The compressible turbulent boundary layer developing over atwo-dimensional bump which leads to a supersonic pocket with aterminating shock wave has been studied. The measurements havebeen made with hot-wire anemometry and Particle ImageVelocimetry (PIV). A method to calibrate hot-wire probes in compressible ow hasbeen developed which take into account not only the ow velocitybut also the inuence of the Mach number, stagnation temperatureand uid density. The calibration unit consists of a small jetow facility, where the temperature can be varied. The hot wiresare calibrated in the potential core of the free jet. The jetemanates in a container where the static pressure can becontrolled, and thereby the gas density. The calibration methodwas verfied in the at plate zero pressure gradient turbulentboundary layer in front of the bump at three different Machnumbers, namely 0.3, 0.5 and 0.7. The profiles were alsomeasured at different static pressures in order to see theinuence of varying density. Good agreement between the profilesmeasured at different pressures, as well as with the standardlogarithmic profile was obtained. The PIV measurements of the boundary layer ow in front ofthe 2D bump showed good agreement with the velocity profilesmeasured with hotwire anemometry. The shock wave boundary layerinteraction was investigated for an inlet Mach number of 0.69.A lambda shock wave was seen on the downstream side of thebump. The velocity on both sides of the shock wave as measuredwith the PIV was in good agreement with theory. The shock wavewas found to cause boundary layer separation, which was seen asa rapid growth of the boundary layer thickness downstream theshock. However, no back ow was seen in the PIV-data, probablybecause the seeding did not give enough particles in theseparated region. The PIV data also showed that the shock wavewas oscillating, i.e. it was moving approximately 5 mm back andforth. This distance corresponds to about five boundary layerthicknesses in terms of the boundary layer upstream theshock. <b>Descriptors:</b>Fluid mechanics, compressible ow,turbulence, boundary layer, hot-wire anemometry, PIV, shockwave boundary layer interaction, shape factor. / NR 20140805

Our research focuses on re-using a waste a material, cross-linked polyethylene abbreviated XLPE, which is a widely used coating for wires. XLPE is strong and has excellent thermal properties due to its chemical structure - what leads to the significance of recycling this valuable polymer. Properties of XLPE include good resistance to heat, resistance to chemical corrosion, and high impact strength. A wire is usually composed of a metal core conductor and polymeric coating layers. One creates a new coating, including little pieces of recycled XLPE in the lower layer adjacent to the wire, and virgin XLPE only in the upper layer. Industries are often wasting materials which might be useful. Mostly, some returned or excess products could be recycled to create a new type of product or enable the original use. This method helps cleaning the waste, lowers the costs, and enhances the income of the manufacturing company. With the changing of the thickness of the outer layer, the roughness changes significantly. Moreover, different processing methods result in surfaces that look differently.

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第18612号 / エネ博第308号 / 新制||エネ||63(附属図書館) / 31512 / 京都大学大学院エネルギー科学研究科エネルギー応用科学専攻 / (主査)教授 平藤 哲司, 教授 馬渕 守, 教授 土井 俊哉 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DGAM

京都大学 / 0048 / 新制・論文博士 / 博士(工学) / 乙第13015号 / 論工博第4140号 / 新制||工||1650(附属図書館) / 32943 / (主査)教授 斧 髙一, 教授 木村 健二, 教授 立花 明知 / 学位規則第4条第2項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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Der Kontakt Fahrdraht - Schleifleiste hat die Aufgabe, elektrischen Strom zwischen der Oberleitung und dem Stromabnehmer des Triebfahrzeuges mittels eines Gleitkontaktes zu übertragen. Das Kontaktverhalten und der dabei entstehende Verschleiß sind von einer Vielzahl von Parametern und Einflussfaktoren sowie deren Verknüpfungen abhängig. Der Verschleiß lässt sich in elektrischen und mechanischen Verschleiß unterteilen. Die vorliegende Arbeit beschreibt erstmals zusammenhängend und umfassend das Kontakt- und Verschleißverhalten von Fahrdraht und Schleifleiste. Daraus geht hervor, dass der Kontaktwiderstand eine herausragende Bedeutung für den elektrischen Verschleiß besitzt. Zur Berechnung des Kontaktwiderstandes existieren für einen stationären Kontakt mehrere Modelle, die jedoch auf einer Vielzahl von Annahmen und Vereinfachungen beruhen. Die Messung des Kontaktwiderstandes zwischen dem Fahrdraht und der Schleifleiste ist somit zwingend erforderlich. Dafür wurde an der TU Dresden ein Versuchsstand errichtet, mit dem der Kontaktwiderstand unter möglichst realen Bedingungen gemessen werden kann. Untersucht wurde die Kontaktpaarung Kupferfahrdraht und Kohlenstoffschleifleiste. Die durchgeführten Messungen des Kontaktwiderstandes und der Temperaturen von Fahrdraht und Schleifleiste im Stillstand und bei Fahrt werden beschrieben und ausgewertet. Dabei zeigt sich, dass die Kontaktkraft und der Kontaktstrom den größten Einfluss auf den Kontaktwiderstand besitzen. Der Kontaktwiderstand bzw. die Kontaktspannung bilden die Grundlage zur Berechnung der Erwärmung des Kontaktbereiches. Es wird ein Verfahren vorgestellt, mit welchem die maximalen Temperaturen in Fahrdraht und Schleifleiste ermittelt werden können. Die auf diese Weise ermittelten Temperaturen erlauben tendenzielle Aussagen zum elektrischen Verschleiß.

The electrochemical behavior of nickel (Ni) in different concentrations of sulfuric acid (H2SO4) was studied via cyclic voltammetry (CV) over a range of potentials (0.0 V– 3.0 V) at room temperature. The presented work displays novel experiments where external forcing by a platinum (Pt) electrode changed the proton concentration at a Ni electrode surface in order to control the frequency and magnitude of periodic oscillations produced. When studying unique phenomena such as the Ni phenomena in this thesis, efficient, durable, and inexpensive technology is always beneficial. A coupled microelectrode array sensor or CMAS which has been used for over four decades to study pitting corrosion, crevice corrosion, intergranular corrosion, galvanic corrosion, and other heterogeneous electrochemical processes were fabricated in a novel, systematic, inexpensive, and time efficient process. The presented work shows how to make the CMAS and proved that they functioned properly.

In the first part of this thesis, the FE program MSC.Marc is applied for coupled thermomechanical simulations of wire-rod rolling. In order to predict material behaviour of an AISI 302 stainless steel at high strain rates generated during wire-rod rolling, a material model based on dislocation density is applied. Then, the evolution of temperature, strain rate and flow stress is predicted in the first four rolling passes of a wire block. In the second part of the thesis, an alternative approach to simulation of shape rolling is evaluated. The approach is applied in order to save the computational time in cases where many shape-rolling passes are to be simulated. The approach is a combination of the slab method and a 2D FEM with a generalized plane-strain formulation. A number of various isothermal shape-rolling passes are simulated applying the simplified approach. The simulations are carried out using an in-house 2D FE code implemented in Matlab. The results are compared to fully 3D FE analyses. The comparison shows that the simplified approach can predict roll forces and roll torques with a fair accuracy, but the predicted area reductions are a bit underestimated. The reasons for the deviations between the simplified approach and the 3D FEM are discussed. / QC 20101123

Calcium treatment is an established operation in the production of steels. Most importantly, it serves to modify detrimental inclusions in the melt for improved castability and superior product properties. Due to calcium’s low melting point and high vapour pressure, its addition to liquid steel is challenging and yields are generally low. The current standard method for addition is cored wire feeding, in which a calcium-bearing compound is injected into the melt inside a sacrificial metal tube. The depth at which the compound is released has a pronounced impact on its yield and depends on the rate at which the wire is injected. A mathematical model is constructed to predict the time after which release occurs and thus estimate injection depth. It is based on one-dimensional heat transfer and respects phase change effects, i.e., solidification of melt on the cold wire surface and subsequent melting of the wire and compound. Equations are derived using the finite difference method and the model is solved numerically using an implicit method. The model is applied to two different steel grades – one austenitic (AISI 316L), one super-duplex (SAF 2507) – and predictions are tested for the former grade in a 75-ton industrial ladle furnace. Results indicate that a decreased feeding rate (&lt;100 m/min) leads to better calcium yield. Positive effects were also observed with downward melt stirring and a good slag coverage. Improved yield can lead to savings in process and material cost. The results also provide insights into the cored wire feeding process which may be useful for future process development, both for calcium and other additions. / Kalciumbehandling är en etablerad process vid tillverkning av stål. Framförallt används den för modifieringen av skadliga inneslutningar i smältan för att förbättra gjutbarheten och produktegenskaper. På grund av kalciums låga smältpunkt och höga ångtryck är det svårt att tillsätta det till flytande stål och utbytet är i allmänhet låg. Den nuvarande standardmetoden för tillsats är inmatning av tråd, där ett kalciumhaltig ämne matas in i smältan inuti en metallhölje som smälter bort. Djupet på vilket ämnet frigörs påverkar utbytet och beror på hur snabbt tråden matas. En matematisk modell konstrueras för att beräkna den tid efter vilken frisättning sker. Den bygger på endimensionell värmeöverföring och tar hänsyn till fasförändringseffekter, dvs. stelning av smältan på den kalla trådytan och smältning av tråd och kalciumämne efteråt. Ekvationer härleds med hjälp av finita differensmetoden och modellen löses numeriskt med hjälp av en implicit metod. Modellen tillämpas på två olika stålsorter – en austenitisk (AISI 316L) och en superduplex (SAF 2507) – och förutsägelser testas för den förstnämnda sorten i en 75-tons industriell skänkugn. Resultaten visar att en minskad matningshastighet (&lt; 100 m/min) leder till ett ökat kalciumutbyte. Positiva effekter observerades med nedåtgående smältomrörning och god slaggtäckning. Ett förbättrat utbyte kan leda till besparingar i fråga om process- och materialkostnader. Resultaten ger också insikter i processen för inmatning av tråd, vilket kan vara användbart för framtida processutveckling, både för kalcium och andra tillsatser.

This bachelor thesis project in mechatronics involved making a working prototype of an automatic wire cutter and evaluating its accuracy. The accuracy of the machine was increased by analysing measurements of the machine’s initial precision and thereafter performing a calibration to diminish the eect of unwanted errors. Before calibration the machine’s accuracy was ± 0.73 cm and after calibration it was calculated to be ± 0.06 cm in its intended operating range of 5-20 cm. The main limitations of the machine’s accuracy were determined to be slippage in the feeding mechanism, the mathematical model that was used, the step resolution of the stepper motors, the oset between the blades in the cutting mechanism as well as the wires bending when being fed. / I detta kandidatexamnesarbete inom mekatronik designades och tillverkades en fungerande prototyp av en automatisk kabelklippare, och dess noggrannhet undersöktes sedan. Maskinens noggrannhet förbättrades genom att först undersöka maskinens ursprungliga noggrannhet och därefter kalibrerades maskinen för att minska effekten av oönskade fel. Före kalibrering var maskinens noggrannhet ± 0,73 cm och efteråt räknades den ut att vara ± 0,06 cm i dess tilltänkta driftintervall på 5-20 cm. De huvudsakliga begränsningarna för maskinens noggrannhet visade sig vara glidning i matningsmekanismen, den matematiska modellen, stegmotorns stegupplösning, avståndet mellan bladen i klippmekanismen samt att kablarna böjer sig under frammatning.