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Moore, Michael Wayne. "Measuring the second harmonic amplitude of an oscillating torsion pendulum to detect small forces /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/9666.
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Hanekom, Alwyn Nicolaas. "A torque ripple analysis on reluctance synchronous machines." Thesis, Cape Peninsula University of Technology, 2006. http://hdl.handle.net/20.500.11838/1145.
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Thesis MTech(Electrical Engineering))--Cape Peninsula University of Technology, 2006Reluctance Synchronous Machines (RSM) have, due to their rotor geometry, an inherently high torque ripple. This torque ripple is defined as the deviation of the minimum and maximum torque from the average value. It is unwanted as it indicates uneven pull on the rotor causing deformation of it and hence different air-gaps along the rotor circumference as well as acoustic noise. In applications such as power steering, robotics and radar positioning systems where high precision movement is vital, oscillating torque will lead to the malfunction of these devices and therefore suppressed the use and development of RSMs. Unlike the Induction machine (IM), the RSM has no copper losses in the rotor, which reduces the operating temperature significantly. With the development of electronic drives the quality of the output torque could be improved by means of accurate current- and flux space phasor control methods with much success and made the RSM a possible replacement for the IM. However, reducing torque ripple by means of purely geometrical changes is still a challenge to the machine designer. This thesis will focus on the reduction of torque ripple while leaving the average torque relatively unchanged by changing the rotor geometry. The rotor changes will take place by means of flux barriers and cut-outs while the stator has either semi-closed slots or magnetic wedges. In this work rotor structures with equal harmonic magnitudes but their angles 1800 apart. will be combined to form one machine and identify how torque harmonics respond. The change in average torque and power factor will be evaluated with all geometrical changes made to these machines throughout this work.
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Hussain, Hyder. "Torsion fatigue system for mechanical characterization of materials." Ohio : Ohio University, 2000. http://www.ohiolink.edu/etd/view.cgi?ohiou1172002877.
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Taylor, Brian. "The design of a lathe attachment for grinding non-circular cross- section shafts suitable for torque transmission." Thesis, University of Newcastle Upon Tyne, 1987. http://hdl.handle.net/10443/769.
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The principle concern of this work is the design of a lathe attachment for grinding non-circular 'polygonal' shaped workpieces suitable for use as torque transmitting machine elements. In the course of the work substantial attention is also given to the general theory and development of computer aided error analysis procedures for planar linkage mechanisms. A further smaller part of the work investigates the torsion of polygonal shafts. The non-circular shapes considered here may be loosely defined as polygonal profiles. Their application is in torque transmitting couplings for which they represent an alternative to keyed and splined couplings, although, in comparison to keys and splines, their application has been limited, mainly due to the specialised nature of their manufacture. The main objective of this work is to investigate suitable profiles and the means for their production using an attachment which can be mounted on a conventional machine tool, such as a lathe or grinding machine. The work progresses from initial consideration of shapes produced by various geometric generating methods and conception of an 'ideal' profile generating linkage mechanism through to detailed design of a precision, polygonal profile grinding, lathe attachment, and final assessment of its feasibility based on a profile precision criterion. In order to assess the precision of the attachment, computer-aided procedures are developed, after consideration of existing error analysis methods and their limitations for use in this case. These consider the various effects of tolerances, clearances and deflections upon mechanism output. As a coincidental investigation, the mechanical behaviour and strength of polygonal shaft-hub connections is reported. In particular, the torsion of a polygonal bar is theoretically analysed, using a stress function method, to determine maximum shear stresses.
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Fox, Gordon R. "Joining of Shape-Memory NiTi Torque Tubes to Structural Materials." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1331157030.
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Patel, Vinit A. "Biomechanical Evaluation Of Locked and Non-locked Constructs Under Axial And Torsion Loading." Wright State University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=wright1228776190.
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Malchárek, Miroslav. "Měření torzní tuhosti vozidla s využitím 3D scanneru." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231528.
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This thesis deals with the measurement of the torsional stiffness of the frame using Tritop system. There is described development of the frame due to the complexity of torsional stiffness. Further there is outlined a brief overview of the types of measurement and the effect of torsional stiffness on the driving behavior of the vehicle. The aim of the work is to develop a method for measuring torsional stiffness of the vehicle Formula Student and from the results of repeated measurements to assess the accuracy and repeatability of measurements.
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Diemer, Franck. "Utilisation en rotation continue des instruments de préparation canalaire en nickel-titane : évaluation des contraintes." Toulouse 3, 2006. http://www.theses.fr/2006TOU30283.
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The first part of this work exposes a bibliographical synthesis about properties of memory-shape alloys and the characteristics of the small electric motors. The second part is experimental. We compared the resistance of instruments characterized by different profiles. We measured the differences induced by profile and pitch length on stresses generated by endodontic instrument used in continuous rotation. Then we try to evaluate the conditions of disengaging of different electric motors and contra-angles. We finally use, with a torque control motor, a file with the tip maintained in a screw-locking device. These studies show the role of instrument profile. Regarding the safe use of files, it appears more effective to work on the instruments design than to use controlled torque motor which are far away from manufacturers’ specifications. The use of badly calibrated disengaging or coupled to reversed rotation is completely ineffective.
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Ehlers, Hendrik Petrus. "Lag screw effect on the biomechanical torsion stability in the I.S.I monocortical mandible angle system." Diss., University of Pretoria, 2010. http://hdl.handle.net/2263/30368.
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In a recent in vitro biomechanical stability study by F.J. Jacobs, a unique, patented inclined screw insertion (I.S.I.) mandibular angle, intra-oral trauma-plate was evaluated for torsion and compression stability and compared to conventional plating of simulated angle fractures in polyurethane mandibular replicas. This in vitro comparative pilot study is an extension of the above-mentioned study. Similar I.S.I. mini-plates with 45º inclined screw holes in quadrant 3 (Fig 1), were used but in the one sample 13mm-long lag screws were used to transect the fracture lines where in the other group non-lagging screws of similar length were used to fixate simulated mandibular angle fractures in polyurethane mandible replicas. A uniquely designed and manufactured jig, incorporated in a Zwick machine, was utilized to apply torsion forces within clinical relevant load values. The load-displacement values for torsion forces was determined and compared for the two groups. It was established that 5 lag screws significantly improved the torsion stability of the lag-plate group to that of the non-lag group. During the stability testing, two factors were identified, which had a critical influence on the compression generated by the lag screw between the fracture fragments. An adequate amount of bone must be maintained between the first screw hole, directly distal to the fracture line, and the fracture line. All screws must be inserted in the correct sequence in order to insure sufficient compression between the fracture fragments as a result of the lag-effect. AFRIKAANS : In `n onlangse in vitro studie deur F.J. Jacobs, is `n gepatenteerde, unieke geanguleerde miniplate, waarvan die skroefgate geanguleer is, die sg. Inklineerde Skroef Inplasing (I.S.I.) kaak-hoek, intra-orale traumaplaat geevalueer vir torsie en kompressie stabiliteit en vergelyk met konvensionele plate op gesimuleerde kaakhoek frakture in poli-uretaan mandibular replikas. In hierdie in vitro loodstudie, is I.S.I. miniplate met skroefgate wat teen 45º geanguleer is, gebruik in kombinasie met `n enkele 13mm lange grypskroef (“lag screw”) om gesimuleerde kaakhoek frakture in poli-uretaan mandibula replikas te fikseer. Deur gebruik te maak van `n spesiaal ontwerpte en vervaardigde monterings-apparaat wat binne in `n Zwick masjien geïnkorporeer word, is die I.S.I gefikseerde replikas onderwerp aan torsie kragte, binne klinies relevante ladingswaardes. Die verplasings en ladingswaardes is geregistreer en vergelyk met identiese I.S.I miniplate sonder `n grypskroef. Die loodstudie resultate het getoon dat die frakture wat gefikseerd is met die I.S.I. miniplaat-grypskroef kombinasie betekenisvol beter stabiliteit toon as die frakture wat met slegs die miniplaat, sonder `n grypskroef, gefikseerd is vir klinies relevante ladingsen verplasingswaardes. Tydens biomeganiese toetsing van die mandibula replikas, is twee faktore wat `n kardinale rol speel in die stabiliteit wat verkry word deur `n miniplaat grypskroef kombinasie te gebruik, geïdentifiseer. Voldoende hoeveelheid been tussen die eerste skroefgat, direk distaal van die fraktuurlyn, en die fraktuurlyn asook die korrekte volgorde waarin die skroewe geplaas word, moet gehandhaaf word om maksimale kompressie van die fragmente deur die grypskroef te verseker. Deur `n I.S.I miniplaat, met geanguleerde skroefgate van 45º, te kombineer met `n grypskroef, kan die stabiliteit van die gefikseerde mandibulere kaakhoek betekenisvol verbeter word en verleen dit meer stabiliteit wanneer vergelyk word met frakture gereduseer met `n I.S.I miniplaat sonder grypskroef plasing.Dissertation (MSc)--University of Pretoria, 2010.
Maxillo-Facial and Oral Surgery
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Liu, Bingxiao. "Laplacien hypoelliptique et formule des traces tordue." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS165/document.
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Dans cette thèse, on donne une formule géométrique explicite pour les intégrales orbitales semisimples tordues du noyau de la chaleur sur un espace symétrique, en utilisant la méthode du laplacien hypoelliptique développée par Bismut. On montre que nos résultats sont compatibles avec les résultats classiques de la théorie de l'indice équivariant local sur les espaces localement symétriques compacts. On utilise notre formule explicite pour évaluer le terme dominant dans l'asymptotique quand d -> + ∞ de la torsion analytique équivariante de Ray-Singer associée à une famille de fibrés vectoriels plats Fd sur un espace localement symétrique compact. On montre que le terme dominant peut être calculé à l'aide de W-invariants au sens de Bismut-Ma-ZhangIn this thesis, we give an explicit geometric formula for the twisted semisimple orbital integrals associated with the heat kernel on symmetric spaces. For that purpose, we use the method of the hypoelliptic Laplacian developed by Bismut. We show that our results are compatible with classical results in local equivariant index theory. We also use this formula to evaluate the leading term of the asymptotics as d -> + ∞ of the equivariant Ray-Singer analytic torsion associated with a sequence of flat vector bundles Fd on a compact locally symmetric space. We show that the leading term can be evaluated in terms of the W-invariants constructed by Bismut-Ma-Zhang
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Kriegel, Franziska [Verfasser], and Jan [Akademischer Betreuer] Lipfert. "Torsional properties of DNA probed with magnetic (torque) tweezers / Franziska Kriegel ; Betreuer: Jan Lipfert." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2017. http://d-nb.info/114950983X/34.
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Martinez, Metzmeier César. "Two problems in arithmetic geometry. Explicit Manin-Mumford, and arithmetic Bernstein-Kusnirenko." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMC224/document.
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Dans la première partie de cette thèse, on présente des bornes supérieures fines pour le nombre de sous-variétés irréductibles de torsion maximales dans une sous-variété du tore complexe algébrique $(\mathbb{C}^{\times})^n$ et d'une variété abélienne. Dans les deux cas, on donne une borne explicite en termes du degré des polynômes définissants et la variété ambiante. De plus, la dépendance en le degré des polynômes est optimale. Dans le cas du tore complexe, on donne aussi une borne explicite en termes du degré torique de la sous-variété. En conséquence de ce dernier résultat, on démontre les conjectures de Ruppert, et Aliev et Smyth pour le nombre de points de torsion isolés dans une hypersurface. Ces conjectures bornent ce nombre en terme, respectivement, du multi-degré et du volume du polytope de Newton d'un polynôme définissant l'hypersurface.Dans la deuxième partie de cette thèse, on présente une borne supérieure pour la hauteur des zéros isolés, dans le tore, d'un système de polynômes de Laurent sur un corps adélique qui satisfait la formule du produit. Cette borne s'exprime en termes des intégrales mixtes des fonctions toit locales associées à la hauteur choisie et le système des polynômes de Laurent. On montre aussi que cette borne est presque optimale dans quelques familles d'exemples. Ce résultat est un analogue arithmétique du théorème de Bern\v{s}tein-Ku\v{s}nirenkoIn the first part of this thesis we present sharp bounds on the number of maximal torsion cosets in a subvariety of a complex algebraic torus $(\mathbb{C}^{\times})^n$ and of an Abelian variety. In both cases, we give an explicit bound in terms of the degree of the defining polynomials and the ambient variety. Moreover, the dependence on the degree of the polynomials is sharp. In the case of the complex torus, we also give an effective bound in terms of the toric degree of the subvariety. As a consequence of the latter result, we prove the conjectures of Ruppert, and Aliev and Smyth on the number of isolated torsion points of a hypersurface. These conjectures bound this number in terms of the multidegree and the volume of the Newton polytope of a polynomial defining the hypersurface, respectively.In the second part of the thesis, we present an upper bound for the height of isolated zeros, in the torus, of a system of Laurent polynomials over an adelic field satisfying the product formula. This upper bound is expressed in terms of the mixed integrals of the local roof functions associated to the chosen height function and to the system of Laurent polynomials. We also show that this bound is close to optimal in some families of examples. This result is an arithmetic analogue of the classical Bern\v{s}tein-Ku\v{s}nirenko theorem
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King, Jason. "Energy Release Management Through Manipulated Geometries of Surgical Devices." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1342730044.
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Arias, Pujol Antoni. "Improvements in direct torque control of induction motors." Doctoral thesis, Universitat Politècnica de Catalunya, 2001. http://hdl.handle.net/10803/6317.
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This thesis is mainly devoted to the investigation of speed control methods for three phase cage induction motors with particular emphasis being given to Direct Torque Control (DTC) improved techniques.Classical Direct Torque Control has inherent disadvantages such as: problems during starting resulting from the null states, the compulsory requirement of torque and flux estimators, and torque ripple. In the classical DTC induction motor drive a voltage vector is applied for the entire period, and this causes the stator current and electromagnetic torque exceeds its reference value early during the cycle, causing a high torque ripple. Switching cycles then follows this, in which the zero switching vectors are applied in order to reduce the electromagnetic torque to reference value. This thesis suggests a technique based on applying to the inverter the selected active states just enough time to achieve the torque and flux references values. The rest of the switching period a null state is selected which won't almost change both the torque and the flux. Therefore, a duty ratio has to be determined each switching time. By means of varying the duty ratio between its extreme values (0 up to 1) it is possible to apply any voltage to the motor. The optimum duty ratio per sampling period is a non-linear function of the electromagnetic torque error, the stator flux position and the working point, which is determined by the motor speed and the electromagnetic torque. It is obvious that it is extremely difficult to model such an expression since it is a different non-linear function per working point. Therefore, this thesis is focused on performing a fuzzy-logic-based duty-ratio controller, where the optimum duty ratio is determined every switching period. Additionally, this Fuzzy Controller is adaptive and may be applied to any induction motor.
A stator flux reference optimum controller is also designed, which not only helps to achieve a smaller torque ripple, but also reduces the reactive power consumption of the drive taken from the main supply. This is achieved by changing the stator flux reference value with reference being made to the correspondent torque reference value. Therefore, the stator flux reference value chosen is to be just of sufficient value to produce the desired torque
Simulated results are shown in order to compare the classical DTC and the Fuzzy Logic based DTC.
The control algorithms have been implemented on a PC/DSP based board that facilitates the use of parallelism in software design. A 1.5kW, three-phase induction motor drive has been designed and experimental data obtained from it in order to verify the results achieved by simulation.
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Swanson, William J. "Determination of diesel engine cylinder gas torques from speed fluctuations with a high-fidelity crankshaft torsional model." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA359161.
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Thesis (M.S. in Mechanical Engineering and Mechanical Engineer) Naval Postgraduate School, December 1998."December 1998." Thesis advisor(s): Knox T. Millsaps, Jr. Includes bibliographical references (p. 105-107). Also available online.
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Farshidianfar, A. "Optimisation of torsional vibrations in driveline systems : an investigation into the sensitivity of a driveline system when subjected to shock torque and optimisation of high and low frequency vibration." Thesis, University of Bradford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.632856.
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Volek, Matěj. "Implementace zátěžného stavu “Creeping” do multi-body simulace." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-382566.
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Tato diplomová práce je zaměřena na implementaci procesu simulace zatěžovacího zatížení do stávajícího rozhraní používaného pro multi-body simulace hnacího vozidla. „Creeping“ bylo definováno jako řízení vozidla bez nárazu na plynový pedál v nízkých převodech. Bylo rozhodnuto simulovat tento stav zavedením sil Jízdních odporů – Aerodynamická odporová síla Fa, síla Valivého odporu Fr a horizontální část Gravitační síly Fgx. Tyto síly byly modelovány v softwaru SimulationX a byl definován model pro zatížení „Creeping“ – ten byl založen na změně stoupání kopce, což dalo výsledky potřebné pro analýzu chování při stavu „Creeping“. Poté byly vytvořeny soubory v softwaru Matlab potřebné pro běh a následné zpracování simulace, které analyzují výsledky v závislosti na čase nebo průměrném točivém momentu motoru. Potom byla správnost procesu kontrolována ve srovnání s experimentálními daty. Toto srovnání ukázalo, že proces pracuje bez velkých problémů; výsledky vykazovaly podobný trend, byly ale ovlivněny nedostatkem vstupních dat z experimentu.
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López, Neumann Daniel. "Kuperberg invariants for sutured 3-manifolds." Thesis, Université de Paris (2019-....), 2020. http://www.theses.fr/2020UNIP7036.
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Dans cette thèse, on étudie les invariants quantiques des 3-variétés de Kuperberg, qui sont basées sur les algèbres de Hopf. On montre que, pour les super-algèbres de Hopf involutives, les invariants de Kuperberg s’étendent à la classe, plus générale, des 3-variétés suturées balancées et en particulier aux compléments d’entrelacs. Pour accomplir ceci, on relève plusieurs aspects de la théorie des torsions de Reidemeister au monde des invariants quantiques, tels que la procédure pour tordre des invariants, le calcul de Fox et les structures Spin^c, et on clarifie les aspects de la théorie des algèbres de Hopf auxquels ils correspondent. Quand notre construction est spécialisée au cas d’une algèbre extérieure, on montre qu’elle calcule la torsion de Reidemeister tordue des 3-variétés suturéesIn this thesis, we study Kuperberg's Hopf algebra approach to quantum invariants of closed 3-manifolds. We show that, for involutive Hopf superalgebras, Kuperberg invariants extend to the more general class of balanced sutured 3-manifolds, and in particular, to link complements. To achieve this, we bring many aspects of Reidemeister torsion theory into the realm of quantum invar-iants, such as twisting, Fox calculus and Spin^c structures and we make clear to which aspects of Hopf algebra theory these correspond. When our construction is specialized to an exterior algebra, we show that it recovers the twisted Reidemeister torsion of sutured 3-manifolds
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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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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.
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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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Benali, Khairidine. "Commande d'un système robotisé de type torse humanoïde pour le transport de colis de taille variable." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMLH22.
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Dans les entrepôts logistiques, les moyens robotiques sont de plus en plus fréquemment utilisés pour réduire les temps non productifs, déplacer des charges lourdes, limiter les risques d'erreurs pendant les opérations de préparation de commandes (picking, de/palettisation,...), faire des inventaires (drones,...) et améliorer les conditions de travail des opérateurs humains. Bien que l'homme reste incontournable pour les tâches de préparation de commande à cause de son adresse et de son aptitude à s'adapter à des tâches toujours différentes, l'augmentation de la productivité est souvent synonyme d'augmentation de la pénibilité au travail (troubles musculo-squelettiques,...). Les travaux de recherche présentés dans cette thèse sont une contribution à la robotisation des opérations de dé/palettisation pour des colis de taille variable qui exigent une grande polyvalence du système de préhension. La solution innovante que nous proposons consiste à utiliser un torse humanoïde équipé de deux bras manipulateurs munis de préhenseurs adaptés à la saisie d'objets de taille et de masse différentes. La principale contribution porte sur la conception d'une loi de commande hybride Force/Position-Position avec commutations, estimation du glissement de l'objet, prise en compte de la compliance et correction de la force de serrage pendant la manipulation. Cette solution suppose d'assurer la collaboration entre les deux bras manipulateurs et de s'adapter à l'environnement matériel et humain (cobotique)In logistics warehouses, automation in the sense of robotization is frequently being employed to cut down production times by efficiently managing the processes of picking heavy loads, place, pack and palletize, while reducing the risks and errors to improve the working conditions of human operators along the way. The flexibility of human is fundamental for order preparation owing to adaptive skills for task variation, but at the same time increasing productivity is complemented with fatigue (musculoskeletal disorders). In this context the research presented in this thesis is a contribution in the robotization of palletization operations requiring exceptional versatility of manipulation and gripping. We have proposed an innovative solution of utilizing a humanoid torso equipped with two manipulator arms with adaptive grippers to grasp and hold the objects of variable size and mass. The main contribution of research is the development of a hybrid Force / Position-Position control law with commutation and estimation of the object surface slip, while taking into account the compliance and correction of the clamping force during handling. The execution of the control involves the collaboration of the two arms for coordinated manipulation and adaptation to the material and the human environment (cobotics)
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Poloprudský, Jakub. "Struktura a mechanické vlastnosti materiálů na bázi hořčíku zpracovaných metodou HPT." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-400834.
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This thesis is focused on processing of pure magnesium by high pressure torsion method (HPT). This process belongs to the group of intensive plastic deformation methods (SPD). SPD methods are in the centre of scientific interest for several decades. Theoretical part of this thesis puts an effort to summarize basic knowledge and principles of SPD methods with extra focus on method HPT. As theoretical part continues magnesium as technical material is presented. Influence of SPD on use and properties of pure magnesium is then presented. This trend is further developed in effort to describe the effect of individual HPT process variables on the properties of pure magnesium and its alloys. Focus of practical part of this thesis is in influence of number of revolutions. Samples were processed at 1/8, 1/4, 1/2, 1, 4 and 8 turns at room temperature. Speed of process was 1rpm and applied pressure was 6 GPa. The structure of commercially pure magnesium prepared by casting and moulding were observed with focus on differences caused by input material. The structure was observed by both light microscopy and back scattered electron diffraction (EBSD), focusing on structure development, grain size and grain orientation. Compared to other works on similar topic, the emphasis here is on observing the microhardness on the vertical edge of the sample. The hardness shows a steep increase right after 1/8 of a turn. With increasing number of turns gradual homogenization of microhardness is presented accompanied by slight decrease in microhardness. No trend in microhardness relative to the distance from anvil has occurred. Structure observed with EBSD shows a bimodal character with larger grains oriented in the same direction. The three-point bending test didn’t end up as expected, and the approach to evaluation of magnesium-based HPT needs to be re-evaluated for future work. A three-point bending test was designed for the initial assessment of the basic mechanical properties of the material.
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Tayba, Ahmad. "Amélioration de la partie supérieure du robot HYDROïD pour les tâches bi-manuelles et la manipulation." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLV102/document.
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Ma thèse vise à contribuer au développement et l’amélioration de la cinématique de la partie supérieure du robot HYDROïD pour des tâches bi-manuelles, tout en basant sur une étude biomécanique de cette partie chez l’être humain.Pour atteindre notre objectif majeur, ce travail adopte dans un premier temps une nouvelle structure hybride de 4 degrés de liberté (ddl) pour le torse du robot, distribués en 3 ddl au niveau lombaire et un ddl au niveau thoracique. Cette structure était identifiée après une analyse de l’espace de travail d’un modèle multi-corps simulant la colonne vertébrale d’un être humain, et une étude d’optimisation de ce modèle permettant la synthèse de la structure envisagée.Dans un second temps, une amélioration de la cinématique du bras du robot a été mise en place, en introduisant la notion de l’épaule complexe au présente structure. Le choix de ce nouveau degré de liberté était le fruit d’une approche systématique pour augmenter l’anthropomorphisme géométrie du bras souhaité vers un bras humain de la même taille.Les 2 structures proposées ont passé par la suite par la phase de conception mécanique tout en respectant les contraintes géométriques et en se basant sur l’énergie hydraulique comme étant l’énergie d’ actionnement de ces systèmes. Enfin, le Modèle Géometrique Inverse (MGI) pour la solution générique du torse a été établi et son adaptation à notre cas particulier a été identifiée. Une solution optimisée pour ce mécanisme basée sur 2 différents critères a ensuite été donnéeMy thesis aims at contributing to the development and improvement of the upper body of HYDROïD robot for bi-manual tasks, while basing on a bio-mechanical study of this part of the human being. To reach our major goal, this work adopts, at first, a novel hybrid structure of 4 degrees of freedom (DOF) for the trunk of the robot, distributed in three DOF at the lumbar level and one DOF at the thoracic level. This structure was identified after an analysis of the work-space of a multi-body model feigning the vertebral column of a human being, and an optimization study of that model allowing the synthesis of the envisaged structure. Secondly, an improvement of the kinematics of the robor arm was organized, by introducing the notion of the shoulder complex in the present structure. The choice of this new degree of freedom was the fruit of a systematic approach to increase the anthropomorphism geometry of the arm wished towards a humanitarian arm of the same size.The two proposed structures crossed afterward by the mechanical design phase while respecting all the geometrical constraints and by using the hydraulic energy as being the type of actuation of these systems. Finally, the Inverse Geometrical Model (IGM) for the generic solution of the trunk was established and its adaptation to our particular case was identified. An optimized solution for this mechanism based on 2 various criteria was then given
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Melendy, Robert F. "Noncontact measurement of shaft torsional displacements by optical means /." 1994. http://hdl.handle.net/1957/9457.
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DUAN, FU-YUAN, and 段富元. "The torsion sheet analysis and design torque calculation formula of a laptop hinge mechanism." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/cun4um.
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碩士國立臺北科技大學
製造科技研究所
107
The notebook pivot mechanism is a combination of several torsion plates, pivots, fixing plates, support frames and nuts. The main core of the pivotal structure is that the torsion piece and the pivot are interference fit, and the frictional force of the inner hole and the pivotal contact surface of the torsion piece is generated by the rotation. The main research direction of this thesis is that the axial hole interference formula combined with the torsion formula is the main axis. By using the torque test as the verification method, a set of torsion empirical formula system is finally established. In this study, for the analysis of torsion film, the SolidWorks 2017 Simulation system is used to analyze the displacement and the axis hole interference formula to input relevant parameters, and the error comparison is used to improve the reliability. Since the actual torsion piece opening is 60 degrees, it is necessary to analyze the displacement state of each opening angle by analysis and replace the pressure caused by the same displacement, and then multiply the pressure value of each angle with the pressure value without the opening angle. In order to use the formula, it can be converted into a torque or pressure value at the required angle. Torque sheets of different materials are used to match the pivots of the same material. By combining the change of the interference amount and the number of different torsion pieces, the torque test is performed to compare the measured data with the torsion empirical formula. Finally, a set of torsion empirical formula system is established. The system can be used to input the required design parameters to obtain the torque value as a reference, so as to achieve the effect of quickly selecting design parameters.
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Issembert, David. "Résistance à la fracture de boîtiers en céramique soumis à une contrainte de torque par le biais d'un fil en torsion, en acier ou en nickel-titane." Thèse, 2005. http://hdl.handle.net/1866/15789.
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Ehlers, Hendrik Petrus. "Lag screw effect on the biomechanical torsion stability in the I.S.L monocortical mandible angle system." Diss., 2009. http://hdl.handle.net/2263/30368.
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In a recent in vitro biomechanical stability study by F.J. Jacobs, a unique, patented inclined screw insertion (I.S.I.) mandibular angle, intra-oral trauma-plate was evaluated for torsion and compression stability and compared to conventional plating of simulated angle fractures in polyurethane mandibular replicas. This in vitro comparative pilot study is an extension of the above-mentioned study. Similar I.S.I. mini-plates with 45º inclined screw holes in quadrant 3 (Fig 1), were used but in the one sample 13mm-long lag screws were used to transect the fracture lines where in the other group non-lagging screws of similar length were used to fixate simulated mandibular angle fractures in polyurethane mandible replicas. A uniquely designed and manufactured jig, incorporated in a Zwick machine, was utilized to apply torsion forces within clinical relevant load values. The load-displacement values for torsion forces was determined and compared for the two groups. It was established that 5 lag screws significantly improved the torsion stability of the lag-plate group to that of the non-lag group. During the stability testing, two factors were identified, which had a critical influence on the compression generated by the lag screw between the fracture fragments. An adequate amount of bone must be maintained between the first screw hole, directly distal to the fracture line, and the fracture line. All screws must be inserted in the correct sequence in order to insure sufficient compression between the fracture fragments as a result of the lag-effect. AFRIKAANS : In `n onlangse in vitro studie deur F.J. Jacobs, is `n gepatenteerde, unieke geanguleerde miniplate, waarvan die skroefgate geanguleer is, die sg. Inklineerde Skroef Inplasing (I.S.I.) kaak-hoek, intra-orale traumaplaat geevalueer vir torsie en kompressie stabiliteit en vergelyk met konvensionele plate op gesimuleerde kaakhoek frakture in poli-uretaan mandibular replikas. In hierdie in vitro loodstudie, is I.S.I. miniplate met skroefgate wat teen 45º geanguleer is, gebruik in kombinasie met `n enkele 13mm lange grypskroef (“lag screw”) om gesimuleerde kaakhoek frakture in poli-uretaan mandibula replikas te fikseer. Deur gebruik te maak van `n spesiaal ontwerpte en vervaardigde monterings-apparaat wat binne in `n Zwick masjien geïnkorporeer word, is die I.S.I gefikseerde replikas onderwerp aan torsie kragte, binne klinies relevante ladingswaardes. Die verplasings en ladingswaardes is geregistreer en vergelyk met identiese I.S.I miniplate sonder `n grypskroef. Die loodstudie resultate het getoon dat die frakture wat gefikseerd is met die I.S.I. miniplaat-grypskroef kombinasie betekenisvol beter stabiliteit toon as die frakture wat met slegs die miniplaat, sonder `n grypskroef, gefikseerd is vir klinies relevante ladingsen verplasingswaardes. Tydens biomeganiese toetsing van die mandibula replikas, is twee faktore wat `n kardinale rol speel in die stabiliteit wat verkry word deur `n miniplaat grypskroef kombinasie te gebruik, geïdentifiseer. Voldoende hoeveelheid been tussen die eerste skroefgat, direk distaal van die fraktuurlyn, en die fraktuurlyn asook die korrekte volgorde waarin die skroewe geplaas word, moet gehandhaaf word om maksimale kompressie van die fragmente deur die grypskroef te verseker. Deur `n I.S.I miniplaat, met geanguleerde skroefgate van 45º, te kombineer met `n grypskroef, kan die stabiliteit van die gefikseerde mandibulere kaakhoek betekenisvol verbeter word en verleen dit meer stabiliteit wanneer vergelyk word met frakture gereduseer met `n I.S.I miniplaat sonder grypskroef plasing.Dissertation (MSc)--University of Pretoria, 2010.
Maxillo-Facial and Oral Surgery
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YANG, SHU FAN, and 楊書帆. "Torsion Experiment and Cracking Torques of Solid and Hollow Prestressed Concrete Beams." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/9em7b7.
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碩士國立暨南國際大學
土木工程學系
105
As a succeeding part of the previous researches of prestressed concrete (PC) beams, this study extended the torsional experiment by conducting test on one solid and four hollow PC beam specimens subjected to pure torsion. The test results of eleven PC beam specimens, which consist of the five specimens in this study and six other specimens from the previous researches, are compared with predicted values calculated using a rational formula for pre-cracking torque-twist responses for reinforced concrete (RC) members. This study uses the test apparatus and method of the previous researches. Each of the PC beam specimens consists of three parts, namely, the RC block at the fixed end, the middle longitudinal test beam, and the cruciform transverse beams at the twist end. The anchorage bearing plates and longitudinal prestressing duct were embedded in the concrete of each specimen. After the specimen had been cast and reached its concrete strength, the longitudinal prestressing forces were applied by tensioning the individual strands one by one. Eight quantities were experimentally determined for each specimen using continuous measurement and automatic data reading and recording: (1) torque, (2) twist angle, (3) thickness of shear flow zone, (4) strain of nonprestressing reinforcing steel bar, (5) diagonal compressive strain at the concrete surface, (6) diagonal tensile strain at the concrete surface, (7) longitudinal prestressing force, and (8) longitudinal elongation of test beam. Test results of the five specimens exhibited a high degree of linearity in the initial branches of the five experimental torque-twist curves, showing a high level of accuracy in the small-twist measurement. The comparison between the test results of the eleven PC beam specimens and the values calculated using the rational formula for RC members showed that the cracking-torque ratio increases with the increase of the prestress ratio . For the solid PC specimens, the cracking-torque ratio increases from 1.2 to 1.8 almost linearly when the prestress ratio increases from 0.09 to 0.16, and approaches asymptotically to the upper limit 1.8 when exceeds 0.16.
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CHEN, MENG-HUNG, and 陳孟弘. "Effect of Large Twist on the Critical End Torques of Torsion Buckling of Rods." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/85044723715052315171.
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碩士國立臺灣大學
機械工程學研究所
91
In this thesis we consider the effects of large twist on the critical end torques of torsion buckling of a rod with circular cross section. The conventional formulation of the critical end torques, summarized in Ziegler’s book, neglected the twist angle between cross sections. However, this assumption is questionable because the rod may undergo a twist angle in the order of 3.7 PI before it buckles, which is hardly small. We are interested in modifying the conventional prediction of the critical torques when this large twist angle is taken into account. Two methods are tried in deriving the critical torques. One is the energy method and the other is based on Love’s equilibrium equations of a rod under large bending and twist simultaneously. While the equilibrium equations formulated from the energy method predicts that the rod will never buckle, Love’s equations provides a reasonable modification of the conventional prediction by Ziegler. The approach based on Love’s equations is then adopted to study the five typical cases of torsion bucking with different boundary condition combinations.
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Tsai, Jong-ian, and 蔡忠諺. "Torsional Torques and Fatigue Life Expenditure for Large-Scale Steam Turbine-Generator Shafts and Blades Due to Power System Harmonics." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/61034261955865217022.
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博士國立中山大學
電機工程學系研究所
92
During the three decades, the torsional impact on turbine-generator sets due to power system disturbances has been extensively discussed in many research works. However, most of them are focused on the fatigue damage of turbine shafts due to large-signal disturbances. For example, network faults occur. Obviously, the torsional effect subject to small-signal disturbances has not received much attention. In fact, although the small disturbances would not immediately damage the turbine mechanism, the cumulative long-term damaging effects may not be negligible under certain circumstances. Many operating conditions in power systems may lead to small disturbances on blades; for examples, shedding loads, switching transmission line, resetting control system parameters, and harmonics etc. Nevertheless, others only cause short-term or transient non-resonant disturbances occasionally except the power system subharmonics which could results in electro-mechanical resonance. Therefore, two types of subharmonics in power systems are proposed so as to investigate the toque impact and long-term fatigue life expenditure in turbine shafts and blades. Firstly, from the steady-state disturbance viewpoint, the long-term cumulative fatigue estimation based on the three-year project of the GE Co. shows that there are potential damages for both the shafts and the blades of the nearby generators caused by the subharmonic excitations of the HVDC link. The fatigue life sensitivity works are also carried out to provide the recommendations for the safety operation. The optimal damper type and disposition scheme for depressing the resonant torque and prolonging the turbine lifetime is consequently motivated, which is based on participation factor of linear systems with the electromechanical analogy. The effectiveness of this scheme on suppressing vibration torque arising from network faults is also satisfying. In addition, the authors propose the new electromechanical supersynchronous resonance phenomenon for the turbine-generators near the inverter station owing to asymmetric line faults near the rectifier station. Secondly, the dramatic real and reactive power consumption during the melting period of an electrical arc furnace load. The voltage flicker pollution is mainly caused by the reactive power fluctuation while the stochastic subsynchronous oscillation in turbine mechanism is excited by the electromagnetic torque of the subsynchronous frequency which is induced by the real power fluctuation. Such a small stress imposed on the low-pressure long turbine blade combined with its evitable corrosive environment contributing to the corrosion fatigue effect. Although the voltage flicker severity at the point of common coupling is still within the limit, the blade may have been damaged from the long-term corrosion fatigue life expenditure estimation. In other words, the conventional voltage flicker limit established to make human-eye comfortable might not protect the blade from damaging risk. The long-term influence resulted from the electric arc furnace loads cannot always be neglected. It is necessary to take care of the blade material intensity and operating environment. If there is the potential of blade damage, one has to strengthen the output capacity at the power plant or separate the peak load durations among the steel plants to limit the over-fluctuation real power of the generator.