Thesis (M.S.)--West Virginia University, 2005 / Title from document title page. Document formatted into pages; contains xii, 71 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 59-61).

Galvanized sheet is produced commercially by hot dipping steel sheet in a galvanizing bath to produce a thin zinc rich protective coating on the steel. This investigation is concerned with the solidification of the galvanized layer with particular reference to the growth of large "spangles" in the galvanized layer. The manner in which the galvanized layer solidifies was found to be dependent on a number of factors including melt supercooling, nucleation rate, dendritic growth, bath composition, bath impurities, and cooling rate. The present results show that the supercooling necessary to activate nucleating sites in a typical galvanizing bath is less than 1°C. The supercooling which occurs in the galvanized layer as it solidifies is also generally less than 1°C, contrary to results reported in the literature. This suggests that grains nucleate in the bulk of the galvanized layer, and not necessarily at the air or iron surfaces of the melt as has been reported. No clear evidence was obtained which shows that spangles, with large dendrite spikes, are associated with large melt supercooling. Accordingly, spangle formation cannot be attributed to higher dendritic velocities resulting from large thermal supercooling. The surface topography of the galvanized layer is a property of major consideration in industrial applications of the galvanized product. Present measurements show that the surface topography is strongly dependent on the solidification structure of the galvanized layer. Large spangles solidify dendritically with large variations in the surface topography. The spangles have shiny and frosty sectors, which are relatively smooth and rough respectively, and inclined to the steel sheet surface. Large depressions are present at the boundaries between adjacent spangles, termed "pulldown", which can markedly reduce the effective thickness of the galvanized layer, and cannot be removed by subsequent treatment of the galvanized sheet. Increasing the concentration of lead in the bath increased the pulldown. The mechanism of pulldown formation is not clear. Volume shrinkage during solidification cannot account for the large depressions observed. The hot dipped galvanized samples prepared in this investigation used galvanized sheets as starting material. Observation of the distribution of bath alloy additions in the samples, using microprobe analysis and radioactive tracers, clearly showed that the original galvanized layer was replaced by the metal from the bath. Solute segregation in a galvanized layer containing spangles is directly associated with the dendritic growth of the spangles. Solute is depleted in the dendrite spikes and concentrated between the spikes. No solute concentration was observed at the grain boundaries between adjacent spangles. Some preferential surface segregation, associated with shiny and frosty sectors of a spangle, was observed. The growth of large spangles in the galvanized layer is directly related to the galvanizing bath composition. Large spangles are obtained with alloying additions which have very limited solid solubility in zinc and relatively low liquid surface tensions. The diameter of the spangles decrease as the surface tension of the alloy addition increases. Spangle growth is associated with dendritic growth. Dendritic growth occurs as a result of constitutional supercooling at the dendrite tip due to solute segregation during growth at the solid/liquid interface. It is proposed that the presence of a thin layer of highly concentrated solute at the dendrite tip changes the curvature of the tip. The change is related to the liquid surface tension of the solute. Solutes with lower values of surface tension decrease the tip curvature which results in an increase in dendrite velocity and larger spangles. The orientation of the spangles is shown to vary appreciably. The basal plane of a spangle is observed to be inclined to the surface of the steel sheet at angles between 8 and 80 degrees. This differs from reports which indicate that the basal plane is nearly parallel to the steel sheet. The growth of a spangle is primarily associated with dendritic growth. Small (0001) platelets of solid form at heterogeneous nucleating sites in the melt from which <1010> spikes grow. Each spangle forms from a single nucleating source which is randomly oriented with respect to the surface of the steel sheet. As the dendrite spikes grow they shortly encounter the melt/air interface or the melt/steel interface. The spikes will continue to grow along the surfaces at a high velocity in a direction defined by the initial <1010> direction of the growing spikes. As the primary spike grows, secondary and tertiary spikes form, generally inclined to the melt surface and in <10l0> directions when possible. The secondary branches of a primary stalk which grow along the melt/air interface form shiny spangle segments. The secondary branches on the opposite side of the primary spike grow along the melt/steel surface and form frosty sectors. The difference is not due to an orientation difference between the spangles as reported in the literature. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Impinging high-speed planar jets are susceptible to self-excited aeroacoustic feedback mechanisms due to the coupling of the highly unstable shear layer and upstream travelling pressure waves created by the jet impingement. This aeroacoustic feedback mechanism results in intense narrowband acoustic tones and large amplitude oscillations of the jet column which are undesirable for its use as an actuator for coating weight control in the continuous gas-jet wiping line. This thesis experimentally investigates the use of auxiliary high-speed planar jets for the purpose of interrupting and reducing the amplitude of the negative effects of the aeroacoustic feedback mechanism. Testing was performed using a planar multi-slot nozzle jet over a range of impingement distances, velocities and nozzle widths. The amplitudes of the acoustic tones were found to be a function of the ratio of velocities between the main and auxiliary jets with the tones found to be eliminated at sufficiently high-velocity ratios. Larger auxiliary jet widths were found to further reduce the amplitude of the tones in conjunction with the velocity ratio. The reduction of the amplitude of the tones was accompanied by a reduction in the maximum fluctuating pressure at the plate by 75% and an increase in the maximum static pressure by 30% indicating a reduction in the oscillations of the jet column. A proper orthogonal decomposition of particle image velocimetry vector fields revealed that an increase in the auxiliary jet velocity increased the percentage of the kinetic energy of the mean flow field of the jet but decreased the percentage of the kinetic energy of the modes associated with the aeroacoustic feedback mechanism. The vorticity of the modes associated with the aeroacoustic feedback mechanism shows that the coherent structures inherent to the feedback mechanism reduce in size and strength with increasing auxiliary jet velocity. Time-averaged particle image velocimetry vector fields revealed that at jet conditions where the acoustic tones were reduced, the interaction of the auxiliary jets reduced the maximum vorticity of the shear layer by 35% at the jet exit. Smaller amplitude and thicker shear layers are known to result in smaller maximum growth rates of disturbances in shear layers. The reduced growth rate resulted in smaller coherent structures in the jet shear layer which resulted in the smaller jet column oscillations and the elimination of the acoustic tones. / Thesis / Candidate in Philosophy

Along with science and technology gradually make progress, there is no distance between country. WTO world commerce cloggy eliminate, have no frontier's confine to make product and service that almost be obvious everywhere in the world. Under economic liberalization and internationalize affection, make enterprise management no longer confine to one area or single country. Economic globalization impact everywhere in the world. Iron and steel industry can¡¦t also avoid meeting severely impact and change. In 2002, because global economies gradually change better, lead to international steel market demand to grow up quickly. It is fourth season to reach the best. Price appears take on upspring, too. Due to every important manufacturer rob to buy materical each other in the world, appear steel materical demand to exceed supply. At the end of the year 2003, America, European union, mainland China cancel import restriction successively. At the beginning of the year 2004, price of freight, iron ore, coalmine, scrap steel (Steel ingredient) increases largely at the same time. Many countries ensure steel requirement materials at home, so steel importation tariff transfer fall successively. It makes strict confine measure gradually change to loose. Hot Rolled Galvanized Steel Sheet requires mean consumption to grows up 4.4% near five years in the world. Price also rise along with the price of Hot-Rolled Steel Coil is on raise at the same time. Steel market changes quickly like electronic product¡¦s life. Steel industry face structure change and reform management. In the world, all steel industry is toward competition and cooperative style. Industry internationalize brings manufacture and sales mode's changed. Industry protection policy already do not exist. With environment changed quickly, enterprise do the best increase management performance. It just be able to abidingly run and develop. The study chiefly use questionaire as interview style to get information and organize theoretical document to review and research. Let us know Hot Rolled Galvanized Steel Sheet and Prepainted Hot-Dip Zinc Coated Steel Sheet company how to develop in the world now. It is as Yiehphui company for example, explore Hot Rolled Galvanized Steel Sheet and Prepainted Hot-Dip Zinc Coated Steel Sheet industry how to take advantage of limited source and face industry environmental change to upgrade management technique. By industry internationalization working principles, make enterprise management risk asunders and create industry competition advantage. It becomes industry developmental reference. The study shows some conclusions as follows: 1. Materials source need stability and multiplication. It avoid confining provider but have no method to acquire advantaged negotiate. 2. International steel area integrated tendency have already formed. Major company become bigger and bigger can not avoid. Individual company should cooperation or tactic federation at home with same industry company, form area economy magnitude and debases competition pressure. 3. Push and import TPM management system and TSM work safe management system to healthy company operate constitution and attract elitist. 4. Global market runs for springboard as strengthen developmental technology, develop high affixation value product and new product use domain. It aggravates brand impression and difference product to used for seize more market area and market benefit.

Thesis (M.S.)--West Virginia University, 2003. / Title from document title page. Document formatted into pages; contains ix, 73 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 72-73).

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Thesis (Professional Degree)--University of Missouri, School of Mines and Metallurgy, 1935. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed June 15, 2010)

This research investigation studied the effects of galvanization on the fatigue life of high mast illumination poles. Reports that galvanization of high masts caused initial cracks to form at the toe of the weld connecting the base plate to the shaft of the pole were first validated. The effects of these initial cracks on fatigue strength were then checked through experimental testing. A variety of variables were tested for both their effects on the occurrences of the initial cracks and effects on fatigue life. These variables included testing galvanized against ungalvanized specimens, testing of varying fabricators and galvanizers, and testing of various types of connection details. These test results were compared against inspection results provided by Texas Department of Transportation inspectors. Also, methods of mitigating the effects of toe cracks on the fatigue life of poles were investigated. A method for repairing specimens both in the fabrication shop and in the field were developed and tested. Both methods showed strong improvement in fatigue life of the specimens providing a possible repair solution. / text

Thesis (Ph. D.)--West Virginia University, 2007. / Title from document title page. Document formatted into pages; contains xvii, 181 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 167-181).

Thesis (M.S.)--West Virginia University, 2006. / Title from document title page. Document formatted into pages; contains x, 82 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 74-75).