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DAMENTO, MICHAEL ANTHONY. "DETECTION OF MAGNETIZATION REVERSAL IN A NEODYMIUM-IRON-BORON MAGNET USING A HALL-EFFECT MICROPROBE." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183945.
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Magnetization processes in a sintered Nd-Fe-B permanent magnet (NEOMAX-35) were examined on a small scale using a Hall-effect microprobe with an active area 75 μm on a side. Probes were made by evaporating bismuth through a stencil mask onto glass slides. Experiments were performed by placing a probe onto the polished pole face of a Nd-Fe-B magnet and inserting the probe-magnet assembly into an electromagnet. Barkhausen steps, indicating rapid domain wall motion, were observed (superimposed upon the blank probe signal) in the demagnetization of a fully magnetized magnet. Magnetization traces for a thermally demagnetized Nd-Fe-B magnet did not exhibit measurable Barkhausen steps until a field of approximately 1.2 T was applied. The following observations were made for two thermally demagnetized samples which were cycled through minor hysteresis loops (maximum applied field of approximately 2 T): (1) virgin magnetization traces did not contain measurable Barkhausen steps, however all other forward and reverse magnetization traces did; (2) the initial reverse magnetization trace exhibited more and larger Barkhausen steps than subsequent traces; and (3) some Barkhausen steps were repeatable, that is, occurring at approximately the same field on each subsequent forward or reverse trace. Hall voltage signals were on the order of millivolts for probe currents of 10 mA.
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Lopez, Gomez Partida Fausto. "Design of a Permanent Magnet Synchronous Generator with Alnico Magnets." Thesis, Uppsala universitet, Elektricitetslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-395215.
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Following the trends to diminish the fossil fuel energy production new technologies known for their renewable sources have become a signficant option for helping combat climate change and handle the current oil prices. These new technologies base their power production on already established physical principles that convert mechanical power to electrical power. Generators are the fundamental piece of machinery for electricity production. Among the various types of generators that exist, permanent magnet synchronous generators (PMSGs) are commonly used for renewable electricity production. At present, the most used magnets for PMSGs are alloys of neodymium, iron, and boron which form a tetragonal crystalline structure known as Neodymium magnets (NdFeB). These types of magnets contain rare-earth materials, which makes them highly non-sustainable materials. Research to find new magnet compositions to substitute rare earth magnets or to reduce the weight and increase the efficiency of PMSGs is currently being studied. One option is to use Alnico magnets. This thesis project explores this option. With the help of a finite element analysis (FEA) software (COMSOL Multiphysics), three types of Alnico grades 5, 8 and 9 were implemented in the rotor of a spoke type generator to study the load limits of the rotor magnets, and together with this observe the demagnetization and impact that it has on the power production of the generator, in two different scenarios: 1) When the generator is connected to a nominal load under normal conditions and 2) when the generator is connected to a nominal load after a short circuit (SC). The simulations provided an insight into the load limitations that the generator has by each type of Alnico studied. Alnico 9 showed to be the best candidate magnet from the three magnets implemented with less demagnetization and higher electrical power output, followed by Alnico 8, which presented a good electrical power output at the nominal load scenario. Regardless of the higher demagnetization of Alnico 5, it proved to be a better candidate than Alnico 8 at the SC scenario.
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Torreblanca, Humberto. "Multitube helicon source with permanent magnets." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1563028441&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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CHO, HYOUNG JIN. "MICROMACHINED PERMANENT MAGNETS AND THEIR MEMS APPLICATIONS." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1014839747.
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Hilton, Geoffrey. "The analysis of magnetic drives using rare earth permanent magnets." Thesis, University of Sunderland, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368123.
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Pollard, Robert James. "The microstructure and magnetic properties of NdFeB based permanent magnets." Thesis, University of Salford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328260.
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Tituana, Luis Rodrigo. "IMPLEMENTATION OF A PLANAR MAGNETIC MANIPULATOR WITH ROTATABLE PERMANENT MAGNETS." OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2664.
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The development of new techniques for control of magnetic objects by external magnetic fields has been in constant improvement. These advancements range from the design and fabrication of magnetic nanoparticles to design and control of actuators that enable their manipulation. The ability to guide such magnetic objects at a distance without any direct mechanical contact is an attractive feature with great potential in medical applications. Magnetic fields are not distorted by their interaction with nonmagnetic materials, like those in the human body; and pose no harm to living tissues, which make them convenient tools for minimally invasive techniques and treatments. Moreover, several actuator configurations have been proposed to achieve the remote motion of a magnetic particle or magnetic fluids. Arrays of electromagnets have been widely utilized due to their lack of mechanical parts and flexibility to accurately and rapidly change their magnetic field by controlling the current through their coils. However, they are relatively weak for their size and electrical power, making them inefficient for medical applications which need large magnetic forces at relatively long distances. On the other hand, permanent magnets have a much higher strength-to-size ratio than electromagnets and allow for control from larger distances. The disadvantage is that their magnetic fields cannot be turned off and a mechanical actuator is needed to modify their position and orientation to change their field. In this work, a magnetic manipulator used as a testbed to manipulate a magnetic bead is designed. It consists of an array of six diametrically magnetized cylindrical permanent magnets evenly spaced around a petri dish, following the work in [11]. Servomotors are utilized to precisely adjust the direction of the magnets according to a control law developed by other researchers in the past. A monochromatic camera located above the petri dish provides the feedback on the position of the bead and a set of hall-effect sensors provides the location of the poles of the magnets. The dynamics of the system is modeled by a linearized set of state-space equations where the magnetic field is estimated with an analytical expression for the geometry of the magnets. The testbed has been designed with the CAD software SolidWorks and its structure has been completely 3D printed with polylactic acid (PLA) filament. The design is tested under different speeds of the servomotors and initial orientations of the magnets. Some recommendations are presented at the end for improvement and considerations for future designs.
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Borghi, Chiara Caterina <1986>. "Continuous-Flow Magnetic Separation with Permanent Magnets for Water Treatment." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6233/1/Borghi_ChiaraCaterina_tesi.pdf.
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More efficient water treatment technologies would decrease the water bodies’ pollution and the actual intake of water resource. The aim of this thesis is an in-depth analysis of the magnetic separation of pollutants from water by means of a continuous-flow magnetic filter subjected to a field gradient produced by permanent magnets. This technique has the potential to improve times and efficiencies of both urban wastewater treatment plants and drinking water treatment plants. It might also substitute industrial wastewater treatments. This technique combines a physico-chemical phase of adsorption and a magnetic phase of filtration, having the potential to bond magnetite with any conventional adsorbent powder. The removal of both Magnetic Activated Carbons (MACs) and zeolite-magnetite mix with the addition of a coagulant was investigated. Adsorption tests of different pollutants (surfactants, endocrine disruptors, Fe(III), Mn(II), Ca(II)) on these adsorbents were also performed achieving good results. The numerical results concerning the adsorbent removals well reproduced the experimental ones obtained from two different experimental setups. In real situations the treatable flow rates are up to 90 m3/h (2000 m3/d).
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Borghi, Chiara Caterina <1986>. "Continuous-Flow Magnetic Separation with Permanent Magnets for Water Treatment." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6233/.
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More efficient water treatment technologies would decrease the water bodies’ pollution and the actual intake of water resource. The aim of this thesis is an in-depth analysis of the magnetic separation of pollutants from water by means of a continuous-flow magnetic filter subjected to a field gradient produced by permanent magnets. This technique has the potential to improve times and efficiencies of both urban wastewater treatment plants and drinking water treatment plants. It might also substitute industrial wastewater treatments. This technique combines a physico-chemical phase of adsorption and a magnetic phase of filtration, having the potential to bond magnetite with any conventional adsorbent powder. The removal of both Magnetic Activated Carbons (MACs) and zeolite-magnetite mix with the addition of a coagulant was investigated. Adsorption tests of different pollutants (surfactants, endocrine disruptors, Fe(III), Mn(II), Ca(II)) on these adsorbents were also performed achieving good results. The numerical results concerning the adsorbent removals well reproduced the experimental ones obtained from two different experimental setups. In real situations the treatable flow rates are up to 90 m3/h (2000 m3/d).
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Malloy, Adam. "Thermal management of the permanent magnets in a totally enclosed axial flux permanent magnet synchronous machine." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/25094.
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Elevated magnet temperature in Axial Flux Permanent Magnet Synchronous Machines (AF PMSM) adversely affects torque production, material cost, and the risk of demagnetisation. These machines show promise in applications requiring high power density, however the factors which affect magnet temperature have rarely been investigated. This is therefore the focus of the thesis. A multiphysics numerical model was formulated which predicted the loss, flow, and temperature fields within an AF PMSM. A criterion for estimating the relative importance of the fluctuating component of a periodic heat source on the temperature response of a device was proposed and validated. In this work it was used to justify a steady state, rather than transient, thermal analysis. Thermometric and electrical measurements were taken from an instrumented AF PMSM to validate the numerical predictions. A novel magnet loss measurement technique was implemented; losses were determined by measuring the initial temperature rise rate of the magnets. This was achieved via a calibration relating temperature rise to voltage constant. It was found that 99% of the heat generated in the magnets was convected to the inner cavity of the machine, due to the inner cavity's recirculating flow structure this heat was dissipated to the casing and core. As a proportion of all heat entering the inner cavity 56-62% left to the casing while 28-41% left to the core. Magnet hot spots were found to be up to 13% greater than the mean temperature rise. Their location was influenced by the distribution of losses and the direction of shaft rotation. Temperature gradients within the inner cavity caused the magnet's trailing edge to incur a 10% greater temperature rise than the leading edge. As increasing temperature decreases the coercivity of magnet materials these findings are a crucial contribution to the understanding of devices where local demagnetisation is of concern.
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Thang. "Permanent magnets based on iron-platinum alloys." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2003. http://dare.uva.nl/document/69891.
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Matsumoto, Kenshi. "Crystal Structural Control of Nanomaterials toward High-Performance Permanent Magnets." Kyoto University, 2019. http://hdl.handle.net/2433/245309.
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De, Silvestri Federica. "Investigation of the magnetic levitation between HTS bulks and permanent magnets." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.
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Lo scopo di questa ricerca è lo studio della levitazione magnetica risultante dall'interazione fra bulk di superconduttori ad alta temperatura critica e magneti permanenti. E' stato realizzato un modello numerico 2D in Comsol che simula l'interazione fra i due componenti, per studiare la forza di levitazione ottenuta. Il modello è stato successivamente validato con i risultati sperimentali ottenuti nei laboratori del dipartimento di Ingegneria dell'Energia Elettrica dell'Università di Bologna, ottenendo un buon riscontro sia per quanto riguarda i valori della forza sia per quanto riguarda le distribuzioni di campo e di corrente.
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Anocibar, Héctor Rolando. "Histerisímetro de Entreferro Variável HEV : uma proposta alternativa para a caracterização de ímãs permanentes." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2007. http://hdl.handle.net/10183/117449.
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A determinação das principais propriedades magnéticas de um ímã permanente geralmente requer sistemas de medição sofisticados e custosos. Este trabalho analisa e propõe um sistema de caracterização de ímãs permanentes de Terras Raras à temperatura ambiente de baixo custo e de implementação mais simples e rápida. Ele consiste de um circuito magnético formado pelo ímã permanente sob caracterização, uma culatra de aço, um entreferro variável e uma sonda de efeito Hall com seu respectivo gaussímetro para a medição da intensidade do campo magnético no entreferro. Como introdução se apresenta o estado da arte da caracterização dos ímãs permanentes, conceitos básicos de magnetismo e em relação aos ímãs permanentes, sua história, os principais tipos, sua importância e suas aplicações principais. Os resultados teóricos e experimentais são comparados a resultados certificados, validando o método como proposto.<br>Determining the main magnetic properties of a permanent magnet usually requires sophisticated and expensive measurement setups. This work analyses and proposes a low-cost system to characterize Rare Earth permanent magnets at ambient temperature with easy and fast implementation. It consists of a magnetic circuit with the permanent magnet under test, appropriate pole pieces, a variable air gap and a Hall Effect probe with its respective Gaussmeter. As an introduction, it is presented the state of the art of permanent magnets characterization, basic concepts of magnetism and its history, the main types of permanent magnets, their importance and applications. The theoretical and experimental results are compared to certified ones, validating so the method as proposed.
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Amrani, Mustapha. "Development of small electrical machines utilising permanent magnets." Thesis, University of Manchester, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329764.
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Lorenz, Amanda Leigh. "Improvement of NdFeB permanent magnets via diffusion annealing." Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/10142.
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Mestrado em Ciência e Engenharia de Materiais<br>Os magnetos sinterizados de Nd-Fe-B, têm o maior produto de energia de todos os magnetos e têm vindo a substituir progressivamente os magnetos ferróicos em aplicações onde é necessária uma maior densidade de energia. São áreas como carros híbridos, acionamento de turbinas eólicas, bobines de motores, e também na miniaturização de dispositivos eletrónicos. Um parâmetro importante é a sua coercividade, e respetiva dependência na temperatura, que determina o intervalo de temperatura de aplicação. A fim de melhorar as temperaturas de funcionamento, elementos diversos, especialmente terras raras pesadas (HRE), tais como disprósio ou térbio, têm sido adicionadas como um meio de aumentar a coercividade, levando, no entanto, a uma diminuição da remanência. Embora as HREs sejam tradicionalmente incorporadas durante o processo de sinterização, foi demonstrado que a aplicação de uma camada superficial de Dy, seguida de recozimento pode exigir menos Dy, a fim de obter uma determinada coercividade. Este processo utiliza a difusão por fronteiras de grão (Grain Boundary Diffusion, GBD).
O objetivo deste trabalho foi reduzir a quantidade de Dy necessário para atingir um desejado aumento da coercividade em pequenos magnetos de Nd-Fe-B utilizando processos GBD e experimentação com adições de Cu. Os magnetos foram revestidos usando deposição física de vapor (PVD), sujeitos a tratamento térmico e, em seguida caracterizados utilizando técnicas de medição magnética, bem como microscopia electrónica de varrimento SEM. As medições magnéticas foram também usadas para avaliar o processo de difusão de Cu e Dy durante o recozimento. A coercividade aumentou com o tempo de recozimento, em que Dy é difundido no sistema, alcançando melhorias de cerca de 50% na coercividade. No entanto, a distância de difusão foi limitada a cerca de 100 μm a partir da superfície da amostra. Os aumentos relativos na coercitividade por unidade de Dy adicionado ao sistema usando GBD foram maiores do que com Dy incorporado durante a sinterização. A Inclusão de Cu não foi considerada benéfica para o sistema.<br>Sintered Nd-Fe-B rare earth (RE) magnets have the highest energy product of any magnets and have been progressively replacing ferrous magnets in applications where a high energy density is needed. This pertains to areas such as hybrid cars, direct-drive wind turbines, voice coil motors, as well as the miniaturization of electronic devices. An important parameter of these magnets is their coercivity, respectively the temperature dependence thereof, which determines the temperature range accessible to the magnets. In order to improve the working temperatures, various elements, most notably heavy rare earth (HRE) elements such as dysprosium or terbium, have been alloyed in order to increase the coercivity; however, a remanence decrease results. Although HREs are traditionally included during the sintering process, it has been shown that applying the Dy as a coating after sintering followed by annealing may require less Dy in order to reach a given coercivity. This process is called Grain Boundary Diffusion (GBD).
The aim of this work was to reduce the amount of Dy needed to attain a desired increase in coercivity in small Nd-Fe-B magnets by employing GBD processes and experimentation with Cu additions. Magnets were coated using physical vapor deposition (PVD) techniques, heat treated, and then assessed using magnetic measurement techniques as well as scanning electron microscopy (SEM). Magnetic measurements were also used to assess the diffusion process of Dy and Cu into the magnets during annealing. The coercivity increased as annealing time progressed and Dy interdiffused throughout the system, reaching improvements in coercivity of about 50%. However, the diffusion distance was limited to about 100 μm from the sample surface. For small Dy additions, the relative gains in coercivity per unit Dy added to the system using GBD were greater than magnets with Dy incorporated during sintering. Inclusions of Cu were not found to be beneficial to the system.
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Anocibar, Héctor Rolando. "Alternativa para caracterização de ímãs permanentes com destacada anisotropia magnetocristalina sem desmagnetização irreversível." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/34745.
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A determinação das principais propriedades magnéticas de um ímã permanente geralmente requer sistemas de medição sofisticados e custosos. Este trabalho analisa e propõe um sistema de caracterização de ímãs permanentes de Terras Raras e Cerâmicos à temperatura ambiente de baixo custo e de implementação mais simples. Para isso, o Histerisímetro de Entreferro Variável, HEV, é concebido e estudado. Ele consiste de um circuito magnético formado pelo ímã permanente sob caracterização, uma culatra de aço, um entreferro variável, bobinas de magnetização e desmagnetização de baixa potência, uma sonda de efeito Hall com seu respectivo gaussímetro, um fluxímetro com sua bobina exploradora, o circuito eletrônico de comando das bobinas de excitação e a interface a um sistema de instrumentação virtual. Para demonstrar os desenvolvimentos do trabalho são apresentados o estado da arte da caracterização dos ímãs permanentes, conceitos básicos de magnetismo em relação aos ímãs permanentes, instrumentação necessária para sua caracterização, a concepção e modelagem do HEV, os resultados dos testes realizados e uma abrangente análise de suas incertezas. Com isso é demonstrado que o Histerisímetro de Entreferro Variável é uma alternativa de caracterização de ímãs permanentes com desmagnetização linear com incertezas dentro do que é definido pela norma.<br>The determination of the main magnetic properties of permanent magnets usually requires sophisticated and expensive measuring systems. This work analyses and proposes a low-cost system for the characterization of Rare Earth and Ceramics permanent magnets at room temperature with simpler implementation. It comprehends a magnetic circuit with the permanent magnet under test, a steel yoke with appropriate pole pieces, a variable air gap, low power magnetization and demagnetization coils, a Hall Effect probe with its respective gaussmeter, a fluxmeter with its own search coil, a coil driver electronic circuit and a virtual instrumentation system (computer plus graphical interface software). To demonstrate the developments of the work, it is presented the state of the art of permanent magnets characterization, basic concepts of magnetism related to permanent magnets, the instrumentation required for its characterization, the HEV design and modeling, the results of the tests and a comprehensive analysis of related uncertainties. Thus, it is shown that the Variable Gap Hysteresimeter is an alternative characterization system for linear demagnetization permanent magnets with uncertainties within those defined by the standards.
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Gangla, Vineeta. "Analytical methods for electromechanical forces and torque computation in brushless permanent magnet machines." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-12052009-020038/.
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Chen, Hansheng. "Correlating the microstructure, magnetic domain structure, and magnetic properties of rare earth permanent magnets." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/18996.
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Rare earth permanent magnets have been broadly integrated into various applications, such as advanced electric motor technologies which partly relieve the current energy crisis worldwide by taking advantages of their extraordinary magnetic properties. Traditional approaches for increasing the intrinsic coercivity (Hci) of rare earth permanent magnets typically come at the expense of remanence, resulting in a reduction of maximum magnetic energy product [(BH)max]. Therefore, novel design and processing strategies are in urgent need to circumvent this trade-off in the advanced rare earth permanent magnets. It is well known that the Hci and (BH)max of rare earth permanent magnets can be improved via tuning their microstructure/microchemistry at the nanoscale. Furthermore, the understanding and controlling the magnetic reversal process is equivalently essential in developing high-performance rare earth permanent magnets, since the magnetic domain structure determines the magnetic properties intrinsically. It is therefore of utmost importance to understand the correlation among microstructure, magnetic domain structure, and magnetic properties of rare earth permanent magnets. The thesis consists of three major topics, which are (i) strip cast Nd-Fe-B flake; (ii) sintered Nd-Fe-B magnet, (iii) sintered Sm2Co17 type magnet. To fully understand the effects of microstructure/composition on magnetic domain structure and magnetic properties of these rare earth permanent magnets, we investigated the effects of different heat treatment approaches on magnetic structure and magnetic properties of the aforementioned rare earth permanent magnets by integrating multiple cutting-edge microscopic techniques, including scanning electron microscopy, energy dispersive x-ray spectroscopy, electron backscatter diffraction, focused ion beam, transmission electron microscopy, magnetic force microscopy and atom probe tomography, in conjunction with micromagnetic simulations.
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Dudáš, Juraj. "Návrh synchronního motoru s vnějším rotorem a s permanentními magnety." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2015. http://www.nusl.cz/ntk/nusl-221153.
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The diplomatic thesis will describe the principle functions of synchronous motors with permanent magnets, for therein analysis of PMSM and BLDC motors. We will make calculation of the required parameters from the power unit for glider Discus 2. We will create a design of BLDC and PMSM motor from specified parameters. Features of the proposed engines will be verified with the help of the programs FEMM, RMxprt, Maxwell. At the end of the work will make conclusion about the diplamatic project and diffrences between PMSM and BLDC motor.
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Bollero, Real Alberto. "Isotropic nanocrystalline (Nd,Pr)(Fe,Co)B permanent magnets." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2003. http://nbn-resolving.de/urn:nbn:de:swb:14-1069758225796-19366.
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Nanokristalline Permanentmagnete zeigen ungewöhnliche magnetische Eigenschaften aufgrund von Oberflächen- und Grenzflächeneffekten, die verschieden von denen massiver oder mikrokristalliner Materialien sind. Diese Arbeit zeigt Ergebnisse einer systematischen Untersuchung der Beziehung zwischen Mikrostruktur und magnetischen Eigenschaften von isotropen nanokristallinen (Nd,Pr)(Fe,Co)B-Permanentmagneten. Hochkoerzitive Magnete vom Typ (Nd,Pr)FeB wurden durch hochenergetisches Mahlen in der Kugelmühle oder Rascherstarrung hergestellt. Der Einfluss geringer Mengen von Zusätzen wie Dy und Zr und die Substitution von Nd durch Pr auf die magnetischen Eigenschaften wird dargestellt. Weiterhin wurde eine Einschätzung des Warmumformverhaltens dieser Materialien durchgeführt. Hochenergetisches Kugelmahlen einer Legierung mit der Anfangszusammensetzung Pr9Nd3Dy1Fe72Co8B6.9Zr0.1 führte, nach Glühbehandlung, zu fast einphasigem Magnetpulver mit einem maximalen Energieprodukt von (BH)max~140 kJm-3. Das hochenergetische Kugelmahlen wurde zu einer sehr vielseitigen Technik zur Herstellung hochleistungsfähiger Nanokompositmagnete weiterentwickelt. Das Zulegieren unterschiedlicher Anteile von weichmagnetischem alpha-Fe ist damit sehr effektiv möglich. Der Zusatz von 25 Gew.-% alpha-Fe führt zu einem hohen (BH)max=178kJm-3. Dies wird auf eine sehr effektive Austauschkopplung zwischen den hart- und weichmagnetischen Phasen zurückgeführt. Die Natur der intergranularen Wechselwirkungen kann durch die Wohlfarth´sche Remanenzanalyse (?deltaJ-plot¡§) beschrieben werden. Im speziellen wurden deltaJ-Diagramme für verschiedene (i) alpha-Fe Gehalte, (ii) Korngrößen und (iii) Austauschlängen erstellt. Es konnte gezeigt werden, dass in den Nanokompositmagneten auf Pr-Basis keine Spinumorientierung auftritt. Abschließend zeigt die Arbeit die Möglichkeit der Nutzung einer mechanisch aktivierten Gas-Festkörper-Reaktion auf, mit der eine sehr feinkörnige Mikrostruktur erhalten wird. Die Untersuchungen wurden mit stöchiometrischen Nd2(Fe1-xCox)14B-Legierungen begonnen (x=0-1). Die Verbindungen wurden unter höheren Wasserstoffdrücken und Temperaturen gemahlen, wodurch sie zu NdH2+delta und krz-(Fe,Co) (x=0-0.75) oder kfz-Co (x=1) entmischt wurden. Die Korngrößen des rekombinierten Nd2(Co,Fe)14B-Materials liegen im Bereich von 40-50 nm<br>Nanocrystalline permanent magnets present unusual magnetic properties because of surface/interface effects different from those of bulk or microcrystalline materials. This work presents results of a systematic investigation of the relationship between microstructure and magnetic properties in isotropic nanocrystalline (Nd,Pr)(Fe,Co)B permanent magnets. Highly coercive (Nd,Pr)FeB-type magnets have been produced using high energy ball milling and melt-spinning. The influence of small amounts of additives, Dy and Zr, and the substitution of Nd by Pr on the microstructural and magnetic properties are shown. An assessment of the hot deformation behaviour has been carried out. Intensive milling of an alloy with starting composition Pr9Nd3Dy1Fe72Co8B6.9Zr0.1 yields, after annealing treatment, nearly single-phase magnet powders with a maximum energy product (BH)max?î140kJm-3. Co has a beneficial effect on the intrinsic magnetic properties but also on the microstructure, with a mean grain size of 20nm. Intensive milling is used to produce high-performance nanocomposite magnets by blending this latter alloy with different fractions of soft magnetic alfa-Fe. Addition of 25wt.% alfa-Fe leads to a high (BH)max=178 kJm-3 due to an effective exchange-coupling between the hard and the soft magnetic phases. The intergrain interactions between the crystallites of the nanocomposite structure are analysed. Demagnetisation recoil loops of the nanocomposite magnets show relatively open minor loops due to the exchange-spring mechanism. Information about the intergrain interactions during demagnetisation are obtained by plotting the deviation of the demagnetising remanence from the Wohlfarth-model (¡§deltaJ-plot¡¨). Exchange-coupling phenomena are studied by analysing the evolution of the corresponding deltaJ values when varying (i) the alfa-Fe content, (ii) the annealing temperature, i.e. the grain size and (iii) the measurement temperature. Low temperature measurements do not reveal any sign of spin reorientation for these Pr-based nanocomposite magnets. The work concludes showing the possibility of using a mechanically activated gas-solid reaction to obtain an effective grain refined microstructure starting from stoichiometric Nd2(Fe1-xCox)14B alloys (x=0-1). These compounds were milled under enhanced hydrogen pressure and temperature leading to their disproportionation into NdH2+delta and bcc-(Fe,Co) (x=0-0.75) or fcc-Co (x=1). Grain sizes of recombined Nd2(Fe,Co)14B materials were found to be 40-50nm
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Jubb, Gary Anthony. "Production and properties of neodymium-iron-boron permanent magnets." Thesis, University of Bradford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236470.
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Kottenstette, Nicholas E. (Nicholas Eugene). "Designing mechanisms with shape memory alloys and permanent magnets." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/43923.
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Anagnostopoulou, Evangelia. "A new route for rare-earth free permanent magnets : synthesis, structural and magnetic characterizations of dense assemblies of anisotropic nanoparticles." Thesis, Toulouse, INSA, 2016. http://www.theses.fr/2016ISAT0045/document.
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Cette thèse a eu pour objectif la préparation d’aimants nanostructurés sains terres rares à base d’un assemblage dense de nanobâtonnets de cobalt (Co NBs). Nous avons démontré la faisabilité d’un changement d’échelle du procédé polyol, avec des conditions d’agitation contrôlées, pour obtenir 5 g de NBs monodisperse. La modification de l’agent nucléant nous a permis de contrôler la taille et la forme des NBs conduisant à des valeurs élevées de champ coercitif. La réalisation d’aimants macroscopiques denses et robustes a été possible via la dispersion des bâtonnets dans du chloroforme et son évaporation sous champ magnétique à température ambiante. La valeur de (BH)max résultante a atteint dans le meilleur des cas une valeur de 165 kJ·m-3. Des résultats préliminaires sur la compaction d’assemblées de NBs montre que la fraction volumique magnétique peut être augmenté significativement (jusqu’à 30%). Cette étude prouve que l’approche « bottom-up» est très prometteuse pour obtenir des nouveaux matériaux magnétiques durs qui peuvent compléter le panorama des aimants permanents et combler le fossé entre les ferrites et les aimants NdFeB<br>The objective of this thesis is the preparation of nanostructured rare earth free permanent magnets based on dense assemblies of Co nanorods. We demonstrate the up-scaling of the polyol process for the synthesis of 5 g of monodispersed cylindrical Co NR with controlled cylindrical-like shape. Modification of the nucleating agent allows optimizing further the nanorods’ shape, leading to the highest coercivity values measured. Dense and robust macroscopic magnets were obtained via the rods’ alignment under a magnetic field presenting an ideal hysteresis loop. Additional structural and magnetic characterization was accomplished via small angle neutron scattering. A quantitative assessment of the (BH)max values showed a maximum of 165 kJ·m-3. Preliminary compaction experiments resulted in the fabrication of bulk magnets with increased magnetic volume fraction (up to 30%). We prove that the bottom-up approach is very promising to get new hard magnetic materials that can compete in the permanent magnet panorama and fill the gap between the ferrites and the NdFeB magnets
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FARIA, JUNIOR RUBENS N. de. "The Structures and properties of Pr/Nd-Fe-B-(Cu) permanent magnets and alloys." reponame:Repositório Institucional do IPEN, 1993. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10359.
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04760.pdf: 5699610 bytes, checksum: c39af246787ef81d5c48ece3cf888efc (MD5)<br>Thesis (Ph.D)<br>IPEN/T<br>University of Birmingham, Birmingham, England
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Stangel, Anders. "Magnetocrystalline Anisotropy in(FexNi1-x)2B Materials." Thesis, Uppsala universitet, Materialteori, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-301992.
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The magnetic properties of the (FexNi1-x)2B family of materials are explored using DFT calculations utilizing the FPLO and SPR-KKR code packages. It is found that a uniaxial magnetocrystalline anisotropy exists at around x = 0.8 with a magnetocrystalline anisotropy energy at around 0.3 MJ/m^3. A calculation of the lattice constant for these materials were attempted but failed due to the emergence of local minima and the calculations of magnetic properties were instead done using lattice parameters interpolated between known experimental values.
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Lwin, Mark. "The dynamic compaction of the metastable hard magnet powder Sm!b2!sFe!b17!sNx to form bulk magnets." Thesis, Queensland University of Technology, 1994.
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Edström, Alexander. "Theoretical Magnet Design : From the electronic structure of solid matter to new permanent magnets." Licentiate thesis, Uppsala universitet, Materialteori, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-231810.
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A good permanent magnet should possess a large saturation magnetisation (Ms), large mag- netocrystalline anisotropy energy (MAE) and a high Curie temperature (TC). A difficult but important challenge to overcome for a sustainable permanent magnet industry is to find novel magnetic materials, exhibiting a large MAE, without the use of scarcely available elements such as rare-earth metals. The purpose of this thesis is to apply computational methods, including density functional theory and Monte Carlo simulations, to assess the three above mentioned permanent magnet properties and in particular to discover new replacement materials with large MAE without the use of critical materials such as rare-earths. One of the key results is the theoretical prediction of a tetragonal phase of Fe1−xCox-C with large Ms and significantly increased MAE which is later also experimentally confirmed. Furthermore, other potential materials are surveyed and in particular the properties of a number of binary alloys in the L10 structure, FeNi, CoNi, MnAl and MnGa, are thoroughly investigated and shown to posses the desired properties under certain conditions.
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Manakshya, Nikhil. "Permanent magnet synchronous machine using ferrite vs rare earth magnets : how do they compare?" Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302658.
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Permanent magnet synchronous machines (PMSM are considered as viable options for automotive and traction applications. Rare earth magnets such as Neodymium Iron Boron (NdFeB is the most common choice in the PMSM for electric vehicles to achieve high power density machines. However, rare earth magnets are problematic from ethical and sustainability perspectives. From these perspectives, there are better magnet alternatives, such as ferrites. Ferrite magnets are well known for lower environmental impact, abundance and low cost. Due to a lower residual flux density of a ferrite magnet than that of a rare earth magnet, a larger amount of ferrite magnets are needed to achieve the same performance. This master thesis is aimed to compare a PMSM using NdFeB magnets with a PMSM using ferrite magnets in terms of different parameters such as torque production, power factor, drive cycle efficiency, losses mapping, cost, and environmental impact. The machines are designed based on the Volvo XC40 vehicle requirements. In order to compare both the machines, ferrite based machine with different types of rotor structures such as arc and spoke type configurations are designed in Ansys Maxwell and compared with the reference PMSM holding NdFeB magnet. The demagnetisation study was performed on the ferrite magnets at lower temperature in order to investigate the feasibility of the design. In order to reduce the risk of demagnetisation, a parametric analysis of the rotor structure has been conducted. Furthermore, the mechanical integrity was investigated at top speed.<br>Permanent magnet-synkronmaskiner (PMSM) betraktas som lönsamma alternativ för fordons och dragapplikationer. Sällsynta jordartsmagneter som Neodymiumbor (NdFeB) är det vanligaste valet i PMSM för elfordon att uppnå maskiner med hög effektdensitet. Sällsynta jordartsmagneter är emellertid problematiska ur etiska perspektiv och hållbarhetsperspektiv. Ur dessa perspektiv finns det bättre magnetalternativ, såsom ferriter. Ferrit är välkänt för lägre miljöpåverkan, överflöd och låga kostnader. På grund av låg restflödestäthet hos en ferritmagnet än en sällsynt jordartsmagnet behövs en större mängd ferritmagneter för att uppnå samma prestanda. Detta examensarbete syftar till att jämföra en PMSM med hjälp av NdFeB-magneter med en PMSM som använder ferritmagneter i termer av olika prestandaparametrar såsom vridmomentproduktion, effektfaktor, drivcykeleffektivitet, kartläggning av förluster, kostnad och miljöpåverkan. Maskinerna är designade baserat på Volvo XC40 fordons krav. För att jämföra båda maskinerna utformas ferritbaserad maskin med olika typer av rotorstruktur, såsom båg- och ekertypskonfiguration i Ansys Maxwell och jämförs med referensen PMSM som håller NdFeB-magneten. Demagnetiseringsstudien utfördes på ferritmagneterna vid lägre temperatur för att undersöka designens genomförbarhet. För att minska risken för demagnetisering har den parametriska analysen av rotorstrukturen genomförts. Dessutom undersöktes mekanisk integritet i toppfart.
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Judge, Andy. "Air Gap Elimination in Permanent Magnet Machines." Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-dissertations/123.
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In traditional Permanent Magnet Machines, such as electric motors and generators, power is transmitted by magnetic flux passing through an air gap, which has a very low magnetic permeability, limiting performance. However, reducing the air gap through traditional means carries risks in manufacturing, with tight tolerances and associated costs, and reliability, with thermal and dynamic effects requiring adequate clearance. Using a magnetically permeable, high dielectric strength material has the potential to improve magnetic performance, while at the same time offering performance advantages in heat transfer. Ferrofluids were studied as a method for improved permeability in the rotor / stator gap with a combined experimental and computational approach. Results show promise for the ferrofluid technique. An off-the-shelf motor system showed improved performance with ferrofluids vs. fluids of equivalent viscosity, and improved performance vs. an air gap at low RPM. New generator designs showed design dependent performance gains, although some potential for negative performance effects. A proof of concept generator was built and tested, with increased voltage vs. RPM predicted through virtual prototyping, and validated through experimentation, showing ~10% improvement on voltage vs. RPM at the <600 RPM range. More repeatable engineering tests demonstrated a ~30% increase in the voltage / RPM relationship for designs with an isolated stator chamber and a large stator - rotor gap. However, the effects were negative for a similar system with a small stator-rotor gap due to leakage flux effects. New contributions to the body of knowledge in this area include: • Application of the ferrofluid technique to axial flux designs. • Development of a virtual prototype, including variations in the fluid viscosity due to ferrohydrodynamic effects. • Consideration of negative effects of ferrofluid immersion, such as shear losses and increases in leakage flux. • Optimization of the design to eliminate increased viscous losses. The improved design has been designed, built, and tested, featuring isolation of the ferrofluid from the rotating region. This offers all of the performance gain of improved magnetic permeability, while minimizing the offsetting losses from increased shear effects.
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Conkey, Andrew P. "Vibration sensors utilizing fiber fabry-perot interferometers and permanent magnets." Thesis, [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1541.
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Sjökvist, Stefan. "Demagnetization Studies on Permanent Magnets : Comparing FEM Simulations with Experiments." Licentiate thesis, Uppsala universitet, Elektricitetslära, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-236301.
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In a world where money often is the main controlling factor, everything that can be tends to be more and more optimized. Regarding electrical machines, developers have always had the goal to make them better. The latest trend is to make machines as efficient as possible, which calls for accurate simulation models where different designs can be tested and evaluated. The finite element method is probably the most popular approach since it makes it possible to, in an easy and accurate way, get numerical solutions to a variety of physics problems with complex geometries and non-linear materials. This licentiate thesis includes two different projects in which finite element methods have had a central roll. In the first project, the goal was to develop a simulation model to be able to predict demagnetization of permanent magnets. It is of great importance to be able to predict if a permanent magnet will be demagnetized or not in a certain situation. In the worst case, the permanent magnets will be completely destroyed and the machine will be completely useless. However, it is more probable that the permanent magnets will not be completely destroyed and that the machine still will be functional but not as good as before. In a time where money is more important than ever, the utilization has to be as high as possible. In this study the demagnetization risk for different rotor geometries in a 12 kW direct driven permanent magnet synchronous generator was studied with a proprietary finite element method simulation model. The demagnetization study of the different rotor geometries and magnet grades showed that here is no risk for the permanent magnets in the rotor as it is designed today to be demagnetized. The project also included experimental verification of the simulation model. The simulation model was compared with experiments and the results showed good agreement. The second project treated the redesign of the rotor in the generator previously mentioned. The goal was to redesign the surface mounted NdFeB rotor to use a field concentrating design with ferrite permanent magnets instead. The motivation was that the price on NdFeB magnets has fluctuated a lot the last few years as well as to see if it was physically possible to fit a ferrite rotor in the same space as the NdFeB rotor. A new rotor design with ferrite permanent magnets was presented together with an electromagnetic and a mechanical design.
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Lixandru, A. "Recycling of Nd-Fe-B permanent magnets by hydrogen processes." Phd thesis, Technische Universität Darmstadt, 2018. https://tuprints.ulb.tu-darmstadt.de/7392/1/10.%20Dissertation%20Lixandru%20-%20lite-3.pdf.
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This thesis is based on the work carried out since January 2014 as a Ph.D. student in the Functional Materials department at Technische Universität Darmstadt. In the first part of my thesis, different waste streams of electrical and electronic equipment from an industrial recycling plant were analyzed in order to localize, identify and collect rare-earth permanent magnets of Nd-Fe-B type. This particular type of magnets were mainly found in hard disk drives from laptops and desktop computers, as well as in loudspeakers from compact products such as flat screen TVs, PC screens, and laptops. The study includes a systematic survey of the chemical composition of the Nd-Fe-B magnets found in the selected waste streams, which illustrates the evolution of the Nd-Fe-B alloys over the years. The study also provides an overview over the types of magnets that are integrated in different waste electric and electronic equipment. After localizing, identifying and recovering the rare-earth permanent magnets from waste electrical and electronic equipment, these magnets were processed together with other Nd-Fe-B scrap magnets from electric motors with a hydrogen based recycling process (hydrogen decrepitation (HD) and hydrogenation disproportionation desorption and recombination (HDDR) processes). The effects of the main HDDR processing parameters: hydrogen pressure, hydrogen desorption rate and temperatures on the magnetic properties of the recycled materials have been investigated systematically and are presented in the second section of the chapter 4. The optimum hydrogen pressures required for the complete disproportionation of the various magnet compositions were determined. It was found that a hydrogen heat treatment composed of two steps (780 °C and 840 °C) and a moderate desorption rate can be used for the magnets having a higher Dy and Co content to obtain high quality anisotropic HDDR powders. In addition to this section, it was performed a study where it was investigated the effects of increasing the Dy content on the processing parameters of the HDDR process. The variation of the magnetic properties for the magnets with different Dy contents processed at different hydrogen pressure, temperature and hydrogen desorption rate are presented in this study. The obtained recycled powders by HD and by HDDR were consolidated by either sintering, spark plasma sintering or bonding with epoxy resin. For the scrap magnets with a low content of Dy and Co, a better recovery of the magnetic properties (above 90%) was achieved compared with the magnets from electric motors (high Dy and Co) where the recovery rate is ~60%. For these magnets a “refreshing” of the recycled powders with 10% Nd90Al10 and Pr75Cu6.25Co18.75 was applied. Different post sintering treatments were applied for these recycled magnets in order to equally distribute the fresh added powder. All these treatments are presented in this study.
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Samin, Adib J. Jr. "An analysis of neutron radiation effects on NdFeB permanent magnets." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1405899609.
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Neto, Teofilo Mendes. "Estudo microestrutural e propriedades magnéticas em ímãs permanentes sinterizados a base de PrFeCoBNb com adições de elementos de ligas." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-28092011-094845/.
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Neste estudo, as propriedades magnéticas dos ímãs sinterizados, produzidos a partir de uma mistura de ligas Pr16Fe76B8 e Pr14FebalCo16B6Nb0,1Mx, onde M= Al, Cu, P, Si, Gd, Ga, Dy, Tb e x= 0,1, 0,3, 0,5 % at. em iguais proporções, foram correlacionadas com as características microestruturais através de microscopia eletrônica de varredura (MEV) e de transmissão (MET). Utilizou-se microscopia eletrônica de varredura (MEV) e processamento computacional das micrografias, na investigação das características associadas ao tamanho e formato dos grãos magnéticos (Φ). A correlação utilizada indicou que fatores de quadratura superiores estão associados a grãos mais arredondados e com distribuição de tamanho mais estreita. Considerando que a variação no tamanho de grão e os valores de coercividade não se mostraram conclusivas com MEV, utilizou-se o recurso da microscopia eletrônica de transmissão (MET), microanálise com EDS e padrão de difração eletrônica. A associação da coercividade com a microestrutura foi feita com base nas investigações das fases não magnéticas, ricas em praseodímio dos pontos triplos e nos contornos de grãos. Com o microscópio de transmissão de alta resolução (HRTEM), foi possível observar a presença de uma camada contínua e regular entre os grãos da fase magnética para o ímã com adição de Ga 0,25% at. A modificação da microestrutura no contorno de grão do ímã com adição de Ga pode ser indicada como responsável pelo aumento de 10% na coercividade (1100 mT) comparado com o ímã Pr15FebalCo8B7Nb0,05.<br>In this study the magnetic properties of sintered magnets, prepared with a mixture of Pr16Fe76B8 and Pr14FebalCo16B6Nb0.1Mx alloys, where M = Al, Cu, P, Si, Gd, Ga, Dy, Tb and x = 0.1, 0.3, 0.5 at.% in the same proportions, were correlated with the microstructural features by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM and computer processing of the micrographs were used in order to provide the characteristics associated with the size and shape of the magnetic grains (Φ phase). The correlation used shows that superior squareness factors are associated with rounder and narrower size distribution grains. Considering that the variation in the grain size and coercivity values were not conclusive with SEM, it has been used TEM, micro analysis by EDS and electron diffraction pattern. The coercivity relation with the microstructure was based on investigations of non-magnetic phases, in triple points, and in the grain boundary. With a high resolution transmission microscope (HRTEM), it was possible to observe a regular and continuous layer between the grains of the magnetic phase for the magnet with 0.25 at.% of Ga. The presence of such boundary can be indicated as responsible for higher coercivity values of this magnet. Microstructure was modified in the grain boundary by Ga addition and can be indicated as responsible for coercivity value (1100 mT) 10% higher than Pr15FebalCo8B7Nb0.05 magnet.
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Harrison, Simon Andrew. "Characterisation of the mechanisms of magnetisation change in permanent magnet materials through the interpretation of hysteresis measurements." University of Western Australia. School of Physics, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0048.
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The mechanisms by which magnetisation changes occur in magnetic materials may be investigated by a variety of hysteresis measurements. During this study both alternating and rotational hysteresis measurements were used to characterise the mechanisms of magnetisation change in a number of permanent magnet materials. Studies of the time dependence of magnetisation, remanent magnetisations and the dependence of the reversible magnetisation on the irreversible magnetisation were undertaken. These studies revealed that in sintered rare-earth iron magnets the magnetisation change is predominately controlled by domain nucleation, with a lesser contribution from domain wall pinning within the boundary regions of the grains. Similar mechanisms control the magnetisation change in the larger grains of melt-quenched rare-earth iron magnets. In the single domain grains of the melt-quenched materials incoherent rotation mechanisms control the changes of magnetisation. Magnetisation change in MnAlC and sintered AlNiCo was found to be controlled by domain wall pinning within the interior of the grains of the materials. Two devices were constructed for the measurement of rotational hysteresis. The first measures the angular acceleration of a sample set spinning in a magnetic field, from which the rotational hysteresis loss may be determined. The second employs rotating search coils to make direct measurements of the component of magnetisation that contributes to rotational hysteresis loss during the rotation of a sample in a field. Both devices were found to produce data consistent with that in the literature and to be useful for the characterisation of rotational hysteresis in permanent magnet materials. A simple model was used to examine the dependence of rotational hysteresis loss on various material parameters. It was found that the value of the rotational hysteresis integral is dependent on interactions and to a lesser extent distributions in anisotropy. This is contrary to assumptions commonly made in the literature but consistent with published experimental data, which has been reinterpreted. Measurements of rotational hysteresis losses in the materials studied were found to be effected by geometric demagnetisation effects. A method by which such data may be corrected for these effects is proposed. Following correction and consideration of the interactions within the materials, the rotational hysteresis data was found to be consistent with the characterisations performed in linearly alternating fields.
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Riahi, Nayereh. "Design, Optimization, And Feedback Control Of A Planar Noncontact Magnetic Manipulator With Rotatable Permanent Magnets." OpenSIUC, 2021. https://opensiuc.lib.siu.edu/dissertations/1940.
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This dissertation addresses different aspects of employing permanent magnets in the structure of noncontact magnetic manipulators. These systems employ controllable arrays of magnets to generate proper magnetic fields within their operation region and steer magnetic objects remotely without mechanical contact. This noncontact feature makes magnetic manipulators of particular interest in medical applications. They allow physicians to drive magnetic objects in closed and hard-to-reach environments including the human body for non- or minimally invasive diagnostic and therapeutic applications. As a case study, a magnetic manipulator composed of six diametrically magnetized permanent magnet cylinders is proposed. Each magnet in this scheme is equipped with an independent servomotor that can rotate as required. Number and size of the magnets for this proposed magnetic manipulator are then studied and optimized. An analytical model is introduced and employed to describe behavior of diametrically magnetized permanent magnet cylinders that are used in the proposed magnetic manipulator. Accuracy of this model is experimentally verified via employing real data extracted from a 3-axis magnetic field mapper. Dynamics of a magnetic object motion under the influence of magnetic force and resisting force in the proposed system are presented through a nonlinear set of state-space equations. Unstable nature of magnetic manipulators indicated by the describing equations, dictates utilizing feedback control as an essential part in magnetic manipulators. Thus, linear feedback control and nonlinear technique of feedback linearization are explored in this dissertation to address the control problem of steering a magnetic object by means of the proposed permanent magnetic manipulator. Performance of the linear feedback controller is improved through optimizing the equilibrium point for linearization purpose. To implement feedback linearization, two different methods are used resulting in approximate feedback linearization and exact feedback linearization. For the latter, nonlinear algebraic equations of the system are numerically solved via homotopy continuation technique. To enhance efficiency of this technique, scalar homotopy is also developed and its results are compared to vector homotopy, which is the basic approach to implement homotopy. Furthermore, direction control is developed in an open-loop manner to provide 3-D planar control of a magnetic object by means of the proposed magnetic manipulator.
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Emura, Marilia. "Propriedades Magnéticas de Ímãs Aglomerados e Nanocristalinos." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/43/43133/tde-09102012-145903/.
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Imãs são corpos de materiais magnetizáveis utilizados para gerar um forte campo magnético em sua vizinhança. Essa característica faz com que sejam empregados em diversas aplicações na vida moderna, tais como motores para a indústria eletroeletrônica e automobilística, como elementos de fixação e em acoplamentos magnéticos na indústria mecânica. O mercado de ímãs permanentes movimenta atualmente cerca de US$ 5 bilhões por ano e está em plena expansão, sendo estimado um crescimento de 12% por ano até o final desta década de 90. Tal crescimento é atribuído aos \"novos materiais\" desenvolvidos a partir da década de 80 (ímãs de terras-raras) e aos novos mercados, que foram gerados pelos próprios \"novos materiais\" (Hart, 1996). Tratando-se de materiais tão ligados às facilidades da vida moderna, a pesquisa na área de imãs está intimamente ligada ao seu desenvolvimento tecnológico. Procura-se desenvolver imãs com as melhores propriedades magnéticas para as suas aplicações, investigando ao mesmo tempo os fenômenos que regem os mecanismos físicos de magnetização.<br>Permanent magnets composed of magnetic powders bonded with a polymer represent the fastest growing sector of the magnetic materials market since they are ideal for the fabrication of small motors. This work presents a magnetic and structural characterization of TIve eommereial bonded magnets, Reversible and irreversible components of the total magnetization as well as magnetic interactions in the five commereial magnets are also studied, the magnets are composed by ferrite and MQP-Q nanoerystelline powders and mixtures of these two powders with 80%, 60% and 40% ferrite. Magnelie interactions were analyzed by Henkel plots, gM plots and switching field distributions. In bonded magnets, since the magnetic particles are separated from each other by a binder, it is expected that interactions are mainly dipolar in Nature. There is a progressive change in the data as the fraction of MQP-Q powder is increased. The sample with 100% ferrite shows strong magnetizing interactions at low fields. Date for hybrid magnets present increasing demagnetizing interactions as the fermion of MQP-Q increases and for the 100% MQP-Q sample, the data indicate demagnetizing effects. Reversible and irreversible magnetization components were obtained by applying two methods commanly used in magnetic materials characterization, the DCD -IRM method and the reversible susceptibility method. For the 100% ferrite magnet, in which the reversible component is small, the methods lead lo similar results. The results for both methods diverge as the reversible component! Increases, which in this case occurs with the increase of the MQP-Q powder fraction. The divergence is attributed to the idealized conditions of non-inleracting particles assumed by the DCD-IRM method. Magnetic interactions and lotai magnetization components were also studied in a melt-spun nanocrystalline Nd9Fe85B5 sample. This composition is similar to that of the MQP-Q powder and the magnetic behavior of both the bonded magnetic and the nanocrystalline precursor could be compared. Micromagnetic simulations allowed the evaluation of exchange, anisotropy and magnetostatic interactions on the magnetization reversal of nanocryslalline romposlle systems. The Monte Carlo method was applied lo a linear array of 300 magnetic moments distributed in three grains, two magnetically hard with a soft grain between them.
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Fliegans, Jérôme. "Coercivity of NdFeB-based sintered permanent magnets : experimental and numerical approaches." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAY071.
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Les aimants permanents Nd-Fe-B sont actuellement les plus puissants du marché. Ils sont indispensables pour des applications telles que les moteurs des véhicules électriques ou les générateurs des éoliennes. Leurs propriétés exceptionnelles viennent des propriétés magnétiques intrinsèques de la phase Nd2Fe14B et de leur microstructure. Cependant, les machines électriques fonctionnent entre 120 et 180°C et les propriétés magnétiques extrinsèques telles que la coercitivité et la rémanence diminuent avec la température. Un moyen d’améliorer la coercitivité des aimants frittés Nd-Fe-B est la substitution du Nd par des terres rares lourdes comme le Dy, afin d’augmenter l’anisotropie magnétocristalline. Néanmoins, le Dy est un matériau critique et un objectif majeur de la recherche est actuellement de développer des aimants possédant d’excellentes propriétés magnétiques extrinsèques et contenant peu de Dy. Cela nécessite une meilleure compréhension du lien entre microstructure et coercitivité. Dans les aimants frittés Nd-Fe-B, un des points-clés est le contrôle de la taille de grain et de la répartition des phases secondaires aux joints de grains de façon à limiter la nucléation du retournement de l’aimantation et à garantir un bon découplage magnétique des grains. La première partie de la thèse est une étude comparative des caractérisations magnétiques en circuit ouvert et fermé réalisées sur des aimants frittés Nd-Fe-B. Les différences de coercitivité observées sont expliquées par les phénomènes de viscosité magnétique et d’effets de champ démagnétisant. La deuxième partie traite du procédé de diffusion aux joints de grains appliqué aux aimants frittés Nd-Fe-B et utilisant des alliages Dy-Co. Des caractérisations microstructurales ont été réalisées en complément de mesures magnétiques afin de déterminer les profils de diffusion et de coercitivité, et ainsi d’établir le lien entre les variations locales de composition chimique et le champ coercitif. De plus, des simulations micromagnétiques ont permis de décrire le retournement de l’aimantation à l’échelle nanométrique dans un modèle simplifié cœur-coquille. Enfin, la dernière partie de la thèse constitue une discussion sur la coercitivité des aimants diffusés au Dy-Co (à gradient de champ coercitif) à l’aide d’un modèle de diffusion et de simulations sur un modèle polycristallin<br>Nd-Fe-B permanent magnets are the most powerful among all commercially available magnets. They play a significant role in energy applications, such as motors of electric vehicles and generators of windmills. Their outstanding properties come from the excellent intrinsic magnetic properties of the Nd2Fe14B phase and from their microstructure. However, electrical machines operate at about 120-180°C and extrinsic magnetic properties such as coercivity and remanence decrease rapidly with temperature. One way of improving coercivity of Nd-Fe-B sintered magnets is to substitute Nd with a heavy rare earth such as Dy, so as to increase the magnetocrystalline anisotropy. However, Dy is a strategic element and a major objective of the research community is therefore to develop Nd-Fe-B magnets that possess excellent extrinsic magnetic properties with a reduced content of Dy. This requires a better understanding of the link between microstructure and coercivity. The key point is the control of the grain size and the distribution of secondary phases at grain boundaries to prevent magnetization reversal and magnetic coupling. The first part of this thesis concerns a comparison of open-circuit and closed-circuit magnetization measurements carried out on Nd-Fe-B sintered magnets. The observed differences in coercivity values are discussed in terms of magnetic viscosity and demagnetizing field effects. The second part deals with the grain boundary diffusion process performed on Nd-Fe-B sintered magnets using Dy-Co alloys. Microstructural observations and magnetic measurements have been carried out to characterize the diffusion and coercivity profiles and to establish the link between local variations in composition and coercivity. Moreover, micromagnetic simulations have been performed to describe magnetization reversal at the nanoscale in a simple core-shell model. The last part constitutes a discussion about coercivity in graded magnets via a diffusion model and further simulations on a polycrystalline model
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Chaaban, Farid B. "Computer aided analysis, modelling and experimental assessment of permanent magnet synchronous machines with rare earth magnets." Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293710.
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Liu, Zhejie. "Investigation of coupled thermo-electromagnetic problems in relation to applications of permanent magnets to electromagnetic devices." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239956.
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Corfield, Martin Richard. "Production of sintered permanent magnets based on (Nd/Pr)Fe-B alloys." Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410302.
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Zheng, Mei. "Novel stator wound field synchronous machines with permanent magnets on slot openings." Thesis, University of Sheffield, 2018. http://etheses.whiterose.ac.uk/19976/.
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Fazil, Sadia. "Simulation of stray radiation and demagnetization of permanent magnets in EXFEL undulators." Thesis, Stockholms universitet, Fysikum, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-193335.
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Patel, Anup. "Pulsed field magnetization of composite superconducting bulks for magnetic bearing applications." Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/256579.
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Permanent magnets are essential components for many devices such as motors, which currently account for 45 % of global electricity consumption, generators and also superconducting magnetic bearings used for applications such as flywheel energy storage. But even the most powerful rare-earth magnets are limited to a remanent field of 1.4 T, whereas superconducting materials such as YBCO in their bulk form have the extraordinary ability to trap magnetic fields an order of magnitude higher, whilst being very compact. This gives them the potential to increase efficiency and allow significant volume and weight reductions for rotating machines despite the need for cooling. A new design of superconducting magnetic bearing has been developed which uses magnetized bulks as the field source, eliminating permanent magnets. Finite element modelling shows that the bulk – bulk design can achieve much higher force densities than existing permanent magnet – bulk designs, giving it potential to be used as a compact magnetic bearing. A system was created to magnetize bulks using a pulsed magnetic field down to 10 K and then measure levitation force. In proving the concept of the proposed design, the highest levitation forces ever reported between two superconducting bulks were measured, including a levitation force of 500 N between a 1.7 T magnetized YBCO bulk and a coaxial $MgB_{2}$ bulk tube. The biggest factor limiting the use of magnetized bulks in applications is magnetizing them in the first place. Using a pulsed magnetic field is most practical but generates excessive heat dissipation leading to a loss of flux in conventional bulk superconductors, which are 100% superconductor. Although multi-pulse techniques help maximise the trapped field, the poor thermal properties of bulk (RE)BCO are a limiting factor. New composite superconducting structures are reported which can overcome these problems by using high thermal conductivity materials, the motivation for which came from finite element modelling of the critical state coupled with heat transfer. In particular, composite structures created by cutting and stacking 12 mm wide (RE)BCO superconducting tape are shown experimentally to have exceptional field trapping ability due to superior thermal and mechanical properties compared to existing bulks. Up to 2 T was trapped in a stack of commercially available tape produced by SuperPower Inc. in the first reported pulsed magnetization of such a stack. Over 7 T was trapped between two stacks using field cooling at 4.2 K, the highest field yet trapped in such a sample.
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Xu, Yan 1963 Jan 31. "Effect of quench rate on the coercivity of Nd-Fe-B permanent magnets." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55669.
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Ortega, Dulanto Adrian. "Design of a Synchronous Reluctance Motor Assisted with Permanent Magnets for Pump Applications." Thesis, KTH, Elektrisk energiomvandling, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-163280.
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This Master thesis focuses on the design of a high efficiency Permanent-Magnet-Assisted Synchronous Reluctance Motor (PMASynRM) intended for pump applications. The new motor is designed to replace an existing Induction Motor (IM) in a pump product. The basic principles of SynRM, and PMASynRM Motors and a good analytical model were introduced. Due to the complexity and high non-linearity of this specific electrical machine, Finite Element Method (FEM) and an analytical model were combined. First, a parameter sensitivity analysis was carried out with the software SPEED. However, SPEED does not give appropriate results for the sensitivity analysis of the distance from the shaft to the first barrier, and in this case, the FEM software FLUX was used instead. Using FEM as well, the risk of demagnetization of the magnets was controlled for the nominal current and for overload conditions. Furthermore, some conclusions were drawn in terms of the losses, and efficiency for the selected design. The design fulfills the required efficiency placing either ferrite or neodymium iron bore magnets in the rotor barriers. However, if ferrite magnets are employed, the maximum current should be controlled to avoid demagnetization. Finally, a ferrite PMASynRM prototype was built and tested in the lab. The simulation results as well as the measurement of other possible technologies including IM and Line Start Permanent Magnets (LSPM) machine were compared with the measurements of the prototype in terms of efficiency, power factor and cost. It is concluded that the designed PMASynRM is a good alternative as it surpassed the required efficiency and the results from the simulation were close to the test measurements.<br>Detta examensarbete fokuserar på konstruktion av en högverkningsgradmotor av typen Permanent-Magnet-Assisterad Synkronreluktansmotor (PMASynRM) avsedd för pumpapplikationer. Syftet är att asynkronmotorn i befintliga pumpar ska bytas ut mot den nya konstruktionen. På grund av maskinens komplexitet och dess höga olinjäritet kombinerades Finite Element Modelling metoden (FEM) och en analytisk metod. Till en början genomfördes en parameterberoende analys med SPEED för att komma fram till hur modellens olika parametrar påverkar maskinens prestanda. FEM beräkning gav mer pålitligt resultat för parameterstudie när det gällde avståndet från axeln till den första barriären (jämför med SPEED). Detta val hade fördelen att man även kunde studera avmagnetiseringsrisken vid märkström samt undersöka vid vilken ström magneterna faktiskt avmagnetiserades. Därutöver drogs slutsatser om verkningsgrad, prestanda och förluster. PMASynRM uppfyller önskad verkningsgrad med ferrit eller neodymmagneter. Om ferritmagneter används bör den maximala strömmen kontrolleras för att undvika avmagnetisering. Till slut byggdes och testades en PMASynRM prototyp. Resultaten från simulationen samt mätningarna av andra möjliga teknologier, som asynkronmotor och nätstartande permanentmagnetiserad motor (LSPM), jämfördes med mätningarna av prototypen med avseende på verkningsgrad, effektfaktor och kostnad. Slutsatsen är att PMASynRM är ett bra alternativ eftersom den överträffade den önskade verkningsgraden och eftersom resultaten från simulationen låg mycket nära testmätningarna.
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Attanasio, Steven A. 1967. "Corrosion and environmentally-assisted cracking of rapidly solidified neodymium-iron-boron permanent magnets." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/39748.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1996.<br>Vita.<br>Includes bibliographical references (p. 383-388).<br>by Steven A. Attanasio.<br>Ph.D.
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Patel, Hardik D. "Use of Permanent Magnets to Improve the Seismic Behavior of Light-Framed Structures." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/42707.
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Light-framed wood structures generally have satisfied the life safety objective of
the current seismic design approach. The main source of energy dissipation in such
structures is the inelastic behavior of the connectors connecting framing and sheathing
elements. Wood framed structures when subjected to strong ground excitations experience
structural and non-structural damage which may incur large repair/replacement costs or
may even render the structure out of service. Thus, it is very important to apply
techniques to mitigate the seismic response of the light-framed structures and avoid large
monetary losses.
It is proposed to use commercially available permanent magnets, incorporated in
the form of passive friction dampers, to dissipate a part of input energy induced due to
strong ground motions, thereby reducing the inelastic energy dissipation demand of the
lateral load resisting system. The force of attraction between the permanent magnet and
ferromagnetic material like steel was utilized to produce the required friction resistance. A
sliding wall configuration consisting of flexible permanent magnets and steel plates
sandwiched between the plywood sheets was analyzed for its effectiveness in mitigating
the response of a two story wood shear wall structure. The structural analysis program
SAP2000 was used to perform nonlinear dynamic analysis of the finite element models
generated using the meshing algorithms incorporated into â WoodFrameMeshâ . Nonlinear
link elements available in SAP2000 were used to model the friction between the flexible
magnet sheet and the steel plate. The effects of various modeling parameters on the
solution of the nonlinear analysis were studied so as to arrive at appropriate values to
represent the friction problem. Also the friction damped structure was analyzed to study
its forced and free vibration characteristics. Further, the responses of the friction damped
structure and the undamped structure were compared when subjected to different ground
accelerations. The response of the friction damped structure was also compared to that of
the structure in which the proposed friction dampers were replaced by normal shear walls.
A huge reduction in the response of the friction damped structure was observed when
compared to the response of the undamped structure. The friction damped structure was
also analyzed for different values of modal damping ratios. Over all about 60-80% of the
input energy was dissipated by friction damping in all the cases. The slip resistance of a
flexible permanent magnet sheet was also verified in the laboratory. Above all the
magnetic properties of commercially available permanent magnets and the effects of
strong permanent magnets on human health were also studied.<br>Master of Science
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Zhu, Li. "A distributed modular self-reconfiguring robotic platform based on simplified electro-permanent magnets." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30060.
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Un système robotique distribué et reconfigurable (MSRR) est composé de plusieurs modules ayant certaines fonctions de mouvement, de perception et d'action. Ils peuvent s'adapter à l'environnement et aux objectifs en se connectant et en se déconnectant pour obtenir la configuration et la forme désirées. Les MSRR contiennent souvent deux systèmes : l'un constitué d'actionneurs pour le mouvement, l'autre pour la connexion. A l'heure actuelle, de nombreuses institutions travaillent sur les MSRR ; la conception, la miniaturisation, l'économie d'énergie, les algorithmes de contrôle ont fait l'objet de recherches dans ce domaine. Cependant, il existe peu d'études conjointes sur le matériel et les algorithmes correspondants. Cette thèse décrit la conception, la fabrication, les résultats expérimentaux, l'algorithmique distribuée et un simulateur d'une plate-forme MSRR. En nous appuyant sur le calcul et la simulation numérique, nous présentons un aimant électro-permanent simplifié (SEP) qui ne consomme pas d'énergie lorsque le module est connecté à un autre module. Un nouveau concept de moteur linéaire basé sur les SEP est également proposé. Ensuite, nous présentons DILI, un MSRR cubique, de longueur 1,5cm. Le module DILI peut coulisser sur une surface plane, la vitesse maximale pouvant atteindre 20mm/s. Avec le nouvel actionneur, DILI peut réaliser les fonctions de mouvement et de connexion. Un module DILI peut se connecter avec quatre autres modules. Enfin, un algorithme distribué est proposé et un simulateur est conçu pour permettre de simuler le système distribué, de tester et valider les algorithmes distribués<br>A distributed modular self-reconfiguring robotic (MSRR) system is composed of many repeated basic modules with certain functions of motion, perception, and actuation. They can adapt to environment and goals by connecting and disconnecting to achieve the desired configuration and shape. MSRRs often contain two hardware systems: one is for actuation (motion), another one is for connection. At present time many institutions work on MSRRs; structural design, miniaturization, energy saving, control algorithms have been the focus of research in this area. However, only a few of them work on both the hardware and the corresponding algorithms. This thesis describes the design, fabrication, experimental results, distributed algorithm, and simulator of a MSRR platform. Via theoretical calculation and numerical simulation, we present the simplified electro-permanent (SEP) magnet which can change the magnetic field direction and does not require energy consumption while connected. A new concept of linear motor based on SEP is proposed. Then we construct DILI, a cubical MSRR, the length of each module is 1.5cm. DILI module can slide on a flat surface; the maximum speed can reach 20mm/s. With the new actuator, DILI can achieve the functions of motion and connection with only one system inside. Finally, a distributed algorithm is proposed in order to build a smart conveyor, and a simulator is designed that permits one to perform distributed simulations, test and validate distributed algorithms