Thesis (M.S.)--Ohio University, June, 1989. / Title from PDF t.p.

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Thesis (M.Sc.)(Chemistry)--University of Pretoria, 2004. / Summaries in English and Afrikaans. Includes bibliographical references.

The objective of this investigation was to determine the influence of work roll cooling on roll thermal behavior. The investigation has been conducted utilizing a previously developed computer model [1]. Three industrial operations were evaluated and features of an optimum configuration have been identified. The magnitude of the thermal zone near the roll surface within which the cyclic temperature variation is confined has been evaluated for different roll cooling conditions. A two dimensional thermal model of a work roll has been developed to predict the thermal field inside the roll, based on which the thermal crown of the roll was calculated under an assumption of axi-symmetric deformation. The heat transfer equation was solved by the numerical finite difference method, the Alternating Direction Implicit (ADI) method. This method makes it possible to solve the problem on a personal computer making it suitable for industrial application due to the minimum requirements of computer storage and time. Also because the thermal model simulates operating conditions including the cooling configuration it is of value in studying a variety of industrial rolling conditions. The influence of roll spray arrangement, roll gap heat transfer and mill pacing on roll thermal crown has been investigated. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Please read the abstract in the section, 00front of this document / Dissertation (M Eng (Electronic Engineering))--University of Pretoria, 2002. / Electrical, Electronic and Computer Engineering / MEng / unrestricted

Thesis (M.S.)--Ohio University, March, 1994. / Title from PDF t.p.

This thesis investigates the design of a strip tension regulator by analytical techniques. The tension transfer function is non-linear and is derived for two conditions, first with only elastic deformation in the strip, and second with plastic flow in the strip resulting from reduction in the roll bite. The resulting transfer function consists of the one developed for elastic deformation with a degenerative feedback around it. This feedback is a result of reduction in the roll gap. The block diagram of the tension system reduces to a form containing two non-linear expressions. One is a second order equation describing the load and the other is third order equation describing the motor and the load effect on it. The motor is linearized by the addition of a high response armature current regulator. The tension regulator then reduces to a type I third order system. To compensate for the second order non-linearity in the regulator, a non-linear second order lead circuit is developed. This lead is modified continually as a function of strip velocity as well as coil radius and inertia. With the addition of this compensation, the tension regulator can be analyzed as a type I, first order system. / M.S.

AC main drives, such as cycloconverters, offer the possibility of higher speed and torque response over their DC counterparts. The price to be paid, however, is torque ripple which is a function of the operating frequency. Even a small value of ripple, at an underdamped plant resonant frequency, may be multiplied by the plant "Q" to a large enough value to cause trouble. Typical classical approaches used in the rolling mill industry to deal with mechanical resonance tend to fall apart with large values of time lag. We investigate a modified LQR/LQE approach using a torque sensor as the feedback element. The result is a low order SISO filter that suppresses the effects of the torque ripple on the underdamped plant. / Master of Science

This thesis investigates optimization of the control of electrical and thermal equipment by using FEM and CFD modeling in combination with dynamic simulation models. The thesis focuses on the production of electrical strips and the control system with the aim of reducing losses and improving magnetic properties. Several parameters and factors contribute to core losses. Thickness deviations in strip production, high levels of impurities in the core, orientation, ageing, surface oxidation, overloading, and hot spot temperature are among the reasons for losses in the core. Some of the losses occur during strip cutting and core assembly. This dissertation focuses on the reduction of losses in the cold rolling, annealing and manufacturing stages. The cold rolling process has a direct influence on the accuracy of the strip thickness and magnetic ageing of sheets. Some disturbances such as eccentricity, working rolls gap deviation, shape and edge deflections have to be removed in order to achieve accurate thickness. Thickness measurement makes up an important portion of loss evaluation in electrical equipment. Impurities and dirty strip surfaces in the cold rolling step can increase the carbon content of strips that pass through the annealing furnaces after cold rolling. The slab should be cleaned before reeling and rewinding. As the strip passes through the annealing furnaces, the temperature should be homogenous over the entire strip. According to simulations of furnace and strip temperature computed in the COMSOL environment, homogenous temperatures may be achieved using high electrical power reflectors which are equipped with molybdenum disilicide (MoSi2) electrical heating elements to replace the gas fired burners that are currently used. Modelling of the cold rolling process is conducted in order to find the correlation between control system parameters. A multivariable mathematical model for the rolling process is derived here, which reveals the interactions of the influencing variables. This approach provides numerically efficient algorithms, which are necessary for running in a real-time environment. A control model is applied in the MATLAB environment in order to determine the strip thickness at online-offline state using a robust algorithm. The critical problem in the thickness control loop is analysed, and an adaptive control algorithm is proposed. A number of control methods are investigated to improve the final strip properties. Cold rolled strip thickness deviations, eccentricities and shape defects are compensated for. The simulation results are verified with measurement data and the most significant sources of disturbances are detected. Finally, to solve the hottest spot problem in large scale electric power transformer, a new apparatus, oil spraying, is proposed and analysed. / Denna avhandling behandlar optimering och kontroll av elektrisk och termisk utrustning med hjälp av FEM och CFD-modellering i kombination med dynamiska simuleringsmodeller. Avhandlingen fokuserar på produktion av remsor och styrsystemet i syfte att minska förluster och ge bättre magnetiska egenskaper. Flera parametrar och faktorer bidrar till förluster i kärnan. Tjockleksavvikelser i remsor, höga nivåer av föroreningar i kärnan, orientering, åldrande, yta oxidation, överbelastning och temperaturer i heta punkter finns bland orsakerna till förlusterna i kärnan. Några av de förluster som uppstår under klippning av remsor och ihopsättningen av kärnan. Denna avhandling fokuserar på att minska förlusterna i produktionsstegen för kallvalsning och  glödgning. Kallvalsningen har ett direkt inflytande på riktigheten av remsornas tjocklek och magnetiska åldrande. Vissa störningar i till exempel excentriciteten, gapet mellan valsarna, form och kanter måste minimeras för att uppnå korrekt tjocklek. Tjockleksmätningar utgör en viktig del av utvärderingen av förluster  i elektrisk utrustning. Föroreningar och smutsiga bandytor i kallvalsningssteget kan öka kolhalten i band som passerar genom ugnar efter kallvalsning. Valsämnet bör rengöras innan avhaspling och upprullning. När bandet passerar genom glödgningsugnar bör temperaturen vara homogen över hela remsan. Enligt simuleringar av ugnen och remsans temperatur kan homogen temperatur uppnås med elektriska värmeelement (Molybden disilikat, MoSi2) insatta i reflektorer. De kan ersätta den gaseldade brännare som för närvarande används. Modellering av kallvalsningsprocessen sker i syfte att hitta korrelation mellan styrsystemparametrar. En multivariabel matematisk modell för valsningsprocessen har tagits fram som använder korrelation mellan variabler. Denna metod ger numeriskt effektiva algoritmer som behövs för att köra i en realtids-miljö. En modell har tagits fram för att bestämma remsornas med tjocklek för kontinuerlig och icke-kontinuerligt tillstånd med hjälp av en robust algoritm. Det kritiska problemet i reglerloopen för tjocklek har analyserats, och en adaptiv regleralgoritm föreslås. Ett antal metoder har undersökts för att förbättra de slutliga bandegenskaperna. Avvikelser i kallvalsade band med avseende på tjocklek, excentriciteter och form kompenseras. Simuleringsresultaten har verifierats med mätdata och de viktigaste källorna till störningar upptäckts.   Slutligen, för att lösa problemet med heta punkter i stora transformatorer föreslås en ny metod för oljesprutning, vilken också analyseras i avhandlingen.

The thesis focuses on the optimization of the central lubrication system for the lubrication of rolling bearings of rolling mills in the operation continuous wire rod mill. The work is divided into theoretical and practical part. The first part of the theoretical work is focuses on the search of rolling and tribodiagnostics. The next part focuses on the description of modern central lubrication systems, explanation of their principle and practical use. The practical part explains the function of the old lubrication system for rolling mill bearings with an analysis of its problems. Next is described the technical design of a new central lubrication system, its application into operation and its actual commissioning are described. The last part of the thesis is the conclusion and evaluation of the benefits of the new central lubrication system compared to the old one.