[No abstract available] / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

published_or_final_version / Electrical Engineering / Doctoral / Doctor of Philosophy

Thesis--Ph. D., University of Hong Kong, 1982. / Also availalbe in microfilm.

Thesis (Ph. D.)--Northwestern University, 1926. / Cover title: The slow acting relay; an investigation of Eddy current and magnetism during release ... Engineering bulletin 304. Bibliography: p. 39.

Thesis (Ph. D.)--Northwestern University, 1926. / Cover title: The slow acting relay; an investigation of Eddy current and magnetism during release ... Engineering bulletin 304. Bibliography: p. 39.

10A) was necessary to produce the large current densities typically found in railguns, and was able to simulate the skin effect on both the Cu rails and Al armature under static, long-term testing conditions. In this method, the effects of electromigration were discerned clearly, in dissociation from various movement related damage phenomena. The aluminum from the armature quickly reached its melting point via Joule heating due to high contact resistance at the armature-rail contact. Once liquid aluminum was formed, it rapidly migrated along the copper rail towards the negative terminal. This transport of liquid aluminum along the copper rails was attributed to electromigration of the liquid under the influence of the direct electric field. Once the aluminum began to be transported along the rail towards the cathode terminal, it alloyed with the copper rails and the resistance steadily increased in the circuit. Electromigration is shown to be a contributing factor to the degradation of aluminum armatures performance and copper rails lifespan in the railgun.

Thesis (Ph.D)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Salant, Richard F.; Committee Member: Bair, Scott; Committee Member: Cowan, Richard S; Committee Member: Danyluk, Steven; Committee Member: Scott, Waymond R. Part of the SMARTech Electronic Thesis and Dissertation Collection.

The purpose of the study is to better understand the factors that affect melt-wear in the armature-to-rail contact interface of an electromagnetic launcher (EML). In order to investigate the factors, the study uses finite element analysis (FEA) to vary parameters of a lab-scale EML at the Georgia Institute of Technology. FEA is used due to the complex nature of the system, which includes the geometry and various engineering aspects that the EML incorporates. The study focuses on an uncoupled analysis of the structural, electromagnetic (EMAG), thermal, and modal aspects. The reason for the uncoupled analysis was because the system was complex and there were computational limits. Also, by uncoupling the analysis fields, the way the parameters affected melt-wear could be viewed separately. The study varied the geometry of the armature, the stiffness of the rail system (compliance layer), and the material of the armature. The structural analysis was for the initial contact of the rail to the armature and found the von Mises stresses, contact area, and contact pressure. The EMAG analysis found the Lorentz forces in the system based on a current curve used in the lab-scale EML. The thermal analysis consisted of friction heating and Joule heating. The modal analysis was for the unstressed and pre-stressed armature. Based on the study conducted, it was found that aluminum would provide the best speeds due to its lighter mass, but lacked in the thermal resistance area. Tungsten provided the better thermal resistance, but lacked in the potential speed due to its heavier mass.

De nos jours, la corrosion des armatures engendre une usure accrue des structures en béton armé suscitant une inquiétude grandissante de la population. Afin d’éliminer ce problème, l’utilisation de barres d’armature en polymères renforcés de fibres (PRF) représentent une solution de substitution des barres d’armature en acier. Le projet de recherche s’effectue dans le cadre de la réfection complète en armatures composites de la dalle du quai de déchargement à l’incinérateur de la ville de Québec. En fait, les matériaux composites sont considérés, car ils constituent une solution alternative à l’acier et sont très avantageux considérant leurs propriétés mécaniques et leur comportement. Cependant, il y a toujours un manque d’informations sur la durabilité de ces types de barres soumises à des charges cycliques dans un environnement agressif. Le projet de recherche vise à étudier le comportement en service sur une toute nouvelle application, soit une dalle d'un quai de déchargement de déchets et l’expérimentation s’est effectuée à l’incinérateur de Québec. L’objectif global du projet est de caractériser le comportement en service (flèche, fissuration, déformation) des PRFV sous des sollicitations environnementales particulières et sous des charges importantes à l’intérieur du bâtiment. L’ouvrage est constitué d’une dalle de béton unidirectionnelle de 200 mm d'épaisseur supportée par des poutres de béton à travées multiples variant approximativement de 6 à 11,5 m. Cette dalle, ayant une surface approximative de 1300 mètres carrés, est conçue conformément à la norme CAN/CSA-S806-02¹ ainsi que la norme CAN/CSA-S6-06². Lors de la construction, des équipements de mesure ont été installés à des endroits stratégiques, ce qui a permis d’effectuer des études paramétriques, plus particulièrement sur la flèche, la fissuration ainsi que sur l’augmentation des contraintes et des déformations. Ces études sont requises étant donné que les critères en service prônent sur les critères de résistance lors de la conception. Afin de caractériser le comportement en service de l’ouvrage, des essais de chargement ont été réalisés, et ce, avec les camions-vidanges. La validation et la comparaison des résultats expérimentaux et théoriques ont permis de déterminer si les normes actuelles surestiment certaines valeurs pour le calcul des états limites de service.

The thesis shows a simplified representation for an armature rectifier driving a DC motor load. This representation was obtained from the nonlinear equations relating the output current of the armature rectifier into the DC motor as a function of the input control variable for continuous and discontinuous current conduction. Using this simplified representation, a velocity regulator with gears connecting the DC motor to an inertia load was examined by the Bode diagram method to observe the effects of twist in the load shaft and backlash in the gears on the stability of the velocity regulator. Velocity damping and friction were neglected in the analysis. It was discovered that the armature rectifier operating in discontinuous current presented stability problems which are not encountered in a velocity regulator using a conventional rotating armature supply to drive a DC motor. Linear stabilization techniques were used to stabilize the control system to overcome the effects of twist in the load shaft and backlash in the gears for both continuous and discontinuous conduction of the armature rectifier. / M.S.