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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
781

Resolving relationships between deep-sea benthic diversity and multi-scale topographic heterogeneity

Du Preez, Cherisse 02 January 2015 (has links)
Resolving diversity patterns and their underlying drivers has application for both ecological theory and ocean management. Because seafloor characteristics are often used to assess bottom habitat, I examined the relationship between deep-sea benthic (bottom-living) diversity and multi-scale topographic heterogeneity. Most work occurred on the Canadian Pacific continental shelf at Learmonth Bank with additional sites in Strait of Georgia (BC) and Gulf of Maine (Atlantic shelf). High-resolution species distribution and seafloor data were annotated from remotely operated vehicle benthic imagery surveys while large-scale seafloor data were derived from multibeam sonar. New method development to address problems of current methods and to facilitate comparison among ecosystems is a major outcome. My new MiLS method (microtopographic laser scanning) can profile the deep seafloor at a resolution of ~1-2 cm with high accuracy and precision. I also developed a new ACR (arc-chord ratio) rugosity index as a measure of 3-D topographic heterogeneity that is simple, accurate and highly versatile. Model systems and scales vary among my studies but results consistently yield a positive relationship between diversity and topographic heterogeneity and identify bottom hydrodynamics as an important underlying driver. Rockfish Sebastes spp. associate with higher seafloor rugosity non-randomly and select for deep-sea corals and sponges over inert substrata alone. Data indicate that degradation of biogenic structures is a long-term detriment to rockfish species. Gorgonian coral- and sponge-dominant biotopes strongly associate with a single substratum type. These relationships were used to map coral and sponge distributions. This work, which collectively adds new information on the ecological relevance and distribution of corals and sponges, is pertinent to the conservation and management of fish stocks and vulnerable marine ecosystems. Epibenthic community variables abundance, richness, and Shannon diversity positively correlated with both the local microtopographic heterogeneity on a scale of 10 m2 and with the surrounding regional large-scale topographic heterogeneity on scales of 25 to 250,000 m2. Relationships were strongest between epibenthic community variables and the largest scale rugosity and were used to generate and test predictive diversity models. Where management strategies rely on surrogate measures in data-poor areas, mapping benthic diversity using ACR rugosity will provide good indicators. Although bottom hydrodynamics is consistently identified as an underlying driver of epibenthic patterns related to topographic heterogeneity, data suggest the nature of the relationship varies across spatial scales. At small scales, high topographic heterogeneity likely increases diversity by increasing the number of available niches (including hydrodynamic gradients; e.g., the abrupt vertical rugosity created by tall corals and sponges provides rockfish refuge from currents) while at large scales, high topographic heterogeneity increases local diversity less directly through distant hydraulic events that alter bottom flow hydrodynamics. / Graduate / 0329 / 0416 / 0799 / cdupreez@uvic.ca
782

Τρισδιάστατη αριθμητική προσομοίωση υπερκρίσιμης ροής σε ανοιχτό αγωγό με πλευρικά στοιχεία τραχύτητας

Βάσσης, Ευάγγελος 12 June 2015 (has links)
Στην παρούσα εργασία μελετάται αριθμητικά η ροή σε σήραγγα υπό συνθήκες ελεύθερης επιφάνειας και έντονης κλίσης πυθμένα 1:10. Διερευνάται η δυνατότητα μείωσης της ταχύτητας ροής μέσω κατακόρυφων, πλευρικών στοιχείων τραχύτητας. Συγκεκριμένα γίνεται τρισδιάστατη προσομοίωση της ροής με χρήση του μοντέλου ANSYS – Fluent και τα αποτελέσματα συγκρίνονται με εκείνα που προέκυψαν από αντίστοιχο πείραμα που πραγματοποιήθηκε στο Εργαστήριο Υδραυλικής Μηχανικής του Τμήματος Πολιτικών Μηχανικών του Πανεπιστημίου Πατρών. Αφορμή για το συγκεκριμένο σχεδιασμό αποτέλεσε η διερεύνηση της εκτροπής των πλημμυρικών παροχών από ορεινή λεκάνη σε κατάντη ταμιευτήρα μέσω σήραγγας και συγκεκριμένα από το οροπέδιο Λασιθίου στον ταμιευτήρα του φράγματος Αποσελεμή. Με δεδομένα τα ανωτέρω, επιθυμείται να αποφευχθεί η κατασκευή βαθμίδων ή στοιχείων τραχύτητας στον πυθμένα και, επομένως, απαιτείται η μόρφωση «πτυχώσεων» στα τοιχώματα έτσι ώστε να αναπτυχθεί δευτερογενής ροή και με εισρόφηση αέρα. Η αποτελεσματικότητα του σχεδιασμού διερευνήθηκε σε υδραυλικό ομοίωμα κλίμακας 1:12.5 που βασίσθηκε σε συνθήκες δυναμικής ομοιότητας κατά Froude για χαρακτηριστικές τιμές παροχής. Η επεξεργασία των μετρήσεων έδειξε ότι με κατάλληλη διάταξη πλευρικών στοιχείων τραχύτητας ελέγχεται η τιμή της ταχύτητας και ικανοποιείται η απαίτηση μεγίστου βάθους ροής σε σχέση με τις διαστάσεις της σήραγγας. Για την υπολογιστική επίλυση του προβλήματος αξιοποιήθηκαν οι εξισώσεις Reynolds-Averaged Navier-Stokes (RANS), ενώ για το κλείσιμο της τύρβης χρησιμοποιήθηκε το μοντέλο δυο εξισώσεων k-ω, το οποίο επεξηγείται αναλυτικά. Η διαχείριση της ελεύθερης επιφάνειας έγινε με τη μέθοδο Volume of Fluid (VOF), ενώ η αριθμητική επίλυση βασίστηκε στη μέθοδο των πεπερασμένων όγκων και πραγματοποιήθηκε με το υπολογιστικό πακέτο Fluent CFD της ANSYS inc. Για την ροή στον υπό εξέταση αγωγό η ροή είναι υπερκρίσιμη με κλίση πυθμένα S_0=0.10. Για λόγους ελέγχου της ακρίβειας της αριθμητικής μεθόδου που χρησιμοποιήθηκε, αρχικά επιλύθηκε η περίπτωση τρισδιάστατου καναλιού ορθογωνικής διατομής χωρίς πλευρικά στοιχεία τραχύτητας και τα αποτελέσματα που προέκυψαν συγκρίθηκαν με αναλυτικά αποτελέσματα μονοδιάστατης ροής (κατακόρυφο επίπεδο) υπεράνω επίπεδου πυθμένα. Τα αποτελέσματα βρέθηκαν σε καλή συμφωνία μεταξύ τους, γεγονός που επιβεβαίωσε την καταλληλότητα της μεθόδου. Για το τρισδιάστατο πρόβλημα με τα κατακόρυφα πλευρικά στοιχεία τραχύτητας, η ανάλυση έδειξε ότι το διάμηκες προφίλ της ελεύθερης επιφάνειας παρουσιάζει κυματισμούς σε όλη την περιοχή των στοιχείων τραχύτητας. Το βάθος ροής κατέρχεται σταδιακά από το αρχικό κρίσιμο βάθος μέχρι να φθάσει στο επίπεδο του βάθους των 0.06 m, το οποίο δεν είναι το ομοιόμορφο βάθος αφού η ροή συνεχίζει να επιταχύνεται. Επιπροσθέτως, παρατηρήθηκε η δημιουργία μιας περιοχής ανακυκλοφορίας της ροής ανάμεσα στα πλευρικά στοιχεία τραχύτητας. Τα αποτελέσματα που πρόεκυψαν από το αριθμητικό μοντέλο συγκρίθηκαν με τα πειραματικά αποτελέσματα και η συμφωνία μεταξύ αριθμητικών προβλέψεων και πειραματικών δεδομένων είναι ιδιαίτερα ικανοποιητική. / A three-dimensional CFD numerical model has been utilized to simulate the 3D free-surface flow under supercritical flow conditions in a 10% sloping channel over vertical roughness elements on the side walls. The effectiveness of vertical roughness elements on the side walls is investigated, with the aim to reduce flow velocity in the tunnel. The program, ANSYS Fluent, solves the Reynolds-Averaged Navier-Stokes (RANS) equations on an unstructured five-hedral grid using PISO method and the flow is treated as steady while the k-omega model is used as turbulence model. The numerical simulation has been based on the Volume of Fluid method (VOF) approach. Available experimental measurements of the free-surface in a sloping channel, under various supercritical flow regimes, have been used to validate the proposal numerical methodology. These experiments were conducted at the Hydraulic Engineering Laboratory of the Civil Engineering Department, University of Patras. In all test cases the 3D numerical model gives reasonable comparisons with measurements for the water depth.
783

The Hydrodynamic Effects of Long-line Mussel Farms

Plew, David Russell January 2005 (has links)
The hydrodynamic effects of long-line mussel farms are studied through a two-pronged approach. Large-scale hydrodynamic effects are investigated through the use of field measurements, primarily at a large mussel farm in Golden Bay, New Zealand (230 long-lines, covering an area of 2.45 km by 0.65 km). The research focuses on three areas: the effect of the farm on currents, mixing and stratification, and the dissipation of wave energy. Measurements are also made of the forces on long-line anchor ropes, and a limited investigation is made of phytoplankton depletion. The second approach is the use of laboratory drag measurements and Particle Tracking Velocimetry (PTV) to study the effect of mussel dropper (vertical lengths of mussel-encrusted crop rope) roughness and spacing on flow at small scales. These experiments provide data on very rough cylinders, and on cylinder arrays. The field measurements show that the local effects of mussel farms on currents are significant, but that magnitudes of the effects depend on dropper density, mussel sizes, orientation of the long-lines to the flow, and other parameters that are necessary to characterise the complex interactions between a farm and the flow. The drag on the submerged structures reduces water velocities within the Golden Bay farm by between 47% and 67%. Mussel farms present a porous obstacle to the flow, and flow that does not pass through the farm must be directed around or beneath it. The field measurements indicate that at the study site, most of the flow is diverted around the farm despite its large horizontal dimensions. The droppers at the study site extend over most of the water column (average dropper length ~ 8 m, average water depth ~ 11 m), providing a restriction to the flow beneath the farm. The strength of the density stratification may also favour a horizontal diversion. The flow around the farm is essentially two-dimensional. This suggests that two-dimensional numerical models should be sufficient to obtain reasonable predictions of the velocity drop within, and the diversion around, mussel farms. A simple two-dimensional pipe-network model gives reasonable estimates of the velocity within the farm, demonstrating that the drag of the farm may be adequately parameterised through local increases of bed friction. A wake in the form of reduced velocities extends downstream of the farm, and a mixing layer analogy suggests that this wake spreads slowly. The downstream extent of the wake cannot be determined, although it is likely to be limited by the tidal excursion. The degree of vertical mixing caused by the flow through a mussel farm cannot be quantified, although there are clear interactions between the stratification and the farm. Two mixing mechanisms are considered. A shear layer is generated beneath the farm due to the difference in velocities between the retarded flow within the farm and the flow beneath. Shear layers beneath mussel farms are likely to be weak unless the ambient currents are strong. It will be necessary for stratification to be weak or non-existent for this mechanism to generate significant mixing. The second mechanism is smaller-scale turbulence generated by the mussel droppers. Although the efficiency of this form of mixing is likely to be low, the large number of mussel droppers suggests that there will be some enhancement of vertical mixing. Frequency-dependent wave attenuation is recorded, and is predicted with some success by an analytical model. Both the model and the field data show that wave dissipation increases as the wave period decreases. Wave energy dissipation at the study site averages approximately 10%, although the measurements are made during a period of low wave heights (Hs < 0.25 m). Measurements of long-line anchor rope tension at two study sites indicate that the loadings are induced by the tide, currents, and waves. Dynamic wave loadings may be significant, and higher wave forces are measured at the offshore end of a long-line. The issue of seston or phytoplankton depletion is considered briefly through the examination of fluorescence, turbidity, and acoustic backscatter data. Although the results are consistent with a reduction of seston within the farm, differences between the inside and outside of the farm are not statistically significant. Mussel droppers resemble extremely rough circular cylinders, with the mussel shells forming the surface roughness elements. Drag measurements and PTV flow visualisation are used to investigate the importance of the large surface roughness, and the influence of dropper spacing and long-line orientation on flow. Drag measurements conducted with smooth and rough cylinders show that high surface roughness (ks/D ~ 0.092) has little effect on the drag coefficient of single cylinders in the range 4,000 < Re < 13,000, yet increases the drag coefficient of a row of cylinders normal to the flow. High surface roughness on single cylinders has the effect of shortening the near-wake region, increasing the peak turbulent kinetic energy (TKE) behind the cylinder, and decreasing the Strouhal number (St = 0.21, 0.19, 0.17 for ks/D = 0, 0.048, and 0.094 respectively). Arrays of rough cylinders (ks/D = 0.094) demonstrate similar flow characteristics to those of smooth cylinders. At cylinder spacings of S/D < 2.2, the surface roughness acts to favour the formation of a particular metastable wake pattern, whereas different metastable wake patterns are formed each run behind the smooth cylinders. The experiments show that the drag on single row arrays of cylinders are related to the cylinder spacing (increasing drag with decreasing spacing), and the drag also varies with the sine of the angle to the flow, except where the array is at low angles to the flow. The PTV measurements provide new data regarding the two-dimensional distributions of velocity, TKE, and turbulence statistics behind the cylinder arrays.
784

Experimental Study of Roughness Effect on Turbulent Shear Flow Downstream of a Backward Facing Step

Essel, Ebenezer Ekow 16 January 2014 (has links)
An experimental study was undertaken to investigate the effect of roughness on the characteristics of separated and reattached turbulent shear flow downstream of a backward facing step. Particle image velocimetry technique was used to conducted refined velocity measurements over a reference smooth acrylic wall and rough walls produced from sandpaper 36 and 24 grits positioned downstream of a backward facing step, one after another. Each experiment was conducted at Reynolds number based on the step height and centerline mean velocity of 7050. The results showed that sandpaper 36 and 24 grits increased the reattachment length by 5% and 7%, respectively, compared with the value obtained over the smooth wall. The distributions of the mean velocities, Reynolds stresses, triple velocity correlations and turbulence production are used to examine roughness effects on the flow field downstream of the backward facing step. Two-point auto-correlation function and proper orthogonal decomposition (POD) are also used to investigate the impact of wall roughness on the large scale structures.
785

Virus and Virus-sized Particle Transport in Variable-aperture Dolomite Rock Fractures

Mondal, Pulin Kumar 18 December 2012 (has links)
In this thesis a study of the factors affecting virus and virus-sized particle transport in discrete fractured dolomite rocks is presented. Physical and chemical characteristics of two fractured rocks were determined, including fracture aperture distribution, rock matrix porosity, mineral composition, and surface charge. Hydraulic and transport tests were conducted in the fractures with a conservative solute (bromide) and carboxylate-modified latex (CML) microspheres of three sizes (20, 200, and 500 nm in diameter). The earlier arrival of larger microspheres as compared to bromide indicated the effects of pore-size exclusion and preferential flow paths in the fractures. The tailing of the bromide and the smaller microsphere (20 nm) in the breakthrough curves (BTC) indicated the diffusive mass transfer between the mobile water (flowing) and immobile water (stagnant water in the low aperture areas and porous rock matrix). The effects of ionic strength and cation type on the transport of viruses (bacteriophages MS2 and PR772) and virus-sized microspheres (20 and 200 nm) were determined from the transport tests in a fracture at three levels of ionic strength (3, 5, and 12 mM) and composition (containing Na+ and/or Ca2+ ions). Retention of the microspheres and bacteriophages increased with increasing ionic strength. The addition of divalent ions (Ca2+) influenced the retention to a greater extent than monovalent ions (Na+). The effects of the aperture distribution variability, matrix diffusion, and specific discharge on the solute and microsphere transport were determined from the transport tests conducted in two fractures. The higher variability in the aperture distribution contributed to higher solute dispersion, and flow channeling as evident from the breakthrough curves for individual spatially distributed outlets. A three-dimensional model simulation of the bromide transport with varying matrix porosity identified that the porous matrix influenced the solute transport. In the transport tests, retention of the microspheres decreased with increasing specific discharge in both fractures. The results of this research have helped in identifying the important factors and their effects on solute, virus, and virus-sized colloid transport in fractured dolomite rocks, which can be useful in determining the risk of pathogen contamination of water supplies in fractured dolomite rock aquifers.
786

Mechanisms of microstructure development at metallic-interlayer/ceramic interfaces during liquid-film-assisted bonding

Sugar, Joshua D. January 2003 (has links)
Thesis (M.S.); Submitted to the University of California, Berkeley, CA (US); 1 Dec 2003. / Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--54185" Sugar, Joshua D. USDOE Director. Office of Science. Basic Energy Sciences (US) 12/01/2003. Report is also available in paper and microfiche from NTIS.
787

Les effets de la rugosité de surface du moule sur a microstructure et la résistance à la déchirure à chaud pour un alliage A1 - 4.5%p/p Cu /

Fortier, Martin, January 2000 (has links)
Mémoire (M.Sc.A.)--Université du Québec à Chicoutimi, 2000. / Document électronique également accessible en format PDF. CaQCU
788

Análise de superfícies de peças retificadas com o uso de redes neurais artificiais

Paula, Wallace Christian Feitosa de [UNESP] 26 January 2007 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:23:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-01-26Bitstream added on 2014-06-13T18:09:42Z : No. of bitstreams: 1 paula_wcf_me_bau_prot.pdf: 7449514 bytes, checksum: 2e4729f72ced2d131784cfe27d6be1ad (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O cenário mundial tem apresentado um ambiente de alta competição industrial, pressionando cada vez mais as indústrias a tornarem seus processos produtivos mais eficientes. Além da eficiência, a precisão é de extrema importância num ambiente onde as empresas tentam manter padrões e procedimentos que se adaptem às normas internacionais. Um dos processos de acabamento mais utilizados na fabricação de componentes mecânicos de precisão é a retificação, e um dos critérios preponderantes na qualidade final de um produto é a integridade superficial, influenciada principalmente por fatores térmicos e mecânicos. Assim, o objetivo deste trabalho foi investigar as relações intrínsecas entre a qualidade superficial de peças retificadas e o comportamento dos sinais correspondentes de emissão acústica e potência de corte para retificação tangencial plana utilizando-se redes neurais artificiais. A caracterização da qualidade superficial das peças foi analisada por meio de parâmetros de queima superficial, rugosidade e microdureza. Verificou-se que o uso de redes neurais artificiais na caracterização da qualidade de superfícies de peças retificadas obteve bons resultados, apresentando-se como uma proposta interessante para implementação de sistemas inteligentes em ambientes industriais. / The world scenario has presented a high industrial competition, pressuring each time more the industries to change its more efficient productive processes. Besides efficiency, the precision is of extremely in a world where the companies try to maintain patterns and procedures that fit international demands. One of the most used final processes in the manufacturing of mechanical precision components is grinding, and one of the main criteria in the final quality of a product is its surface integrity, mainly influenced by thermal and mechanical factors. Thus, the objective of this work is to investigate the existing relationships between the surface quality of grinding workpieces and the behavior of correspondent signal of acoustic emission and cutting power to the surface grinding machines using artificial neural network. The characterization of the surface quality of the workpieces was analyzed through surface burning parameters, surface roughness and microhardness. It was verified that the use of artificial neural networks in the characterization of quality of surfaces grinding workipieces had positive results, being presented as an interesting proposal to implementation of intelligent systems in the industrial environments.
789

Efeito do fresamento com alta velocidade de corte na integridade superficial de aços ferríticos com grãos ultrafinos

Suyama, Daniel Iwao [UNESP] 20 September 2010 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:27:13Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-09-20Bitstream added on 2014-06-13T20:35:21Z : No. of bitstreams: 1 suyama_di_me_ilha.pdf: 1507336 bytes, checksum: 25314bb28cba6a4bdcb4957ea5b7de49 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A usinagem é um dos processos de fabricação mais utilizados mundialmente. Com destacada importância no setor industrial, este processo se encontra em contínua evolução com o surgimento de novos materiais (com propriedades melhoradas), novas ferramentas (mais resistentes ao desgaste e de custo reduzido) e novas máquinas (mais rígidas, mais precisas e com maior nível de tecnologia embarcada). Neste contexto surgiu a usinagem com altas velocidades de corte que, apesar do surgimento na década de 1930, tem pesquisas realizadas no meio acadêmico e industrial, mais aberta e divulgadamente, há cerca de 20 anos. Entretanto, a maioria dos trabalhos refere-se, de um modo geral, a estudos sobre produtividade, custo, desempenho de ferramentas e máquinas-ferramentas, entre outros. Poucos estudos procuram investigar possíveis efeitos desse tipo de usinagem na integridade superficial do produto usinado. Em função dessa lacuna e do aprimoramento de processo de obtenção de aços ferríticos com grãos ultrafinos (com refino de grão em toda seção transversal), este trabalho visou descobrir se há efeito do fresamento com alta velocidade de corte (High-Speed Cutting - HSC) sobre a rugosidade quantitativa e visual, sobre o campo de tensões residuais presentes na superfície (mensurados por difração de raios X) e sobre comportamento em fadiga (através de flexão em quatro pontos) da peça usinada. Observou-se que, quantitativamente, a rugosidade melhorou 63% quando comparada à usinagem feita sob condições ditas convencionais. De modo análogo, o campo de tensões residuais (de tração para ambas as condições convencional e HSC) foi reduzido em 73% e a resistência à fadiga para um determinado número de ciclos foi elevada, porém com limite de fadiga igual para todas as condições de usinagem. Em suma, do ponto de vista do desempenho, a usinagem HSC provém melhorias significativas ao componente usinado / Machining is one of the most widely used manufacturing processes worldwide. With outstanding importance in the industrial sector, this process is continually evolving with the emergence of new materials (with improved properties), new tools (more wear resistance and low cost) and new machines (more stiffness, more precision and with a higher level of embedded technology). In this context came the machining with high speed cutting that, despite the rise in the 1930s, has researches conducted in academy and industry, with more emphasis, about 20 years ago. However, most of the works refers, in general, to studies on productivity, cost, performance of tools and machine tools, among others. Few studies seek to investigate possible effects of this type of machining on surface integrity of the machined product. Because of this gap on this subject and the enhancement of the process to obtain low carbon ferritic steels with ultrafine grains (with grain refinement throughout the whole cross section), this work searched whether there is effect of milling with high speed cutting (High-Speed Cutting - HSC) on the quantitative and visual roughness, on the residual stress field on the surface (measured by X-ray diffraction) and on the fatigue limit (by four point bending) of the workpiece. It was observed that, quantitatively and in average, the roughness reduced 63% when compared to machining done under stated conventional conditions. Similarly, the residual stress field (tensile for both conventional and HSC conditions) was reduced by 73% and the fatigue strength was improved, but with fatigue limit equal to all cutting conditions. In short, from the standpoint of performance, HSC machining brings significant improvements for the machined component
790

Efeito do fresamento com alta velocidade de corte na integridade superficial de aços ferríticos com grãos ultrafinos /

Suyama, Daniel Iwao. January 2010 (has links)
Resumo: A usinagem é um dos processos de fabricação mais utilizados mundialmente. Com destacada importância no setor industrial, este processo se encontra em contínua evolução com o surgimento de novos materiais (com propriedades melhoradas), novas ferramentas (mais resistentes ao desgaste e de custo reduzido) e novas máquinas (mais rígidas, mais precisas e com maior nível de tecnologia embarcada). Neste contexto surgiu a usinagem com altas velocidades de corte que, apesar do surgimento na década de 1930, tem pesquisas realizadas no meio acadêmico e industrial, mais aberta e divulgadamente, há cerca de 20 anos. Entretanto, a maioria dos trabalhos refere-se, de um modo geral, a estudos sobre produtividade, custo, desempenho de ferramentas e máquinas-ferramentas, entre outros. Poucos estudos procuram investigar possíveis efeitos desse tipo de usinagem na integridade superficial do produto usinado. Em função dessa lacuna e do aprimoramento de processo de obtenção de aços ferríticos com grãos ultrafinos (com refino de grão em toda seção transversal), este trabalho visou descobrir se há efeito do fresamento com alta velocidade de corte (High-Speed Cutting - HSC) sobre a rugosidade quantitativa e visual, sobre o campo de tensões residuais presentes na superfície (mensurados por difração de raios X) e sobre comportamento em fadiga (através de flexão em quatro pontos) da peça usinada. Observou-se que, quantitativamente, a rugosidade melhorou 63% quando comparada à usinagem feita sob condições ditas convencionais. De modo análogo, o campo de tensões residuais (de tração para ambas as condições convencional e HSC) foi reduzido em 73% e a resistência à fadiga para um determinado número de ciclos foi elevada, porém com limite de fadiga igual para todas as condições de usinagem. Em suma, do ponto de vista do desempenho, a usinagem HSC provém melhorias significativas ao componente usinado / Abstract: Machining is one of the most widely used manufacturing processes worldwide. With outstanding importance in the industrial sector, this process is continually evolving with the emergence of new materials (with improved properties), new tools (more wear resistance and low cost) and new machines (more stiffness, more precision and with a higher level of embedded technology). In this context came the machining with high speed cutting that, despite the rise in the 1930s, has researches conducted in academy and industry, with more emphasis, about 20 years ago. However, most of the works refers, in general, to studies on productivity, cost, performance of tools and machine tools, among others. Few studies seek to investigate possible effects of this type of machining on surface integrity of the machined product. Because of this gap on this subject and the enhancement of the process to obtain low carbon ferritic steels with ultrafine grains (with grain refinement throughout the whole cross section), this work searched whether there is effect of milling with high speed cutting (High-Speed Cutting - HSC) on the quantitative and visual roughness, on the residual stress field on the surface (measured by X-ray diffraction) and on the fatigue limit (by four point bending) of the workpiece. It was observed that, quantitatively and in average, the roughness reduced 63% when compared to machining done under stated conventional conditions. Similarly, the residual stress field (tensile for both conventional and HSC conditions) was reduced by 73% and the fatigue strength was improved, but with fatigue limit equal to all cutting conditions. In short, from the standpoint of performance, HSC machining brings significant improvements for the machined component / Orientador: Alessandro Roger Rodrigues / Coorientador: Ruis Camargo Tokimatsu / Banca: Hidekasu Matsumoto / Banca: Anselmo Eduardo Diniz / Mestre

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