No description available.

The purpose of this work was to develop a steel tempering model that is useful to the commercial heat treater. Most of the tempering models reported address isothermal conditions which are not typical of most heating methods used to perform the tempering heat treatment. In this work, a non-isothermal tempering model was developed based on the tempering response of four steel alloys. This tempering model employs the quantity resulting from the numerical integration of the time-temperature profiles of both the heating and cooling portions of the tempering cycle. The model provided a very good agreement between experimental and predicted hardness when secondary hardening did not occur. The developed tempering model was then used as the basis for a process simulation model of a large indirect gas-fired furnace. Unlike the small-scale laboratory experiments performed in the development stage of this work, the temperature variation in this furnace was significant. Recording the temperature with time at 29 locations within the furnace allowed for suitable characterization of the temperature variation. The thermal data was used as inputs in a finite element method model and the time – temperature profiles of three production heavy truck side rails were then simulated. The tempering model provided a good prediction of the tempered hardness compared to experimental measurements. Finally, conclusions are drawn and suggestions are made for future work. / Ph. D.

[pt] Nós começamos essa dissertação com um panorama geral e introdutório dos tópicos de Sensibilidade a Ruído e Percolação . Como essas áreas podem ser desconhecidas por muitos estudantes de pós-graduação, nós apresentamos o material de uma maneira acessível, com o intuito de divulgar importantes técnicas e resultados dessas áreas. Nós também vamos introduzir o modelo para Percolação de Voronoi e apresentar resultados sobre probabilidades de cruzamentos neste modelo. Nos últimos dois capulos nós iremos considerar Sensibilidade a Ruído para Percolação do tipo quenched. Em particular, no penúltimo capítulo nós vamos apresentar resultados do artigo Quenched Voronoi Percolation de Daniel Ahlberg, Simon Griffiths, Robert Morris e Vincent Tassion, e no último capítulo provaremos um teorema que melhora uma das cotas deste artigo. / [en] We begin this dissertation by giving an introductory overview of the topics of Noise Sensitivity and Percolation. As these areas may be unfamiliar to many graduate students, we present the material in an accessible way, with the objective of publicising important techniques and results in these areas.We shall also introduce the model of Voronoi Percolation and present results of Vincent Tassion on crossing probabilities in this model. In the last two chapters we consider Noise Sensitivity of Quenched Voronoi Percolation. In particular, in the penultimate chapter we present the results of the paper Quenched Voronoi Percolation by Daniel Ahlberg, Simon Griffiths, Robert Morris and Vincent Tassion, and in the final chapter we prove a theorem which improves one of the bounds of that paper.

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第19200号 / 人博第741号 / 新制||人||178(附属図書館) / 27||人博||741(吉田南総合図書館) / 32192 / 京都大学大学院人間・環境学研究科共生人間学専攻 / (主査)教授 宇敷 重廣, 教授 森本 芳則, 准教授 木坂 正史 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DGAM

In this PhD thesis, we investigate instances of how quenched disorder, charge fluctuations, and reduced spatial symmetries can alter the nature of phases and/or phase transitions in many-body systems with active -- and often frustrated -- magnetic degrees of freedom. The thesis is divided into three parts, each of which focuses on the impact of one of the aforementioned perturbations on a different type of physical system. Part I is concerned with the influence of quenched disorder on spiral spin liquids, i.e., correlated states of matter in which a frustrated magnet evades order by fluctuating between a set of degenerate (or quasi-degenerate) coplanar spin spirals. Using the classical J1-J2 Heisenberg model on the honeycomb lattice as a prototype, we analyze effects driven both by (i) isolated impurities and (ii) nonvanishing concentrations of defects at zero temperature. We address (i) by employing perturbative analytical techniques to identify different order-by-quenched-disorder mechanisms and characterize the impurity-induced spin textures. Besides demonstrating that systems hosting spiral spin liquids are exceptionally susceptible to long-range deformations, we prove that the textures generally acquire an oscillatory out-of-plane component which carries direct information about the ground-state manifold and, remarkably, constitutes a bosonic analogue of Friedel oscillations in metals. We investigate (ii) by performing extensive numerical simulations as a means to characterize the zero-temperature phases realized for different types of disorder. Our results show that the competition between incompatible order-by-quenched-disorder mechanisms can, already at a low to moderate concentrations of defects, destabilize long-range order and induce 'spiral spin-glass' states, in which spins are frozen despite displaying spatial correlations akin to those of a spiral spin liquid. We interpret this finding in the light of effective low-energy theories, which allow us to make concrete statements about the fate of the system at nonzero temperatures. Finally, we discuss extensions of our conclusions to three-dimensional models, as well as their applications to experiments. In Part II, we examine how strong valence fluctuations affect quantum phase transitions marked by the breakdown of coherent Kondo screening in metals with lattices of local magnetic moments. To this end, we study a generalized Anderson lattice model via a parton mean-field theory that describes various Kondo-screened phases in addition to a fractionalized Fermi liquid -- an unscreened phase where electron-like quasiparticles from the conduction sea coexist with fractionalized excitations of a quantum spin liquid. Our results indicate that, at fixed chemical potential, abrupt valence changes can coincide with Kondo breakdown transition and render it discontinuous. We also show that, at a fixed total filling, this translates into phase-separation tendencies which, upon the inclusion of long-range Coulomb interactions, give rise to inhomogeneous states where Kondo-screened and unscreened regions coexist on a mesoscopic scale. We conclude by connecting our findings to experiments in heavy-fermion compounds and other condensed-matter systems. Finally, Part III discusses how the reduction of the spatial symmetries of an SU(2) or generalized SU(N) antiferromagnet can induce different types of magnetic order. This thread includes two separate projects. First, we study the precise means through which a collinear SU(2) Heisenberg antiferromagnet becomes a ferrimagnet once all symmetries between its magnetic sublattices are eliminated. Using general symmetry principles, we elucidate that this process is associated with the splitting of degenerate magnon bands and that the unequal thermal population of the latter is ultimately what generates a uniform magnetization. We thus establish that, in the systems under consideration, ferrimagnetism is induced by thermal fluctuations and that the resulting magnetization curve has a nonmonotonic temperature dependence. This prediction is then supported by an explicit linear spin-wave calculation for a layered variant of a J1-J2 Heisenberg model on a square lattice, which allows us to analytically derive the low-temperature behavior of the uniform magnetization. We show that the same T^4 power law and general qualitative behavior is obtained for a layered and distorted version of the Shastry-Sutherland model. Finally, we complement our results by positively identifying fluctuation-induced ferrimagnetism in Mn2Mo3O8 and discussing the prospects for its emergence in the high-pressure phases of SrCu2(BO3)2. Second, we demonstrate that the concept of altermagnetism, a type of magnetic order that has attracted great interest lately as a potential gateway to unconventional phases of matter and novel technological applications, can be extended to SU(N) magnets with N>2. To begin, we indicate how simple models for such generalized altermagnets can be constructed by reducing the spatial symmetries of SU(N) Heisenberg Hamiltonians with N-color antiferromagnetic ground states. We then apply this procedure to concrete examples with N<5 and conduct comparative analyses of our N=2 and N=3 models via linear spin-wave and flavor-wave calculations. As a result, we find that both systems share the same characteristic behavior of insulating altermagnets, namely a symmetric splitting between magnon bands with different sets of quantum numbers and definite chiralities. Finally, we show that the analogy between the models persists when they are supplemented with charge carriers to become metallic. Much like its SU(2) counterpart, the SU(3) altermagnet exhibits flavor-split electronic bands with crossings determined by a combination of spin and lattice symmetries.:1 Introduction I Magnetic frustration, quenched disorder, and their interplay 2 Elements of frustrated magnetism 2.1 Heisenberg magnetism in Mott insulators 2.2 Frustration and classical ground-state degeneracies 2.3 Order by disorder 2.3.1 Thermal order by disorder 2.3.2 Quantum order by disorder 2.3.3 Conceptual differences and possible competition between thermal and quantum order by disorder 2.3.4 Pseudo-Goldstone modes and experimental realizations 2.4 Classical spin liquids 2.5 Quantum spin liquids 3 Quenched disorder in magnetic systems 3.1 Types of disorder and their consequences 3.2 Random-field disorder: Stability of long-range order and the Imry-Ma argument 3.3 Random-mass disorder: Rounding of first-order phase transitions and the Harris criterion 3.4 Spin glasses: Basic concepts and experimental signatures 3.4.1 The spin glass transition 4 Spiral spin liquids 4.1 J1-J2 Heisenberg model on the honeycomb lattice 4.1.1 Teaser: Enhanced ground-state degeneracy at J2/J1 = 1/2 4.2 Classical ground states and the spiral contour 4.3 Influence of thermal fluctuations 4.3.1 Low temperatures: Thermal order by disorder and nematic order 4.3.2 Intermediate temperatures: Spin liquid regimes 4.4 Linear spin-wave theory and quantum order by disorder 5 Disorder effects in spiral spin liquids 5.1 Disordered J1-J2 Heisenberg model on the honeycomb lattice 5.2 Isolated impurities 5.2.1 Linear response theory: Spin textures and energy corrections 5.2.2 Order by quenched disorder 5.2.3 Friedel-like oscillations 5.2.4 In-plane textures and their impact on long-range order 5.3 Numerics on clean finite systems 5.4 Nonvanishing concentration of impurities 5.4.1 Bond defects of the same type and orientation 5.4.2 Bond defects of random orientation: Emergent glassiness from competing order-by-quenched-disorder mechanisms 5.4.3 Randomly distributed vacancies 5.5 Effects or thermal fluctuations and additional couplings 5.5.1 J1-J2 honeycomb model 5.5.2 Spiral spin liquids in three dimensions 5.6 Connections to experiments 5.7 Summary and outlook II Quantum phase transitions in local-moment metals 6 Single-impurity and lattice Kondo effects: Experimemtal signatures, theory basics, and Kondo breakdown 6.1 Dilute magnetic impurities in metals and the Kondo effect 6.1.1 The Anderson impurity model and local moment formation 6.1.2 From the Anderson to the Kondo model 6.1.3 Kondo temperature and the onset of screening 6.1.4 Breakdown of the Kondo effect in quantum impurity models 6.2 Heavy-fermion metals and Kondo lattices 6.2.1 Anderson and Kondo lattice models 6.2.2 Heavy Fermi liquid 6.2.3 RKKY interaction 6.2.4 Doniach picture and quantum criticality in heavy-fermion systems 6.2.5 Breakdown of screening in Kondo lattices 7 Kondo-breakdown transitions and phase-separation tendencies in valence-fluctuating heavy-fermion metals 7.1 Anderson-Heisenberg lattice model and relevant limits 7.2 Parton mean-field theory 7.2.1 Mean-field equations 7.2.2 Implementation: Lattice, numerics, and temperature regime 7.3 Mean-field phases and phase diagrams 7.3.1 Mean-field phases 7.3.2 Phase diagram and Kondo breakdown at a fixed chemical potential 7.3.3 Phase diagram and Kondo breakdown at a fixed filling 7.4 Discussion: Fluctuation effects, frustrated phase separation, and inhomogeneous states 7.5 Summary and outlook III Modifying magnetic order by symmetry reduction 8 Classification of nonrelativistic collinear magnetic states 8.1 Spin-space and spin point groups 8.1.1 Four classes of collinear magnetism 8.2 Application to collinear magnets in metallic systems 8.3 Application to collinear magnets in insulating systems 8.3.1 Linear spin-wave theory for a collinear Heisenberg magnet 8.3.2 Symmetries of the linear spin-wave spectrum 9 Fluctuation-induced ferrimagnetism 9.1 Ferrimagnetism from thermal fluctuations in a toy model 9.1.1 The toy model, its symmetries, and its ground state 9.1.2 Ground-state antiferromagnetism 9.1.3 Spin-wave spectrum 9.1.4 Uniform magnetization at T>0 9.1.5 Discussion: Nonmonotonic magnetization curves and the influence of magnetic anisotropies 9.2 Ferrimagnetism in a layered and distorted Shastry-Sutherland model 9.2.1 Background: The Shastry-Sutherland model 9.2.2 The layered and distorted Shastry-Sutherland model 9.2.3 Spin-wave theory: Magnon spectrum and ferrimagnetism 9.2.4 Application to SrCu(BO3)2 under pressure 9.3 Summary and outlook 10 From SU(2) to SU(N) altermagnetism 10.1 Prelude: Elements of the theory of su(N) algebras, their representations, and applications to magnetism 10.1.1 The {M,0} irreps of SU(N): Schwinger bosons and the Holstein-Primakoff transformation 10.2 Heisenberg models for SU(N) altermagnetism 10.2.1 Symmetries and good quantum numbers 10.2.2 SU(2) Heisenberg model on the checkerboard lattice 10.2.3 SU(3) Heisenberg model on the hexatriangular lattice 10.2.4 SU(4) Heisenberg model on the cross-cubic lattice 10.3 Spin-wave and flavor-wave theories: Magnon spectra and their symmetries 10.3.1 SU(2) altermagnet 10.3.2 SU(3) altermagnet 10.4 Magnon chirality 10.4.1 SU(2) altermagnet 10.4.2 SU(3) altermagnet 10.5 Electronic band structure: Spin- and flavor-split bands 10.5.1 SU(2) checkerboard Kondo lattice model 10.5.2 SU(3) hexatriangular Kondo lattice model 10.6 Summary and outlook Appendices A Ground-state degeneracy at J2/J1 = 1/2 (Chapter 4) B Iterative minimization algorithm (Chapter 5) C Details on derivations from Chapter 5 C.1 Derivation of Eq. (5.10) C.2 Derivation of Eq. (5.16) C.3 Asymptotic behavior of Friedel-like oscillations for a circular spiral contour D In-plane component of impurity-induced textures: A case study (Chapter 5) D.1 Implementation D.2 Nearest-neighbor bond defect D.3 Next-nearest-neighbor bond defect D.4 Vacancy D.4.1 Changes in textures with increasing J2/J1 E Different parton mean-field theories (Chapter 7) E.1 Fermionic SU(N) and Sp(2N) theories E.1.1 SU(N) large-N limit E.1.2 Sp(2N) large-N limit E.2 Compressibility of different homogeneous spin-liquid states Bibliography

No description available.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Neste trabalho estudamos o espectro das massas de blindagem mais baixas em teorias do tipo Yang_Mills na rede.Utilizamos os grupos de calibre SU(2) e SU(3) em 2+1 e 3+1 dimensões. Os cálculos foram realizados perto da temperatura crítica da transição de fase confinamento-desconfinamento. Obtivemos valores para as razôes entre as massas consistentes com os valores previstos a partir de universidade. / In this work we study the spectrum of the lowest screening masses for Yang-Mills theories on the lattice. We used the gauge groups SU(2) and SU(3) in 2 + 1 and 3 + 1 dimensions. Calculations were done near the critical temperature of the confinement-desconfinement phase transition. We obtained values for the ratios of the screening masses consistent with predictions from universality arguments.

Submitted by RONIVALDO RODRIGUES DA SILVA (rds.roni@yahoo.com.br) on 2016-03-01T13:46:53Z No. of bitstreams: 1 Tese Doutorado RONIVALDO R. SILVA.pdf: 3318357 bytes, checksum: 82fadd527a2ede34e2a0a237a881e8f8 (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-03-01T18:27:48Z (GMT) No. of bitstreams: 1 silva_rr_dr_sjrp.pdf: 3318357 bytes, checksum: 82fadd527a2ede34e2a0a237a881e8f8 (MD5) / Made available in DSpace on 2016-03-01T18:27:48Z (GMT). No. of bitstreams: 1 silva_rr_dr_sjrp.pdf: 3318357 bytes, checksum: 82fadd527a2ede34e2a0a237a881e8f8 (MD5) Previous issue date: 2016-02-12 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Aspártico (E.C. 3.4.23), cisteíno (E.C. 3.4.22) e serino peptidases (E.C. 3.4.21) são endopeptidases, cujos modos de ação são dependentes de resíduos de ácido aspártico, cisteína e serina presentes no sítio catalítico, respectivamente. Atualmente, vários estudos são realizados na busca por novas enzimas com relevantes propriedades bioquímicas para aplicação industrial. Neste contexto, nós propomos a produção de enzimas em bioprocesso submerso, purificação, estudo das propriedades bioquímicas e determinação da especificidade catalítica das peptidases secretadas pelos fungos filamentosos Rhizomucor miehei, Phanerochaete chrysosporium e Leptosphaeria sp. Inicialmente, após produção por bioprocesso submerso, estas enzimas foram purificadas utilizando cromatografias de exclusão molecular e troca iônica. Em ensaios de inibidores na atividade enzimática, notamos inibição das peptidases por pepstatina A (R. miehei), ácido iodoacético/N-Etilmaleimida (P. chrysosporium) e fluoreto de fenil metil sulfonila (Leptosphaeria sp), sendo então definidas como aspártico, cisteíno e serino peptidases, respectivamente. Por SDS-PAGE (12%), as massas moleculares foram estimadas em 37 kDa (aspártico), 23 kDa (cisteíno) e 35 kDa (serino). O máximo de atividade proteolítica foi alcançado em pH 5,5 e 55 ºC para peptidase aspártica secretada por R. miehei; pH 7 e faixa de temperatura 45-55 ºC para cisteíno peptidase secretada por P. chrysosporium, e pH 7 e 45 ºC para serino peptidase secretada por Leptosphaeria sp. Sob efeito de incubação a diferentes pH, a peptidase aspártica mostrou-se estável em condições ácidas (pH 3-5); cisteíno peptidase foi estável em ampla faixa de pH (pH 4-9), e serino peptidase mostrou-se mais estável em condições com tendências alcalinas e pH ligeiramente ácido (pH 5-9). Em todas estas faixas de pH citadas, as peptidases apresentaram atividade proteolítica acima de 80% por 1 hora de incubação. Quanto à estabilidade térmica, a cisteíno peptidase mostrou-se mais termoestável dentre as três enzimas e serino peptidase descreveu a menor tolerância à temperatura. Em incubação com agentes desnaturantes, observamos redução na atividade proteolítica sob efeito de surfactantes iônicos (0,02-1%): dodecil sulfato de sódio (SDS) e brometo de cetil-trimetil amônio (CTAB); íon cobre II (5 mM); Ditiotreitol (DTT) e guanidina (ambos na faixa de 10-200 mM) para todas as peptidases. Por último, em estudo de especificidade catalítica destas enzimas, observamos a preferência por aminoácidos aromáticos (F e W), básicos (K e R) e apolares (em particular, resíduo de metionina) para peptidase aspártica. Alta especificidade descrita por cisteíno peptidase, cuja preferência catalítica é notória por aminoácidos básicos (K, H e R), especialmente na posição P3 e lisina-dependência para catálise na posição P'3. Em serino peptidase, notamos maior aceitação por aminoácidos apolares (G, I, L, M e V), básicos (H e R) e polares neutros (N e Q) para as diferentes posições avaliadas no substrato. / Aspartic (EC 3.4.23), cysteine (EC 3.4.22) and serine peptidases (EC 3.4.21) are endopeptidases whose modes of action are dependent on aspartic acid, cysteine and serine residues present in the catalytic site, respectively. Currently, several studies are conducted in the search for new enzymes with relevant biochemical properties for industrial application. In this context, we propose the production of enzymes in submerged bioprocess, purification, the study of biochemical properties and determining the catalytic specificity peptidases secreted by the filamentous fungus Rhizomucor miehei, Phanerochaete chrysosporium and Leptosphaeria sp. Initially, after production submerged bioprocess, these enzymes have been purified using size-exclusion and ion exchange chromatographies. In the effect of inhibitors on enzyme activity, we note peptidase inhibition by pepstatin A (R. miehei), iodoacetic acid/ N-Ethylmaleimide (P. chrysosporium) and phenyl methyl sulfonyl fluoride (Leptosphaeria sp), suggesting that these enzymes are aspartic, cysteine and serine peptidases, respectively. For SDS-PAGE (12%), molecular weights were estimated at 37 kDa (aspartic), 23 kDa (cysteine) and 35 kDa (serine). Maximum proteolytic activity was achieved at pH 5.5 and 55 °C for aspartic peptidase secreted by R. miehei; pH 7 and temperature range 45-55 °C for cysteine peptidase secreted by P. chrysosporium and pH 7 and 45 °C for serine peptidase secreted by Leptosphaeria sp. Under incubation at different pH effect, aspartic peptidase was stable under acidic conditions (pH 3-5); cysteine peptidase was stable in wide pH range (pH 4-9), and serine peptidase was more stable under alkaline conditions and pH slightly acidic (pH 5-9). In all these pH ranges mentioned, peptidases showed proteolytic activity above 80% by 1 hour incubation. As regards the thermal stability, cysteine peptidase was more thermostable enzyme and serine peptidase described the lowest temperature tolerance. In incubation with denaturing agents, we observed a decrease in proteolytic activity under the effect of ionic surfactant (0.02-1%) sodium dodecyl sulfate (SDS) bromide and cetyl-trimethyl ammonium bromide (CTAB); copper (II) ion (5 mM); Dithiothreitol (DTT) and guanidine (both in the range of 10-200 mM) for all peptidases. Finally, the study of catalytic specificity of these enzymes, we found a preference for aromatic amino acids (F and W), basic (K and R) and nonpolar (in particular, methionine residue) to aspartic peptidase. High specificity described by cysteine peptidase, which a catalytic preference is notorious for basic amino acids (K, R and H), especially in position P3 and lysine-dependence for catalysis at position P'3. In serine peptidase, for different evaluated positions, we noticed greater acceptance by nonpolar amino acids (G, I, L, M and V), basic (M and R) and neutral polar (N and Q).

Made available in DSpace on 2014-12-17T14:58:24Z (GMT). No. of bitstreams: 1 IgorLA_DISSERT.pdf: 5014153 bytes, checksum: b4c50270935571b9e1c875a8c15841c3 (MD5) Previous issue date: 2014-02-26 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / In machining of internal threads, dedicated tools, known as taps, are needed for each profile type, diameter, and low cutting speed values are used when compared to main machining processes. This restriction in the cutting speed is associated with the difficulty of synchronizing the tool s rotation speed and feed velocity in the process. This fact restricts the flexibility and makes machining lead times longer when manufacturing of components with threads is required. An alternative to the constraints imposed by the tap is the thread milling with helical interpolation technique. The technique is the fusion of two movements: rotation and helical interpolation. The tools may have different configurations: a single edge or multiple edges (axial, radial or both). However, thread milling with helical interpolation technique is relatively new and there are limited studies on the subject, a fact which promotes challenges to its wide application in the manufacturing shop floor. The objective of this research is determine the performance of different types of tools in the thread milling with helical interpolation technique using hardened steel workpieces. In this sense, four tool configurations were used for threading milling in AISI 4340 quenched and tempered steel (40 HRC). The results showed that climb cut promoted a greater number of machined threads, regardless of tool configuration. The upcut milling causes chippings in cutting edge, while the climb cutting promotes abrasive wear. Another important point is that increase in hole diameter by tool diameter ratio increases tool lifetime / Na usinagem de roscas internas, ferramentas dedicadas, conhecidas como machos r?gidos s?o necess?rios para cada tipo de perfil e di?metro, al?m de reduzidos valores de velocidade de corte quando comparado aos principais processos de usinagem. Esta restri??o na velocidade de corte est? associada ? dificuldade de sincroniza??o da rota??o e velocidade de avan?o da ferramenta no processo. O fato restringe a flexibilidade e torna os tempos de usinagem longos diante da manufatura de componentes com roscas. Uma alternativa as restri??es impostas pelos machos r?gidos na usinagem de roscas ? o fresamento com a t?cnica de interpola??o helicoidal. A t?cnica ? a fus?o de dois movimentos: rota??o e interpola??o helicoidal. As ferramentas podem ter diferentes configura??es: uma ?nica aresta ou m?ltiplas arestas (no sentido axial, radial ou em ambos). Contudo, o fresamento de roscas com a t?cnica de interpola??o helicoidal ? relativamente novo e restritas pesquisas existem sobre o tema, fato que promove desafios para sua ampla aplica??o no ambiente de manufatura. O objetivo desta pesquisa ? determinar o desempenho dos diferentes tipos de ferramentas no fresamento de roscas com a t?cnica de interpola??o helicoidal em a?os endurecidos. Neste sentido, quatro ferramentas com diferentes configura??es foram utilizadas para usinagem de roscas em a?o AISI 4340 no estado temperado e revenido (40 HRC de dureza). Os resultados mostraram que a utiliza??o do corte concordante possibilitou a usinagem de um maior n?mero de roscas, independentemente do tipo de ferramenta. A utiliza??o do corte discordante causou avaria de lascamento nas arestas de corte, enquanto que o corte concordante promoveu desgaste abrasivo. Outro ponto relevante ? que o aumento da rela??o di?metro do furo e di?metro da ferramenta possibilitou incremento da vida da ferramenta