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Gerick, Felix. "Modes magnéto-Coriolis rapides et couples de pression résultant des modes de torsion d'Alfvén dans les noyaux planétaires." Thesis, Université Grenoble Alpes, 2020. https://thares.univ-grenoble-alpes.fr/2020GRALU027.pdf.
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Le champ magnétique terrestre et le taux de rotation de la Terre changent sur des périodes de plusieurs années.Dans cette thèse, on cherche à savoir si et comment de tels changements peuvent être causés par des modes (ondes stationnaires) dans le noyau liquide et conducte.Pour ce faire, un modèle de noyau planétaire en rotation rapide et électriquement conducteur est développé, capable de gérer des champs magnétiques complexes et une frontière non sphérique.Nous exploitons la rotation rapide pour simplifier notre modèle, en utilisant l'hypothèse dite quasi-géostrophique, où les composantes horizontales de la vitesse deviennent invariantes le long de l'axe de rotation.En dérivant un tel modèle dans une géométrie non axisymétrique, nous sommes en mesure d'étudier le couple de pression exercé sur la limite noyau-manteau par des modes, qui sont des solutions linéaires au modèle.Les modes d'Alfvén dits de torsion sont particulièrement intéressants, car ils consistent en des cylindres géostrophiques en rotation différentielle les uns par rapport aux autres, potentiellement porteurs d'un moment angulaire axial.Ces cylindres agissent contre la tension des lignes de champ magnétique radiales cisaillées, ce qui montre leur nature Alfvénique.Dans le noyau terrestre, on suppose qu'ils ont des périodes de quelques années et on les a corrélés aux changements de la longueur du jour.Nos résultats suggèrent que le couple de pression associé à de tels modes de torsion Alfvén est inefficace pour expliquer les changements observés dans la longueur du jour terrestre sur des périodes d'environ 6 ans.Il s'avère que l'amplitude de la pression associée à ces modes devrait être indépendante de la vitesse de rotation, si le volume ne permet pas de prendre en compte les contours géostrophiques non fermés.Il convient d'étudier si le couple de pression peut être augmenté en considérant des géométries plus complexes que l'ellipsoïde, considéré ici.Sinon, les modes de torsion Alfvén dans le noyau doivent être couplés à une couche électriquement conductrice dans le manteau inférieur ou par couplage gravitationnel pour expliquer les changements observés dans la longueur du jour.Dans une deuxième partie, nous avons étudié les modes de Magneto-Coriolis dans un modèle de noyau sphérique et homogène, où nous pouvons exprimer le champ magnétique de manière à pouvoir calculer les changements de champ magnétique à la surface du noyau.Sur Terre, les observations du champ géomagnétique à la surface révèlent des changements du champ magnétique à différentes échelles de temps, allant de plusieurs millions d'années à des changements interannuels.En projetant les observations à travers le manteau, les changements interannuels du champ magnétique à la surface du noyau sont interprétés comme le résultat d’une magnétohydrodynamique simple dans le noyau externe liquide.Dans notre modèle, nous calculons les modes de Magneto-Coriolis de périodes de plusieurs années.Ces modes de Magneto-Coriolis rapides montrent une forte focalisation de leur énergie cinétique et magnétique dans la région équatoriale, tout en maintenant une structure spatiale relativement importante le long de la direction azimutale.Leurs propriétés concordent avec certaines propriétés des observations magnétiques et des mouvements à la surface du noyau récemment proposés.De plus, contrairement à ce qui a été supposé précédemment, nous constatons que ces modes ne sont pas affectés de manière significative par la diffusion magnétique.Le nouveau modèle ouvre une nouvelle façon d'inverser les observations géomagnétiques pour en déduire les mouvements et le champ magnétique dans les profondeurs du noyau externe de la TerreEarth's magnetic field and rotation rate change on periods of several years.In this thesis it is investigated if and how such changes can be caused by modes (standing waves) in the liquid and conducting core.To do so, a model for a rapidly rotating and electrically conducting planetary core is developed that is able to handle non-idealized magnetic fields and a non-spherical boundary.We exploit the rapid rotation of the fluid to simplify our model, using the so-called quasi-geostrophic assumption, where the horizontal components of the velocity become invariant along the axis of rotation.By deriving such a model in a non-axisymmetric geometry, we are able to investigate the pressure torque exerted onto the core-mantle boundary by modes, which are linear solutions to the model.So-called torsional Alfvén modes are of particular interest, as they consist of differentially rotating geostrophic cylinders, potentially carrying axial angular momentum.These cylinders act against the tension of sheared radial magnetic field lines, showing their Alfvénic nature.In Earth's core they are assumed to have periods of a few years and they have been correlated to changes in the length of day on periods of about 6 yr.Our results suggest that the pressure torque associated to such torsional Alfvén modes is inefficient to explain the observed changes in Earth's length of day
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Ponte, Felgueiras Olivier. "Nouvelle méthode d'évaluation de la santé d'un composite fondée sur l'interaction des modes de flexion et de torsion." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLM055.
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Au regard de l’intérêt porté aux matériaux composites (performance mécanique et réduction de masse), il est un domaine dans lequel leur utilisation est encore peu développée, notamment dans l’industrie du transport: les éléments de liaisons au sol (trains avant et arrière, éléments de suspension et de direction, ...). Afin de garantir la sûreté de fonctionnement de ces pièces de sécurité, il est indispensable d’être en mesure de bien les dimensionner dès la phase de conception, de valider correctement les organes prototypes et surtout, de savoir diagnostiquer, tout au long de leur durée de vie, leur état de santé. De nos jours, bon nombre de méthodes sont utilisées, mais les moyens de mesure qu’elles nécessitent sont bien souvent onéreux, avec des durées d’acquisition et de post-traitement conséquentes, et pour lesquelles il est bien souvent nécessaire d’immobiliser le moyen de transport voire d’extraire la structure de son environnement mécanique. C’est donc pour pallier ces difficultés, que nous souhaitons développer une méthode de mesure non intrusive qui permette de rendre compte des dégradations qui apparaissent, de l’échelle mésoscopique jusqu’à l’échelle de la structure (fissuration intralaminaire, délaminage, ...), sans qu’il ne soit nécessaire de démonter la structure. En nous appuyant sur le principe de l’analyse modale expérimentale (voire opérationnelle), nous cherchons à établir un lien fort entre l’évolution de certains paramètres modaux d’une éprouvette et la nature des dégradations qui apparaissent au cours d’essais de traction monotone. L'idée consiste à introduire une dégradation spécifique, en la faisant apparaître de manière naturelle, puis à suivre l’interaction de sa propagation sur le comportement modal de l’éprouvette en l’interrogeant à différents paliers de chargement, par l’intermédiaire d’un stimulus. L’excitation vibratoire est assurée par l’intermédiaire d’un actuateur piézoélectrique, la réponse du système est mesurée par un vibromètre laser 3D monopoint, et l’identification des dégradations s’effectue le long de la tranche de l’éprouvette par l’intermédiaire d’un microscope optique motorisé. Nous proposons ainsi d’élaborer un critère vibratoire qui s’appuie sur la combinaison de 2 modes spécifiques que sont la flexion et la torsion. Ce critère de santé vibratoire expérimental est ensuite confronté à son homologue numérique afin de valider sa pertinenceDespite high interest in composite materials (mechanical performance and mass reduction), their application in the automotive transport industry is still limited: suspension, wheels, steering connection elements. In order to ensure the reliability of these safety-critical parts (regardless of the application industry), it is essential to dimension them properly in the design phase to validate the prototypes correctly and, especially, to be able to diagnose their health status throughout their lifetime. Nowadays, multiple methods are available, but measuring equipment they use is often expensive, with long acquisition and post-processing times, and often requiring immobilising the vehicle or extracting parts of its structure. It is therefore desirable to develop a non-intrusive measurement method allowing the assessment of material degradation, from a mesoscopic to a structural scale (cracking, delamination, ...), without the need to disassemble the structure. Using the principles of experimental modal analysis, we aim at establishing a clear link between the evolution of certain modal parameters and the damage observed under monotonous tensile tests. The idea consists, in introducing specific degradation, controlled by the orientation of composite plies, and then allowing it in the specimen to appear in a natural way (for instance originating from a porosity) in order to characterise the modal basis for several stages of loading and degradations. In order to do this, the vibratory excitation is applied via a piezoelectric actuator, the response of the system is measured by a 3D vibrometer laser and the damage identification is carried out along a section of the specimenusing a motorised optical microscope. We propose a vibration criterion, using a combination of bending and torsion modes. This experimental vibration health criterion is then compared to its digital counterpart in order to validate its relevance
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Glodic, Nenad. "Sensitivity of Aeroelastic Properties of an Oscillating LPT Cascade." Licentiate thesis, KTH, Kraft- och värmeteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-123504.
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Modern turbomachinery design is characterized by a tendency towards thinner, lighter and highly loaded blades, which in turn gives rise to increased sensitivity to flow induced vibration such as flutter. Flutter is a self-excited and self-sustained instability phenomenon that may lead to structural failure due to High Cycle Fatigue (HCF) or material overload. In order to be able to predict potential flutter situations, it is necessary to accurately assess the unsteady aerodynamics during flutter and to understand the physics behind its driving mechanisms. Current numerical tools used for predicting unsteady aerodynamics of vibrating turbomachinery components are capable of modeling the flow field at high level of detail, but may fail in predicting the correct unsteady aerodynamics under certain conditions. Continuous validation of numerical models against experimental data therefore plays significant role in improving the prediction accuracy and reliability of the models. In flutter investigations, it is common to consider aerodynamically symmetric (tuned) setups. Due to manufacturing tolerances, assembly inaccuracies as well as in-service wear, the aerodynamic properties in a blade row may become asymmetric. Such asymmetries can be observed both in terms of steady as well as unsteady aerodynamic properties, and it is of great interest to understand the effects this may have on the aeroelastic stability of the system. Under certain conditions vibratory modes of realistic blade profiles tend to be coupled i.e. the contents of a given mode of vibration include displacements perpendicular and parallel to the chord as well as torsion of the profile. Current design trends for compressor blades that are resulting in low aspect ratio blades potentially reduce the frequency spacing between certain modes (i.e. 2F & 1T). Combined modes are also likely to occur in case of the vibration of a bladed disk with a comparatively soft disk and rigid blades or due to tying blades together in sectors (e.g. in turbines). The present investigation focuses on two areas that are of importance for improving the understanding of aeroelastic behavior of oscillating blade rows. Firstly, aeroelastic properties of combined mode shapes in an oscillating Low Pressure Turbine (LPT) cascade were studied and validity of the mode superposition principle was assessed. Secondly, the effects of aerodynamic mistuning on the aeroelastic properties of the cascade were addressed. The aerodynamic mistuning considered here is caused by blade-to-blade stagger angle variations The work has been carried out as compound experimental and numerical investigation, where numerical results are validated against test data. On the experimental side a test facility comprising an annular sector of seven free-standing LPT blades is used. The aeroelastic response phenomena were studied in the influence coefficient domain where one of the blades is made to oscillate in three-dimensional pure or combined modes, while the unsteady blade surface pressure is acquired on the oscillating blade itself and on the non-oscillating neighbor blades. On the numerical side, a series of numerical simulations were carried out using a commercial CFD code on a full-scale time-marching 3D viscous model. In accordance with the experimental part the simulations are performed using the influence coefficient approach, with only one blade oscillating. The results of combined modes studies suggest the validity of combining the aeroelastic properties of two modes over the investigated range of operating parameters. Quality parameters, indicating differences in mean absolute and imaginary values of the unsteady response between combined mode data and superposed data, feature values that are well below measurement accuracy of the setup. The findings of aerodynamic mistuning investigations indicate that the effect of de-staggering a single blade on steady aerodynamics in the cascade seem to be predominantly an effect of the change in passage throat. The changes in steady aerodynamics are thereby observed on the unsteady aerodynamics where distinctive effects on flow velocity lead to changes in the local unsteady pressure coefficients. In order to assess the overall aeroelastic stability of a randomly mistuned blade row, a Reduced Order Model (ROM) model is introduced, allowing for probabilistic analyses. From the analyses, an effect of destabilization due to aero-asymmetries was observed. However the observed effect was of moderate magnitude.QC 20130610
Turbokraft
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Jrad, Wassim. "Dynamic behavior of thin-walled beams : Analytical, numerical and experimental approaches." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0271.
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Les poutres à parois minces à sections ouvertes sont des éléments de base des ouvrages courants en génie civil, de l'automobile et de l'aéronautique. En raison de leur élancement et la forme des sections, elles sont très sensibles à la torsion et aux instabilités aussi bien en statique qu’en dynamique. En dynamique, les modes de vibration en torsion sont plus dominants par rapport au modes de flexion classiques. Pour ces raisons, les défaillances planaires de telles structures sont connues pour être une exception plutôt qu'une règle. Dans ce travail de thèse, on s’intéresse au comportement dynamique de poutres à parois minces et à section ouvertes arbitraires. En se basant sur le modèle de Vlasov qui prend en compte de la torsion et du gauchissement, les équations de mouvement 3D sont dérivées à partir du principe d’Hamilton. Des solutions analytiques originales pour différentes conditions aux limites sont dérivées pour des modes supérieurs en vibrations libres. Dans ces solutions, les effets des termes de rotation inertiels en flexion et torsion sont pris en compte. Pour des cas généraux, un modèle élément fini de poutre 3D est décrit et implémenté. Dans le modèle, un degré de liberté (ddl) est affecté au gauchissement. Toutes les matrices de rigidité masse de base sont calculées par intégration numérique (intégration de Gauss). Dans le modèle, les calculs en vibrations libres et forcées sont possibles. Le modèle est validé par comparaison aux solutions numériques et expérimentaux de la littérature. Une comparaison aux simulations des codes commerciaux est aussi suivie. Afin de valider le modèle théorique et numérique utilisé, une campagne d’essais a été suivie au LEM3 à Metz. Des essais de vibration libre et forcée sont effectués sur des poutres à parois minces avec différentes conditions aux limites. Les solutions analytiques, numériques et les mesures expérimentales sont comparées et validées. Un bon accord entre les différentes solutions est constaté. Le modèle est étendu aux poutres 3D retenues latéralement par des entretoises. Des ressorts élastiques et visqueux 3D sont ajoutés dans le modèle numérique. L'effet des entretoises est étudié dans le but d’améliorer le comportement des poutres à parois minces vis-à-vis des modes indésirables de type flexion latérale et torsionThin-walled beams with open section constitute main elements in engineering applications fields as in civil engineering, automotive and aerospace construction. Due to slenderness and cross section shapes, these elements are very sensitive to torsion and instabilities in both statics and dynamics. In dynamics, the torsional and flexural-torsional modes of vibration are often lower frequencies compared to the classical plane pure bending modes. Thus, planar failures of such structures are known to be an exception rather than a rule. In torsion, warping is important and governs the behavior. In this thesis work, we are interested with the dynamic behavior of thin-walled beams with arbitrary open cross sections. Based on the Vlasov’s model accounting for warping, the 3D motion equations are derived from the Hamilton’s principle. Original analytical solutions for different boundary conditions are derived for higher free vibration modes. In these solutions, the effects of the inertial rotation terms in bending and torsion are taken into consideration. For more general cases, a 3D beam finite element model is described and implemented. Compared to conventional 3D beams, warping is considered as an additional Degree Of Freedom (DOF). The mass and stiffness matrices are obtained by numerical integration (Gauss method). In the model, free and forced vibration analyses are possible. The model is validated by comparison with benchmark solutions available in the literature and other numerical results obtained from simulation on commercial codes. In order to validate the present model, laboratory test campaign is undertaken at the LEM3 laboratory in Metz. Tests are carried out on thin-walled beams with different boundary conditions. Free and forced vibration tests are performed using impact hammer and shaker machine. In the presence of arbitrary sections, flexural-torsional vibration modes are observed. The analytical, the numerical and the experimental solutions are compared and validated. Moreover, the numerical and experimental dynamic response spectra are compared. A good agreement between the various solutions is remarked. The model is extended to 3D beams in presence of lateral braces. 3D elastic and viscous springs are added in the finite element model. The effect of the springs is studied in order to improve the behavior of thin-walled beams against undesirable lateral bending and torsion modes
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Parsons, Simon Paul. "Abelian dualities and sigma models." Thesis, University of Liverpool, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367188.
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Thomas, Jossian, and Barenys Assís Arañó. "Evaluation of 3D dynamic effects induced by high-speed trains on double-track slab bridges." Thesis, KTH, Bro- och stålbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-188850.
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In addition to a static design, a dynamic analysis has to be performed for bridges for which the maximum permissible train speed exceeds 200 km/h. This analysis requires a lot of computing time, for this reason Svedholm and Andersson (2016) have developed a simple tool describing the relationship between the first eigenfrequency of the bridge, the span length and the minimum mass to fulfill the regulation specified in EN-1990. However, these diagrams are based on 2D beam models in which the 3D dynamic effects are not considered. An evaluation of the torsional modes has been performed by analyzing parametrized 3D bridge models, in order to obtain design diagrams including these effects. To do so, a frequency domain analysis has been implemented, based on a steadystate step previously performed in a FEM software. This approach provides a fast way to solve the equation of motion due to the Fourier transform properties, and allows applying several load configurations which are convenient for a parametric study. From this analysis it can be concluded that the thickness to fulfill the demands is larger for 3D models than for 2D. On one hand, contribution of torsional modes of vibration is more significant for the shortest span length, and on the other hand shear-lag effects lead to a reduction of the total resisting bending section.
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Mirjalili, Vahid. "Modelling the structural efficiency of cross-sections in limited torsion stiffness design." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99780.
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Most of the current optimization techniques for the design of light-weight structures are unable to generate structural alternatives at the concept stage of design. This research tackles the challenge of developing an optimization method for the early stage of design. The main goal is to propose a procedure to optimize material and shape of stiff shafts in torsion.Recently introduced for bending stiffness design, shape transformers are presented in this thesis for optimizing the design of shafts in torsion. Shape transformers are geometric parameters defined to classify shapes and to model structural efficiency. The study of shape transformers are centered on concept selection in structural design. These factors are used to formulate indices of material and shape selection for minimum mass design. An advantage of the method of shape transformers is that the contribution of the shape can be decoupled from the contribution of the size of a cross-section. This feature gives the designer insight into the effects that scaling, shape, as well as material have on the overall structural performance.
Similar to the index for bending, the performance index for torsion stiffness design is a function of the relative scaling of two cross-sections. The thesis examines analytically and graphically the impact of scaling on the torsional efficiency of alternative cross-sections. The resulting maps assist the selection of the best material and shape for cross-sections subjected to dimensional constraints. It is shown that shape transformers for torsion, unlike those for bending, are generally function of the scaling direction.
The efficiency maps ease the visual contrast among the efficiency of open-walled cross-sections and that of close-walled cross-sections. As expected, the maps show the relative inefficiency of the former compared to the latter. They can also set the validity range of thin- and thick-walled theory in torsion stiffness design. The analytical results are validated with the numerical data obtained from ANSYS to guarantee the consistency of the models. The thesis concludes with three case studies that demonstrate the method.
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Stryhalski, Joel. "Crescimento de trincas em fadiga torsional." Universidade do Estado de Santa Catarina, 2011. http://tede.udesc.br/handle/handle/1788.
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With increasing competition and reliability in modern equipment, is of vital importance to studies on the structural fatigue life in the time domain and frequency domain, the advance speed and cost reduction in computing greatly simplifies the prediction fatigue life. But it is also necessary to know the modes of fatigue crack growth, and its mechanisms. After a review appropriate to implement a program to estimate the loss of torsional stiffness in a specimen with a crack in Mode II, was developed a device torsional fatigue tests in an attempt to identify the onset of macroscopic crack and study its growth. With learning the operation of the drive system, the system data acquisition device testing, and design and construction of an electronic circuit to shutdown device tests at the beginning of the crack in the specimen, an adequate control and calibration of these components was performed, generating confidence in that joint. This document is the experimentally determined curve of fatigue specimens of SAE 1020 Steel, Grey Cast Iron and Aluminum 6063. They also studied the failure modes of cracks from the beginning until the final rupture of the specimen to verify the failure modes, the crack initiation and propagation of macroscopic materials. It still made a numerical prediction by finite element method the size of the crack.
Com aumento da competitividade e da confiabilidade em equipamentos modernos, é de vital importância os estudos em relação à vida em fadiga estrutural no domínio do tempo e no domínio da freqüência, o avanço da velocidade e redução de custos na área computacional facilita bastante a previsão de vida em fadiga. Mas é necessário também conhecer os modos de crescimento de trinca por fadiga, e seus mecanismos. Após revisão bibliográfica adequada, com implementação de um programa para estimar a perda de rigidez torsional em um corpo de prova com trinca no Modo II, foi desenvolvido um dispositivo de testes de fadiga torsional na tentativa de identificar o início da trinca macroscópica e estudar o seu crescimento. Com o aprendizado do funcionamento do sistema de acionamento, do sistema de aquisição de dados do dispositivo de testes, e a elaboração e construção de um circuito eletrônico para desligamento do dispositivo de testes ao início da trinca no corpo de prova, um adequado controle e calibração destes componentes executou-se, gerando confiabilidade nestes conjuntos. Neste documento é determinada experimentalmente a curva de fadiga de corpos de prova de Aço SAE 1020, Ferro Fundido Cinzento e Alumínio 6063. Também são estudados os modos de falha desde o início da trinca até a ruptura final do corpo de prova para verificar os modos de falha, início e propagação da trinca macroscópica desses materiais. É feita ainda uma previsão numérica através do Método dos Elementos Finitos do tamanho da trinca.
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Johansson, Jonas. "Investigation of Mode Superposition as Modelling Approach for Crankshaft Torsion." Thesis, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-69453.
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With tougher emission standards for heavy duty trucks, good control of the engine is of importance. By taking into consideration the torsional vibrations occurring in the crankshaft, the engine control can be improved. This could be done by implementing a torsion model that would give feedback to the engine control unit to reduce the cycle-to-cycle variations in the cylinders, which is partly due to the torsion in the crankshaft. It is therefore of interest to determine if a torsion model can be developed with a reduced computational complexity and still have sufficient accuracy. In this thesis a model was developed in Matlab for estimation of torsion in the crankshaft of an inline 6 cylinder diesel engine. By applying Newtons second law, the equations of motion that describe the torsional vibrations in the crankshaft were set up. The equations of motion were transformed using modal analysis and with the use of mode superposition it was investigated how reducing the number of vibrational modes in the model, affected the models accuracy in its estimation of torsion. Two model reductions were evaluated where the first three and four vibrational modes were used to calculate the torsional displacement between the flywheel and the cylinders. Using measured pressure curves for a number of operating points of the engineas input to the model, results were produced for different crank angle intervalsshowing deviations between the developed torsion models and a reference models estimation of torsion. Due to the damping approximation used in the model, high initial deviations could be found at certain operating points beforereducing the number of vibrational modes. These initial deviations weregreatest for the first two cylinders. Results from the model reductions showed that using the first three vibrational modes in the torsion model, is sufficient for estimating the torsional displacement between the flywheel and all cylinderswith an accuracy of within 0.1 degrees, with the exception of the first two cylinders for the early and late combustion interval.
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Khademolhosseini, Farzad. "Nonlocal continuum shell models for torsion of single-walled carbon nanotubes." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/12549.
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Carbon nanotubes (CNTs) have attracted much attention from scientists and engineers because of their relevance to a wide range of applications. Various approaches have been used for the characterization of CNT properties, among which continuum modeling has generated much interest due to computational efficiency. However, at the nanoscale the dimensions of a system are comparable to the inter-atomic or inter-molecular spacing of that system, and the material cannot be modeled as a continuum. This is known as the “size-effect”. To overcome the limitations of classical continuum mechanics, modified continuum models have been proposed, among which models based on the concept of nonlocal elasticity have proven effective in quantifying the size-dependent mechanical response of CNTs.
This thesis investigates the “small-size” effects in the torsional response of single walled carbon nanotubes (SWCNTs) by developing a modified nonlocal continuum shell model for their torsion. The purpose is to facilitate the design of devices based on CNT torsion by providing a simple, accurate and efficient continuum model that can predict the torsional buckling loads, the frequency of torsional vibrations and the propagation speed of torsional waves. To this end, Eringen’s equations of nonlocal elasticity are incorporated into the classical models for torsion of cylindrical shells given by Timoshenko and Donnell. In contrast to the classical models, the nonlocal model developed here predicts non-dimensional buckling loads that depend on the values of certain geometric parameters of the CNT, allowing for the inclusion of size-effects. In the case of torsional vibrations and propagation of torsional waves, the classical and nonlocal models predict non-dispersive and dispersive behavior, respectively. Molecular dynamics simulations of torsional buckling, axial buckling and torsional vibration of various SWCNTs are also performed, the results of which are compared with the classical and nonlocal models and used to extract consistent values of the nonlocal elasticity constant. Interestingly, the nonlocal elasticity constant depends on the existence of circumferential and/or longitudinal modes in the deformed shape of the CNT. In all loading cases the superiority of the nonlocal model over the classical elasticity model in predicting the size-dependent mechanical response of SWCNTs is established.
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Říha, Stanislav. "Viskózní tlumič torzních kmitů plynového vidlicového šestnáctiválce." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-229308.
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Master’s thesis with title Viscous torsional vibration damper of a gas v-sixteen engine deals with torsion vibrafon of the crankshaft and chance how to eliminated it. First part of diploma thesis containes calculation of torsion vibrafon without damper. In second part is added damper. In the end of this thesis is equaiont made of both parts.
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Xu, Jian. "Development of a general dynamic hysteretic light-frame structure model and study on the torsional behavior of open-front light-frame structures." Online access for everyone, 2006. http://www.dissertations.wsu.edu/Dissertations/Fall2006/j_xu_120606.pdf.
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SANCHEZ, ELEAZAR CRISTIAN MEJIA. "DEVELOPMENT OF A TENSION-TORSION FATIGUE TESTING MACHINE TO EVALUATE INCREMENTAL PLASTICITY MODELS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=35541@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
FUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
PROGRAMA DE EXCELENCIA ACADEMICA
BOLSA NOTA 10
A avaliação experimental de modelos de plasticidade incremental e a predição da vida à fadiga sobre cargas combinadas requer o uso de máquinas de testes multiaxiais. Neste trabalho é desenvolvida uma máquina tração-torção (MTT) para avaliar modelos de plasticidade incremental. Este sistema eletromecânico utiliza como atuadores principais dois motores de corrente contínua conectados a caixas de redução para gerar os carregamentos de tração axial e/ou torção. O projeto da MTT compreende a análise de sua integridade estrutural, seu dimensionamento, e o cálculo da vida à fadiga de seus principais componentes; o projeto e desenvolvimento de uma célula tração-torção (LTC - load torque cell); o desenvolvimento e implementação das técnicas de controle; e finalmente sua construção e avaliação. Uma técnica de controle PID por modos deslizantes (PID Sliding Mode control) foi especialmente desenvolvida para esta máquina, consistindo em aplicar um sinal de controle descontínuo que força o sistema a deslizar ao longo de uma superfície de convergência. Esta técnica de controle tem a capacidade de controlar continuamente a força axial e/ou o torque aplicado ao corpo de prova de maneira independente, o que permite gerar histórias de cargas não-proporcionais. Os métodos de controle são implementados em uma plataforma computacional em tempo real CompactRio. Deste modo, é possível gerar uma máquina de ensaios de fadiga multiaxial compacta, de fácil manuseio, que não precise de um sistema de controle complexo, e a um baixo custo. A máquina tração-torção foi projetada para atender a uma ampla gama de ensaios de fadiga multiaxial, com uma capacidade de força axial máxima de mais ou menos 200 kN e torque máximo de mais ou menos 1300 N.m. O desempenho da MTT foi avaliado experimentalmente através de ensaios de plasticidade incremental. Para tanto, foram usados corpos de prova de tração-torção para medir seus comportamentos sobre cargas multiaxiais. Ensaios de encruamento não-proporcional, ratcheting (fluência cíclica) multiaxial e ratcheting uniaxial foram realizados em corpos de prova de aço inox 316, aço 1020, alumínio 7075 e alumínio 6063 na MTT, assim como em uma máquina Instron de 100 kN. Um simulador de plasticidade incremental para carregamentos de tração-torção foi desenvolvido, incorporando o modelo de encruamento cinemático não-linear de Jiang-Sehitoglu, e o modelo incremental de encruamento não-proporcional de Tanaka. Os parâmetros do material foram calibrados a partir de ensaios experimentais, permitindo que as simulações fossem capazes de prever o comportamento do material sobre diferentes histórias de carregamento, assim como as taxas de encruamento não-proporcional e de ratcheting. Os experimentos e simulações confirmaram tanto a adequabilidade da MTT desenvolvida, quanto do simulador de plasticidade incremental implementado, baseado nos modelos não-lineares de Jiang-Sehitoglu e Tanaka.
The experimental evaluation of incremental plasticity models and fatigue life prediction under combined loads requires the use of multiaxial testing machines. In this work, an axial-torsion machine (MTT) was developed to evaluate incremental plasticity models. This electromechanical system uses as a main actuators two DC motors connected to gearboxes to generate the axial and/or torsion loads. The design of axial-torsion machine comprises the analysis of its structural integrity, its dimensioning and fatigue life prediction its major components; the design and development of a load torque cell – LTC; the development and implementation of control techniques, and finally, its construction and its performance evaluation. A PID Sliding Model control technique has been specially developed for this machine, which consists in applying a discontinuous control signal that forces the system to slide along a surface convergence. This control technique has the ability to control the axial force and/or torsion applied to specimen test in an independent manner, which allows to generate a non-proportional loading histories. The control methods are implemented on a computing platform in real time CompactRio. Thus, it s possible to developed a compact multiaxial fatigue testing machine, easy to handle, which does not require a complex control system, and at a low cost. The tensiontorsion machine was designed to meet a wide range of multiaxial fatigue tests, with a maximum capacity of axial force of more or less 200 kN and torque of more or less 1300 N.m. The MTT performance was evaluated experimentally by incremental plasticity testing. For this purpose, tensile / torsion specimens were used to measure their behavior under multiaxial loads. Testing of non-proportional hardening, multiaxial ratcheting and uniaxial ratcheting (cyclic creep) were performed on specimens of 316 stainless steel, 1020 steel, 7075 aluminum and 6351T6 aluminum in the MTT, as well as a Instron Machine of more or less 100 kN. A simulator of incremental plasticity to tensile-torsion loads has been developed, incorporating the non-linear kinematic hardening model of Jiang-Sehitoglu, and non-proportional hardening model of Tanaka. The material parameters were calibrated using experimental tests, allowing the simulations to predict the material behavior under different load histories, as well as rates of non-proportional hardening and ratcheting. The experiments and simulations confirmed both the suitability of the developed MTT, as well as the simulator of incremental plasticity implemented, based on non-linear models of Jiang-Sehitoglu and Tanaka.
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Arizou, Ramin. "Distortional Lateral Torsional Buckling of Doubly Symmetric Wide Flange Beams." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41574.
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Distortional lateral-torsional buckling theories assume that the flanges remain undistorted, while the web is free to distort as a thin plate. Most theories adopt a cubic polynomial distribution along the web height to relate the lateral displacement of the web to the displacements and angles of twist both flanges. The present study develops a family of finite element solutions for the distortional buckling of wide flange beams in which the flanges are assumed to remain undistorted. In contrast to past theories, the lateral displacement distribution along the web height is characterized by superposing (a) two linear modes intended to capture the classical non-distortional lateral-torsional behavior and (b) any number of user-specified Fourier terms intended to capture additional web distortion. In the longitudinal direction, all displacement fields characterizing the lateral displacements are taken to follow a cubic distribution.
The first contribution of the thesis develops a finite element formulation that is able to replicate the classical non-distortional lateral torsional buckling solutions when the distortional modes are suppressed while enabling more accurate predictions for distortional lateral torsional buckling compared to those solutions based on the conventional cubic interpolation of the lateral displacement. The formulation is used to conduct an extensive parametric study to quantify the reduction in critical moments due to web distortion relative to the classical non-distortional predictions in the case of simply-supported beams, cantilevers, and beams with an overhang. The solution is then used to generate interaction curves for beams with an overhang subjected to various proportions of uniformly distributed and point loads.
The second contribution of the thesis adds two additional features to the formulation (a) to capture the destabilizing effect due to the load height relative to the shear center and (b) a module that incorporates any number of user-defined multi-point kinematic constraints. The additional features are employed to investigate the effect of load height, bracing height, and combined effects thereof in practical design problems. A distortional indicator is then introduced to characterize the distribution of web distortion along the beam span as the beam undergoes distortional lateral buckling. A systematic design optimization technique is then devised to identify the location(s) along the span at which the addition of transverse stiffeners would maximize the critical moment capacity.
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Filipowicz, Dean. "A Biomechanical Comparison of 3.5 Locking Compression Plate Fixation to 3.5 Limited Contact Dynamic Compression Plate Fixation in a Canine Cadaveric Distal Humeral Metaphyseal Gap Model." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/33558.
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Objective- To compare the biomechanical properties of 3.5 locking compression plate (LCP) fixation to 3.5 limited contact dynamic compression plate (LC-DCP) fixation in a canine cadaveric, distal humeral metaphyseal gap model in static axial compression and cyclic axial compression and torsion.
Study Design- Biomechanical in vitro study.
Sample Population- 30 paired humeri from adult, medium to large breed dogs.
Methods- Testing was performed monotonically to failure in axial compression on ten pairs of humeri, cyclically in axial compression for 10,000 cycles on ten pairs and cyclically in torsion for 500 cycles on the last ten pairs.
Results- Humeral constructs stabilized with LCPs were significantly stiffer than those plated with LC-DCPs when loaded in axial compression (P=0.0004). When cyclically loaded in axial compression over 10,000 cycles, the LC-DCP constructs were significantly stiffer than those constructs stabilized with LCPs (P=0.0029). Constructs plated with LC-DCPs were significantly more resistant to torsion over 500 cycles than those plated with LCPs (P<0.0001), though no difference was detected during the first 280 cycles.
Conclusions- The increased stiffness of LCP constructs in monotonic loading compared to constructs stabilized with non-locking plates may be attributed to the stability afforded by the plate-screw interface of locking plates. The LCP constructs demonstrated less stiffness in dynamic testing in this model, likely due to plate-bone offset secondary to non-anatomic contouring and occasional incomplete seating of the locking screws when using the torque-limiting screw driver.
Clinical Relevance- LCPs yield less stiff fixation under dynamic loading than conventional LC-DCPs when applied to severely comminuted, metaphyseal fractures. Improving anatomical contouring of the plate and insuring complete screw insertion into the locking plate hole may improve stiffness when using LCPs in comminuted fractures.Master of Science
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Xiao, Qiuwu. "Lateral Torsional Buckling of Wood Beams." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31174.
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Structural wood design standards recognize lateral torsional buckling as an important failure mode, which tends to govern the capacity of long span laterally unsupported beams. A survey of the literature indicates that only a few experimental programs have been conducted on the lateral torsional buckling of wooden beams. Within this context, the present study reports an experimental and computational study on the elastic lateral torsional buckling resistance of wooden beams.
The experimental program consists of conducting material tests to determine the longitudinal modulus of elasticity and rigidity modulus followed by a series of 18 full-scale tests. The buckling loads and mode shapes are documented. The numerical component of the study captures the orthotropic constitutive properties of wood and involves a sensitivity analysis on various orthotropic material constants, models for simulating the full-scale tests conducted, a comparison with experimental results, and a parametric study to expand the experimental database.
Based on the comparison between the experimental program, classical solution and FEA models, it can be concluded that the classical solution is able to predict the critical moment of wood beams. By performing the parametric analysis using the FEA models, it was observed that loads applied on the top and bottom face of a beam decrease and increase its critical moment,respectively. The critical moment is not greatly influenced by moving the supports from mid-span to the bottom of the end cross-section.
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田中, 啓介, Keisuke TANAKA, 義明 秋庭, Yoshiaki AKINIWA, 照明 御厨, Teruaki MIKURIYA, 光一 田中, and Kouichi TANAKA. "繰返しねじり荷重条件下での予き裂からのき裂進展と停留." 日本機械学会, 2001. http://hdl.handle.net/2237/9156.
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Regensburger, Martin [Verfasser], and Beate [Akademischer Betreuer] Winner. "Adult neurogenesis in transgenic animal models of DYT1 primary torsion dystonia / Martin Regensburger. Betreuer: Beate Winner." Regensburg : Universitätsbibliothek Regensburg, 2011. http://d-nb.info/1022872877/34.
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Larsen, Gerrit T. "Piezoresistive Models for Polysilicon with Bending or Torsional Loads." Diss., CLICK HERE for online access, 2009. http://contentdm.lib.byu.edu/ETD/image/etd3165.pdf.
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Bairán, García Jesús Miguel. "A non-linear coupled model for the analysis of reinforced concrete sections under bending, shear, torsion and axial forces." Doctoral thesis, Universitat Politècnica de Catalunya, 2005. http://hdl.handle.net/10803/6177.
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La mayoría de las estructuras de hormigón armado se someten a solicitaciones combinadas de esfuerzos axiles, flexión, cortante y torsión. La fisuración del hormigón, plastificación de las armaduras y otros efectos no-lineales hacen que las secciones transversales de estos elementos presenten un comportamiento anisótropo que deriva en el acoplamiento de los esfuerzos normales y tangenciales. Es decir, esfuerzos normales o momentos flectores pueden producir deformaciones de corte y vice versa. Aunque en algunas ocaciones, esta interacción es considerada de forma simplificada en el dimensionamiento de estructuras, hasta el momento no se ha realizado un análisis profundo de los efectos acoplados en secciones de forma arbitraria bajo cargas 3D generales utilizando modelos de fibras.El objetivo principal de esta tesis es generalizar el análisis de secciones de hormigón armado mediante fibras, de forma que se pueda reproducir la res-puesta no-lineal acoplada frente a esfuerzos normales y tangenciales bajo solicitaciones tridimensionales generales. De igual forma, se pretende obtener, para los esfuerzos cortantes y torsión, la misma capacidad de representación de geometrías y combinación de materiales que ofrecen los modelos de fibras para esfuerzos de flexo-compresión.
La primera problemática estriba en representar adecuadamente la cinemática de la sección transversal. Con la excepción de las deformaciones normales contenidas en el plano de la sección, no existe una teoría cinemática que a priori pueda dar la distribución del resto de deformaciones o tensiones en la sección, sin dejar de satisfacer las condiciones de equilibrio interno o continuidad entre las fibras que componen la misma.
Por otra parte, para materiales anisótropos, como el hormigón fisurado, en general todos los esfuerzos internos pueden estar acoplados. Además, es preciso considerar la distorsión de la sección transversal para satisfacer el equilibrio entre fibras.
El problema se aborda de forma general, considerando una sección de forma y materiales cualesquiera. Se parte del problema diferencial de equilibrio de un sólido con el que se ha podido deducir un sistema de equilibrio entre fibras (equilibrio a nivel sección). Se puede demostrar que éste es complementario al problema estándar de vigas. El sistema complementario permite recuperar información tridimensional que normalmente se pierde al resolver un problema de vigas.
Posteriormente, se propone una solución interna del problema complementario, en la que el alabeo y la distorsión de la sección quedan expresados como una función de las deformaciones generalizadas de una viga: deformaciones axil y cortantes, curvaturas de flexión y torsión. No son necesarios grados de libertad adicionales a nivel estructura ni hipótesis a-priori sobre la forma de los campos de deformación o tensión interna.
A partir de la formulación teórica, se desarrolla un modelo de elementos finitos plano de la sección transversal. El modelo está preparado para servir como respuesta constitutiva de cualquier tipo de elemento viga en sus puntos de integración. %Se evita así la necesidad de realizar un modelo de elementos sólidos de toda la barra para estudiar la respuesta frente a una combinación general de esfuerzos normales y tangenciales.
Se implementan una serie de modelos constitutivos para distintos materiales. En particular, se implementa un modelo constitutivo triaxial para hormigón fisurado, considerando la anisotropía inducida por la fisuración e incluyendo la superficie de rotura según un criterio multiaxial.
La formulación seccional es validada mediante varios casos de estudio teóricos y experimentales. La respuesta no-lineal acoplada bajo diversas combinaciones de esfuerzos normales y tangenciales es reproducida con precisión, lo cual queda patente tanto en las curvas esfuerzo-deformación obtenidas como en las matrices de rigidez seccionales.
Finalmente, se recopilan las conclusiones derivadas de la presente investigación y se
ofren recomendaciones para futuros trabajos.
Most RC structures are subjected to combined normal and tangential forces, such as bending, axial load, shear and torsion. Concrete cracking, steel yielding and other material nonlinearities produce an anisotropic sectional response that results in a coupling between the effects of normal and shear forces, i.e. normal force or bending moments may produce shear strains and vice versa. Although this interaction is sometimes taken into account, in a simplified manner, in the design of RC structures, a deep analysis of the coupling effects of RC sections using fiber models has not yet been made for arbitrary shape sections under general 3D loading.
The main objective of this thesis is to generalize the fiber-like sectional analysis of reinforced concrete elements, to make it capable of considering the coupled non-linear response under tangential and normal internal forces, from a general 3D loading.
Similarly, it is desired to obtain, for torque and shear forces, the same capacity and versatility in reproducing complex geometry and materials combination that fiber-like sectional representations offers for bending and stretching.
The first problematic lies in finding a proper representation of the section's kinematics under such general loading. Except for in-plane normal strains, there is no single kinematical theory capable of a-priori representing the correct distribution of the others strains or stresses satisfying, at the same time, inter-fiber equilibrium and continuity. On the other hand, for rather anisotropic materials, such as cracked concrete, all internal forces are, in general, coupled. It is also required that distortion is allowed for the section's kinematics in order to guarantee satisfaction of internal equilibrium.
The problem is dealt in a general form considering arbitrary shaped sections and any material behaviour. Starting from the differential equilibrium of a solid, an inter-fiber equilibrium system (equilibrium at the sectional level) was deduced. This system, which is complementary to the standard equilibrium problem of a beam-column, allows to recuperate information of the three-dimensional problem that is generally lost when solving a beam problem.
Further, a solution of the equilibrium at the sectional level is proposed in which the section's warping and distortion are posed as a function of the generalized beam-column strains (axial and shear strains, bending and torsion curvatures). No additional degrees of freedom are required at the structural level nor a-priori hypotheses on the distribution of the internal strains or stresses.
After the theoretical formulation, a planar finite element model for cross-sectional analysis is developed. The model can be used as a constitutive law for general beam column elements at their integration points.
A series of constitutive models have been implemented for several materials. In particular, a triaxial constitutive model for cracked concrete is implemented considering crackinduced anisotropy and a multiaxial failure criterion.
The sectional formulation is validated by means of various theoretical and experimental case studies. Non-linear coupled response under normal and tangential internal forces is reproduced with accuracy, as can be seen both in the predicted internal force-strain curves and in the sectional stiffness matrixes.
Finally, the conclusions drawn from the current research are summarized and
recomendations for future works are given.
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Mátyás, Attila. "Modifikace čtyřválcového vznětového motoru na zkušební jednoválec." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417592.
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This thesis deals with modification of an existing four-cylinder diesel engine to a singlecylinder research engine. The work is divided into four main parts. The first part is theoretical, briefly describes research engines, their individual types and provides an overview of their functions. The second part of the work includes the modification of a four-cylinder diesel engine to a single-cylinder research engine, focusing mainly on balancing inertia forces. The third, most extensive chapter contains the structural analysis of the crankshaft. The last part contains the design of a torsional coupling, which ensures the connection of the engine with the dynamometer.
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Shoukr, Shoukry Latif. "Contact stresses in interference-fit joints with application to sugar-mill roller assemblies." Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184928.
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The interference-fit joint is widely used in machine design to connect two cylindrical machine elements. Its popularity comes from the simplicity of the assembly and the low cost of the production process. Even so, no study has examined the boundary non-linearities in the assembly of these joints. Moreover, the contact stresses and the stress concentration factors in interference-fit joints under torsional loads have not yet been examined in detail. In addition, the interface stresses and stress concentration factors in interference-fit joints subjected to bending loads have not been approached theoretically before. The sugar-mill roller is one of the oldest and most important examples of the interference-fit joints. The frequent fatigue failure of the sugar-mill rollers under reversed bending causes costly emergency line-shut downs. The versatility of the finite element method and the capability of the point-matching technique in handling contact problems have been combined, in the present work, to produce a surface-matching technique. It has been found that the complete-cohesion contact assumption may be acceptable for coefficients of friction ≥ 0.2, which is the case for most of the normally machined surfaces. An approach combining the semi-inverse displacement finite element method and the surface-matching technique has been developed to perform the torsional analysis. It has been found that the governing non-dimensional quantities are the ratio of the cohesion-length to the interface-length and the coefficient of friction divided by the load-level. The load-level is the ratio between the angle of twist of the shaft per unit length when the torque acts on the shaft alone and the amount of the diametral interference divided by the shaft diameter. A finite element model, using 8-noded solid elements together with linear interface elements, has been employed to locate the cohesion and slippage-zones in the sugar-mill roller under bending. The contact pressure increases along the compression side and decreases along the tension side. On the contrary, the interface shear decreases along the compression side due to bending and increases along the tension side. Subsequently, a larger slippage-length has been detected along the tension side.
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Wierschin, Torsten [Verfasser]. "Graphical models for protein-protein interaction interface prediction / Torsten Wierschin." Greifswald : Universitätsbibliothek Greifswald, 2015. http://d-nb.info/1072253771/34.
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Hofner, Benjamin Verfasser], and Torsten [Akademischer Betreuer] [Hothorn. "Boosting in structured additive models / Benjamin Hofner. Betreuer: Torsten Hothorn." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2011. http://d-nb.info/1020362065/34.
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Hofner, Benjamin [Verfasser], and Torsten [Akademischer Betreuer] Hothorn. "Boosting in structured additive models / Benjamin Hofner. Betreuer: Torsten Hothorn." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-138053.
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Rejnuš, Miroslav. "Modifikace tříválcového vznětového motoru na zkušební jednoválec." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-449787.
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The master thesis deals with the design of a single-cylinder diesel piston internal combustion test engine by modifying the initial mass-produced three-cylinder engine. The first part of the thesis is devoted to the introduction to the problems of diesel and experimental single cylinder engines. Subsequent chapters focus on the adaptation of the baseline engine itself, including balancing of inertial forces. Furthermore, the crankshaft operability is checked, including the determination of safety against high-cycle fatigue. The last chapter deals with the design of the connection of the adapted unit to the dynamometer.
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Yurtsever, Ayhan. "Nanotribological surface characterization by frequency modulated torsional resonance mode AFM." Diss., kostenfrei, 2008. http://edoc.ub.uni-muenchen.de/8718/.
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Chandler, Adrian Mark. "Coupled torsional response of single-storey building models to earthquake loading." Thesis, King's College London (University of London), 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308733.
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Ching, Siok Siong. "Ultrasonic coagulating shears in laparoscopic surgery : a comparative study of longitudinal and torsional modes." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496122.
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Johansson, Robert. "Modeling of Engine and Driveline Related Disturbances on the Wheel Speed in Passanger Cars." Thesis, Linköpings universitet, Institutionen för systemteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-78104.
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The aim of the thesis is to derive a mathematical model of the engine and driveline in a passenger car, capable of describing the wheel speed disturbances related to the engine and driveline. The thesis is conducted in order to improve the disturbance cancelation algorithm in the indirect tire pressure monitoring system, TPI developed by NIRA Dynamics AB. The model consists of two parts, the model of the engine and the model of the driveline. The engine model uses an analytical cylinder pressure model capable of describing petrol and diesel engines. The model is a function of the crank angle, manifold pressure, manifold temperature and spark timing. The output is the pressure in the cylinder. This pressure is then used to calculate the torque generated on the crankshaft when the pressure acts on the piston. This torque is then applied in the driveline model. Both a two wheel and a four wheel driveline model are presented and they consist of a series of masses and dampers connected to each other with stiff springs. The result is a 14 and 19 degrees of freedom system of differential equations respectively. The model is then validated using measurements collected at LiU during two experiments. Measurements where conducted of the cylinder pressure of a four cylinder petrol engine and on the wheel speed of two different cars when driven in a test rig. The validation against this data is satisfactory and the simulations and measurements show good correlation. The model is then finally used to examine wheels speed disturbance phenomenon discovered in the huge database of test drives available at NIRA Dynamics AB. The effects of the drivelines natural frequencies are investigated and so is the difference between the disturbances on the wheel speed for a petrol and diesel engine. The main reasons for the different disturbance levels on the front and rear wheels in a four wheel drive are also discussed.
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Möst, Lisa [Verfasser], and Torsten [Akademischer Betreuer] Hothorn. "Conditional transformation models : interpretable parametrisations and censoring / Lisa Möst. Betreuer: Torsten Hothorn." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2015. http://d-nb.info/1070763020/34.
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Chamoun, Simon, and Marwan Trabulsi. "Modal analysis of pedestrian-induced torsional vibrations based on validated FE models." Thesis, KTH, Bro- och stålbyggnad, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209956.
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Finite element (FE) models serve as the base of many different types of analysis as e.g. dynamic analysis. Hence, obtaining FE models that represent the actual behaviour of real structures with great accuracy is of great importance. However, more often than not, there are differences between FE models and the structures being modelled, which can depend on numerous factors. These factors can consist of uncertainties in material behaviour, geometrical properties and boundary- and continuity conditions. Model validation is therefore an important aspect in obtaining FE models that represents reality to some degree. Furthermore, model verification is also important in terms of verifying theoretical models, other than FE models, in fields such as fatigue-, fracture- and dynamic analysis. In this thesis, two pedestrian steel bridges, the Kallhäll bridge and the Smista bridge, have been modelled in a FE software based on engineering drawings and validated against experimental results with regard to their natural frequencies. Furthermore, in this thesis, a model has been developed in MATLAB based on modal analysis that accounts for pedestrian-induced torsional vibrations, the 3D SDOF model. This model has been verified against the previously mentioned FE models. The aim of this thesis is hence two parted where the first part is to develop three-dimensional FE models of two pedestrian bridges and validate them against measured data regarding the natural frequencies. The second part is to further develop a model for analysing the effect of pedestrian-induced torsional vibrations and to investigate whether the model captures the actual dynamic response of such loading. The results showed that the natural frequencies for the first bending- and torsional mode from the FE models corresponded well to the measured ones with the largest difference of 5 \% obtained for the natural frequency of the first bending mode for the Smista bridge. Furthermore, the 3D SDOF model was able to capture the dynamic response of torsional vibrations with an overall difference of less than 2 \% in comparison to the FE models. The model can be improved by further studying the pedestrian-structure interaction as well as studying the effect of using approximative functions describing the mode shapes.Finita elementmodeller (FE-modeller) utgör en bas för många olika typer av analyser som exempelvis dynamiska analyser. Därmed är det av stor betydelse att FE-modeller representerar det faktiska beteendet av verkliga strukturer med stor noggrannhet. Ofta är det emellertid skillnader mellan FE-modeller och de verkliga strukturer man modellerar. Dessa skillnader kan bero på en rad faktorer såsom exempelvis osäkerheter i materialbeteende, geometriska egenskaper samt upplag- och randvillkor. Modellvalidering är därför en viktig aspekt i att erhålla FE-modeller som representerar verkligheten i olika omfattningar. Utöver modellvalidering är även modellverifiering viktigt, inte endast för verifiering av FE-modeller utan även för verifiering av andra teoretiska modeller inom områden såsom utmaning-, fraktur- och dynamiska analyser. I detta arbete har två GC-broar, Kallhäll- och Smistabron modellerats i ett FE-program baserat på konstruktionsritningar och validerats mot experimentella resultat med avseende på de naturliga frekvenserna. Vidare har det i detta arbete utvecklats en modell i MATLAB som tar hänsyn till människo-inducerade torsionsvibrationer baserat på modalanalys, benämnd 3D SDOF modellen. Modellen har även verifierats mot de tidigare nämnda FE-modellerna. Målet med detta arbete är således uppdelat i två delar, där den första delen består av att utveckla tredimensionella FE-modeller av två GC-broar samt validera dessa mot mätdata vad gäller de naturliga frekvenserna. Den andra delen består av att utveckla en modell för att analysera effekten av människo-inducerade torsionsvibrationer och undersöka huruvida modellen fångar den dynamiska responsen. Resultaten visade att de naturliga frekvenserna för den första böj- och vridmoden från FE-modellerna motsvarade de uppmätta frekvenserna med en största relativ skillnad på 5 \% för den fösta böjmoden för Smistabron. Vidare visade resultaten att den utvecklade 3D SDOF modellen kunde fånga den dynamiska responsen av torsionsvibrationer med en skillnad på mindre än 2 \% i jämförelse med resultat från de FE-modellerna. Modellen kan förbättras genom att vidare studera interaktionen mellan fotgängare och gångbro samt studera effekten av att använda approximativa funktioner som beskriver modformen.
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Guerrero, Madrid Robinson Francisco. "Estudio experimental de los modos de falla predominantes en perfiles XL de acero estructural." Tesis, Universidad de Chile, 2017. http://repositorio.uchile.cl/handle/2250/148213.
Full textAbstract:
Ingeniero CivilEl presente trabajo de título tiene como objetivo estudiar los modos de falla predominantes en perfiles XL de acero estructural sometidos directamente a cargas monotónicas y cíclicas incrementales, con el fin de comprobar si se cumplen las relaciones entre la curva de pandeo y las relaciones geométricas de esbeltez encontradas en memorias anteriores. Para ello se llevan a cabo 6 experimentos en el Laboratorio de Estructuras del Departamento de Ingeniería Civil de la Facultad de Ciencias Físicas y Matemáticas de la Universidad de Chile, donde se prueban 3 pares de perfiles XL diseñados en base a las normas de la AISC, conformados por ángulos de iguales dimensiones, soldados a placas gusset de iguales características, y con 3 conectores intermedios soldados ubicados en los cuartos de su longitud de pandeo, variando solo esta última medida entre los pares, nombrados como cortos , intermedios y largos . Durante los ensayos se utilizan LVDT s, inclinómetros y una celda de carga para registrar los desplazamientos de la sección transversal, el cambio de longitud de los especímenes, los movimientos del montaje experimental, y la fuerza de reacción provocada por la riostra. El resultado esperado era que los perfiles más cortos mostraran un pandeo torsional, que los de longitud intermedia tuvieran un pandeo flexo-torsional, y que los más largos exhibieran un pandeo de flexión pura. Sin embargo, los 6 perfiles XL manifiestan un pandeo de flexión en torno a su eje geométrico vertical, por lo que no se cumple la relación entre su esbeltez y el modo de falla encontrada en los estudios numéricos de elementos finitos. No obstante, hay que mencionar que los experimentos se diferenciaban de los modelos en las restricciones de desplazamiento y giro del conector central y en la esbeltez local de los ángulos. Por otro lado, todos los especímenes muestran una rótula plástica ubicada en el ala horizontal de un ángulo, entre el conector central y uno extremo, que separa la riostra en 2 tramos y permite la libre rotación de ambas partes en los desplazamientos a compresión, donde se propaga paulatinamente una grieta por fatiga de material, es decir, sin falla frágil, siendo este mecanismo el que produce la mayor disipación de energía. Además, la deformación fuera del plano durante la compresión es tan grande que se produce la fluencia del material en las fibras traccionadas por flexión, en el ángulo opuesto de la formación de la rótula, que luego se manifiesta como un pandeo en aquel punto al momento de enderezar el perfil. Finalmente, 4 de los perfiles superan la capacidad esperada a compresión, mientras que los perfiles cortos solo sobrepasan la nominal calculada con la fluencia experimental del acero componente. Asimismo, ningún espécimen fue capaz de superar la capacidad nominal a tracción dada por la fluencia del estudio de materiales.
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Demirkol, Onur Ali. "Segmentation Of Torso Ct Images." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/2/12607431/index.pdf.
Full textAbstract:
Medical imaging modalities provide effective information for anatomic or
metabolic activity of tissues and organs in the body. Therefore, medical
imaging technology is a critical component in diagnosis and treatment of
various illnesses. Medical image segmentation plays an important role in
converting medical images into anatomically, functionally or surgically
identifiable structures, and is used in various applications. In this study,
some of the major medical image segmentation methods are examined and
applied to 2D CT images of upper torso for segmentation of heart, lungs,
bones, and muscle and fat tissues. The implemented medical image
segmentation methods are thresholding, region growing, watershed
transformation, deformable models and a hybrid methodwatershed transformation and region merging. Moreover, a comparative analysis is performed among these methods to obtain the most efficient segmentation method for each tissue and organ in torso. Some improvements are proposed for increasing accuracy of some image segmentation methods.
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Robinzonov, Nikolay [Verfasser], and Torsten [Akademischer Betreuer] Hothorn. "Advances in boosting of temporal and spatial models / Nikolay Robinzonov. Betreuer: Torsten Hothorn." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2013. http://d-nb.info/1032131233/34.
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Guzzomi, Andrew Louis. "Torsional vibration of powertrains : an investigation of some common assumptions." University of Western Australia. School of Mechanical Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2008.0032.
Full textAbstract:
The area of powertrain dynamics has received considerable attention over a number of years. The recent introduction of more stringent emission requirements together with economic pressure has led to a particular focus on increasing powertrain efficiency. This has seen the incorporation of on-board, real-time measurements to predict system behaviour and engine condition. In this domain, accurate models for all powertrain components are important. One strategy to improve accuracy is to evaluate the assumptions made when deriving each model and then to address the simplifications that may introduce large errors. To this end, the aim of the work presented in this dissertation was to investigate the consequences of some of the more common assumptions and simplifications made in low frequency torsional powertrain models, and to propose improved models where appropriate. In particular, the effects of piston-tocylinder friction, crank/gudgeon pin offset, and the torsional behaviour of tyres were studied. Frequency and time domain models were used to investigate system behaviour and model predictions were compared with measurements on a small single cylinder engine. All time domain engine and powertrain models also include a variable inertia function for each reciprocating mechanism. It was found that piston-to-cylinder friction can increase the apparent inertia variation of a single reciprocating engine mechanism. This has implications for the nonlinear behaviour of engines and the drivetrains they are connected to. The effect of crank/gudgeon pin offset also modified the nonlinear behaviour of the mechanism. Though, for typical (small) gudgeon offset values these effects are small. However, for large offset values, achievable practically with crank offset, the modification to the nonlinear behaviour should not be ignored. The low frequency torsional damping properties of a small pneumatic tyre were found to be more accurately represented as hysteretic rather than viscous. Time domain modelling was then used to extend the results to a multi-cylinder engine powertrain and was achieved using the Time Domain Receptance (TDR) method. Various powertrain component TDRs were developed using Laplacians. Powertrain simulations showed that piston-to-cylinder friction can provide additional excitation to the system.
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Carandente, Rosalba. "Interaction between the fundamental torsional guided wave mode and complex defects in pipes." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9484.
Full textAbstract:
The presence of defects in pipelines is a concern especially in petrochemical applications where the service integrity of pipes is a fundamental requirement to avoid process interruptions and to fulfil safety standards. Guided wave inspection is now routinely used in industry for screening long lengths of pipe for corrosion, any suspect areas then being followed up with conventional ultrasonic thickness gauging. However, this is difficult in cases where the suspect area is inaccessible (e.g. buried pipelines or pipes passing though walls), so it would be very useful to apply guided wave techniques for sizing as well as the detection and location of defects. This target is challenging due to the complexity of the profiles encountered in practice. The present work aims to improve the understanding of the scattering of the fundamental torsional mode T(0, 1) from complex shaped discontinuities and to determine the controlling parameters of this phenomenon. The overall analysis starts with a study of the reflection from axi-symmetric tapered steps and notches in pipes. After that the scattering from three dimensional (3D) defects with different shapes has been studied. Firstly, flat-bottomed defects with different surface profiles have been analyzed, and then the study of the reflection behavior from 3D defects with varying depth profile has been carried out. All of the work presented here uses the T(0,1) mode for inspection. It is revealed that the reflection coefficient maxima from axi-symmetric tapered defects decrease with increasing frequency as the slope of the taper becomes more gradual, this effect being more pronounced when the ratio of the average defect length to the wavelength increases. Tapered defects are therefore expected to be more difficult to detect at higher inspection frequencies; this effect is more evident for shallower tapers. It is also found that at a given maximum depth of a finite discontinuity, the peak of the reflection coefficient from a defect is linearly dependent on the circumferential extent of the defect, and is independent of its shape. The results from these analyses have been used to propose a practical approach to determine the maximum depth of a complex discontinuity from the reflection coefficient behavior, provided that the external circumferential extent of the defect is known. This method has been applied to real corrosion patches and the results validated with experiments. Its main limitation is on defects with a gradual corrosion section profile, but with a sudden change of the depth over a small circumferential region. It is shown then that a possible way to diagnose sharp circumferential profile changes is to measure the reflection coefficient spectrum at frequency higher than usually used in long range guided wave inspection.
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Reuter, Kimberly Marie. "A finite element model to study the torsional fracture strength of a composite tibia." Thesis, Wichita State University, 2009. http://hdl.handle.net/10057/2544.
Full textAbstract:
Screws are common orthopaedic hardware used to secure a fractured bone. After the
bone has healed, the screws may be removed, and the vacant screw holes introduce a potential
site for re-fracture, which is a known complication. The current study simulated a laboratory
torsional fracture test of a composite analogue tibia with vacant screw holes by using a finite
element (FE) model, and the results from the simulation were compared to those obtained
experimentally. Variations of the FE model were also analyzed to investigate the effects of
failure model, screw holes, element size, rotation direction, and simplification of the model's
geometry. This FE model was set up the same as the experimental torsion test, with a section
from the distal portion of the tibia. The proximal end of the section was subjected to an axial
load and rotated, while the distal end was fixed. The FE model contained 102,126 first order
tetrahedral elements and 24,817 nodes, and it utilized an isotropic linear elastic material law with
material properties obtained from the composite analogue manufacturer. Comparisons between
the FE model variations considered the fracture torque, fracture angle, torsional stiffness,
principal stress contour, and maximum shear stress contour. The results predicted a fracture
torque within the standard deviation of the experimental data, and the percent of strength
reduction caused by the screw holes agreed with experimental data.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering
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Wagener, Benjamin. "Géométrie Arithmétique sur les variétés Abéliennes : minoration explicite de la hauteur de Faltings et borne sur la torsion." Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC305/document.
Full textAbstract:
Ce travail comporte essentiellement deux conclusions. D'une part nous déterminons une minoration de la hauteur de Faltings d'une variété abélienne quelconque sur un corps de nombres faisant intervenir de nouveaux invariants non archimédiens. Il s'agit de la première partie de ce travail dans lequel nous introduisons systématiquement ces invariants. Ils sont liés à la géométrie non archimédienne aux places de mauvaise réduction des variétés abéliennes.Dans une deuxième partie nous donnons une évaluation approximative de ces invariants nous permettant d'établir une minoration de la hauteur de Faltings faisant intervenir le nombre de composantes de la fibre spéciale du modèle de Néron des variétés abéliennes aux places de mauvaise réduction.On déduit de ces estimations un corollaire qui fournit une borne sur le cardinal du groupe des points rationnels de torsion des variétés abéliennes faisant essentiellement intervenir la hauteur de Faltings. Cette borne est jusqu'à présent la meilleure connueThis thesis leads essentially to two conclusions. On the one hand we determine a lower bound for the Faltings height of abelian varieties over number fields in which enter new non-archimedean invariants. It consists in the first part of this work in which we introduce systematically this invariants. They are directly linked to the non-archimedean geometry of abelian varities at places of bad reduction.In a second part we provides an approximative evaluation of this invariants which leads to a lower bound on the Faltings heights in terms of the number of components of the special fiber of the Néron model of abelian varieties at places of bad reduction.We deduce from this estimates a corollary that provides an upper bound on the cardinality of the group of rational torsion points of abelian varieties essentially in terms of the Falting height. This bound is the best bound known till now
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Perez, Miguel A. "Empirical Evaluation of Models Used to Predict Torso Muscle Recruitment Patterns." Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/35381.
Full textAbstract:
For years, the human back has puzzled researchers with the complex behaviors it presents. Principally, the internal forces produced by back muscles have not been determined accurately. Two different approaches have historically been taken to predict muscle forces. The first relies on electromyography (EMG), while the second attempts to predict muscle responses using mathematical models. Three such predictive models are compared here. The models are Sum of Cubed Intensities, Artificial Neural Networks, and Distributed Moment Histogram. These three models were adapted to run using recently published descriptions of the lower back anatomy. To evaluate their effectiveness, the models were compared in terms of their fit to a muscle activation database including 14 different muscles. The database was collected as part of this experiment, and included 8 participants (4 male and 4 female) with similar height and weight. The participants resisted loads applied to their torso via a harness. Results showed the models performed poorly (average R2's in the 0.40's), indicating that further improvements are needed in our current low back muscle activation modeling techniques. Considerable discrepancies were found between internal moments (at L3/L4) determined empirically and measured with a force plate, indicating that the maximum muscle stress selected and/or the anatomy used were faulty. The activation pattern database collected also fills a gap in the literature by considering static loading patterns that had not been systematically varied before.Master of Science
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Deere, Matthew. "Guided wave evaluation of pipes using the first and second order torsional wave mode." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/15307.
Full textAbstract:
Guided wave inspection is a form of ultrasonic testing used for non-destructive testing (NDT). Guided waves are capable of propagating long distances bounded by the geometries of the specimen, such as pipes and plates. The technique is commercially used to detect defects in pipelines and is capable of a full volumetric screening many metres (often up to around 100m) from one location. Fundamental axisymmetric wave modes are used to inspect pipelines and are used to quantify defects and features. However, as the technology has progressed, a demand for improving defect sensitivity, spatial resolution and developing the technology into new fields has been recognised. Operating at medium range frequencies is one possibility that could provide the increase in defect sensitivity and spatial resolution required that may not be achieved at low range frequencies. The use of higher order wave modes could also provide additional information useful for defect sizing. Guided wave inspection is a complex ultrasonic technique due to the many wave modes that exist and testing at medium range frequencies requires some challenges to be overcome. The research presented here investigates the potential of using the second order torsional wave mode at medium range frequencies and provides a new sizing technique that for some applications is likely to offer advancement in guided wave inspection and monitoring. The approach firstly included the design and implementation of a setup for analysing the complex signal responses in order to access the higher order torsional wave mode T(0,2) for defect sizing. An efficient method of using FEA has been presented using segmented models to provide the capability of analysing defects with small increment changes that could not be achieved using a full 3D model of the pipe. Using a pipe segment to virtually represent the full pipe also allowed small changes in defect size to be investigated, which would otherwise be extremely difficult to accurately machine experimentally. The FEA modelling technique is also based on broadband signals in comparison to the conventional approach of using narrowband signals and is capable of obtaining a wide frequency spectrum from one model, which significantly reduces the number of models needed to conduct a frequency analysis. Following on from this work, a high density transducer array was developed and compared against a conventional transducer array used in guided wave inspection for the purpose of medium range frequency inspection, which can also be applied to conventional low range frequency inspection. Finally, a new defect sizing method using T(0,2) is presented, which is capable of predicting the depth using peak amplitude responses from spectral analysis and by comparing this to the cut-off frequency of the remaining wall thickness of the defect. The technique has the potential to improve defect sizing, defect sensitivity, increase spatial resolution, and increase the performance of medium range inspection.
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Metzler, Torsten [Verfasser]. "Models and Methods for the Systematic Integration of Cognitive Functions into Product Concepts / Torsten Metzler." München : Verlag Dr. Hut, 2016. http://d-nb.info/1094117277/34.
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Trimborn, Torsten Verfasser], Martin [Akademischer Betreuer] Frank, Michael [Akademischer Betreuer] [Herty, and Lorenzo [Akademischer Betreuer] Pareschi. "Kinetic modeling of financial market models / Torsten Trimborn ; Martin Frank, Michael Matthias Herty, Lorenzo Pareschi." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1162629665/34.
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Trimborn, Torsten [Verfasser], Martin Akademischer Betreuer] Frank, Michael [Akademischer Betreuer] [Herty, and Lorenzo [Akademischer Betreuer] Pareschi. "Kinetic modeling of financial market models / Torsten Trimborn ; Martin Frank, Michael Matthias Herty, Lorenzo Pareschi." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://d-nb.info/1162629665/34.
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Trimborn, Torsten [Verfasser], Martin [Akademischer Betreuer] Frank, Michael [Akademischer Betreuer] Herty, and Lorenzo [Akademischer Betreuer] Pareschi. "Kinetic modeling of financial market models / Torsten Trimborn ; Martin Frank, Michael Matthias Herty, Lorenzo Pareschi." Aachen : Universitätsbibliothek der RWTH Aachen, 2018. http://nbn-resolving.de/urn:nbn:de:101:1-2018071209165262004331.
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Shaarbaf, Ihsan Ali Saib. "Three-dimensional non-linear finite element analysis of reinforced concrete beams in torsion : reinforced concrete members under torsion and bending are analysed up to failure : a non-linear concrete model for general states of stress including compressive strength degradation due to cracking is described." Thesis, University of Bradford, 1990. http://hdl.handle.net/10454/3576.
Full textAbstract:
This thesis describes a non-linear finite element model suitable for the analysis of reinforced concrete, or steel, structures under general three-dimensional states of loading. The 20 noded isoparametric brick element has been used to model the concrete and reinforcing bars are idealised as axial members embedded within the concrete elements. The compressive behaviour of concrete is simulated by an elasto-plastic work hardening model followed by a perfectly plastic plateau which is terminated at the onset the . crushing. In tension, a smeared crack model with fixed orthogonal cracks has been used with the inclusion of models for the retained post-cracking stress and the reduced shear modulus. The non-linear equations of equilibrium have been solved using an incremental-iterative technique operating under load control. The solution algorithms used are the standard and the modified Newton-Raphson methods. Line searches have been implemented to accelerate convergence. The numerical integration has been generally carried out using 15 point Gaussian type rules. Results of a study to investigate the performance of these rules show that the 15 point rules are accurate and computationally efficient compared with the 27(3X3X3) point Gaussian rule. The three- dimensional finite element model has been used to investigate the problem of elasto-plastic torsion of homogeneous members. The accuracy of the finite element solutions obtained for beams of different cross-sections subjected to pure and warping torsion have been assessed by comparing them with the available exact or approximate analytical solutions. Because the present work is devoted towards the analysis of reinforced concrete members which fail in shear or torsional modes, the computer program incorporates three models to account for the degradation in the compressive strength of concrete due to presence of tensile straining of transverse reinforcement. The numerical solutions obtained for reinforced concrete panels under pure shear and beams in torsion and combined torsion and bending reveal that the inclusion of a model for reducing the compressive strength of cracked concrete can significantly improve the correlation of the predicted post-cracking stiffness and the computed ultimate loads with the experimental results. Parametric studies to investigate the effects of some important material and solution parameters have been carried out. It is concluded that in the presence of a compression strength reduction model, the tension-stiffening parameters required for reinforced concrete members under torsion should be similar to those used for members in which bending dominates.
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Phillips, Peter Louis. "Integrated Multiaxial Experimentation and Constitutive Modeling." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1492598070791388.
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Back, Sung-Yong. "A shear-flexible finite element model for lateral torsional buckling analysis of thin-walled open beams." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/20999.
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Hudson, James W. "Development and calibration of a torsional engine model for a three-cylinder, two-stroke diesel engine." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1997. http://handle.dtic.mil/100.2/ADA343145.
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Thesis (M.S. in Mechanical Engineering) Naval Postgraduate School, December 1997."December 1997." Thesis advisor(s): Knox T. Millsaps, Jr. Includes bibliographical references (p. 57-58). Also available online.
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Schladitz, Frank, and Manfred Curbach. "Textilbewehrter Beton als Torsionsverstärkung." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244048995744-78708.
Full textAbstract:
Anhand von Versuchsergebnissen wird gezeigt, dass Stahlbetonbauteile mit textilbewehrtem Beton verstärkt werden können. Sowohl die Torsionstragfähigkeit als auch die Gebrauchstauglichkeit werden durch die textilbewehrte Verstärkungsschicht deutlich verbessert. Vergleichsrechnungen zeigen, dass die Torsionstragfähigkeit mit bereits bekannten Stabwerksmodellen ermittelt werden kann.