Academic literature on the topic 'Torsion modes'
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Journal articles on the topic "Torsion modes"
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Men, Jin Jie, Qing Xuan Shi, and Qiu Wei Wang. "Unity Equation of Torsional Capacity for RC Members Subjected to Axial Compression, Bend, Shear and Torque." Advanced Materials Research 163-167 (December 2010): 874–79. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.874.
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The mechanics performance of reinforced concrete members subjected to axial compression, bending, shear and torque is very complex. Several calculation models have been established to estimate the torsional capacity of combined torsion members; however, the calculation results of different models have a great variation. In this paper, variable-angle space truss model is adopted to analyze the mechanics performance of reinforced concrete members subjected to combined torsion. With respect to various shapes of specimens, various load modes, and various strength of concrete, a unity equation about torsional capacity of combined torsional member is obtained. Based on the unity equation, the torsional capacity of 59 combined torsional specimens is calculated. In contrast with the equation of ACI and the code of China, the torsional capacity calculated by the unity equation agrees well with the results of experiment and much better than the results of ACI code and China code. It is concluded that the unity equation can provide valuable reference for calculation and design of combined torsion members.
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Jeong, Byeong-Woo. "Transitional Failure of Carbon Nanotube Systems under a Combination of Tension and Torsion." Journal of Nanomaterials 2012 (2012): 1–6. http://dx.doi.org/10.1155/2012/847307.
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Transitional failure envelopes of single- and double-walled carbon nanotubes under combined tension-torsion are predicted using classical molecular dynamics simulations. The observations reveal that while the tensile failure load decreases with combined torsion, the torsional buckling moment increases with combined tension. As a result, the failure envelopes under combined tension-torsion are definitely different from those under pure tension or torsion. In such combined loading, there is a multitude of failure modes (tensile failure and torsional buckling), and the failure consequently exhibits the feature of transitional failure envelopes. In addition, the safe region of double-walled carbon nanotubes is significantly larger than that of single-walled carbon nanotubes due to the differences in the onset of torsional buckling.
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Senent, María Luisa, and Samira Dalbouha. "Large Amplitude Motions of Pyruvic Acid (CH3-CO-COOH)." Molecules 26, no. 14 (July 14, 2021): 4269. http://dx.doi.org/10.3390/molecules26144269.
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Torsional and rotational spectroscopic properties of pyruvic acid are determined using highly correlated ab initio methods and combining two different theoretical approaches: Second order perturbation theory and a variational procedure in three-dimensions. Four equilibrium geometries of pyruvic acid, Tc, Tt, Ct, and CC, outcome from a search with CCSD(T)-F12. All of them can be classified in the Cs point group. The variational calculations are performed considering the three internal rotation modes responsible for the non-rigidity as independent coordinates. More than 50 torsional energy levels (including torsional subcomponents) are localized in the 406–986 cm−1 region and represent excitations of the ν24 (skeletal torsion) and the ν23 (methyl torsion) modes. The third independent variable, the OH torsion, interacts strongly with ν23. The A1/E splitting of the ground vibrational state has been evaluated to be 0.024 cm−1 as it was expected given the high of the methyl torsional barrier (338 cm−1). A very good agreement with respect to previous experimental data concerning fundamental frequencies (νCAL − νEXP ~ 1 cm−1), and rotational parameters (B0CAL − B0EXP < 5 MHz), is obtained.
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Fan, Xiang-Dong, Qi Liu, Lin-Xia Liu, Vadim Milyukov, and Jun Luo. "Coupled modes of the torsion pendulum." Physics Letters A 372, no. 5 (January 2008): 547–52. http://dx.doi.org/10.1016/j.physleta.2007.08.020.
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Wang, Mei, Guo Ding Chen, and Yong Xiao. "Lightweight Analysis of Torsion Spring Based on Reliability Constraint in Multi-Failure Modes." Advanced Materials Research 308-310 (August 2011): 494–98. http://dx.doi.org/10.4028/www.scientific.net/amr.308-310.494.
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The generalized stress and strength distribution interference theory is introduced to establish the reliability model of torsion spring in multi-failure modes. Using it as constraint condition, the lightweight optimization model of torsion spring based on reliability constraint in multi-failure modes is presented. And then an optimization design for a given structure of torsion spring is made to use the theoretical model under operating conditions and the reliability constraint. The weight of the opti-mized torsion spring is lighter than that of non-optimization. This verified the validity of the opti-mization method. The optimization method may contribution to design of aerospace equipments which demand strictly in weight.
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Cusumano, J. P., and D. C. Lin. "Bifurcation and Modal Interaction in a Simplified Model of Bending-Torsion Vibrations of the Thin Elastica." Journal of Vibration and Acoustics 117, no. 1 (January 1, 1995): 30–42. http://dx.doi.org/10.1115/1.2873864.
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This paper presents a numerical study of bifurcation and modal interaction in a system of partial differential equations first proposed as a simplified model for bending-torsion vibrations of a thin elastic beam. A system of seven ordinary differential equations obtained using the first six bending and first torsional normal modes is studied, and Floquet theory is used to locate regions in the forcing frequency, forcing amplitude parameter plane where “planar” (i.e., zero torsion) motions are unstable. Numerical branch following and symmetry considerations show that the initial instability arises from a subcritical pitchfork bifurcation. The subsequent nonplanar chaotic attractor is part of a branch of 2-frequency quasiperiodic orbits which undergoes torus-doubling bifurcations. A new statistical technique which identifies interacting modes and the average stability properties of the associated subspaces is presented. The technique employs the Lyapunov vectors used in the calculation of the Lyapunov exponents. We show how this method can be used to split the modes into active and passive sets: active modes interact to contain the attractor, whereas passive modes behave like isolated driven oscillators. In particular, large amplitude modes may simply serve as conduits through which energy is supplied to the active modes.
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Krott, Matthew J., Edward C. Smith, and Christopher D. Rahn. "Coupled and Multimode Tailboom Vibration Control Using Fluidic Flexible Matrix Composite Tubes." Journal of the American Helicopter Society 64, no. 4 (October 1, 2019): 1–10. http://dx.doi.org/10.4050/jahs.64.042007.
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This paper covers the modeling and testing of a helicopter tailboom integrated with a fluidic flexible matrix composite (F2MC) damped vibration absorber. In an advance over previous work, the F2MC absorber presented in this paper treats a combination of tailboom lateral, torsional, and vertical vibrations. A finite element structural model of a laboratory-scale tailboom is combined with a model of attached F2MC tubes and a tuned fluidic circuit. Vibration reductions of over 75% in a coupled 26.8-Hz lateral bending/torsion tailboom mode are predicted by the model and measured experimentally. These results demonstrate that F2MC vibration control is viable at higher frequencies and for more complex vibration modes than previous research had explored. A new absorber with a fluidic circuit that targets two tailboom vibration modes is designed and experimentally tested. On the lab-scale tailboom testbed, the absorber with this circuit is shown to provide vibration reductions of over 60% in both a 12.2-Hz vertical mode and a 26.8-Hz lateral bending/torsion mode. Using this new absorber, vertical and lateral/torsion mode damping are achieved with almost no added weight relative to a purely vertical absorber.
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Jrad, Wassim, Foudil Mohri, Guillaume Robin, El Mostafa Daya, and Jihad Al-Hajjar. "Analytical and finite element solutions of free and forced vibration of unrestrained and braced thin-walled beams." Journal of Vibration and Control 26, no. 5-6 (November 13, 2019): 255–76. http://dx.doi.org/10.1177/1077546319878901.
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In this article, vibration of thin-walled beams with arbitrary open cross-section shape is investigated. Based on the beam element model accounting for warping and flexural–torsional coupling, analytical solutions for different boundary conditions are derived for higher free vibration modes in bending, torsion and flexural–torsional coupled modes. In the model, the effects of rotational inertial kinematic terms are considered. The finite element approach of the model is also investigated. Three-dimensional beams with seven degrees of freedom per node are adopted in the mesh process. Free vibration and forced vibration analyses are possible. In forced vibration, the behaviour of the beams is studied in the frequency domain using the steady-state method (modal analysis). Damping is considered using the Rayleigh model. The model is validated by comparing the results to benchmark solutions found in the literature and to other recent numerical and experimental results. Additional finite element simulations are performed by means of commercial softwares (Abaqus and Adina). In slender unrestrained beams, the vibration behaviour is predominated by torsion and lateral bending modes. In design, recourse to braces is a good compromise. This solution is discussed, and improvement of the vibration behaviour in the presence of intermediate braces is confirmed. Application of higher vibration modes in building and bridge design is outlined. The effects of the number and distribution of the intermediate braces to improve structural stability against vibration behaviour is outlined.
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SETKIT, Monthian, Thanongsak IMJAI, Udomvit CHAISAKULKIET, Reyes GARCIA, Komsan DANGYEM, Katipoj SANUPONG, and Weerasit CHAMNANKIT. "Torsional Strengthening of Low-Strength RC Beams with Post-Tensioned Metal Straps: An Experimental Investigation." Walailak Journal of Science and Technology (WJST) 17, no. 12 (December 1, 2020): 1399–411. http://dx.doi.org/10.48048/wjst.2020.11908.
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This article investigates the behaviour of low-strength reinforced concrete beams under pure torsion with and without strengthening. Four beams were cast and tested in torsion: i) a control beam without vertical reinforcement, ii) two beams with internal stirrups designed for shear and torsion demands using different stirrup spacing (50 and 100 mm), and iii) a beam having steel stirrups with a spacing of 100 mm strengthened using high ductile post-tensioned metal straps (PTMS). The main objective of the PTMS strengthening solution was to investigate the enhancement of torsional strength confined along the beam. The failure modes, torsional capacities, rotation, and strengthening performance in torsion are discussed in in this study. The experimental results indicate that the PTMS improved the cracking torque capacity by up to 15 % compared to the control beam. Moreover, the PTMS also increased the ultimate torque by up to 19 % compared to the unstrengthened beam. Current code equations to predict the torsional capacity of RC beams are also compared with the experimental results. It is found that the predictions obtained by current ACI equation gives a good agreement and yield in general conservative values compared to the experimental ones.
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A. Rosly, N., M. Y. Harmin, and D. L. A. A. Majid. "Preliminary investigation on experimental modal analysis of high aspect ratio rectangular wing model." International Journal of Engineering & Technology 7, no. 4.13 (October 9, 2018): 151. http://dx.doi.org/10.14419/ijet.v7i4.13.21348.
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Procedure of conducting an experimental modal analysis (EMA) of roving hammer test for high aspect ratio (HAR) wing containing geometric nonlinearities is presented along with consideration of various tip store sizes. Two sets of test setups of vertical and horizontal arrangements have been considered, which respectively demonstrates the undeformed and deformed cases. Modal properties in terms of natural frequency and mode shape were experimentally measured using the LMS Test.Lab package and the results were then compared between the undeformed and its corresponding deformed configuration. From the finding, it confirms that the chordwise and torsional modes of the undeformed configurations has respectively turned into chordwise-torsion and torsion-chordwise modes as they are in deformed configuration. Meanwhile, the impact related to bending modes is insignificant. Hence, this may result in inaccurate prediction if conventional aeroelastic solution is employed for HAR wing configuration.
Dissertations / Theses on the topic "Torsion modes"
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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.
Books on the topic "Torsion modes"
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James P. Smith - undifferentiated. Highly accurate beam torsion solutions using the p-version finite element method. [Washington, D.C.?: National Aeronautics and Space Administration, 1996.
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Takahashi, Marc D. A flight-dynamic helicopter mathematical model with a single flap-lag-torsion main rotor. Moffett Field, Calif: NASA Ames Research Center, 1990.
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Sedarat, Hassan. Torsional response characteristics of regular buildings under different seismic excitation levels. Sacramento: California Dept. of Conservation, Division of Mines and Geology, Office of Strong Motion Studies, 1994.
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Atarod, Vida. Impact of synchronous machine constants and models on the analysis of torsional dynamics. Ottawa: National Library of Canada, 1992.
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Hudson, James W. Development and calibration of a torsional engine model for a three-cylinder, two-stroke diesel engine. Monterey, Calif: Naval Postgraduate School, 1997.
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Swanson, William J. Determination of diesel engine cylinder gas torques from speed fluctuations with a high-fidelity crankshaft torsional model. Monterey, Calif: Naval Postgraduate School, 1998.
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Sanford, Fleeter, and Lewis Research Center, eds. The predicted effect of aerodynamic detuning of coupled bending-torsion unstalled supersonic flutter. [Cleveland, Ohio: National Aeronautics and Space Administration, Lewis Research Center, 1986.
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A flight-dynamic helicopter mathematical model with a single flap-lag-torsion main rotor. Moffett Field, Calif: NASA Ames Research Center, 1990.
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A flight-dynamic helicopter mathematical model with a single flap-lag-torsion main rotor. Moffett Field, Calif: NASA Ames Research Center, 1990.
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Center, Ames Research, and United States. Army Aviation Research and Technology Activity., eds. A flight-dynamic helicopter mathematical model with a single flap-lag-torsion main rotor. Moffett Field, Calif: NASA Ames Research Center, 1990.
Find full textBook chapters on the topic "Torsion modes"
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Kandil, Osama A., Essam F. Sheta, and C. H. Liu. "Effects of Coupled and Uncoupled Bending-Torsion Modes on Twin-Tail Buffet Response." In IUTAM Symposium on Dynamics of Slender Vortices, 401–14. Dordrecht: Springer Netherlands, 1998. http://dx.doi.org/10.1007/978-94-011-5042-2_34.
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Sun, Ling, and Elmar Bonaccurso. "Scanning Conductive Torsion Mode Microscopy." In Surface Science Tools for Nanomaterials Characterization, 199–225. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-662-44551-8_6.
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Thomas, T. "8 Softened Truss Model for Torsion." In Unired Theory of Reinforced Concrete, 257–300. CRC Press Taylor & Francis Group 6000 Broken Sound Parkway NW, Suite 300 Boca Raton, FL 33487-2742: CRC Press, 2017. http://dx.doi.org/10.1201/9780203734650-9.
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Cleja-Tigoiu, Sanda. "Elasto-Plastic Models with Dislocations Based on Configuration with Torsion." In Continuum Models and Discrete Systems, 215–20. Dordrecht: Springer Netherlands, 2004. http://dx.doi.org/10.1007/978-1-4020-2316-3_33.
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Arnold, David M., Adolf Mader, Otto Mutzbauer, and Ebru Solak. "A Remak-Krull-Schmidt Class of Torsion-Free Abelian Groups." In Groups, Modules, and Model Theory - Surveys and Recent Developments, 41–68. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-51718-6_3.
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Garrett, Steven L. "Modes of Bars." In Understanding Acoustics, 235–81. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44787-8_5.
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Abstract The perspectives and techniques developed in the previous chapters will now be applied to calculation of wave propagation in solids. Their application to longitudinal and shear waves will be both familiar and simple. Even more satisfying is the success of those same techniques in finding solutions for waves in a system that does not obey the wave equation and exhibit a phase speed that varies with frequency. Measurement of the frequencies of the normal modes of thin bars will be used to determine the bars’ elastic constants to high precision. The relationship between measured modal frequencies and the elastic moduli is particularly simple because the torsional, flexural, and longitudinal modes of bars can be selectively excited and detected. The technique of resonant ultrasound spectroscopy will allow the extraction of moduli from resonance frequencies even for samples with dimensions that are not as conducive as those of thin bars by a process that is significantly more computationally intensive. The flexural rigidity of wires under tension will be analyzed to determine the normal modes of a “stiff string,” and those effects will be discussed in relation to the tuning of pianos
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Zhao, Qian. "Study on Driveline Component Torsional Stiffness Effect on RWD Driveline Torsional Vibration Modes." In Lecture Notes in Electrical Engineering, 87–102. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-33832-8_7.
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Gu, Yu Jiong, Xiao Bo Li, and Cheng Bing He. "Correction on Parameters in Torsion Vibration Model for Turbine-Generator Shafts." In Key Engineering Materials, 2505–8. Stafa: Trans Tech Publications Ltd., 2007. http://dx.doi.org/10.4028/0-87849-456-1.2505.
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Doughty, Timothy A., Willamette Blvd, Mary LeBlanc, Lee Glascoe, and Joel Benier. "Torsion/compression Testing of Grey Cast Iron for a Plasticity Model." In Experimental and Applied Mechanics, Volume 6, 845–53. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-9792-0_117.
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Tesi, Maria Carla. "Geometrical Entanglement in Lattice Models of Ring Polymers: Torsion and Writhe." In Numerical Methods for Polymeric Systems, 83–97. New York, NY: Springer New York, 1998. http://dx.doi.org/10.1007/978-1-4612-1704-6_6.
Full textConference papers on the topic "Torsion modes"
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Vyas, Ashwin, Anil K. Bajaj, and Dimitrios Peroulis. "Nonlinear Resonator With Interacting Flexural-Torsional Modes for Mass Sensing." In ASME 2007 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/detc2007-35117.
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We explore the use of a pedal shaped nonlinear microresonator designed with torsion and flexural modes in 1:2 internal resonance for mass sensing. The higher natural frequency in-plane flexural mode of the resonator is coupled nonlinearly through inertial coupling to the out-of-plane torsional mode with one-half natural frequency. When the flexural mode excited resonantly has response above a threshold, the torsional mode is excited. This response in torsional mode is highly sensitive to any mass perturbation that results in mistuning the two modes away from 1:2 resonance. The mistuning can drastically change the nonlinearly excited torsional response from non-zero amplitude to zero amplitude. The required increase in the actuation strength to reactivate the torsional motion can serve as a measure for the attached mass.
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Arafat, Haider N., and Ali H. Nayfeh. "Transfer of Energy From High- to Low-Frequency Modes in the Bending-Torsion Oscillation of Cantilever Beams." In ASME 1999 Design Engineering Technical Conferences. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/detc99/vib-8159.
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Abstract We investigate the nonlinear bending-torsion response of a cantilever beam to a transverse harmonic excitation, where the forcing frequency is near the natural frequency of the first torsional mode. We analyze the case where the first in-plane bending mode is activated by a nonresonant mechanism. We use the method of time-averaged Lagrangian and virtual work to determine the equations governing the modulations of the phases and amplitudes of the interacting modes. These equations are then used to investigate the nonlinear behavior of limit-cycle oscillations of the beam as the excitation amplitude is slowly varied. As an example, we consider the response of an aluminum beam for which the natural frequency of the first in-plane bending mode is fv1 ≈ 5.7 Hz and the natural frequency of the first torsional mode is fϕ1 ≈ 138.9 Hz.
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Wu, Shanghua, Zhixun Yang, Jinlong Chen, Qingzhen Lu, Qianjin Yue, Jun Yan, and Bo Gao. "Study on the Failure Mechanism of Flexible Pipes Under Large Torsion Considering the Layer Interaction." In ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/omae2018-77710.
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Flexible pipe is the typical multi-layer structure which is designed to resist different loads when it is utilized under the severe deep-water environment. However, there is not any structural layer to withstand the torsion specially. Tension armors are only arranged to bear the tension with consideration of the torque balance. Especially, when flexible pipe is loaded out from the cargo vessel to the installation vessel, twist angle could be accumulated at high level so that all of layers need to resist the torsion. So, the failure mechanism is very complicated due to the interaction effect between different layers. Firstly, the interaction mechanism between layers of flexible pipes is analyzed under large torsion and some potential failure modes are identified, namely the strength failure and buckling failure of tensile armor, collapse failure of the inner layers. The theoretical descriptions of involved failure behaviors are investigated and the governing physical effects of failure modes are discussed. In addition, some failure criteria for predicting the pipe capacity are introduced. Finally, the methodology can be used to predict the flexible pipe torsional capacity and to prevent the torsional failure in engineering.
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Chiang, Hsiao-Wei D., and Chih-Neng Hsu. "Prediction of Shrouded Turbomachinery Blade Forced Response by a Complex Mode Analysis." In ASME Turbo Expo 2006: Power for Land, Sea, and Air. ASMEDC, 2006. http://dx.doi.org/10.1115/gt2006-90112.
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Turbomachinery shrouded rotor blade design has been widely used in fans, compressors, and turbines. By using either tip or mid-span shroud, the blade structural damping and natural frequencies can be increased to reduce flutter or forced response problems. However, shrouded rotor blade design sometimes results in complex system modes with both bending and torsion present at the same time. Since shrouded rotors are rotationally periodic, the bending and torsion combined system mode can be decomposed into a real component and an imaginary component. Using both the real and imaginary mode shapes, coupled with the blade surface flow-field, a complex mode analysis was developed using a modal solution to determine the forced response of the system. This complex mode analysis was applied to both tip and mid-span shrouded rotor blade applications. Bending-dominated or torsion-dominated simple blade modes in general can be analyzed using an existing single mode approach. However, for the bending and torsion combined system modes, the single mode analysis can be misleading. By using the complex mode analysis, it was demonstrated that the combined bending and torsion system mode plays an important role in determining the blade forced response.
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Xu, Li-Hong. "Torsion-vibration energy structure and interactions among the lower vibrational modes of 13cd3oh." In 17th International Conference on Infrared and Millimeter Waves. SPIE, 2017. http://dx.doi.org/10.1117/12.2298239.
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DeSmidt, Hans A., K. W. Wang, and Edward C. Smith. "Coupled Torsion-Lateral Stability of a Shaft-Disk System Driven Through a Universal Joint." In ASME 2001 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2001. http://dx.doi.org/10.1115/detc2001/vib-21423.
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Abstract Understanding the instability phenomena of rotor-shaft and driveline systems incorporating universal joints is becoming increasingly important because of the trend towards light-weight, high-speed supercritical designs. A non-dimensional, periodic, linear time-varying model with torsional and lateral degrees-of-freedom is developed for a rotor shaft-disk assembly supported on a flexible bearing and driven through a U-Joint and stability is investigated with Floquet Theory. It is shown that the interaction between torsional and lateral dynamics results in new regions of parametric instability that have not been addressed in previous investigations. The presence of load inertia and misalignment causes dynamic coupling of the torsion and lateral modes, which can result in torsion-lateral instability for shaft speeds near the sum-type combinations of the torsion and lateral natural frequencies. The effect of angular misalignment, static load-torque, load-inertia, lateral frequency-split, and auxiliary damping on the stability of the system is studied over a range of shaft operating speeds. Also, the effectiveness of auxiliary lateral viscous damping as a means of stabilizing the system is investigated. Finally, a closed-form technique based on perturbation expansions is derived to determine the auxiliary damping necessary to stabilize the system for the least stable case (worst case).
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Vijith, P. P., and Suresh Rajendran. "Horizontal and Torsional Modes of an Ultra Large Container Ship (ULCS)." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18659.
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Abstract The hydro elastic responses of flexible structures under fluid loading is an important concern during the design of large ocean structures. The two-way coupling between the structural responses and the hydrodynamic loads is a complex problem in large flexible floating structures since the structures can vibrate in longitudinal, vertical, horizontal, or torsional modes. The antisymmetric distortion modes may be coupled depending on the location of the centroid and the shear centre. In the case of thin walled open structures, horizontal and torsional vibrations are usually coupled due to the asymmetry of cross section as well as eccentricity between centroid of the section and shear deformation centres. The acurate estimation of dry natural frequency and modes shapes of structure is indispensable since it helps to validate the accuracy of the structural modelling. A numerical method available from one of the existing literatures is used for the estimation of dry and wet natural frequencies, and mode shapes of horizontal and torsional vibrations of an ULCS. The natural frequency and modes are essential parameters for the analysis of interaction between structural responses and hydrodynamic loads. The numerical method is based on a 1D FEM beam model. Distortion due to warping is included in the numerical model since it is well known that containerships with large hatch opening are susceptible to warping. The numerical model is subdivided into 50 stations and the mass distribution and the sectional properties are calculated in order to match the bending, shear, torsion and warping moduli of the experimental model. The dry and wet natural frequency and mode shapes for the horizontal and torsional vibrations of the ULCS is numerically calculated and compared with the experimental results.
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Abdo, Jamil, Edris M. Hassan, Khaled Boulbrachene, and Jan Kwak. "Modeling and Experimental Investigations of Drill Pipe Failure." In ASME 2017 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/imece2017-70369.
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During drilling operations, drill string interacts continuously with rock formation, which result in severe shock and vibrations. Lateral, torsion and axial vibration modes often cause failures of Bottom Hole Assembly (BHA), drill pipe abrasive wear, drill bit and wall borehole damages. It also leads to reduction in Rate of Penetration (ROP) and consequently incur unnecessarily high costs. The Lagrangian approach has been used in this study to attain drill pipe lateral and torsional vibration coupling equations of motion. The mathematical model is expressed in terms of four independent degrees of freedom. The effects of bending and torsion vibrations, and whirling motion of the drill string are incorporated in the developed model. A set of nonlinear equations are solved numerically to obtain the response of the system. In this work, we also present a brief description of an in-house constructed experimental setup. The setup has the capability to imitate the downhole axial, lateral and torsional vibration modes and mechanisms. Experimental investigations for the drill pipe fatigue failure due to lateral and torsional cyclic stresses induced in the drill string are also presented. Such investigations are essential for oil/gas industry as they provide solutions for very common problems such as drill string fatigue failure. The performance of the setup was validated. Numbers of tests were performed to investigate the effects of rotational speeds on the vibration amplitudes of different drill string sizes.
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Saneian, Mohsen, Yifan Gao, Yong Bai, and Ting Liu. "Analysis of Subsea Umbilical Mechanical Behavior Under Simultaneous Bending, Tension and Torsion." In ASME 2019 38th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/omae2019-96596.
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Abstract One of the major failure modes of an umbilical is found to occur under simultaneous bending, tension and torsion. Umbilical cables are compatible in bending but have a rigid response to tension and torsion, hence validation the axisymmetric performance of it, is a significant matter. This paper has applied theoretical models to analyze umbilical cables mechanical behavior under combined loading. Lanteigne (1985) theoretical model, which its feature is a large-diameter central pipe umbilical cross section with homogeneous materials that a number of wires helically wrapped around it, is developed in this article. The equilibrium equations are presented and showed the helical elements effects on bending, tension and torsion of the umbilical cable.
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Chiang, Hsiao-Wei D., Chi-Chin Chen, Chih-Neng Hsu, Gwo-Chung Tsai, and Kwang-Lu Koai. "An Investigation of Turbomachinery Shrouded Rotor Blade Flutter." In ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38311.
Full textAbstract:
Turbomachinery shrouded rotor blade design has been widely used in fans, compressors, and turbines. By using shroud design, the blade structural damping can be increased to prevent blade flutter. However, the shrouded rotor blade design will cause the blade mode shapes to be complex, and in some cases both bending and torsion mode components can be present at the same time in a single mode. Therefore, a complex mode analysis was developed to predict shrouded rotor blade flutter with these bending and torsion combined system modes. Using the blade natural frequencies and mode shapes from a finite element model, and the blade aerodynamic flow-field, the unsteady aerodynamic forces of the system mode can be calculated. A complex mode flutter analysis was then performed using a modal solution to determine the stability of the system. The analysis system was applied to two shrouded rotor blade applications. The bending and torsion combined system mode was decomposed into a real mode component and an imaginary mode component. Bending-dominated or torsion-dominated mode shapes can be analyzed using single mode approach to obtain consistent flutter stability results. However, for the bending and torsion combined mode shape cases, the single mode analysis can be misleading, and the complex mode analysis can be a useful tool.
Reports on the topic "Torsion modes"
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Reedlunn, Benjamin, and Wei Yang Lu. An attempt to calibrate and validate a simple ductile failure model against axial-torsion experiments on Al 6061-T651. Office of Scientific and Technical Information (OSTI), January 2015. http://dx.doi.org/10.2172/1167405.
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Michalski, A,, D. Andersson, R. Rossi, and C. Soriano. D7.1 DELIVERY OF GEOMETRY AND COMPUTATIONAL MODEL. Scipedia, 2021. http://dx.doi.org/10.23967/exaqute.2021.2.020.
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This document describes the industrial application, on which the developments of the project are implemented, and the CFD set-up. The developments are implemented over six analysis cases with increasing complexity starting from a 2D geometry with mean wind inflow to a 3D geometry with turbulent inflow and real-time shape optimization. The application represents the CAARC tall building model, which has served as a benchmark model for many studies since the 1970’s when it was first developed. Base moments (bending and torsional moments) of the building are extracted for validation by comparison of the results with the benchmark study. Page 3 of 19 Deliverable 7.1
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Badia, S., A. Martín, J. Principe, C. Soriano, and R. Rossi. D3.1 Report on nonlinear domain decomposition preconditioners and release of the solvers. Scipedia, 2021. http://dx.doi.org/10.23967/exaqute.2021.2.021.
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This document describes the industrial application, on which the developments of the project are implemented, and the CFD set-up. The developments are implemented over six analysis cases with increasing complexity starting from a 2D geometry with mean wind inflow to a 3D geometry with turbulent inflow and real-time shape optimization. The application represents the CAARC tall building model, which has served as a benchmark model for many studies since the 1970’s when it was first developed. Base moments (bending and torsional moments) of the building are extracted for validation by comparison of the results with the benchmark study. Page 3 of 19 Deliverable 7.1