novel age progression model which synthesises aged faces using a hybrid of these two techniques. First, an invertible model of age synthesis is developed using AAM and sparse partial least squares regression (sPLS). Then the texture details of the face are enhanced using the patch-based synthesis approach. Our results show that the hybrid algorithm produces both unique and realistic images. Furthermore, our method demonstrates that the identity and ageing effects of subjects can be more emphasised.
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James, Stephen M. "Adapting a Beam-Based Rotordynamics Model to Accept a General Three-Dimensional Finite-Element Casing Model." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-05-7967.
Full textAbstract:
The subject of this thesis is an extension of a two-dimensional, axisymmetric, Timoshenko-beam finite-element rotordynamic code to include a three-dimensional non-axisymmetric solid-element casing model. Axisymmetric beams are sufficient to model rotors. Spring and damper forces provide the interface between the rotor and its casing and capture the dynamics of the full model. However, axisymmetric beams limit the modeling of real-case machine structures, where the casing is not axisymmetric.
Axisymmetric and non-axisymmetric 3D finite element casing structures are modeled. These structures are then reduced using a technique called substructuring. Modal equations are developed for axisymmetric and non-axisymmetric casing models. In a 3D non-axisymmetric model, structural dynamics modes can be modeled by lateral modes in two orthogonal planes. Modal information of the complex 3D casing structures are generated, and then incorporated into the 2D code after a series of pre-processing steps.
A reduction method called Component Mode Synthesis (CMS) is used to reduce the large dimensionality involved in calculation of rotordynamic coefficients. The results from the casing structures are merged with the rotor model to create a combined rotor-casing model. The analysis of the combined structure shows that there is a difference in the natural frequencies and unbalance response between the model that uses symmetrical casing and the one that uses non-axisymmetric casing.
XLTRC2 is used as an example of a two-dimensional axisymmetric beam-element code. ANSYS is used as a code to build three-dimensional non-axisymmetric solid-element casing models. The work done in this thesis opens the scope to incorporate complex non-axisymmetric casing models with XLTRC2.
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Lavelle, Francis M. III. "A Lanczos component mode synthesis algorithm for locally nonlinear systems with applications to seismic structural pounding." Thesis, 1991. http://hdl.handle.net/1911/16459.
Full textAbstract:
A Component Mode Synthesis (CMS) algorithm employing load dependent Lanczos vectors is presented. The proposed algorithm yields a sparse set of reduced system equations and is an efficient method for computing the forced vibration response of multi-component and/or locally nonlinear dynamic systems. The beneficial aspects of traditional CMS methods employing fixed interface component normal modes and the computational advantages of load dependent Ritz/Lanczos vectors are combined in the new algorithm. By exploiting the tridiagonal property of Lanczos vectors, the system equations are nearly as sparse as traditional CMS equations. The Lanczos CMS transformation projects the solution onto the same subspace spanned by a previously proposed Ritz CMS transformation. For loads which have fixed spatial distributions, the complete static response of each component is completely represented by its first retained Lanczos vector.
Several numerical integration techniques which take advantage of the special structure of the synthesized equations of motion are studied. Operations counts demonstrate that the integration costs for the proposed algorithm are substantially lower than the costs associated with fully coupled Ritz CMS equations and nearly identical to traditional CMS integration costs.
In general, the accuracy of the proposed algorithm is comparable to traditional CMS algorithms. For specific applications, the rates of convergence of the two methods depend on the applied loading conditions and the degree of interaction between the structural components.
The analysis of several multi-component earthquake engineering problems has lead to an investigation of seismic structural pounding. Structural pounding occurs when the separation between adjacent buildings is not sufficient to prevent collisions during seismic excitations. An inelastic linking mechanism which reduces pounding hazards for a particularly vulnerable class of structures is presented. Inelastic links are a viable retrofitting strategy for many existing buildings which have inadequate separation and dissimilar dynamic characteristics. The analytical model for the linked structures is a two-component locally nonlinear system. The proposed Lanczos CMS reduction algorithm is a efficient method for predicting the seismic response of inelastically linked buildings.
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WANG, GING-GUO, and 汪清國. "The elastodynamic analysis and the component mode synthesis of high-speed flexible robot manipulators with mechanical joints." Thesis, 1988. http://ndltd.ncl.edu.tw/handle/73934655633318387261.
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Vasilescu, M. Alex O. "A Multilinear (Tensor) Algebraic Framework for Computer Graphics, Computer Vision and Machine Learning." Thesis, 2012. http://hdl.handle.net/1807/65327.
Full textAbstract:
This thesis introduces a multilinear algebraic framework for computer graphics, computer vision, and machine learning, particularly for the fundamental purposes of image synthesis, analysis, and recognition. Natural images result from the multifactor interaction between the imaging process, the scene illumination, and the scene geometry. We assert that a principled mathematical approach to disentangling and explicitly representing these causal factors, which are essential to image formation, is through numerical multilinear algebra, the algebra of higher-order tensors.
Our new image modeling framework is based on(i) a multilinear generalization of principal components analysis (PCA), (ii) a novel multilinear generalization of independent components analysis (ICA), and (iii) a multilinear projection for use in recognition that maps images to the multiple causal factor spaces associated with their formation. Multilinear PCA employs a tensor extension of the conventional matrix singular value decomposition (SVD), known as the M-mode SVD, while our multilinear ICA method involves an analogous M-mode ICA algorithm.
As applications of our tensor framework, we tackle important problems in computer graphics, computer vision, and pattern recognition; in particular, (i) image-based rendering, specifically introducing the multilinear synthesis of images of textured surfaces under varying view and illumination conditions, a new technique that we call
``TensorTextures'', as well as (ii) the multilinear analysis and recognition of facial images under variable face shape, view, and illumination conditions, a new technique that we call ``TensorFaces''. In developing these applications, we introduce a multilinear image-based rendering algorithm and a multilinear appearance-based recognition algorithm. As a final, non-image-based application of our framework, we consider the analysis, synthesis and recognition of human motion data using multilinear methods, introducing a new technique that we call ``Human Motion Signatures''.
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Masamha, Tavengwa. "A Logistic regression analysis model for predicting the success of computer networking projects in Zimbabwe." Thesis, 2020. http://hdl.handle.net/10500/26883.
Full textAbstract:
Information and communication technology (ICT) greatly influence today’s business processes
be it in public or private sectors. Everything that is done in business requires ICT in one way or
the other. Research in ICTs is therefore critical. So much research was and is still carried out in
projects that develop or enhance ICT but it is still apparent that the success rate of these projects
is still very low. The extensive coverage of ICTs implies that if the success rate is still that low,
many resources are being wasted in the failed projects; therefore, more research is needed to
improve the success rate. Previous research has focussed on factors which are critical for the
success of ICT projects, assuming that all ICT projects are the same. As a result, literature is full
of different suggestions and guidelines of the factors critical to ICT projects’ success. This
scenario brings challenges to project managers who end up using their own personal judgement
to select which factors to consider for any project at hand. The end result is the high failure rate
of ICT projects since there is a very high chance of applying the same critical success factors to
different types of ICT projects. This research answered the question: which factors are critical
to the success of computer networking projects in Zimbabwe and how these factors could be
used for building a model that determines in advance the success of such projects?
Literature reviewed indicated that most CSFs were not focused on specific types of ICT projects,
hence were generalised. No literature was found on ICT projects’ CSFs in Zimbabwe. More so,
no CSFs were found for computer networking projects as a specific instance of ICT projects. No
model existed that predicts computer networking projects’ success. This study addressed the
gaps by developing a CSF framework for ICT projects in Zimbabwe, determining CSFs for
computer networking projects in Zimbabwe and the development of a logistic regression analysis
model to predict computer networking projects’ success in Zimbabwe.
Data was collected in Zimbabwe using a unique three-staged process which comprise metasynthesis analysis, questionnaire and interviews. The study was motivated by the fact that most
available research focused on CSFs for general ICT projects and that no research was found on
CSFs influencing projects in computer networking. Meta-synthesis analysis was therefore
conducted on literature in order to identify CSFs as given in literature. The approach was
appropriate since the researcher had noticed that there were extensive ICT projects’ CSFs and
that no such research has been carried out in Zimbabwe.
These CSFs formed the basis for the determination (using a questionnaire) of ICT projects CSFs
for Zimbabwe in particular. Project practitioners’ viewpoints were sought through
questionnaires. Once CSFs for ICT projects in Zimbabwe were determined, they formed the
basis for the determination of unique critical success factors for computer networking projects
in Zimbabwe. Interviews were used to get further information that would have been left out by
questionnaires. The interview questions were set to clarify some unclear or conflicting responses
from the questionnaire and providing in-depth insights into the factors critical to computer
networking projects in Zimbabwe. The data i.e. critical success factors for computer networking
projects guided the development of the logistic regression analysis model for the prediction of
computer networking projects’ success in Zimbabwe.
Data analysis from the questionnaire was analysed using SPSS Version 23.0. Factor analysis and
principal component analysis were some of the techniques used in the analysis. Interview data
was analysed through NVivo Version 10.0. From the results it was deduced that factors critical
to ICT project management in Zimbabwe were closely related to those found in the literature.
The only apparent difference was that CSFs for ICT projects in Zimbabwe were more specific
thereby enhancing their applicability. Computer networking projects had fewer CSFs than
general ICT projects. In addition, CSFs for general ICT projects were different from those
critical to computer networking projects in Zimbabwe.
The development of a comprehensive set of general ICT projects’ CSFs was the first contribution
of this study. This was achieved through meta-synthesis analysis. The other contribution was the
development of a CSF framework for ICT projects specific to Zimbabwe and those specific to
computer networking projects in Zimbabwe. The major contribution was the development of the
logistic regression analysis model that predicts computer networking projects’ success in
Zimbabwe. These contributions will provide literature on ICT project management in Zimbabwe
which will subsequently assist ICT project managers to concentrate on specific factors. The
developed prediction model can be used by project managers to determine possible success or
failure of ICT projects; thereby possible reducing wastage of resource.School of Computing