Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 74-77).

The ultimate value of surface roughness and its characteristic for the polishing process was investigated in this thesis. To find out the nature of ultimate surface roughness by means of the hydrodynamic polishing process and can be used for all polishing method. A preliminary mathematical model that was proposed to explain the ultimate surface roughness proceedings and a series of experiments was planed to verify suitable of this model. Starting with the rule for ultimate surface roughness happened. The assumption that abrasive particle at roughness peak and valley machining capability differ less than one atom, the ultimate surface roughness be attained. We can propose the mathematical model of ultimate surface roughness based on this rule and the previous study of hydrodynamic polishing process. Following by useing the computer simulation to help us exploring ultimate surface roughness characteristic and testing experiments fit for the forecasting. Finally, we explain reasons that cause the experiment results not agree with the model anticipation and propose better lubrication condition to polish the optimum surface.

Orientador: Paulo Vatavuk / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo / Made available in DSpace on 2018-08-19T08:44:36Z (GMT). No. of bitstreams: 1 Schroder_FranciscoCarlos_M.pdf: 3459488 bytes, checksum: a1a920f7c561f9c61836a4366dc4a636 (MD5) Previous issue date: 2011 / Resumo: O objetivo deste trabalho é pesquisar e esclarecer as divergências dos valores de rugosidade equivalente de tubos comerciais de diferentes materiais, notadamente os de aço e ferro, que são mais comuns em aplicações industriais e de saneamento, no transporte de líquidos. Como estes valores muitas vezes não são coincidentes, apesar de originarem de materiais e processos similares, geram dúvidas quando de sua escolha para formulação do fator de atrito, que é utilizado para o cálculo de perdas de carga distribuídas em sistemas de bombeamento. O trabalho propõe recomendações para melhorar a estimativa da rugosidade em tubos metálicos rugosos, baseado em casos reais de dimensionamento de perdas por atrito em projetos de bombeamento de água / Abstract: The objective of this study is to investigate and to clarify the differences in the values of equivalent roughness of commercial pipes of different materials especially the steel and iron pipes that are more common in industrial and sanitation applications for transport of liquids. Since these values do not coincide despite similar of materials and processes inaccuracy in the formulation of the friction factor can occur, they create doubts when comes the choice for the formulation of the friction factor, which is used to calculate pressure drops distributed in pumping systems. This work proposes recommendations for improving the estimate of roughness in metallic tubes based on real cases rough sizing of friction loss in water pumping projects / Mestrado / Recursos Hidricos, Energeticos e Ambientais / Mestre em Engenharia Civil

The research presented is part of a larger study, dedicated to investigating flow boiling in small to microchannels. The test facility, originally designed by Huo (2005) and since used by Chen (2006) and Mahmoud (2011), has been used to investigate flow boiling of R134a across a range of channel diameters and both seamless cold drawn and welded channels. These previous studies concluded that one of the reasons for discrepancies in reported data is the result of surface characteristics. The objective of this current study is to further investigate the effect of channel characteristics and changing the refrigerant to R245fa. Surface characteristics are investigated with stainless steel, copper and brass channels, all seamless cold drawn and 1.1 mm internal diameter. Experiments using R245fa were initially conducted in the same stainless steel channel used with R134a by Mahmoud (2011). This allowed for the surface characteristics to be negated and the comparison to be based purely on the changes in the thermophysical properties between R134a and R245fa. Experiments were conducted at inlet pressures of 1.85 and 2.45 bar, mass fluxes of 100 – 400 kg/m2s, heat fluxes from 1 – 60 kW/m2 and vapour qualities from 0 – 0.95. The test section surfaces were evaluated based on scanning electron microscopy (SEM) and confocal laser microscopy (CFLSM). SEM allowed for a visual inspection of the channel surface, with clear differences in the surface stricter evident. The surfaces were then compared based on two CFLSM profilers. The values of the surface parameters differed between the two profilers but the same trend was seen, brass being the roughest surface and copper the smoothest. Changes in the surface parameter values were found to be a function of the scan area, scan resolution and cut-off value. A borosilicate glass tube, at the test section exit, allowed for flow visualisation. Mahmoud (2011) reported bubbly, slug, churn and annular flow for R134a, with no effect of hysteresis. Churn and annular flow were present for R245fa with an increasing heat flux. This was a result of a higher surface tension for R245fa which facilitates annular flow. Hysteresis was evident for R245fa, with bubbly, slug, churn and annular flow seen with a decreasing heat flux. The hysteresis effect is a result of nucleation sites activating during the increase in heat flux and remaining activated as the heat flux is decreased. The activation of nucleation sites depends on the size, which was constant due to the same channel being used, and the wall superheat. The wall superheat is lower for R245fa which does not allow for the nucleation sites to be initially activated with an increasing heat flux. The same effect of hysteresis was evident for copper and brass. Differences in the exit vapour quality and heat flux at which flow patterns occurred were seen between the three materials. The heat transfer coefficient varied in both magnitude and trend between R134a and R245fa. Mahmoud (2011) reported an almost constant heat transfer coefficient with vapour quality at a higher magnitude than seen for R245fa. R245fa showed an increasing trend with vapour quality. Peaks in the heat transfer coefficient were seen to be a result of surface flaw, evident when plotting as a function of the axial location. The test section was reversed in orientation, moving the location of the peak from near the entry of the test section to near the exit. A similar heat transfer coefficient peak was seen at the same axial location, near the exit of the test section, confirming that the peak was a result of a surface flaw and a result of the flow developing. The heat transfer coefficient changed in magnitude and trend for copper and brass. The magnitude of the recorded heat transfer coefficient did not follow the same trend as the surface parameters. The heat transfer correlations in literature did not predict the increase in the heat transfer with vapour quality, performing poorly compared with R134a. The best correlation for the prediction of both refrigerants was that of Mahmoud and Karayiannis I (2012). The pressure drop for R245fa was over 300 % higher than that of R134a, with a steeper increase with heat flux. This is attributed to a higher liquid viscosity and lower vapour density for R245fa. The pressure drop was highest for the roughest channel, brass, but lowest for stainless steel which had the intermediate roughness. The smoothest channel, copper, showed the largest difference in the effect of inlet pressure on the measured pressure drop and the roughest surface, brass, the smallest difference. The effect of surface characteristics on pressure drop is greater than the effect of changes in the fluid properties with inlet pressure. Pressure drop correlations performed poorly for R245fa in comparison with R134a, with the majority under predicting the pressure drop. Only one pressure drop correlation included a function of the surface parameters, Del Col et al. (2013), but this correlation under predicted the effect of the surface parameters on pressure drop. There was no one correlation which gave satisfactory results for all three materials.

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Master of Science / Department of Industrial & Manufacturing Systems Engineering / Shuting Lei / Malgorzata Rys / The demand of synthetic implants for good quality of life is high and increasing continuously due to limitations of autogenous bone grafting. Development of various synthetic bio materials and their manufacturing methods in the fields of orthopedics and dentistry has been done and still under way. Close physical properties with human bone make sintered hydroxyapatite (HAP) a suitable bioceramic material for hard tissue replacement. Newly developed fully dense nanocrystalline hydroxyapatite (nHAP) bioceramic has better mechanical properties than porous hydroxyapatite and has potential to be used alone, without metallic support in certain applications. When being used as implant devices in the human body, the nHAP bioceramic needs to be machined to the closest possible configuration with minimal surface roughness. This study investigates the machinability of nHAP bioceramic in milling operations. Efforts are focused on the effects of various machining conditions on surface integrity. Surface roughness is measured using a surface profilometer and the machined surface is observed using an optical microscope and a scanning electron microscope (SEM). Chip morphology and tool wear are examined using an optical microscope. Machined surface analysis showed that the surface integrity was good and the required surface roughness value (R[alpha]) of 1 - 1.5 [mu]m was achieved in many experiments. It was found that material removal is caused by brittle fracture without plastic flow. A first order surface roughness model for the end milling of nHAP under dry condition has been described. The mathematical model for surface roughness has been developed based on the cutting parameters: cutting speed, feed and depth of cut. The effects of these parameters on surface roughness have been studied using factorial designs and response surface method. Model analysis showed that all three cutting parameters have significant effect on surface roughness. However the current model has limited statistical power for prediction purposes and it demands a higher order model for accurate prediction of surface roughness value.

No description available.

Cricket balls behave differently at various stages of the game depending upon how much wear and tear has taken place due to use. The playing performance of cricket balls depends largely on the surface texture. The ball is swung using the primary seam during the early stages of the game but later the surface roughness starts to affect the lateral movement. This work attempts to find a quantitative measure of the surface roughness of cricket balls and then uses it to discriminate between new and old balls. Area-scale fractal analysis is used to find the surface roughness in order discriminate between the balls. FTEST (a statistical tool) is also used to establish a discriminatory criterion between the old and new balls. Wind tunnel test results are presented to show the relationship between the surface roughness and drag. Finally a correlation between the roughness and drag of the cricket is shown.

Success of acid fracturing treatment depends greatly on the created conductivity under closure stress. In order to have sufficient conductivity, the fracture face must be non-uniformly etched while the fracture strength maintained to withstand the closure stress. While there have been several experimental studies conducted on acid fracturing, most of these have not scaled experiments to field conditions and did not account for the effect of rock weakening and etching pattern. Hence, acid fracture conductivity predictions based on the above works have not been able to match actual results. In order to develop a more appropriate and accurate prediction of acid fracturing treatment outcome, a laboratory facility was developed that is properly scaled to field conditions and enables analysis of etching pattern and rock strength. A systematic experimental study that covered a variety of formations, acid types, and acid contact times was conducted. An acid fracture conductivity correlation was developed based on etched volume, etched pattern, and fracture strength under closure stress. Results suggested that there is an optimal time of acid exposure resulting in maximum fracture conductivity. There were large differences in the conductivity created with the different acid systems tested due to different etching patterns and degree of rock strength weakening. There was an optimal acid system depending on formation type, contact time and overburden stress. The acid fracture conductivities measured did not agree with the predictions of the Nierode-Kruk correlation. The newly developed correlation predicts conductivity much closer as it includes the effect of rock strength and surface etching pattern on resulting conductivity.