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Ritchie, Stephen John Kerr. "The high speed double torsion test." Thesis, Imperial College London, 1996. http://hdl.handle.net/10044/1/11437.
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Smith, Gregory L. "A short range test of the universality of free fall /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/9687.
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Choi, Ki-Young. "A new equivalence principle test using a rotating torsion balance /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/9762.
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Goqo, Sicelo Praisgod. "Computational study of compact tension and double torsion test geometries." Master's thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/9108.
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Includes bibliographical references.In the design of many engineering components subjected to cyclic or repetitive loading,fatigue is an ever-present challenge. The engineer often endeavors to design the structural or component system in such a way that the cyclic stresses are below a particular fatigue limit, or, in fracture mechanics terms, at stress levels below threshold. In the Paris formulation, fatigue threshold, Δҝₜₕ, may be regarded as that value of cyclic stress intensity below which fatigue crack growth does not occur. For a particular material and environment, this threshold value, Δҝₜₕ, is determined experimentally by monitoring growth of a crack (typically in a compact tension ( CT) specimen) and continually reducing cyclic stress levels until the threshold condition is reached. This procedure is very cumbersome and time-consuming, and this project rather considers the design of a fracture mechanics specimen geometry in which there is a decreasing stress in tensity (with crack length) that facilitates determination of the threshold value simply at constant applied cyclic amplitude, and the crack length at which fatigue crack growth arrests.
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Valtorta, Davide. "Dynamic torsion test for the mechanical characterization of soft biological tissues." kostenfrei, 2007. http://e-collection.ethbib.ethz.ch/view/eth:29354.
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Bondar, Carin Anne. "Development of asymmetry in two caenogastropods, a test of the torsion hypothesis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/MQ62549.pdf.
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Khokhar, Aamir Muhammad. "The evaluation of shear properties of timber beams using torsion test method." Thesis, Edinburgh Napier University, 2011. http://researchrepository.napier.ac.uk/Output/4406.
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Russano, Giuliana. "A torsion pendulum ground test of the LISA Pathfinder Free-fall mode." Doctoral thesis, Università degli studi di Trento, 2015. https://hdl.handle.net/11572/367984.
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The LISA Pathfinder geodesic explorer mission for gravitational wave astronomy aims to measure a residual differential acceleration noise approaching the femto-m/s^2/Hz^1/2 levels needed for eLISA. This measurement is complicated by a large, roughly nm/s^2, stable
differential gravitational acceleration that must be actively compensated in order to hold the test particles centred inside an orbiting apparatus. The actuation force applied to compensate this effect introduces a dominant source of force noise in the mission noise budget. To suppress this noise source and avoid actuation instabilities, a “free-fall†actuation control scheme has been designed: actuation is limited to brief impulses, with test masses in free fall in between two “kicks†, with this actuation-free motion then analysed for the remaining
sources of acceleration ultra noise. In this work, we present the results from an extensive on-ground torsion
pendulum test of this free-fall technique, which to date allows an equivalent acceleration noise measurement at the 100 fm/s^2/sqrt(Hz), a factor 3 above the LISA Pathfinder spec. We will discuss both experimental and analysis limitations to the ground experiment and some
implications for the flight test.
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Smith, Brandon Joseph. "Development and Initial Testing of a Micro-Newton Torsion Pendulum with Gas-Dynamic Calibration." Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/88081.
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A novel torsion pendulum thrust test stand for micro-Newton-scale spacecraft thrusters is described. The stand is designed to be robust against electromagnetic interference effects internal or external to the thruster being tested. The design and testing of a
gas-dynamic calibration thruster is included. This thruster is fully self-contained on the pendulum arm, with no external wires or feedlines connected to the device and impacting the dynamic response of the underlying pendulum. Initial calibration results are shown. Zero drift and hysteresis are present in the results, evidenced by a constant steady-state displacement drift and a return to a different displacement after shutdown of the calibration thruster. Results are compared to theoretical solutions of the equation of motion. An external forcing function of facility effects is described for discrepancies between results and the theoretical solution. Further work to eliminate these effects and add damping are proposed.MS
Many recently proposed space missions require very fine vehicle attitude and position control in support of their science objectives. Thrusters with the ability to provide this control are currently in development, from laboratory proofs of concept to initial test flights on pathfinding missions. The low levels of thrust produced by these devices, in the range of less than the weight of a mosquito, require specialized test stands with very fine resolution. This thesis describes a novel torsion pendulum design for measuring these thrusters as well as initial validation results from its calibration system using rarefied gas flow. This calibration device is fully-contained on the device’s arm, removing many common sources of compensation factors which are often needed for other test stand designs. A custom-built displacement measuring system for determining angular motion of the pendulum arm is described which allows for measuring angular displacements of the arm to the level of arcseconds and potentially fractions thereof. Initial results suggest measurement of the expected levels of thrust, while some work remains to remove lingering sources of error and achieve more precise thrust data.
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Heisser, Ronald Henry. "Design, development, and characterization of an experimental device to test torsion-controlled fracture of thin brittle rods." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105705.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (page 40).
As research continues to uncover the many different physical properties of meso- and microscale materials, it becomes more evident that these materials often behave in counterintuitive ways. Characterizing unique phenomena not only provides analogies in nature which inspire innovation at all levels of research and design but also presents new possibilities for future technological development. The discussion presented herein explores the design and development of a low-cost, manual device intended to test a hypothesis rooted in the behavior of breaking pasta that intrigued even Richard Feynman. While the mechanism for why spaghetti breaks into three or more pieces has been described, the experimental discussion presented here focuses on the effect that added torsion has on the fracture bent spaghetti. Specifically, it is possible that twisting the spaghetti a critical angle and bending it will cause it to fracture into only one piece. The idea of torsion being used to exhibit some control over how a material fractures has not been well-investigated; the results which come from this experiment may prove useful for applications even beyond the scope of thin brittle materials. With this said, the sensitivity in quantifying breaking from torsion and bending together requires that the experimental device prevent systematic error stress from negatively impacting the accuracy of the experiment. Thus much time is devoted to explanation and rationale behind the analysis of the experimental device. Alongside the device's characterization this thesis serves to be a reflection of the design process taken while creating this device. Lessons learned from this project are included in all aspects of the discussion and a section in the Appendix is devoted to a more detailed account of the design and fabrication of one device component.
by Ronald Henry Heisser.
S.B.
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Rocco, Emanuele. "Development of a test of Newton's law of gravitation at micrometer distances using a superconducting spherical torsion balance." Thesis, University of Birmingham, 2008. http://etheses.bham.ac.uk//id/eprint/1482/.
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Many theories associated with quantum gravity, such as string theory, predict violations of inverse square law (ISL) of gravity at sub millimetre distances. To search for such experimental signatures we developed a magnetically levitated cryogenic torsion balance, the SSTB, and a set of masses with modulated density across their surfaces. The lateral force has to be measured as one mass is moved in front of the other with a micropositioner without any electrostatic shield between them. The expected Newtonian and electromagnetic forces have been studied to optimise the design of the masses. The torque sensitivity of the SSTB has been modelled and its performances at 4.2 K discussed. A torque sensitivity of 2×10\(^{−10}\) Nm/√(Hz) at 30 mHz has been measured, most probably due to coupling with ground tilt. Two tests with prototypes of the masses has been performed. During the first test a torque due to electrostatic and magnetic forces of 8.4×10\(^{−11}\)±1.5×10\(^{−11}\) Nm has been measured at a mass spacing of 42±14μm at the spatial periodicity of the density modulation. During the second test by using improved masses the detected signal was reduced to 1.91×10\(^{−11}\)±4.7×10\(^{−12}\) Nm at a spacing of 30±10 μm. To look for violations of the ISL of gravity the torque sensitivity of the SSTB has to be further enhanced.
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Ypsilantis, Dominique. "Optimisation de la mise en precontrainte par pretorsionnage et grenaillage des barres de torsion en acier 45scd6." Paris, ENSAM, 1986. http://www.theses.fr/1986ENAM0007.
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Etude de l'optimisation des parametres intensite de grenaillage, couple de pretorsionnage, ordre d'execution du pretorsionnage et du grenaillage. Cette etude a ete conduite par des essais de fatigue, par analyse des contraintes residuelles, par diffraction rx et utilisation d'un critere de fatigue.
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Marchal, Arnault. "Comportement thermomécanique d'aciers déformés par essais de torsion à chaud." Vandoeuvre-les-Nancy, INPL, 1997. http://www.theses.fr/1997INPL013N.
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Cette étude est une contribution à la compréhension des mécanismes de déformation plastique à chaud des aciers bas carbone. Le comportement du matériau est modélisé par une loi de comportement viscoplastique déduite d'essais de torsion rapides. Nous avons développé un nouveau système qui permet l'acquisition instantanée des paramètres expérimentaux, et nous avons mis au point une méthodologie plus adaptée à l'analyse du dépouillement de l'essai. Dans notre étude, pour laquelle les vitesses de déformation sont comprises entre 0. 1 et 10 S-¹, nous avons montré l'influence de la cinématique de chargement et de l'auto-échauffement de déformation sur l'évolution de la contrainte. Enfin, nous avons développé un programme de simulation numérique de l'essai de torsion qui permet d'expliquer les effets du couplage thermique et mécanique sur l'évolution de la contrainte de déformation. Nous montrons en particulier comment l'évolution locale de la température (gradient thermique radial) conduit à l'allure caractéristique des courbes brutes de torsion
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Pham, Keimann, and Jesse Olsson. "Bestämning av skjuvhållfasthet med vridprovning för pågjutna betongkonstruktioner." Thesis, KTH, Byggteknik och design, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-136826.
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Skador och slitage på brokonstruktioner av betong beror på tösalter, armeringskorrosion och frostcykler i kombination med ökande trafiklaster. Den i särklass vanligaste reparationsåtgärden för dessa typer av skador är att göra en pågjutning. Metoden går ut på att först avlägsna det skadade eller dåliga betongskiktet innan en ny betong pågjuts. För att bedöma hur bra ett pågjutningsarbete är behöver vidhäftningen mellan den nya pågjutningen och gamla betongen fastställas. Den mest använda metoden för detta syfte är s.k. dragprovning som bestämmer draghållfastheten i vidhäftningen. I praktiken är dock vidhäftningens skjuvhållfasthet av större intresse och approximeras därför utifrån draghållfastheten, men med en vridprovning kan fogens skjuvhållfasthet direkt bestämmas. Syftet med examensarbetet är att undersöka vridprovningens reliabilitet för att i framtiden eventuellt kunna bestämma skjuvhållfastheten på ett mer direkt och korrekt sätt. I examensarbetet undersöks vridprovningens reliabilitet för att bestämma skjuvhållfastheten i fogen mellan pågjutning och gammal betong med dragprovningen som referens. Studien omfattar åtta parallellprovningar av drag- och vridprovningar där den lägst uppmätta skjuvhållfastheten jämförs med fogens dimensioneringsvärde enligt EK2. Examensarbetet görs i samband med Spårväg city-projektet vid Sergels torg, Stockholm, i uppdrag från Trafikkontoret i Stockholm och CBI Betonginstitutet. Resultaten från provningarna visade att fogbrott, som är av intresse, var vanligare för dragprovning än vridprovning. Den stora spridningen av mätvärdena var en konsekvens av det låga antalet fogbrott för vridprovningen. Medelvärdet för fogens draghållfasthet på 1,43 MPa tyder på god vidhäftning, men fogens skjuvhållfasthet bestämd med vridprovning visar ett medelvärde på endast 1,61 MPa och understiger det förväntade värdet på ca dubbla draghållfastheten d.v.s. 2,9 MPa. Intressant är att det lägst uppmätta värdet på skjuvhållfastheten på 0,83 MPa var ovanligt lågt, men fortfarande större än dimensioneringsvärdet enligt EK2 på 0,59 MPa. Studien har visat att vridprovningen är en svårtydlig metod för att bestämma skjuvhållfastheten i fogen mellan pågjutning och gammal betong. Anledningen till detta beror främst av tre faktorer, för få antal provningar, den stora spridningen av mätvärden samt de svårtolkade brottmoderna från vridprovningen. Trots detta tros vridprovningen vara en framtida metod för konstruktörer och beställare eftersom metoden är ett bra mätverktyg för att bestämma skjuvhållfastheten för pågjutna betongkonstruktioner som helhet och inte bara i fogen mellan pågjutning och befintlig betong.Damages and wear on concrete bridges are due to de-icing salt or salt water, reinforcement corrosion and repeated freeze-thaw cycles in combination with increasing traffic loads. The most common repair operation for these types of damages is to remove the deteriorated concrete and replace it with a new concrete overlay. To evaluate how well a bonded concrete overlay is, the bond strength between the new and old concrete has to be determined. The most widely used method for this purpose is the so-called pull off test to determine the tensile bond strength. In practice however the shear bond strength is of greater interest and is therefore approximated on the basis of tensile bond strength, but with a torsion test the shear bond strength can be directly determined. The purpose of this study is to investigate the reliability of the torsion test to determine the shear bond strength in a more direct and accurate manner. The thesis examines the reliability of the torsion test to determine the shear bond strength with the pull off test as a reference. The study includes eight parallel tests of pull off and torsion tests where the lowest measured shear bond strength is compared with the calculated design value of shear bond strength according to EC2. The work is done in connection with the Spårväg city project at Sergels torg, Stockholm, in collaboration with the Traffic Administration Office in Stockholm and CBI, the Swedish Cement and Concrete Research Institute. The results of the tests showed that the failures in the interface between new and old concrete, which are of interest, were more common for pull off tests than torsion tests where only two of the eight test samples showed failure in the interface. The wide scatter of the measured values is a consequence of the low number of failures in the interface. The mean value of the tensile bond strength was 1,43 MPa, which indicates good bond strength. The shear bond strength however made with torsion tests show a mean value of only 1,61 MPa. Lower than the expected value of about twice the tensile bond strength of 2,86 MPa. Interestingly, the lowest measured value of the shear bond strength of 0,83 MPa was unusually low, but still higher than the calculated design value of shear bond strength of 0.59 MPa according to EC2. The study has shown that torsion test is a difficult method for determining the shear strength of the bond between the new and old concrete. The reason for this is mainly due to three factors, the low number of tests, the large scatter of values, and the difficulty to interpret failures of the test samples. Despite this the torsion test seems to be a future method for structural engineers and contractors as a tool to determine shear strength for repaired concrete structures in general and not only the shear bond strength.
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Santos, Dacleo Cardoso dos. "Projeto, construção e teste de uma máquina de torção." Universidade do Estado de Santa Catarina, 2011. http://tede.udesc.br/handle/handle/1784.
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During the execution of this work it was developed the Project of an equipment to perform the trial of torsion following standard rules available for this test. This equipment was built and tested in the last two years and the main focus of this development was to obtain a low-cost equipment with capacity to run trials with good precision. In addition to this equipment it was built accessories to perform the measurement of torsion and angular variation between two points. The torquemeter was designed in aluminum and using straingage with a circuit in full bridge to the measurement of the torque. The project of this torquemeter followed the same standards as the ones available in the market; however the cost of its building was also very low. The other accessory built was the torsiometer and it wasn´t found in literature (neither commercially) any similar project to the one developed in this work. The measurement of the angular variation between two points was also performed using strain-gage with circuit in ¼ bridge. The curve of torque x torsion angle is the result of the torsion trial from where two main data are obtained: the material shear module and the rupture module (the amount of the shear tension for the material rupture). To test the set of equipment and accessories trials were performed with four different materials: 1035 steel, 1020 steel, aluminum and brass. These results were compared with the ones obtained in the traction trial and with data available in the literature. Along this work it is shown clearly the building details, the costs, the mathematical equation of elastic-plastic torsion and the quality of the results obtained with the equipment developed and built during the execution of this dissertation.
Durante o cumprimento deste trabalho foi criado o projeto de um equipamento para efetuar o ensaio de torção seguindo padrões de normas disponíveis para o teste. O equipamento foi construído e testado nos últimos dois anos, e o principal objetivo de tal desenvolvimento foi obter um aparelho de baixo custo com capacidade de realizar ensaios com boa precisão. Além do equipamento, foram construídos acessórios para as medições de torque e da variação angular entre dois pontos. Projetou-se e construiu-se o torquímetro em alumínio empregando extensometria com circuito em ponte completa para a medição do torque. O projeto do torquímetro atingiu os mesmos padrões daqueles que estão disponíveis no mercado, porém com custo muito baixo. Outro acessório construído foi o torsiômetro, e não se encontrou na literatura (ou comercialmente) nenhum projeto similar ao desta dissertação. A medição da variação angular também se fez com extensometria com circuito em ¼ de ponte. A curva do torque × ângulo de torção é o resultado do ensaio de torção do qual são alcançadas duas propriedades: o módulo de elasticidade transversal do material e o módulo de ruptura (o valor da tensão cisalhante para a ruptura do material). A fim de testar o conjunto equipamento e acessórios, foram realizados ensaios com quatro materiais diferentes: aço 1035, aço 1020, alumínio e latão. Compararam-se os resultados com aqueles atingidos no ensaio de tração e com os dados achados na literatura. Ao longo deste trabalho mostram-se com clareza os detalhes construtivos, os custos, o equacionamento matemático da torção elastoplástica e a precisão dos resultados obtidos com o equipamento desenvolvido com esta dissertação.
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ZHOU, XIAO-WEI. "Contribution au comportement dynamique des materiaux metalliques : etude experimentale de l'alliage al-li en torsion et en compression, simulation numerique du processus de penetration a grande vitesse." Nantes, 1988. http://www.theses.fr/1988NANT2014.
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Etude experimentale sur les alliages al-li soumis a des essais de traction et de compression pour des vitesses de deformation comprises entre 10**(-4) et 310**(3) s**(-1) et de 10**(-3) a 210**(3) s**(-1) respectivement. Auparavant ces alliages ont ete traites thermiquement. Analyse de la sensibilite a la vitesse de deformation. Influence du mecanisme d'activation thermique sur le processus de deformation. Determination du mode de rupture. Analyse des facies de rupture pour les echantillons deformes en traction et de la formation des cellules de dislocation dans ceux deformes en compression. Simulation numerique du processus de penetration a grande vitesse d'une cible mince par un projectile circulaire en utilisant un modele de fluide elasto-plastique. Comparaison avec des resultats experimentaux
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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.
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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.
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Hakem, Naoual. "Etude de l'interaction des dommages de fatigue et de deformation progressive : effet d'un chargement primaire (entraction) sur la resistance a la fatigue oligocyclique en torsion de l'acier 304l a temperature ambiante." Paris 6, 1987. http://www.theses.fr/1987PA066422.
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Etude experimentale sur des eprouvettes tubulaires minces soumises a une variation cyclique d'un angle de torsion sur laquelle est superposee une contrainte de traction constante. Determination d'une courbe de resistance a la fatigue pour chaque niveau de chargement primaire. L'effet du chargement primaire conduit, a une reduction sensible du terme d'endurance dans l'equation de resistance a la fatigue. La rupture a lieu par fatigue et non par deformation, plastique excessive. Analyse de la reduction de la duree de vie associee a l'application d'un changement primaire
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Xavier, Tathy Aparecida. "Comparação dos ensaios de resistência adesiva por torção e por cisalhamento com fio." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/23/23140/tde-22052010-101723/.
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Objetivo: verificar, através de análise por elementos finitos e de uma etapa experimental, se o ensaio de torção, como ensaio de resistência de interfaces adesivas, seria capaz de levar os espécimes à ruptura sob tensões de cisalhamento e se ele seria vantajoso em relação ao ensaio de cisalhamento. Material e Método: para a análise de tensões pelo método dos elementos finitos, os modelos tridimensionais dos dois ensaios foram constituídos por cilindro de compósito, uma camada de adesivo e um cilindro de dentina com maior diâmetro. Os espécimes foram simulados nos tamanhos convencional e micro, numa proporção de 5:1, exceto pela camada de adesivo, de espessura constante. Foram simulados dois módulos de elasticidade do cilindro de compósito (híbrido e baixa viscosidade) e, para os modelos de cisalhamento, variaram as distâncias entre o local de carregamento e a interface adesiva. Foram analisados os valores das tensões máxima principal e cisalhamento máximo e a proporção entre elas ao longo da interface dentina/adesivo; a direção dos vetores de tensão máxima principal; e o local dos picos de tensão. Na etapa experimental, foram construídos cilindros de compósito (híbrido e de baixa viscosidade) nos tamanhos convencional e micro, aderidos a uma superfície de dentina bovina por meio de três sistemas adesivos. O esforço de cisalhamento foi aplicado com fio ortodôntico a uma distância da interface adesiva baseada na literatura e, para os ensaios de torção e microtorção, foram desenvolvidos dispositivos específicos para a aplicação do torque. Os resultados de tensão de ruptura foram submetidos à análise de variância e teste de Tukey. Todas as superfícies de fratura foram analisadas por meio de microscopia eletrônica de varredura. As frequências das fraturas adesivas e coesivas foram submetidas ao teste exato de Fisher e relacionadas aos valores de tensão de ruptura experimentais, bem como suas características foram relacionadas às tensões observadas pelo método dos elementos finitos. Os parâmetros experimentais de comparação entre os ensaios foram: poder de detecção de diferenças significantes entre os sistemas adesivos; constância da classificação relativa dos mesmos ao alterar as configurações dos ensaios e frequências dos tipos de fratura. Resultados: ambos os ensaios apresentaram um estado complexo de tensões com distribuição nãouniforme. Não foi notada menor sensibilidade dos resultados do ensaio de torção às mudanças das configurações do teste, nem uma maior capacidade para detectar diferenças significantes entre os adesivos do que o ensaio de cisalhamento. O ensaio de torção apresentou maior dificuldade de execução prática e maiores frequências de fraturas coesivas, porém, estas ocorreram mais no cilindro de compósito, enquanto no cisalhamento, ocorreram mais na dentina. Não houve certeza sobre o tipo de tensão que tenha levado à fratura nos dois tipos de ensaio. Conclusões: embora não se tenha certeza se o ensaio de torção leva à ruptura sob tensões de cisalhamento e tenham sido notadas desvantagens práticas de execução do ensaio, este apresenta uma característica que sugere novos estudos: ocorrência de fraturas coesivas principalmente no cilindro de compósito, o que poderia, talvez, ser resolvido com o reforço do material do cilindro.Objective: verify, by finite element analysis (FEA) and laboratorial tests, if the torsion bond strength test is able to lead adhesive interface to fracture under shear stress and if it would be more advantageous than wire-loop shear test. Material and method: for stress analysis by finite element method, the 3D models of both tests consisted of a resin composite cylinder, an adhesive layer and a dentin cylinder with a larger diameter. The specimens were simulated with both conventional and micro sizes, in a 5:1 ratio, except for the adhesive layer, kept in a constant thickness. Two values of elastic modulus were simulated for the composite cylinder (hybrid and flowable). For the shear models, different distances were simulated between the load point and the adhesive interface. The values of maximum principal and maximum shear stresses and the ratio between both types were analyzed along the adhesive interface, as well as the maximum principal vectors direction and the local of stress peaks. For the laboratorial tests, cylinders of hybrid and flowable resin composite, in both micro and conventional sizes, were adhered onto dentin surfaces by means of 3 adhesive systems. The shear load was applied with a metallic wire-loop at distances from the interface based on literature and, for the torsion test, the torque was applied by specific apparatus developed for that. The values of bond strength were submitted to analysis of variance and Tukeys test. Fracture surfaces were analyzed by scan electron microscopy. The frequencies of fracture types were compared by Fishers test and its relationship with bond strength values were verified, as well as the relationship between fracture features and stresses results obtained by FEA. The experimental parameters for comparison between both tests were: ability for detecting significant differences among the 3 adhesives, change of adhesives ranking while varying the test configuration and frequency of fracture types. Results: both tests showed non-uniform stress distribution. It was not noticed a lower sensibility of torsion test results to changes of the test configurations, nor a major ability for detecting significant differences among the adhesive systems than showed the shear test. The torsion test showed to be more difficult to execute and exhibited a higher frequency of cohesive fracture, however, that occurred most of the time in the composite cylinder, while it occurred mainly in dentin in shear test. There was no certainty about the kind of stress that lead to specimen fracture in both tests. Conclusions: although there was no certainty about the kind of stress that lead to specimen fracture and the major difficulty of execution of torsion test, this test exhibited a feature that suggests future studies: the occurrence of cohesive fracture mainly in the composite cylinder, which could be solved, maybe, by reinforcing the cylinder material.
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Řehák, Zdenek. "Experimentální a numerická analýza ŽB prvku namáhaného kroucením." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226097.
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The design for load tests of reinforced concrete members subjected to pure torsion. Calculation of ultimate torsional strenght of the reinforced concrete members with different theoretical approaches. Creating a mathematical model in Atena 3D software. Evaluation and comparison of the experimental results with the analytical part of the project. Recommendations for implementation of a similar type of experimental tests.
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Serrano, Munoz Itziar. "Influence of casting defects on the fatigue behaviour of an A357-T6 aerospace alloy." Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0117/document.
Full textAbstract:
L’excellente coulabilité, les coûts de production relativement bas, et ratio poids/résistance mécanique élevé des alliages de fonderie Al-Si-Mg en font une des solutions les plus intéressantes dans le secteur automobile ainsi que dans le domaine aérospatial. Toutefois, il est bien connu que la durée de vie de ces composants moulés à grand nombre de cycles (105 < Nf < 107 cycles) est sévèrement réduite lorsque des défauts de fonderie (notamment pores et oxydes) sont débouchants et/ou subsurfaciques sont présents. Ces défauts concentrent les contraintes et peuvent considérablement réduire la période d’amorçage des fissures de fatigue en fonction de leur taille, forme et des caractéristiques microstructurales du matériau. Les défauts internes (à partir desquels les fissures peuvent amorcer et propager sans interaction avec l’air ambiant) ainsi que les défauts de surface (ceux qui sont placés à la surface et en contact direct avec l’air ambiant) vont également nuire la durée de vie des composants moulés. Toutefois, dans le cas des défauts internes, les coefficients de sécurité préconisés par les règles de conception ne font pas intervenir la distance de défaut par rapport à la surface. Le suivi de fissures de fatigue effectué à la surface d’éprouvettes macroscopiques de traction indique que la présence d’un défaut avec une taille supérieure à celle des fissures microstructuralement courtes (√A ≈ 500 μm, taille contrôlée par la SDAS) produit une remarquable réduction de la durée vie. En revanche, la durée de vie n’est pas affectée lorsqu’un défaut plus petit (√A ≈ 300 μm) est présent à la surface car l’amorçage et les premiers stades de propagation sont encore influencés par la SDAS. Les essais de fatigue en torsion pure montrent que la morphologie des surfaces de rupture est fortement influencée par le niveau de contrainte. De plus, le nombre de cycles à l’amorçage est réduit par rapport à la traction. Cet amorçage est multi-site et plusieurs fissures peuvent croitre simultanément au cours de la durée de vie d’une éprouvette, la rupture finale se produisant lors de la jonction de certaines de ces fissures. La propagation des fissures en torsion est largement influencée par la cristallographie locale et les retassures ne semblent pas être des sites de nucléation préférentiels. Les durées de vie odes échantillons macroscopiques contenant défauts artificiel internes (Øeq ≈ 2 mm) sont pratiquement similaires à celles obtenues avec un matériau de référence. L’amorçage et la propagation de fissures internes a été rarement observé lors des expériences de tomographie synchrotron. Dans les rares cas où de telles fissures ont pu être observées, le chemin de fissuration semble fortement influencé par la cristallographie alors que les fissures amorcées depuis la surface se propagent globalement en mode I. La vitesse de propagation des fissures internes est très inférieure à celle des fissures se propageant à partir de la surfaceThe excellent castability, relatively low production costs, and high strength to weight ratios make Al-Si-Mg cast alloys an attractive choice for use in cheaper and lighter engineering components, in both automotive and aerospace industries. However, it is well known that High Cycle Fatigue (HCF) lives (105 < Nf < 107 cycles) of cast components are severely reduced when casting defects (notably pores and oxides) are present at the free surface or subsurface. They act as stress raisers which can considerably reduce the crack incubation period depending on their size, shape and the microstructural features of the surrounding material. Internal casting defects are of special interest to this work. The application of safety coefficients considers that all casting defects present in a component have the same deleterious effect and no attention is paid, for example, to their distance to the free surface. In other words, internal defects (corresponding to the case where the depth of the defect allows crack nucleation and propagation to essentially occur without interaction with the air environment) are considered as damaging to fatigue life as surface defects (those placed at the free surface and in contact with the air environment). Surface crack monitoring performed on uniaxial fatigue specimens indicates that the presence of a surface microshrinkage exceeding the size of microstructurally small cracks (√A ≈ 500 μm, controlled by the SDAS) readily nucleates a fatigue cracks producing steady crack propagation and remarkable reduction in the expected fatigue life. A smaller surface defect (√A ≈ 300 μm) nucleated a crack that did not reduced the expected fatigue life as in this case early stages of propagation are still nfluenced by the SDAS. Pure torsional cycling reveals that the morphology of fracture surfaces is highly influenced by the stress level. In general, torsional fatigue behaviour is described by having reduced (with respect to uniaxial testing) and multisite crack nucleation periods. Several dominant cracks can evolve simultaneously and the final failure occurs by the linkage of some of those cracks. Crack propagation is controlled by the crystallography and pores do not appear to be preferential nucleation sites. S-N curves show that macroscopic specimens containing Øeq ≈ 2 mm internal artificial defect produce similar fatigue lives to those obtained with a defect-free material. Internal crack nucleation was rarely observed during synchrotron tomography experiments; instead the fatal cracks initiated from much smaller surface defects. Tomographic images show that, in the case of internal propagation, crystallographic paths are formed while surface cracks propagate in mode I. The crack growth rate of internal cracks is much smaller than that of cracks propagating from the free surface
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DOQUET-DARIDON, VERONIQUE. "Comportement et endommagement de deux aciers a structure cubique centree et cubique a faces centrees, en fatigue oligocyclique, sous chargement multiaxial non-proportionnel." Paris, ENMP, 1989. http://www.theses.fr/1989ENMP0137.
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Precision des mecanismes de durcissement cyclique anormal manifeste par certains materiaux sous chargement non proportionnel, ainsi que des reductions d'endurance qui l'accompagnent. Etude dans le cas de l'acier inoxydable austenitique 316 l et d'un acier doux
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MING, YAN LIU. "Comportement viscoplastique des polymères techniques a grande déformation et à grande vitesse de déformation (loi de comportement-critère de la rupture-essais dynamiques-identification, optimisation)." Paris, CNAM, 1986. http://www.theses.fr/1986CNAM0075.
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Étude de polymère semicristallins. Modèle microstructural: influence de la vitesse de déformation et de la température. Proposition d'un modèle cisaillement de la rupture ductile. Essais de torsion à grande vitesse avec le système a de Hopkinson et la machine d'inertie
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Pham, Linh Viet. "Dynamic torsional shear test for hot mix asphalt." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0000914.
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Nazirzadeh, Saeideh. "Dynamic Simulation Of Shaking Table Tests For A Shear-wall Building Having Torsion." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614052/index.pdf.
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Simulating the non-linear response of reinforced concrete (RC) buildings subjected to a sequence of input earthquake records, is an extremely complex concern in the field of the Earthquake Engineering. Buildings with no symmetry in plan have much more complicated behavior under earthquake effects than symmetric buildings. Torsional irregularity in plan is the main topic of many current researches. In previous decades, considerable amount of numerical and experimental studies have been conducted, but more researches are needed in order to confirm a better understanding of the concept of seismic behavior of these structures.
In this study modeling and analyses efforts to simulate the experimental response of a scaled three dimensional reinforced concrete shear wall structure tested on a shaking table, are presented.
The model structure is a ¼scale of a three story reinforced concrete building that has torsion due to plan irregularity and layout of structural walls. In order to simulate response quantities measured for the specimen tested on a shaking table, a series of non-linear time history analyses were performed. This structure subjected to AZALEE shaking table tests in Saclay, France under the project of &ldquo
SMART 2008&rdquo
which was led by CEA (Atomic energy agency). The model building was tested under a set of bi-directional synthetic and real ground motions that have varying intensities, peak ground accelerations ranging from 0.1g to 1g. Ground motions were applied sequentially to the specimen, starting with the one having the smallest intensity. Displacements and accelerations measured at different locations on the plan at third story were compared with the numerically computed values in order to check the validity of the Finite Element Model that has been obtained in ANSYS ver.12.1.
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Zhang, Wenlei. "Mechanical Reliability Enhancement of Single Crystal Silicon Microstructures by Means of Diamond-Like Carbon Film Coating." Kyoto University, 2019. http://hdl.handle.net/2433/236623.
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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.
Full textAbstract:
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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Peressini, Carlo <1973>. "The Dynamics of Passive Torsional Fatigue Test Rigs: Innovative Applications of Universal Joints." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5810/1/Peressini_Carlo_tesi.pdf.
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The dynamics of a passive back-to-back test rig have been characterised, leading to a multi-coordinate approach for the analysis of arbitrary test configurations. Universal joints have been introduced into a typical pre-loaded back-to-back system in order to produce an oscillating torsional moment in a test specimen. Two different arrangements have been investigated using a frequency-based sub-structuring approach: the receptance method. A numerical model has been developed in accordance with this theory, allowing interconnection of systems with two-coordinates and closed multi-loop schemes. The model calculates the receptance functions and modal and deflected shapes of a general system. Closed form expressions of the following individual elements have been developed: a servomotor, damped continuous shaft and a universal joint. Numerical results for specific cases have been compared with published data in literature and experimental measurements undertaken in the present work. Due to the complexity of the universal joint and its oscillating dynamic effects, a more detailed analysis of this component has been developed. Two models have been presented. The first represents the joint as two inertias connected by a massless cross-piece. The second, derived by the dynamic analysis of a spherical four-link mechanism, considers the contribution of the floating element and its gyroscopic effects. An investigation into non-linear behaviour has led to a time domain model that utilises the Runge-Kutta fourth order method for resolution of the dynamic equations. It has been demonstrated that the torsional receptances of a universal joint, derived using the simple model, result in representation of the joint as an equivalent variable inertia. In order to verify the model, a test rig has been built and experimental validation undertaken. The variable inertia of a universal joint has lead to a novel application of the component as a passive device for the balancing of inertia variations in slider-crank mechanisms.
29
Peressini, Carlo <1973>. "The Dynamics of Passive Torsional Fatigue Test Rigs: Innovative Applications of Universal Joints." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/5810/.
Full textAbstract:
The dynamics of a passive back-to-back test rig have been characterised, leading to a multi-coordinate approach for the analysis of arbitrary test configurations. Universal joints have been introduced into a typical pre-loaded back-to-back system in order to produce an oscillating torsional moment in a test specimen. Two different arrangements have been investigated using a frequency-based sub-structuring approach: the receptance method. A numerical model has been developed in accordance with this theory, allowing interconnection of systems with two-coordinates and closed multi-loop schemes. The model calculates the receptance functions and modal and deflected shapes of a general system. Closed form expressions of the following individual elements have been developed: a servomotor, damped continuous shaft and a universal joint. Numerical results for specific cases have been compared with published data in literature and experimental measurements undertaken in the present work. Due to the complexity of the universal joint and its oscillating dynamic effects, a more detailed analysis of this component has been developed. Two models have been presented. The first represents the joint as two inertias connected by a massless cross-piece. The second, derived by the dynamic analysis of a spherical four-link mechanism, considers the contribution of the floating element and its gyroscopic effects. An investigation into non-linear behaviour has led to a time domain model that utilises the Runge-Kutta fourth order method for resolution of the dynamic equations. It has been demonstrated that the torsional receptances of a universal joint, derived using the simple model, result in representation of the joint as an equivalent variable inertia. In order to verify the model, a test rig has been built and experimental validation undertaken. The variable inertia of a universal joint has lead to a novel application of the component as a passive device for the balancing of inertia variations in slider-crank mechanisms.
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Tailony, Rauf. "Internal Combustion Engine Cold Test Driveline Modeling, Analysis and Development." University of Toledo / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1564765172535669.
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Whyte, T. "Adequacy of test standards in evaluating blast overpressure (BOP) protection for the torso." Thesis, Cranfield University, 2016. http://dspace.lib.cranfield.ac.uk/handle/1826/10993.
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The blast wave emanating from an explosion produces an almost instantaneous rise in pressure which can then cause Blast Overpressure (BOP) injuries to nearby persons. BOP injury criteria are specified in test standards to relate BOP measurements in a testing environment to a risk of BOP injury. This study considered the adequacy of test standards in evaluating BOP protection concepts for the torso.
Four potential BOP injury scenarios were studied to determine the likelihood of injury and the adequacy of test standards for appropriate protection concepts. In the case of vehicle blast, BOP injury is unlikely and test standards are adequate. In the scenario involving an explosive charge detonated within a vehicle, and the close proximity to a hand grenade scenario, test standards are not available. The demining scenario was identified as of importance as test standards are available, but do not mandate the evaluation of BOP protection.
A prototype South African Torso Surrogate (SATS) was developed to explore this scenario further. The SATS was required to be relatively inexpensive and robust. The SATS was cast from silicone (selected to represent body tissue characteristics) using a torso mould containing a steel frame and instrumented with chest face-on pressure transducer and accelerometer. The SATS was subjected to an Anti-Personnel (AP) mine test and the Chest Wall Velocity Predictor and Viscous Criterion were used to predict that BOP injuries would occur in a typical demining scenario. This result was confirmed by applying the injury criteria to empirical blast predictions from the Blast Effects Calculator Version 4 (BECV4).
Although limitations exist in the ability of injury criteria and measurement methods to accurately predict BOP injuries, generally a conservative approach should be taken. Thus, it is recommended that the risk of BOP injuries should be evaluated in demining personal protective equipment test standards.
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Erbs, Nicolai [Verfasser], Iryna [Akademischer Betreuer] Gurevych, Eneko [Akademischer Betreuer] Agirre, and Torsten [Akademischer Betreuer] Zesch. "Approaches to Automatic Text Structuring / Nicolai Erbs. Betreuer: Iryna Gurevych ; Eneko Agirre ; Torsten Zesch." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2015. http://d-nb.info/1111911061/34.
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Horsmann, Tobias [Verfasser], and Torsten [Gutachter] Zesch. "Robust part-of-speech tagging of social media text / Tobias Horsmann ; Gutachter: Torsten Zesch." Duisburg, 2018. http://d-nb.info/1158495986/34.
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Che, Kar Suriani Binti. "Oscillatory behaviour and strategy to reduce drilling vibration." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/15831.
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Drill String dynamic behaviour during the oil drilling operation, was a major source for the failure of the Bottom Hole Assembly (BHA). The behaviour produced torsional vibration, which underpins the stick slip phenomena. Besides threatening the safety of the oil drilling process, such failure cause interruptions in the drilling operations and incurred high maintenance cost to the oil drilling company. This issue can be resolved with the implementation of the optimum control mechanism while operating the drill string. In this research, an optimum control mechanism was proposed to suppress the torsional vibration as well as mitigate the risk of stick slip phenomenon from occurring. The mechanism was proposed through a series of rigorous research strategies i.e. updated-mathematical equation modelling, experimentation and simulation. As the first step, a mathematical equation model describing system dynamics was derived to set the parameter of investigation. Representing the freedom torsional of the two degrees - conventional vertical drill string, the model was used to predict the frictional Torque On Bit (TOB) through non-linear friction force, denoting the ground-formation behaviour during drilling activity. Using a velocity feedback system, the drill-string oscillation was reduced while gradually increasing its velocity via gain scheduling method - allowing fast response to load disturbance. To avoid the motor torque from exceeding the maximum threshold, a Weight On Bit (WOB) was introduced. This approach remarks the novel contribution of this research. Next, an experiment on the preliminary test rig within a controlled laboratory set up was conducted. The rotary drill rig was assembled to identify the dynamics (i.e. parameters) of an individual part of the drill string. The results obtained were then applied in the drill string operation experiment, to identify the optimum control mechanism that can avoid the torsional vibration. To enable triangulation of results, a simulation was conducted by applying the same parameters obtained from the test rig experiment in the model- which is the optimum control mechanism that was proposed in this research to minimise torsional vibration, as well as reducing the chance of drill-string failure due to stick-slip phenomenon.
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Hamed, Osama Amin [Verfasser], and Torsten [Akademischer Betreuer] Zesch. "Automatic generation of lexical recognition tests using natural language processing / Osama Amin Hamed ; Betreuer: Torsten Zesch." Duisburg, 2019. http://d-nb.info/1198111313/34.
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Beinborn, Lisa Marina [Verfasser], Iryna [Akademischer Betreuer] Gurevych, Torsten [Akademischer Betreuer] Zesch, and Detmar [Akademischer Betreuer] Meurers. "Predicting and Manipulating the Difficulty of Text-Completion Exercises for Language Learning / Lisa Marina Beinborn ; Iryna Gurevych, Torsten Zesch, Detmar Meurers." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2016. http://d-nb.info/1114885193/34.
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Santos, Viviane Rocha dos. "Desenvolvimento de equipamento Ring Shear para avaliação do comportamento de solos a grandes deformações." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/76086.
Full textAbstract:
Os movimentos de massa de solo, geralmente, estão relacionados com a mobilização da resistência de uma ou várias superfícies de ruptura pré-existentes. Dessa maneira, o conhecimento da propriedade que rege esse comportamento (resistência ao cisalhamento residual) é de extrema importância no estudo da estabilidade de solos. Segundo Skempton (1985), resistência ao cisalhamento residual é a resistência mínima constante que o solo pode atingir, a baixas taxas de cisalhamento, após sofrer grandes deslocamentos. A determinação dos parâmetros de resistência ao cisalhamento residual pode ser realizada através de ensaios de cisalhamento por torção do tipo ring shear, adequado para estudar os mecanismos atuantes na ruptura, uma vez que permite a continuidade dos deslocamentos no solo. Nesse contexto, a pesquisa teve por objetivo desenvolver um equipamento de cisalhamento torsional baseado no ring shear descrito por Bishop et al. (1971) para avaliar o comportamento do solo a grandes deformações. O equipamento projetado foi validado, preliminarmente, segundo os resultados já publicados na literatura.Landslides, generally, are related with the mobilization of shear strength of one or more preexisting rupture surfaces. Thus, knowledge of the property that governs this behavior (residual shear strength) has extreme importance in the stability soils study. According to Skempton (1985), residual shear strength is the minimum constant strength attained at low shear rates, at large displacements. The residual shear strength parameters can be accomplished through ring shear tests, suitable for studying the mechanisms in the rupture, since it provides continuity of displacements in the soil. In this context, the research aimed to develop a device based on ring shear described by Bishop et al. (1971) to evaluate the soil behavior in large deformations. The equipment designed was validated, preliminarily, according to the results already published in the literature.
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Bladh, Johan. "Hydropower generator and power system interaction." Doctoral thesis, Uppsala universitet, Elektricitetslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-182188.
Full textAbstract:
After decades of routine operation, the hydropower industry faces new challenges. Large-scale integration of other renewable sources of generation in the power system accentuates the role of hydropower as a regulating resource. At the same time, an extensive reinvestment programme has commenced where many old components and apparatus are being refurbished or replaced. Introduction of new technical solutions in existing power plants requires good systems knowledge and careful consideration. Important tools for research, development and analysis are suitable mathematical models, numerical simulation methods and laboratory equipment. This doctoral thesis is devoted to studies of the electromechanical interaction between hydropower units and the power system. The work encompasses development of mathematical models, empirical methods for system identification, as well as numerical and experimental studies of hydropower generator and power system interaction. Two generator modelling approaches are explored: one based on electromagnetic field theory and the finite element method, and one based on equivalent electric circuits. The finite element model is adapted for single-machine infinite-bus simulations by the addition of a network equivalent, a mechanical equation and a voltage regulator. Transient simulations using both finite element and equivalent circuit models indicate that the finite element model typically overestimates the synchronising and damping properties of the machine. Identification of model parameters is performed both numerically and experimentally. A complete set of equivalent circuit parameters is identified through finite element simulation of standard empirical test methods. Another machine model is identified experimentally through frequency response analysis. An extension to the well-known standstill frequency response (SSFR) test is explored, which involves measurement and analysis of damper winding quantities. The test is found to produce models that are suitable for transient power system analysis. Both experimental and numerical studies show that low resistance of the damper winding interpole connections are vital to achieve high attenuation of rotor angle oscillations. Hydropower generator and power system interaction is also studied experimentally during a full-scale startup test of the Nordic power system, where multiple synchronised data acquisition devices are used for measurement of both electrical and mechanical quantities. Observation of a subsynchronous power oscillation leads to an investigation of the torsional stability of hydropower units. In accordance with previous studies, hydropower units are found to be mechanically resilient to subsynchronous power oscillations. However, like any other generating unit, they are dependent on sufficient electrical and mechanical damping. Two experimentally obtained hydraulic damping coefficients for a large Francis turbine runner are presented in the thesis.
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Nikitin, Alexander. "Gigacycle Fatigue of the titanium alloy." Thesis, Paris 10, 2015. http://www.theses.fr/2015PA100015/document.
Full textAbstract:
Ce projet de doctorat est aux prises avec un problème de ruptures en fatigue de un alliage de titane aéronautique en raison de haute fréquence chargement. Matériel pour cette enquête a été prise de compresseur du moteur disque de l'avion réel. Essais de fatigue à ultrasons ont été réalisées jusqu'à dépasser la limite de 1010 cycles. Cette région de la durée de vie est connu comme Gigacycle ou fatigue très grand nombre de cycles. Ce projet de thèse montre pour la première fois les résultats des tests de fatigue sur l'lliage de titane aéronautique VT3-1 dans la région Gigacycle. Les propriétés de fatigue de l'alliage de titane ont été déterminées à 109 cycles pour les conditions de chargement différentes: traction-compression, tension-tension et de torsion. Mécanismes d'initiation des fissures typiques ont été identifiés et des défauts critiques de microstructure ont été trouvés. L'effet de l'anisotropie en raison de processus de fabrication sur les propriétés de fatigue de l'alliage de titane VT3-1 forgé a été étudiée. Une influence du processus de fabrication sur les propriétés de fatigue a également été étudiée par comparaison les résultats sur extrudé et forgé VT3-1 alliage de titane. La nouvelle machine de torsion à ultrasons a été conçu et installé pour la longue durée de vie (jusqu'à 1010 cycles) de tests de fatigue en rotation. Les premiers résultats sous la chargement en torsion ultrasons ont été obtenues pour l'alliage de titane réalisé par extrusion et technologies forgésThis PhD project is dealing with a problem of fatigue failures of aeronautical titanium alloy due to high frequency loading. The material for investigation was taken from the real aircraft engine compressor disk. Ultrasonic fatigue tests were carried out up to outrun limit of 1010 cycles. This region of lifetime is known as Gigacycle or very high cycle fatigue. This PhD project shows for the first time the results of fatigue tests on the VT3-1 aeronautical titanium alloy in the Gigacycle region. The fatigue properties of the titanium alloy were determined at 109 cycles for different loading conditions: tension-compression, tension-tension and torsion loading. Typical crack initiation mechanisms were identified and critical defects of microstructure were found. The effect of anisotropy due to fabrication process on the fatigue properties of the forged VT3-1 titanium alloy was studied. An influence of technological process on fatigue properties was also studied by comparison the results on extruded and forged VT3-1 titanium alloy.The new ultrasonic torsion machine was designed and installed for the long life (up to 1010 cycles) fatigue tests under rotation. The first results under ultrasonic torsion loading were obtained for the titanium alloy made by extrusion and forged technologies
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Kostíková, Martina. "Návrh testovací figuríny pro nárazové zkoušky." Master's thesis, Vysoké učení technické v Brně. Ústav soudního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-318116.
Full textAbstract:
The main objective of this thesis is construction of crash test dummy for vehicle-pedestrian crash tests. There is review of nowadays used crash test dummies types in the introduction of this thesis. This is followed by part describing construction itself. Chapter about construction begins by characterizing of used materials features in relation with real human body physiology. Main part of chapter is describing construction of crash test dummy’s skeleton and its individual components including 3D modelling and strength analysis. Thesis is finished by cost assessment.
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Heva, Yasintha Bandula. "Behaviour and design of cold-formed steel compression members at elevated termperatures." Queensland University of Technology, 2009. http://eprints.qut.edu.au/29310/.
Full textAbstract:
Cold-formed steel members have been widely used in residential, industrial and commercial buildings as primary load bearing structural elements and non-load bearing structural elements (partitions) due to their advantages such as higher strength to weight ratio over the other structural materials such as hot-rolled steel, timber and concrete. Cold-formed steel members are often made from thin steel sheets and hence they are more susceptible to various buckling modes. Generally short columns are susceptible to local or distortional buckling while long columns to flexural or flexural-torsional buckling. Fire safety design of building structures is an essential requirement as fire events can cause loss of property and lives. Therefore it is essential to understand the fire performance of light gauge cold-formed steel structures under fire conditions. The buckling behaviour of cold-formed steel compression members under fire conditions is not well investigated yet and hence there is a lack of knowledge on the fire performance of cold-formed steel compression members. Current cold-formed steel design standards do not provide adequate design guidelines for the fire design of cold-formed steel compression members. Therefore a research project based on extensive experimental and numerical studies was undertaken at the Queensland University of Technology to investigate the buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. As the first phase of this research, a detailed review was undertaken on the mechanical properties of light gauge cold-formed steels at elevated temperatures and the most reliable predictive models for mechanical properties and stress-strain models based on detailed experimental investigations were identified. Their accuracy was verified experimentally by carrying out a series of tensile coupon tests at ambient and elevated temperatures. As the second phase of this research, local buckling behaviour was investigated based on the experimental and numerical investigations at ambient and elevated temperatures. First a series of 91 local buckling tests was carried out at ambient and elevated temperatures on lipped and unlipped channels made of G250-0.95, G550-0.95, G250-1.95 and G450-1.90 cold-formed steels. Suitable finite element models were then developed to simulate the experimental conditions. These models were converted to ideal finite element models to undertake detailed parametric study. Finally all the ultimate load capacity results for local buckling were compared with the available design methods based on AS/NZS 4600, BS 5950 Part 5, Eurocode 3 Part 1.2 and the direct strength method (DSM), and suitable recommendations were made for the fire design of cold-formed steel compression members subject to local buckling. As the third phase of this research, flexural-torsional buckling behaviour was investigated experimentally and numerically. Two series of 39 flexural-torsional buckling tests were undertaken at ambient and elevated temperatures. The first series consisted 2800 mm long columns of G550-0.95, G250-1.95 and G450-1.90 cold-formed steel lipped channel columns while the second series contained 1800 mm long lipped channel columns of the same steel thickness and strength grades. All the experimental tests were simulated using a suitable finite element model, and the same model was used in a detailed parametric study following validation. Based on the comparison of results from the experimental and parametric studies with the available design methods, suitable design recommendations were made. This thesis presents a detailed description of the experimental and numerical studies undertaken on the mechanical properties and the local and flexural-torsional bucking behaviour of cold-formed steel compression member at ambient and elevated temperatures. It also describes the currently available ambient temperature design methods and their accuracy when used for fire design with appropriately reduced mechanical properties at elevated temperatures. Available fire design methods are also included and their accuracy in predicting the ultimate load capacity at elevated temperatures was investigated. This research has shown that the current ambient temperature design methods are capable of predicting the local and flexural-torsional buckling capacities of cold-formed steel compression members at elevated temperatures with the use of reduced mechanical properties. However, the elevated temperature design method in Eurocode 3 Part 1.2 is overly conservative and hence unsuitable, particularly in the case of flexural-torsional buckling at elevated temperatures.
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Heva, Yasintha Bandula. "Behaviour and design of cold-formed steel compression members at elevated temperatures." Thesis, Queensland University of Technology, 2009. https://eprints.qut.edu.au/29310/1/Yasintha_Heva_Thesis.pdf.
Full textAbstract:
Cold-formed steel members have been widely used in residential, industrial and commercial buildings as primary load bearing structural elements and non-load bearing structural elements (partitions) due to their advantages such as higher strength to weight ratio over the other structural materials such as hot-rolled steel, timber and concrete. Cold-formed steel members are often made from thin steel sheets and hence they are more susceptible to various buckling modes. Generally short columns are susceptible to local or distortional buckling while long columns to flexural or flexural-torsional buckling. Fire safety design of building structures is an essential requirement as fire events can cause loss of property and lives. Therefore it is essential to understand the fire performance of light gauge cold-formed steel structures under fire conditions. The buckling behaviour of cold-formed steel compression members under fire conditions is not well investigated yet and hence there is a lack of knowledge on the fire performance of cold-formed steel compression members. Current cold-formed steel design standards do not provide adequate design guidelines for the fire design of cold-formed steel compression members. Therefore a research project based on extensive experimental and numerical studies was undertaken at the Queensland University of Technology to investigate the buckling behaviour of light gauge cold-formed steel compression members under simulated fire conditions. As the first phase of this research, a detailed review was undertaken on the mechanical properties of light gauge cold-formed steels at elevated temperatures and the most reliable predictive models for mechanical properties and stress-strain models based on detailed experimental investigations were identified. Their accuracy was verified experimentally by carrying out a series of tensile coupon tests at ambient and elevated temperatures. As the second phase of this research, local buckling behaviour was investigated based on the experimental and numerical investigations at ambient and elevated temperatures. First a series of 91 local buckling tests was carried out at ambient and elevated temperatures on lipped and unlipped channels made of G250-0.95, G550-0.95, G250-1.95 and G450-1.90 cold-formed steels. Suitable finite element models were then developed to simulate the experimental conditions. These models were converted to ideal finite element models to undertake detailed parametric study. Finally all the ultimate load capacity results for local buckling were compared with the available design methods based on AS/NZS 4600, BS 5950 Part 5, Eurocode 3 Part 1.2 and the direct strength method (DSM), and suitable recommendations were made for the fire design of cold-formed steel compression members subject to local buckling. As the third phase of this research, flexural-torsional buckling behaviour was investigated experimentally and numerically. Two series of 39 flexural-torsional buckling tests were undertaken at ambient and elevated temperatures. The first series consisted 2800 mm long columns of G550-0.95, G250-1.95 and G450-1.90 cold-formed steel lipped channel columns while the second series contained 1800 mm long lipped channel columns of the same steel thickness and strength grades. All the experimental tests were simulated using a suitable finite element model, and the same model was used in a detailed parametric study following validation. Based on the comparison of results from the experimental and parametric studies with the available design methods, suitable design recommendations were made. This thesis presents a detailed description of the experimental and numerical studies undertaken on the mechanical properties and the local and flexural-torsional bucking behaviour of cold-formed steel compression member at ambient and elevated temperatures. It also describes the currently available ambient temperature design methods and their accuracy when used for fire design with appropriately reduced mechanical properties at elevated temperatures. Available fire design methods are also included and their accuracy in predicting the ultimate load capacity at elevated temperatures was investigated. This research has shown that the current ambient temperature design methods are capable of predicting the local and flexural-torsional buckling capacities of cold-formed steel compression members at elevated temperatures with the use of reduced mechanical properties. However, the elevated temperature design method in Eurocode 3 Part 1.2 is overly conservative and hence unsuitable, particularly in the case of flexural-torsional buckling at elevated temperatures.
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Dolamune, Kankanamge Nirosha. "Structural behaviour and design of cold-formed steel beams at elevated temperatures." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/33221/1/Nirosha_Dolamune_Kankanamge_Thesis.pdf.
Full textAbstract:
Cold-formed steel members are extensively used in the building construction industry, especially in residential, commercial and industrial buildings. In recent times, fire safety has become important in structural design due to increased fire damage to properties and loss of lives. However, past research into the fire performance of cold-formed steel members has been limited, and was confined to compression members. Therefore a research project was undertaken to investigate the structural behaviour of compact cold-formed steel lipped channel beams subject to inelastic local buckling and yielding, and lateral-torsional buckling effects under simulated fire conditions and associated section and member moment capacities. In the first phase of this research, an experimental study based on tensile coupon tests was undertaken to obtain the mechanical properties of elastic modulus and yield strength and the stress-strain relationship of cold-formed steels at uniform ambient and elevated temperatures up to 700oC. The mechanical properties deteriorated with increasing temperature and are likely to reduce the strength of cold-formed beams under fire conditions. Predictive equations were developed for yield strength and elastic modulus reduction factors while a modification was proposed for the stressstrain model at elevated temperatures. These results were used in the numerical modelling phases investigating the section and member moment capacities. The second phase of this research involved the development and validation of two finite element models to simulate the behaviour of compact cold-formed steel lipped channel beams subject to local buckling and yielding, and lateral-torsional buckling effects. Both models were first validated for elastic buckling. Lateral-torsional buckling tests of compact lipped channel beams were conducted at ambient temperature in order to validate the finite element model in predicting the non-linear ultimate strength behaviour. The results from this experimental study did not agree well with those from the developed experimental finite element model due to some unavoidable problems with testing. However, it highlighted the importance of magnitude and direction of initial geometric imperfection as well as the failure direction, and thus led to further enhancement of the finite element model. The finite element model for lateral-torsional buckling was then validated using the available experimental and numerical ultimate moment capacity results from past research. The third phase based on the validated finite element models included detailed parametric studies of section and member moment capacities of compact lipped channel beams at ambient temperature, and provided the basis for similar studies at elevated temperatures. The results showed the existence of inelastic reserve capacity for compact cold-formed steel beams at ambient temperature. However, full plastic capacity was not achieved by the mono-symmetric cold-formed steel beams. Suitable recommendations were made in relation to the accuracy and suitability of current design rules for section moment capacity. Comparison of member capacity results from finite element analyses with current design rules showed that they do not give accurate predictions of lateral-torsional buckling capacities at ambient temperature and hence new design rules were developed. The fourth phase of this research investigated the section and member moment capacities of compact lipped channel beams at uniform elevated temperatures based on detailed parametric studies using the validated finite element models. The results showed the existence of inelastic reserve capacity at elevated temperatures. Suitable recommendations were made in relation to the accuracy and suitability of current design rules for section moment capacity in fire design codes, ambient temperature design codes as well as those proposed by other researchers. The results showed that lateral-torsional buckling capacities are dependent on the ratio of yield strength and elasticity modulus reduction factors and the level of non-linearity in the stress-strain curves at elevated temperatures in addition to the temperature. Current design rules do not include the effects of non-linear stress-strain relationship and therefore their predictions were found to be inaccurate. Therefore a new design rule that uses a nonlinearity factor, which is defined as the ratio of the limit of proportionality to the yield stress at a given temperature, was developed for cold-formed steel beams subject to lateral-torsional buckling at elevated temperatures. This thesis presents the details and results of the experimental and numerical studies conducted in this research including a comparison of results with predictions using available design rules. It also presents the recommendations made regarding the accuracy of current design rules as well as the new developed design rules for coldformed steel beams both at ambient and elevated temperatures.
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Telue, Yaip K. "Behaviour and design of plasterboard lined cold-formed steel stud wall systems under axial compression." Thesis, Queensland University of Technology, 2001.
Find full textAbstract:
Gypsum Plasterboard is « commonrliningimateriaL It is often used. with cold+ formed steel in wall, frame systems.'· It is used eitheD with lipped or- unlipped- (plain) C-·
sections in the construction of both the load bearing and non-load bearing walls in residential, industrial and commercial buildings. This type of construction is
common in Australia, the USA and Europe. In Australia plasterboard is commonly used in external walls with brick veneer as the outer skin of buildings. Plasterboard, however, is considered as a non-structural material and in the design of the studs in wall frames, the strengthening effects of the plasterboard in carrying axial (or other) loads is ignored. The Australian standard for cold-formed steel structures AS/NZS 4600 ( 1996) permits the use of lateral and rotational support to the steel studs in the plane of the wall provided by the lining material. However, it does not specify the magnitude of lateral or rotational support that can be used for the stud wall frames. Miller and Pekoz (1994a) have carried out experiments on studs
subjected to axial compression loads and concluded that the experimental results contradict the shear diaphragm model assumed by American specification (AISI, ... , ,..,. ..
1986).
A suitable design method to accurately predict the structural behaviour of studs under axial compression, bending and combined ·.axial compression and bending is
required. As a first step in the development of the design methods, the axial compression loads must be studied. The objective of this research is therefore to determine a design model for the gypsum plasterboard lined cold-formed steel stud walls that can accurately represent their behaviour and to accurately predict the ultimate strength of the stud walls under axial compression. For this purpose, an extensive research project was undertaken using the following: 20 full scale tests on typical cold-formed steel stud wall frames (unlined, one side and both sides lined), 24 short stud column tests to study the effects of plasterboard lining on local buckling of flanges, fmite element analysis (FEA) of full scale cold-
Y.K Telue: Behaviour and design of plasterboard lined cold-formed steel studwall·systems formed steel stud wall frames including validation with full scale test results and a
detailed parametric study using FEA. It has been shown in this research that lining the plasterboard on one or both sides can increase the ultimate load of the' stud considerably. The Australian -and AISI specifications were found to be inadequate in predicting the ultimate loads and
failure modes of the studs. This research has shown that by using appropriate effective length factors, the ultimate load and the failure modes of both the unlined and the. lined studs can be accurately .predicted using the provisions of AS/NZS 4600 (1996). In the case of lined studs, it has been shown that the effective length factors in the plane of the wall and· .for torsion can be related to the ratio of the fastener spacing to the total unbraced height' of the studs. The thesis also presents design rules
that can accurately predict the ultimate load and the failure mode of slender web studs lined on one or both sides.
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Turetta, Maxime. "Development of an innovative U-shaped steel-concrete composite beam solution : experimental and numerical studies on the mechanical behaviour." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0203.
Full textAbstract:
Une solution innovante de poutre mixte acier-béton a été développée en tenant compte des problématiques de résistance au feu et de montage sur chantier. La poutre est composée d'une partie métallique en U connectée à une partie en béton armé. En phase de construction, la poutre métallique supporte la dalle et constitue un coffrage pour la retombée en béton armé. La poutre en U résiste aux charges de construction sans système d’étaiement temporaire. Lors du coulage du béton, la poutre en acier est remplie en même temps que la dalle, ce qui permet un gain de temps considérable sur chantier. En phase d'exploitation, la poutre est mixte acier-béton. La connexion entre les deux matériaux est réalisée par des goujons à tête soudée en partie inférieure de la poutre en U. En situation d'incendie, la poutre mixte répond aux durées de stabilité au feu conventionnelles grâce aux armatures longitudinales à l'intérieur de la retombée avec des enrobages suffisants. Un état de l'art sur les solutions existantes répondant aux critères de la thèse est réalisé afin de proposer une solution innovante et optimisée. En phase de construction, sans présence de maintien, la poutre métallique en U est sujette à l’instabilité globale de déversement. Afin de caractériser la stabilité de la poutre, un test à échelle réelle est effectué au Laboratoire de l'Université du Luxembourg. Les résultats de l’essai sont comparés à des simulations numériques et à des études analytiques. Une étude paramétrique portant sur 200 configurations géométriques de la poutre en U est réalisée afin de valider l'utilisation de la courbe « b » pour le dimensionnement au déversement selon l’Eurocode 3. En phase d'exploitation, une fois le béton durci, la poutre présente un comportement mixte acier-béton assuré par la connexion. Pour des raisons de fabrication, la connexion est située dans une zone où le béton est soumis à des efforts de traction induits par la flexion de la poutre. Le béton dans cette zone est potentiellement fissuré, l’efficacité de la connexion et par conséquent le comportement mixte acier-béton sont étudiés. Un autre test, à échelle réelle, est effectué dans le Laboratoire de l'Université du Luxembourg. La ruine de la poutre mixte, par effort tranchant, se produit à très grands déplacements. Cependant, l’échantillon présente un réel comportement mixte avec une ductilité élevée, la connexion est donc très efficace. Les résultats de l’essai sont comparés à des simulations numériques afin de valider le modèle par éléments finis développé. A partir des résultats numériques et des résultats d’essais, une méthode de conception pour déterminer la résistance à la flexion de cette poutre, basée sur l’Eurocode 4, est proposée en tenant compte de la plastification partielle des parois de la section en U. Une méthode de conception analytique globale est proposée pour la solution développée basée sur les Eurocodes, avec des considérations supplémentaires et des conseils de mise en œuvreAn innovative solution of steel-concrete composite beam was developed taking into consideration the fire situation and the construction stage. The beam is composed of a U-shaped steel part connected to a reinforced concrete part. In the construction phase, the beam is supporting the slab and constitutes a formwork for the reinforced concrete part. The U-shaped beam withstands the construction loads without any temporary propping system. When casting concrete, the steel beam is filled at the same time as the slab, this allows considerable time-saving on site. In exploitation stage, the beam behaves as a steel-concrete composite beam. The connection between the two materials is made by welded headed studs on the lower part of the U-shaped beam. In fire situations, the composite beam satisfies conventional fire stability durations due to the longitudinal reinforcements inside the concrete downstand part with sufficient covers. A literature review focuses on modern solutions that fulfils the criteria of the thesis is performed in order to develop an innovative solution optimised. In construction stage, the U-shaped steel beam without restraints is prone to lateral torsional buckling instability. In order to characterise the stability of the beam, a full-scale test is carried out at the Laboratory of the University of Luxembourg. The test clearly showed the lateral torsional buckling of the steel beam. The test results are compared to numerical simulations and analytical studies. A parametrical study, covering 200 geometrical configurations of the U-shaped beam, is carried out to validate the use of the curve "b" for the design of the steel beam for lateral torsional buckling according to Eurocodes 3. In the exploitation phase, once the concrete hardens, the beam has a steel-concrete composite behaviour provided by the shear connection between the two materials. For manufacturing reasons, the connection is located in a zone where the concrete is subjected to tension forces induced by the bending of the beam. The concrete in this zone is potentially cracked, thus the efficiency of the connection and therefore the mechanical steel-concrete composite behaviour is investigated. Another test is therefore carried out in the Laboratory of the University of Luxembourg, this time the specimen tested is made of concrete and steel. The failure mode is a shear mechanism of the composite beam at very large displacements. However, the beam specimen exhibited a real steel-concrete composite behaviour with high ductility, the connection is therefore very efficient. The test results are compared to numerical simulations in order to validate the finite element model developed. From numerical results and test results, an analytical method, based on EN 1994-1-1, is proposed to find the bending resistant of this composite beam by taking into account the partial yield of the side plates of the U-shaped steel section. A global analytical design method is proposed for the developed solution based on the Eurocodes with additional considerations and constructional guidelines
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Lee, Shuh-Kuo, and 李樹國. "THE MEASUREMENT STUDY OF BENDING AND TORSION TEST BY FIBER OPTIC SENSOR." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/45289894337000068429.
Full textAbstract:
碩士元智大學
機械工程學系
92
In this research, the strain of a fiber optic induced by the host structure is investigated through fiber optic bonded on the surface of a specimen subjected to four-point bending and torsion test. The measurement is based on the relationship between the fiber-optic strain and interferometric light intensity which is derived by using the photo-elastic theory and Mach-Zehnder interferometry. We emphasized how to increase effects of that the strain of fiber optic induce by the host structure with shorter bonded length of the fiber optics. The case of Mach-zehnder interferometric fiber sensor in measuring strain is explored. Using another bonded fiber optic will increase the interferometric period and accuracy to get better resolution than Mach-Zehnder interferometric fiber optic sensor. The result show that the resolution of shorter fiber optic bonded on the opposite sides of host structure is twice of Mach-Zehnder interferometric fiber optic sensor.
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LEE, CHAO-FENG, and 李兆豐. "The Shear Capacity Evaluation Of Cross Laminated Timber Using A Torsion Test." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/989nw2.
Full textAbstract:
碩士逢甲大學
土木工程學系
107
Cross Laminated Timber (CLT) is a popular new construction material in Europe and America. CLT has some advantages such as less carbon emission during production, renewable and can be pre-fabricated, and can be used in walls, roofs or ceilings. When CLT is subjected to out of plane loadings, the failure of the panel depends on its weakest rolling shear capacity. In order to get the data for architectural design, we have to do research and analysis about the rolling shear capacity of wood. The purpose of this research is to develop a simple and effective method to obtain the rolling shear capacity of CLT. A torsion machine is applied to simulate the performance of CLT subject to pure shear stresses. The calculated GJ (torsional rigidity) values from strain gages and digital image correlation (DIC) method are compared with the measured GJ values using the inclinometer sensors. The torsion test is performed until the specimen failed. After that, we use the measured critical torque to do finite element analysis for the shear capacity evaluation of CLT. Experimental results show that the shear modulus and shear capacity of the Cryptomeria Japonica are G_LT=0.77GPa,〖 G〗_LR=0.91GPa,〖 G〗_RT=0.08GPa,τ_cr^LR=13.805±2.327 MPa,and τ_cr^RT=2.083±0.15 MPa.
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Heck, Leanne Renee. "Evaluation of the torsion test for determining the shear strength of structural lumber." Thesis, 1997. http://hdl.handle.net/1957/33992.
Full textAbstract:
The torsion test was evaluated as a method for determining the shear
strength of full-size structural lumber. The evaluation involved an experimental
length study, an experimental depth study, and a finite element study.
The length study consisted of fifty nominal 2x4 specimens, ten specimens
for each length, and ten American Society for Testing and Materials (ASTM)
shear blocks. One 14 foot long board yielded one specimen for each length: (a)
21.0", (b) 28.5", (c) 32.0", (d) 35.5", (e) 39.0", and (f) an ASTM D143-94 shear
block. The statistical analysis revealed no evidence that the length affected the
shear strength.
The depth study consisted of fifty specimens, ten specimens for each
depth: (a) 2x4, (b) 2x6, (c) 2x8, (d) 2x10, and (e) 2x12. In addition, fifty ASTM
shear blocks, one block for each specimen, were tested. The statistical study did not reveal convincing evidence of a depth effect on shear strength, even
after accounting for specific gravity and shear span as covariates.
Failure modes for the torsion samples involved a longitudinal shear crack
at the mid-point of the longest side, which propagated toward the ends of the
specimen and through the cross section perpendicular to the growth rings.
The finite element model revealed that uniform shear stress occurs within
the shear span, which begins and ends a distance of approximately two times
the depth plus the grip distance away from each end of the member. In addition,
torsion theory verified that the experimental shear failure plane that occurs
within the shear span is parallel to the grain and the shear slippage is also
parallel to the grain, similar to the known shear failure in specimens subjected to
bending loads.
Based on the results of this study, the torsion test is the best practical
method to determine the pure shear strength of full-size structural lumber,
because the test yields 100% shear failures and the specimen is in a state of
pure shear stress.Graduation date: 1998
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Hou, Li-Shing, and 侯立信. "Test of Cosmic Spatial Isotropy for Polarized Electrons Using a Rotatable Torsion Balance." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/61334907882332175769.
Full textAbstract:
博士國立清華大學
物理學系
87
Abstract The quadrupole and higher order anisotropies in the cosmic microwave background radiation has been discovered by COBE [1] and many other experiments[2]. Here we ask the question: Are the fundamental laws of our Universe also anisotropic? This is a valid question since many people, at present, believe that the early Universe may have gone through phase transitions. If yes, may spin states sense these anisotropies? In this thesis we address to the question whether our laboratory is the same for different spin states of electron. In the classical context, the potential anisotropy could be related to Mach''s principle and depend on the matter and spin distribution of our Universe. In this aspect, it is in the long tradition of Hughes-Drever experiments[3]. In the modern context, the motion of the earth through the cosmic neutrino background, or certain kinds of vacuum states, produces a term of the form gσ‧v in the energy of an electron. Here g is a constant value, σ is the electron spin and v is the velocity of the earth through the cosmic neutrion background or certain kinds of vacuum states. To search for such a term or a term like gσ‧n where n is a particular direction in the Universe, Phillips[4] used a traditional fixed torsion balance carrying a transversely polarized magnet to search for a sinusoidal oscillation of the pendulum with a period of one sidereal day. Our laboratory[5] continued this effort and improved the sensitivity by a factor of 3. For last 4 years, we have been developing a rotatable torsion balance carrying a magnetically shielded transversely spin-polarized ferrimagnetic Dy_{6}Fe_{23} mass for the test of spatial anisotropy with a period of about 1 hour with the period shortened the data taking time and noise are much reduced. With earth''s rotation, the two senses (clockwise and counterclockwise) of torsion balance rotation is modulated differently. With our present data-taking and noise substraction algorithm, this double modulation scheme (torsion-balance rotation plus earth rotation) can detect the anisotropic energy splitting of spin states of electrons in the axial direction of earth rotation also. Analysis of accumulated results of our present experiments gives an improved limit of energy splitting of 5.7 ×10^{-20} eV for transverse direction, a 50-fold improvement compared to fixed torsion balnce, and the splitting of spin states of an electron in the plane normal to the earth rotation axis and a new limit of 9.7× 10^{-19} eV for axial direction.
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Yang, Zhuo. "Torsional Shear Strength and Size Effect in Structural Composite Lumber." 2012. https://scholarworks.umass.edu/theses/964.
Full textAbstract:
The natural variation of strength properties within brittle materials leads to size effect, a well-known phenomenon whereby the mean strength of a material is observed to decrease as the stressed volume increases. An important implication of size effect is that size adjustment parameters must be incorporated into multi-axial constitutive and failure models used in numerical simulations to predict material response to loading. This experimental study seeks to verify and quantify the presence of depth effect under shear failure in the orthotropic principal material directions of parallel strand lumber (PSL) and laminated veneer lumber (LVL). Torsion tests have been performed on specimens of fixed length and differing cross section to get a pure shear failure, by using a Universal Test Machine. The experimental results indicate that there is no depth effect for LVL from torsional shear stresses. PSL testing was limited to one size, and depth effect was not evaluated. A finite element model was built to simulate the torsional test for the 44x140mm LVL specimen. Comparing the experimental test results and the simulation results, the model provided an accurate prediction of the torsional test for Structural Composite Lumber.