Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The demand for rail travel has increased over the years. As a result, it is becoming mandatory for railway industries to maintain very high availability of their assets to ensure that service levels are high. Railway industries require both their infrastructure and rolling stock assets maintained efficiently to sustain reliability. There has been on-going research on how maintenance can be carried out in a cost effective manner. However, the majority of this research has been done for infrastructure and the rolling stock maintenance has not been properly covered. The purpose of this research is to contribute to the maintenance sector of rolling stock for railway industries by developing a decision support model for rolling stock based on reliability and cost. The model is developed as an optimization problem of a system containing several components dependent on each other with different reliability characteristics. In this model, a mixed integer nonlinear problem is developed and solved using an exact method and metaheuristics methods. The Metrorail facility in Cape Town was chosen as a case study. Failure history and cost data were gathered from the facility and the information was applied to the model developed. The case study was investigated and different results were achieved using both exact and metaheuristics methods. The final result from the study is an optimal maintenance schedule based on reliability and cost. The developed model serves as a practical tool railway companies can adopt to schedule rolling stock maintenance to achieve a high level of reliability and at the same time maintaining minimum cost expenditure. / AFRIKAANSE OPSOMMING: Die vraag na spoorvervoer het oor die jare toegeneem. Dus het dit belangrik geword dat die spoorweg se bates hoogs toeganklik moet wees om te verseker dat die vlak van dienslewering hoog bly. Die spoorweg industrie besef dat hulle infrastruktuur, lokomotiewe, waens ens. effektief in stand gehou moet word sodat dit betroubaar kan wees. Navorsing word nog steeds gedoen oor hoe instandhouding op ’n koste-effektiewe wyse gedoen kan word. Die meeste van hierdie navorsing gaan egter oor infrastruktuur en instandhouding word nie ordentlik gedek nie. Die doel met hierdie navorsing is om by te dra tot die instandhoudingsektor van die spoorweg deur om ’n besluit-ondersteunende model vir lokomotiewe, waens, ens wat op betroubaarheid en koste gegrond is, te ontwikkel. Die model is ontwikkel as ’n optimasie probleem van ’n sisteem wat verskillende komponente wat van mekaar afhanklik is maar oor verskillende betroubaarheidskenmerke beskik, inluit. In hierdie model word ’n gemengde, heeltal nie-lineêre probleem ontwikkel en met ’n eksakte metode en metaheuristiese metodes opgelos. Die Metrorail fasiliteit in Kaapstad is vir die gevalle studie gekies. Die geskiedenis van mislukkings en koste data is by die fasiliteit versamel en die inligting is op die model wat ontwikkel is, toegepas. Die gevalle studie is ondersoek, en verskillende resultate is met eksakte en metaheuristiese metodes bereik. Die finale uitkomste van die studie is ’n optimale instandhoudingskedule wat op betroubaarheid en koste gegrond is. Die model wat ontwikkel is dien as ’n praktiese instrument wat spoormaatskappye kan gebruik om die instandhouding van lokomotiewe, waens ens. te reël sodat ’n hoë vlak van betroubaarheid bereik kan word en kostes terselfdertyd tot ’n minimum beperk kan word.

Submitted by Milena Rubi (milenarubi@ufscar.br) on 2017-08-16T14:34:16Z No. of bitstreams: 1 ZANCHETTA_Bianca_2017.pdf: 6817373 bytes, checksum: 19faa9d0aa5279e71d08211f9d262c35 (MD5) / Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2017-08-16T14:34:26Z (GMT) No. of bitstreams: 1 ZANCHETTA_Bianca_2017.pdf: 6817373 bytes, checksum: 19faa9d0aa5279e71d08211f9d262c35 (MD5) / Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2017-08-16T14:34:35Z (GMT) No. of bitstreams: 1 ZANCHETTA_Bianca_2017.pdf: 6817373 bytes, checksum: 19faa9d0aa5279e71d08211f9d262c35 (MD5) / Made available in DSpace on 2017-08-16T14:34:44Z (GMT). No. of bitstreams: 1 ZANCHETTA_Bianca_2017.pdf: 6817373 bytes, checksum: 19faa9d0aa5279e71d08211f9d262c35 (MD5) Previous issue date: 2017-04-27 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Aluminum sheets are produced by rolling followed by annealing. However when submitted to deep drawing earing appears, caused by the plastic anisotropy resulting from the production process. After annealing the main texture is cube {001} , that is recognized as being the cause of this heterogeneity during deep drawing. The literature shows that when shear stress is applied in the deformation process, it leads to texture changes. In this study asymmetric rolling (AR) was used as a technique to produce shear. The shear stress is introduced by the different velocities between the upper and bottom rolls and in this study this was achieved by using roll radius relations (r1/r2) of 1,5 and 2. Rolling reductions of 50% in thickness were applied to aluminum AA1050 sheets. The conventional rolling (CR) was compared to the asymmetric rolling (AR), at two different reduction rates: 5% and 10%. The crystallographic textures were obtained by xray diffraction. Finite element analysis, using the DEFORM software, was used to analyze the effective strain distribution throughout the thickness as well as its components: normal strain, shear strain and rigid body rotation. The samples were annealed in a furnace with 350°C for 05, 10, 15, 20 and 60 minutes. The microstructure was characterized by optical microscopy, electron back scatter diffraction and x-ray diffraction. The plastic anisotropy (Lankford Parameter) was measured by tensile experiments at three different sheet directions and by the Erichsen test. The deformed samples’ microstructure was analyzed at the surface near to the upper roll and at half of the thickness. For the CR the main components were brass (Bs) {011} , Goss (Gs) {011} and copper (Cu) {112} , with 8.8 intensity at the central layer, and 4.5 at the surface. For AR samples the was more random at the surface of the samples with 5% of reduction per pass, added to a component of rotation in the normal direction, what resulted in cube and rotated cube textures or near to these orientations, generating a type of fiber {100}//ND. The maximum intensities for the (r1/r2) of 1,5 and 2 were 3 and 4, respectively. For the samples with 10% of reduction per pass the rolled texture was still presented, with a more intense rotation in the transversal direction related to the rolling direction and shear texture components {100}//ND and . The maximum intensities were 3 and 3.5 , for the (r1/r2) of 1,5 and 2, respectively. In the center layer of the samples with 5% of reduction per pass for (r1/r2) of 1,5 and 2 showed a intensity of 5.26 and 6.56, respectively and the strongest shear texture was rotated Goss (C). (011)[0-1- 1] The samples with 10% reduction per pass showed the greatest reduction of intensity with 3.05 and 3.63, for the (r1/r2) of 1,5 and 2 respectively, and the highest intensity was related to rotate the Goss (011)[0-1-1] component. In the pole figures rotations around the transversal direction (TD) and the normal direction (ND) were observed. Using the finite element analysis the rotation around the TD and ND were quantified and its variation across the thickness were analyzed. The rigid body rotation is superposed to shear , which leads to the observed texture gradients. The rotation around TD is imposed by the velocity difference between top and bottom roll, whereas the ND rotation is imposed by the experimental configuration, which permit variation of the sample alignment at the roll mill entrance. This was stronger for the 5% reduction rate and more concentrated at the samples surface. After 05 minutes the annealed samples were already recrystallized , after 60 minutes the grain average size was 30µm, and hardness 21HV. The annealed texture for the CR sample showed the greatest concentration off Cube texture {001} and intensity of 8.08 times the random. For the AR samples with 5% reduction per pass the intensities for the (r1/r2) of 1,5 and 2 was 5.88 and 6.56, respectively, and for the 10% reduction per pass 2.96 and 2.85, respectively. The AR decreases the annealed texture. In the samples of 5% reduction per pass the most intense shear texture was rotated Goss, the 10% reduction per pass did not have a predominant component. The Lankford parameters showed less anisotropy for the annealed samples with 10% reduction per pass. Based on the values of anisotropy and hardening exponent for each sample, the Limiting Rate of Drawing was calculated. The AR got a superior values than the CR ones, indicating an improvement of the drawability. / Chapas de Alumínio são comumente produzidas por laminação seguida de recozimento. Entretanto, ao serem submetidas à estampagem profunda apresentam problemas de orelhamento, devido à anisotropia plástica. Durante o recozimento a textura predominante é a cubo {001} , esta textura é reconhecida como sendo a causadora da má estampabilidade. A literatura indica que é possível alterar a textura final aplicando cisalhamento durante o processamento do material, neste trabalho aplicamos a Laminação Assimétrica (LA) como forma de produzir cisalhamento sobre a chapa. Utilizando o alumínio AA1050 até atingir um total de 50% de redução em espessura, com relações de assimetria (LA) de (r1/r2) de 1,5 e 2 com 5% e 10% de redução por passe e Laminação Convencional (LC) com taxa de 10% de redução por passe. A deformação experimental foi comparada à simulação de elementos finitos utilizando o software DEFORM, e a distribuição de deformação equivalente foi analisada ao longo da espessura da chapa. As amostras passaram por recozimento em forno tipo MUFLA, a 350°C por 05, 10, 15, 20 e 60 minutos. As amostras deformadas foram caracterizadas por microscopia óptica e sua textura cristalográfica foi obtida por difração de raios-x. As amostras recozidas passaram por caracterização microestrutural por microscopia óptica, difração de elétrons retroespalhados (EBSD) e difração de raios-x. A caracterização mecânica foi feita por ensaios de dureza, de tração e pelo ensaio de embutimento Erichsen. A microestrutura das amostras deformadas foi analisada próxima a superfície do rolo superior e no plano central a espessura. Para a LC foram encontradas concentrações maiores de Bs {011} , Gs {011} , Cu {112} , com intensidade máxima de 8,8 para o centro da chapa e de 4,5 na superfície. Para as amostras LA houve uma maior aleatoriedade das texturas tanto na superfície quanto no plano central. As amostras com 5% de redução por passe apresentaram as melhores reduções de intensidades máximas, somada a uma componente de rotação na direção normal (DN) da chapa, as intensidades máximas para (r1/r2) 1,5 e 2 foram de 3 e 4 respectivamente. Nas amostras de 10% de redução por passe ainda estavam presentes as componentes de laminação com uma rotação mais acentuada ao redor da direção transversal (DT) a direção de laminação as intensidades máximas foram de 3 e 3,5 para (r1/r2) 1,5 e 2 respectivamente. No centro da chapa as amostras de 5% de redução por passe para (r1/r2) 1,5 e 2 apresentam intensidades de 5,26 e 6,56 respectivamente e a textura de cisalhamento mais forte foi a Goss rodado (011) [0 1 1 ] (C). Já as amostras de 10% de redução apresentam as maiores reduções de intensidade com 3,05 e 3,63, para (r1/r2) 1,5 e 2 respectivamente, e uma proporção maior de intensidade Goss rodado (C). A simulação numérica foi utilizada para quantificar as rotações de corpo rígido impostas pela deformação, indicadas nas figuras de pólo pelas rotações ao redor da DN e da DT. Quanto às rotações ao redor da DT, para as reduções de 5% o cisalhamento se concentra na superfície e a rotação de corpo rígido é relativamente mais intensa no centro da amostra; nas reduções de 10% uma contribuição mais intensa tanto da rotação quanto do cisalhamento foi obtida. Quanto à rotação ao redor de DN ela foi mais intensa na superfície da chapa e para a redução de 5%. Após 05 minutos de tratamento as amostras já se encontravam recozidas atingindo um tamanho de grão médio de cerca de 30µm, e dureza em torno de 21HV. A textura de recozimento da amostra LC apresentou maiores concentrações das texturas cubo {001} e intensidade de 8,08. Para a LA com 5% de redução por passe as intensidades são máximas para r1/r2 1,5 e 2 foram 5,88 e 6,56, respectivamente, já para as com 10% de redução por passe, 2,96 e 2,85, respectivamente, apresentando a maior redução de concentração de texturas, assim como no material deformado. A LA promoveu, portanto a redução da intensidade de textura de recozimento Nas amostras de 5% de redução por passe a textura de cisalhamento mais intensa foi a Goss rodado, já para as amostras de 10% não houve uma componente predominante. O ensaio de tração nas três direções apresentou uma menor anisotropia para as amostras recozidas com 10% de redução por passe. Baseado nos valores de anisotropia e encruamento para cada amostra foi calculado a taxa de limite de embutimento, na qual as amostras LA obtiveram um valor superior a LC, indicando possuírem um melhor comportamento ao ensaio.

L’hydrogène constitue un vecteur d’énergie très important. En effet, il est abondant à l’état combiné et sa combustion est très énergétique et non polluante. En revanche, le mode de stockage le plus sécurisant de ce gaz explosif c’est dans les métaux sous forme d’hydrure. Parmi ces métaux, le magnésium est l’un des plus prometteurs car il possède une capacité massique de stockage élevée (7,6%), un faible coût et une abondance naturelle. Cependant ses cinétiques de sorption sont lentes et son hydrure MgH2 est très stable et mauvais conducteur. L’objectif de ce travail de thèse est de contribuer à la résolution des points faibles du magnésium, en lui ajoutant des fibres de carbone comme renfort soit par broyage énergétique pour assurer une bonne intimité entre les deux, soit par coulage en bande, une technique qui permet d’orienter les fibres, pour un maximum de conductivité thermique. Nous étions donc intéressés à l’étude des cinétiques d’absorption/désorption où une amélioration a été observée après l’ajout du carbone par broyage. Une étude de la conductivité thermique était encore intéressante où le matériau préparé par coulage en bande, comme prévu, a présenté un très bon résultat. D’autre part, nous avons effectué des tests d’hydrolyse pour la production délocalisée d’hydrogène. Ayant comme problème la formation d’une couche imperméable de Mg(OH)2 en surface qui bloque la réaction, différents paramètres ont été modifiés (pH, T°, taille des particules, US) et cela a donné un impact positif sur le rendement en hydrogène et la cinétique de la réaction. Finalement, deux procédés de déformation plastique sévère i) le laminage et ii) l’ECAP ont été appliqués sur du TiH2 et du MgH2. Ces deux techniques ont présenté un pouvoir de déstabilisation des hydrures et donc une diminution de la température de déshydruration. Ils ont encore montré un comportement différent du broyage mécanique de point de vue microcontrainte et orientation des plans cristallins. / Hydrogen is a very important energy carrier. Indeed, it is abundant in the combined state and its combustion, very energetic, is non-polluting. However, the safest storage mode of this explosive gas is in the metal hydride form. Among metals, magnesium is one of the most promising one because its high mass capacity storage (7. 6%), low cost and natural abundance. However its kinetics of sorption are slow and its hydride MgH2 is very stable and has a poor thermal conductivity. The objective of this thesis is to resolve most of the weaknesses of magnesium by adding carbon fibers as reinforcement using the ball milling process, a way to ensure a good contact between the two, either by tape casting, a technique to help in the fibers’ orientation, for a maximum of thermal conductivity. We were therefore interested in the study of absorption / desorption kinetics, where an improvement was observed after the addition of carbon by grinding. A study of the thermal conductivity was also interesting, and the material prepared by tape casting, as expected, gave a very good result. On the other hand, we performed some hydrolysis’ tests to produce hydrogen. Having the problem of Mg(OH)2 formation on the surface, that blocks the reaction; different parameters were modified (e. G. PH, T°, particle size, U. S. ), which showed a positive impact on the hydrogen yield and reaction kinetics. Finally, two severe plastic deformation methods: i) cold rolling and ii) ECAP were applied to the TiH2 and MgH2 samples. Both techniques showed a destabilizing power of hydrides and therefore a decrease in the temperature of dehydrogenation. They even showed different behaviors than the mechanical grinding from microstrain and planes orientation point of view.

Examensarbetet har utförts under våren 2017 vid Bergsskolan i Filipstad, i samarbete med voestalpine Precision Strip i Munkfors. Att producera så kostnadseffektivt som möjligt likväl att minimera material som kasseras är något företag idag ser som självklart. På samma gång som detta efterlevs bör även kundnöjdheten maximeras. Utrymmet att göra fel har minskat vilket leder till en ständig strävan att undvika att produkter med oönskade defekter går ut till kund. För att nå detta måste företaget ha en förståelse för vilka mekanismer som påverkar vilka defekter. Syftet med det här arbetet är att dokumentera bandstålets processteg, från råmaterial till halvfabrikat. På så vis kan arbetets mål uppnås, det vill säga att hitta vilka möjliga orsaker som kan påverka bandstålets rakhet, specifikt den så kallade kortkrokigheten. Det finns två typer av rakhet, långkrok och kortkrok. Den som ställer till med problem vid beläggning och slipning av bandstål är den så kallade kortkroken. Därmed är det detta som voestalpine Precision Strip önskat hjälp med att kartlägga. Materialet som studerats var tre olika band av samma stålsort (UHB 20C), dessa var alla tänkta att gå vidare till beläggningen. För att bandet ska kunna beläggas måste materialet vara helt rakt, toleransen är +/- 33 µm, vilket många gånger innebär att bandet ser rakt ut trots en rakhetsavvikelse. Finns en avvikelse går det inte att färdigställa produkten utifrån kundspecifikation och materialet används då till annan slutprodukt, eller i värsta fall skrotas. För att kartlägga vilka mekanismer som bandstålet utsattes för användes den teoretiska ansatsen ”de sju förbättringsverktygen”, en teori utvecklad i Japan som är användbar då kvalitetsförbättringar efterfrågas. Arbetet börjades med litteraturstudier, det var svårt att hitta studier och annan litteratur som behandlar ämnet kortkrok i allmänhet och kortkrok i kallvalsat bandstål i synnerhet. Förutom litteratur erhölls en del information av personal på voestalpine Precision Strip i Munkfors. Det gjordes inga intervjuer utan enbart samtal med personal på plats i Munkfors. Dessa samtal ledde till ökad förståelse för vad problemet innebär och ett orsak-verkan-diagram gjordes. Fem möjliga orsaker till kortkrok vid kallvalsning av stål identifierades. Utifrån detta ritades ett flödesschema över hela processen upp. De fem möjliga orsakerna som studerades närmre var ·        tvärprofil ·        reduktionen i tre olika valsverk ·        kontaktlängd och valsmaterial i valsverken ·        rullsaxen som kantskär och slittar materialet ·        den mänskliga faktorn. Utifrån detta arbete kunde flera alternativa svar på problemet till varför kortkrok uppstår identifieras. Det kan vara stickserien i valsverk 311, bomberingen som var sliten/icke-sliten i valsverk 322, kontaktlängden i valsverk 345, materialet i arbetsvalsen i valsverk 311 eller rullsaxen. Ett antal orsaker som kan påverka att kortkrok uppkommer är överhuvudtaget inte är studerade. Till exempel värmebehandling, friktion och smörjmedel. I arbetet framkom en orsak som mest trolig till varför kortkroken uppstår, rullsaxen. Att rullsaxen påverkat kortkrokens uppkomst kan bero på den mänskliga faktorn likväl som att det kan bero på att den är felkonstruerad för just detta ändamål. I dagsläget saknas exakta rutiner för hur arbetsprocessen vid rullsaxen utförs, vilket inneburit att de som arbetar vid maskinen gör samma sak men på olika vis. Slutresultatet kan ha påverkats av vilken person som arbetat vid valsen. Det finns en möjlighet att voestalpine Precision Strip kan vinna på att ha detaljerade inställningsscheman så det är möjligt att utesluta att slutresultatet påverkas av vem som arbetar vid maskinen. / This thesis has been carried out during the spring of 2017 at Bergsskolan in Filipstad, in cooperation with voestalpine Precision Strip in Munkfors. The demands to produce as cost-effectively as possible is increasing as well as demands to minimize the amount of discarded materials and at the same time maximize customer satisfaction. To achieve this, the company must have an understanding for the mechanisms that influence the defects. The purpose of the thesis is to document the production steps of the strip steel process, from raw materials to processed steel. Doing that the goal can be achieved, i.e. to find the parameters that influence the strip steel's straightness, specifically the so-called camber. There are two types of straightness which causes problems and the important one in this thesis is the so-called camber. The material studied was three different strips of the same steel (UHB20C) which were all supposed to move on to the department CCB (Coated Coater Blades). But to proceed, the material must be perfectly straight. The tolerance is as small as +/-33 microns, which often means that the strip looks straight even when there is a straightness deviation. If so, the material may be used in a different application and occasionally it will be scrapped. To identify the mechanisms the strip steel was exposed to, the theoretical approach “the seven QC-tools", was used. This is a theory usable when quality improvements are demanded. The work begun with literature studies, however, it was very difficult to find studies and other literature that discussed camber in cold-rolled strip steel. In addition to literature some information was obtained through conversations with the staff in Munkfors. This led to better understanding about the problem. Afterwards it was time to draw a chart over the causes effecting the camber. Five parameters were identified as important and was chosen for closer looking. The parameters studied more closely were: ·        transverse profile ·        reductions done in the three different rolling mills ·        contact length and materials in the work roll ·        slitter scorer (the machine that slits the material) ·        human influence Then a flow chart of the entire process was drawn up. There are several alternative answers to the problem this paper is trying to solve. The answer could be among the parameters studied but it may as well be found among causes not studied. For example friction, lubricants or the heat treatment the material is exposed to. Due to all measurements done in this study there is one parameter most likely to be the cause of camber, the slitter scorer seems to influence the material straightness most of all. Though it is not cleared why the slitter scorer affects the camber more than the other production steps. It could be caused by human influence, it is a machine where very small mistakes, probably unconscious, can lead to big consequences. It may also be due to malfunction of the machine. Rolling is a craft which means that the person working at the rolling mill, and the other machines in the production process, has a big influence on final outcome. Voestalpine Precision Strip could probably gain a lot by having detailed setting schedules and measuring instruments that would help the staff doing the exact same thing every time. Hopefully the outcome would not fluctuate as much as it does in the current situation. / <p>Presentationen har redan ägt rum, i juni 2017 på Bergsskolan i Filipstad</p>

Les deux systèmes de création d’une contrainte dans les films polymériques ont été développés, chacun répondant à un gradient de gonflement du polymère dans la direction normale au film. Ce gonflement peut être provoqué soit par la présence d’un gradient de densité de réticulation dans la direction normale à la surface (films de poly(4-vinylpyridine) réticulés par UV ou dans les films de chitosan réticulés thermiquement et ioniquement ; ou soit par une pénétration asymétrique de vapeur de solvant dans le film (ici le polydiméthylsiloxane oxydé en surface). Un troisième système polymérique auto-enroulant a également été réalisé par la création d’une contrainte permanente au sein du film de polydiméthylsiloxane, grâce à l’extraction sélective d’un additif non-réticulé, l’huile de silicone. Un modèle théorique du processus d’auto-enroulement, basé sur la théorie linéaire d’élasticité a ainsi pu être proposé. / Two systems of stress creation in the polymer films were developed, each based on the swelling gradient in the direction normal to the film. This swelling may be caused either by the presence of a crosslinking density gradient in the direction normal to the surface (poly (4-vinylpyridine film) crosslinked by UV or in the thermally or ionically crosslinked chitosan films; or by asymmetric penetration of solvent vapor in the film (here polydimethylsiloxane surface-oxidized). A third self-rolling polymeric system has also been realized by the creation of a permanent strain in the polydimethylsiloxane film by selective extraction of a non-cross-linked additive, silicone oil. A theoretical model of self-rolling process based on the linear theory of elasticity has been proposed.

This paper provides an explanation of the concepts John A. Warden III describes regarding the use of air power and if this theory can be found, within the confines of an unconventional war. The U.S. ability to air power is overwhelming, however the right kind of warfare can force this great power to abandon their military and political objectives by exhausting its resources over time as it becomes increasingly costly, both economically, politically and morally, to wage war. The research deals with operation Rolling Thunder and John A. Warden IIIs theory in relation to this massive bombing campaign. Firstly, you will find an analysis of John. A. Warden III's works. Five concepts can be found: Airspace Control, center of gravity, air interdiction, the enemy as a system and parallel attack. Secondly, a content analysis of relevant literature in the context of a case study on Operation Rolling Thunder. Thirdly a comparative analysis between the two results with a subsequent discussion relating the main problem and an effort is made to determine the outcome of the investigation and if the purpose of this paper has been met. Within the implementation phases of Operation Rolling Thunder, it is possible to distinguish som of Wardens key concepts regarding air power utilization. Even though the four phases illustrate a continuous change in strategy, Wardens theory The Enemy as a system was never implemented. / Denna uppsats ger en förklaring av John A. Warden IIIs teori om nyttjande av luftmakt och de begrepp som utgör grunden för denna. Frågan om grundbegreppen går att återfinna inom ramarna för ett otraditionellt krig tas upp. USAs förmåga till luftmakt är stor, men med rätt sorts krigföring kan även denna makt tvingas överge sina militära och politiska mål genom utmattning över en längre tidsperiod eftersom det blir allt dyrare, både ekonomiskt, politiskt och moraliskt, att föra krig. Här avhandlas operationen Rolling Thunder och John A. Warden IIIs teoris anknytning till denna enorma bombkampanj. Inledningsvis återfinns en innehållsanalys av John. A. Warden IIIs litteratur, vilket utmynnar i fem begrepp: Luftrumskontroll, tyngdpunkter, flyganfall på djupet, fienden som ett system och parallell attack. Efter det följer en innehållsanalys av relevant litteratur inom ramen för en fallstudie om Rolling Thunder och slutligen påträffas en komparativ analys mellan de två resultaten och en efterföljande diskussion knyter an till problemformuleringen och försöker utröna resultatet av undersökningen och om syftet med uppsatsen uppfyllts. I genomförandefaserna av Operation Rolling Thunder är det möjligt att urskilja vissa av Wardens centrala begrepp och tankar om luftmaktens nyttjande, men hans teori som helhet går inte att återfinna i genomförandet av Rolling Thunder. Trots att de fyra faserna åskådliggör en upprepad förändring i strategi, användes aldrig Wardens teori om fienden som ett system.

[pt] O desenvolvimento de um aço microligado para a produção de vergalhões nervurados, busca atender a modernização das estruturas de concreto armado e a industrialização na construção civil que solicitam novos desenvolvimentos nas técnicas de construção e nos materiais aplicados. As barras de aço nervuradas são um dos principais produtos empregados na produção de peças e estruturas de concreto armado sendo usadas largamente por todo o mundo. A otimização da aplicação final, a necessidade de manter baixos custos de produção e atender a combinação de alta resistência com grande ductilidade em um material com características de soldabilidade destinados a armaduras de concreto armado, se tornou um grande desafio para os produtores de vergalhões para a construção civil. Aplicando a tecnologia desenvolvida ao longo dos últimos 50 anos, este trabalho oferece a alternativa de se empregar aços microligados ao vanádio e nióbio para a produção em laminadores de alta produção de rolos de vergalhões capazes de atender a indústria da construção civil nos mais rigorosos atributos solicitados. Os experimentos foram realizados em escala industrial testando aços com faixa de 0,14 porcento a 0,20 porcento de vanádio e até 0,04 porcento de nióbio. Os resultados atendem as normas mais exigentes no mercado mundial. / [en] The development of microalloyed steel for the production of reinforcement bars (rebar) seeks to achieve the modernization of reinforced concrete structures and streamline industrialization in civil construction that demands new developments in techniques and applied materials. Rebar is one of the main products used in the production of reinforced concrete all over the world. The optimization of the final application and the necessity to keep production low costs while attempting to combine high resistance with great ductility in a material with weldability characteristics, became a great challenge for the producers of rebars. Applying the technology developed throughout the last 50 years, this work offers the alternative of using vanadium and niobium microalloyed steel to produce large quantities of rebars in rolling mills. Upon completion these rebar are used in coils capable of meeting the most rigorous demands of the civil construction industry. The experiments made in an industrial environment, applied steels with 0.14 percent to 0.20 percent of vanadium and up to 0.04 percent of niobium. The results met the most demanding standards in the world-wide market.

Submitted by Rosana Amâncio (rosana.amancio@ufcg.edu.br) on 2018-07-19T20:53:36Z No. of bitstreams: 1 LARISSA CAVALCANTE COSTA - DISSERTAÇÃO PPGCNBio 2015..pdf: 1987711 bytes, checksum: 9d66a83ab8d2cec764aeaa785de117d4 (MD5) / Made available in DSpace on 2018-07-19T20:53:36Z (GMT). No. of bitstreams: 1 LARISSA CAVALCANTE COSTA - DISSERTAÇÃO PPGCNBio 2015..pdf: 1987711 bytes, checksum: 9d66a83ab8d2cec764aeaa785de117d4 (MD5) Previous issue date: 2015-07-31 / CNPq / O gênero Begomovirus pertence à família Geminiviridae de vírus que infectam plantas e são transmitidos pelo vetor mosca branca (Bemisia tabaci), também considerado umas das maiores pragas da agricultura. O presente estudo investigou a diversidade de begomovírus presente no vetor mosca branca (B. tabaci) em áreas da Paraíba, Minas Gerais e Distrito Federal. Um total de 17 amostras de moscas brancas foi coletado a partir de 12 espécies vegetaisem áreas da Paraíba, Minas Gerais e Distrito Federal e e usado para detecção do DNA-A de begomovirus por PCR, por RCA e por PCR-RCA, com primers específicos. Amplicons virais foram clonados e os clones recombinantes foram selecionados sob meio de cultura seletivo, contendo X-Gal e IPTG. A presença de amplicons foi confirmada por padrões de restrição gerados pelas enzimas EcoR I e Msp I em DNAs plasmidiais isolados dos clones selecionados e, então, sequenciados. As sequencias de DNA-A de begomovírus isoladas de moscas brancas coletadas em plantas de algodoeiro EMEPA-PB, em Emília, picão preto, barba-de-falcão, jatrofa, berinjela e malvona, presentes na área do Distrito Federal, foram analisadas quanto a porcentagem de identidade de sequencias de nucleotídeos e agrupamentos filogenéticos comparando com outras sequencias de isolados de begomovírus disponíveis no banco de dados GenBank. Como resultado, 5 espécies de begomovírus (SiYBV, CoMoV, SiMMV, BGMV e SiGLSV) evidenciaram a diversidade de begomovírus presente em moscas brancas nas áreas estudadas, mas que não necessariamente está presente nas respectivas plantas onde as moscas foram coletadas. Os primers PAL1v 1978 e PAR1c 496 descritos para detecção de DNA-A de begomovírus a partir de plantas foram eficientes para detecção específica desse componente genômico viral a partir do vetor mosca branca. A detecção específica de DNA-A do componente de begomovírus por PCR a partir do DNA total extraído de moscas brancas foi enriquecida pela amplificação por RCA. O begomovírus BGMV foi predominantemente encontrado em moscas brancas coletadas em plantas na área do Distrito Federal. A diversidade presente nos isolados dos 5 vírus identificados neste trabalho foi agrupada em 4 ramos filogenéticos suportados pela porcentagem de identidade de sequencias de nucleotídeos comparadas com sequencias dos isolados de begomovírus disponíveis no banco de dados GenBank / The Begomovirus genus belongs to Geminiviridae family of viruses that infect plants and is transmitted by whitefly (Bemisia tabaci) vector, which is also considered one of the major pests of agriculture. The present study investigated the diversity of begomovirusesin the whitefly vector (B. tabaci) in areas of Paraíba, Minas Gerais and the Federal District. A total of 17 samples of whiteflies were collected from 12 plant species in areas of Paraíba, Minas Gerais and the Federal District and used for the detection of begomovirus DNA-A by PCR, RCA and RCA-PCR with specific primers. Viral amplicons were cloned and the recombinant clones were selected on selective medium containing X-Gal and IPTG. The presence of amplicons was confirmed by restriction enzyme patterns generated by EcoR I and Msp I on plasmid DNAs of selected clones isolated and then sequenced. The begomovirus DNA-A sequences isolated from whiteflies collected from cotton plants EMEPA-PB, in Emilia, black prick, beard-of-hawk, jatropha, eggplant and malvona present in the Federal District, were analyzed bynucleotide sequence identity percentage and phylogenetic groups compared to other begomovirus strain sequences available in GenBank database. As a result, five species of begomovirus (SiYBV, CoMoV, SiMMV, BGMV e SiGLSV) revealed the diversity of begomovirus present in whiteflies in the studied areas, but that is not necessarily present in the respective plants where the flies were collected. The PAL1v 1978 PAR1c 496 primers described for begomovírus DNA-A detection from plants were also efficient for detection of this specific viral genomic component from whitefly vector. The specific detection of begomovirus DNA-A component by PCR from total DNA extracted from whiteflies was enriched by amplification by RCA. The BGMV begomovirus was found predominantly in whiteflies on plants collected in the Federal District. The diversity present in strains of thefive virus identified in this work was grouped into four phylogenetic branches supported by the nucleotide sequence identity percentage compared to sequences of the begomovirus strains available in GenBank database

L’alliage de magnésium AZ31 présente une très faible densité. Cette caractéristique en fait un matériau apprécié pour la conception de structures légères. La limitation principale de son utilisation industrielle est sa mauvaise formabilité et ce en raison de la texture cristallographique des tôles qui s’avère être peu adaptée aux procédés de mise en forme tel que l’emboutissage. Cette texture résultant du laminage initial, l’ambition de ce travail est de la modifier en utilisant la technique de laminage asymétrique et de mesurer l’impact de cette voie sur la formabilité de l’alliage. Il a été montré que l’asymétrie, produite par un différentiel de vitesses de rotation des cylindres du laminoir, induit systématiquement de fortes instabilités plastiques sous forme de bandes de cisaillement. Des techniques de cartographie sur microscope électronique en transmission (ACOM) et à balayage (EBSD) ainsi que des analyses de texture par DRX ont été utilisées pour analyser les mécanismes physiques concourant à l’émergence de cette instabilité. Il résulte de cette analyse que l’asymétrie du laminage provoque une forte activité du système de glissement basal que ne compense ni les autres systèmes ni le maclage. Ceci conduit à une localisation marquée de la déformation plastique et à la ruine du matériau. / The low density of the magnesium alloy AZ31 makes it valuable for low weight components. The main limitation for industrial applications is the poor formability of sheets during deep drawing type processing. This is linked to the fibre crystallographic texture resulting from rolling. The objective of the present work is to modify the sheet texture through asymmetrical rolling. It has appeared that the asymmetry promoted by monitoring the roll speeds separately induces plastic instabilities through shear banding. The physical mechanisms involved in the instability were analysed with the help of orientation imaging techniques on transmission electron (ACOM/TEM) and scanning electron (EBSD/SEM) microscopes as well as with X-ray measurements. It is concluded that the shear resulting from the asymmetry in roll speeds promotes a dramatic increase of basal slip that neither twinning nor the activities of other slip systems are able to compensate. Such activity induces strain localisation and premature failure of the material.

Made available in DSpace on 2016-06-02T19:19:59Z (GMT). No. of bitstreams: 1 VEGA_Marcelo_2014.pdf: 9141409 bytes, checksum: fd60293925ed2e6a9d8df71ece7c06f5 (MD5) Previous issue date: 2014-08-18 / Financiadora de Estudos e Projetos / It is known that the formability of aluminum alloy AA1050 is not favored when sheets are produced by conventional rolling due to the appearance of intense cube texture {100} <100> after recrystallization heat treatment. The objective of this study was to investigate whether components of shear processes can improve this property. For this work two processes of plastic deformation introducing shear stresses were selected: Equal channel angular extrusion (ECAE) and asymmetric rolling; these processes were compared to conventional rolling. In conventional rolling deformation results mainly compressive stresses. In the ECAE process shear is induced in the intersection of two channels of the same geometry that intersect by an angle &#61542; In the asymmetric rolling the shear stress is basically increased due to the speed variation between the rolls. An AA1050 aluminum sheet produced by the twin roll casting process was used in this study. The deformations were performed basically in 4 paths: i) conventional rolling, 70% reduction, ii) ECAE 1-8 passes, iii) ECAE 1-4 passes followed by conventional rolling with reduction of 70% and iv) Asymetric Rolling with reductions 30-50%. The mechanical and microstructural characterization of the deformed state was performed and the formability after annealing heat treatment was studied. ECAE deformation reduced the grain size, which measured by EBSD and transmission electron microscopy yield 1 micrometer. The evolution of equivalent strain compared with the increase of the hardness indicated a grain size stabilization of the grain/cell after four ECAE extrusion passes. After 8 passes the fraction of high angle boundaries exceeded the low-angle boundaries, ie dynamic recrystallization occurred during deformation. The texture after one pass ECAE approached the ideal texture for a 120 ° ECAE die. For deformations with 4 - 8 ECAE passes, the texture evolved into scattering the orientations having the {111} plane parallel to the surface (&#61543; fiber), and into the formation of rotated cube {100} <110> and rotated Goss {110} <110> orientations. The conventional rolling after ECAE returned the orientations to typical rolling textures: brass, copper and Goss. Deformation by asymmetric rolling with a difference of tangential velocity of 1.2 imposed shear stress, but it was necessary to decrease the reduction rate from 10% to 5% per pass in order to appreciably modify the texture. Comparing the formability of the deformed material, it was observed that ECAE increased the penetration depth in the Erichsen test, while rolling decreased the Erichsen index. Asymmetric rolling reduced the intensity of texture and destroyed the symmetry of the crystallographic orientations. The asymmetric rolled sample presented better formability than the rolled samples. After annealing, the samples of conventional rolling, with or without ECAE pre - strain, showed typical textures of annealed laminated material with high cube texture type. The &#61543; fiber was not stable in the ECAE annealed samples. Although the overall texture intensity remained low, increasing ECAE deformation before heat treatment strengthened the Goss {110} <001> orientation. For the asymmetric rolling the fiber orientations <100>// ND was scattered and both rotated cube and cube orientations were present. The lowest index of planar anisotropy was obtained in the sample annealed after four ECAE passes, representing a lower tendency to fail, This sample also presented an index of penetration in Erichsen testing of the same order of conventionally rolled sheets. It has been shown that both ECA as the asymmetric rolling deformation can significantly modify the texture of deformation and annealing, and improve the characteristics of formability of aluminum alloy 1050. This processing step should be located at the end of mechanical forming process before final annealing. / Sabe-se que a estampabilidade em ligas de alumínio AA1050 não é favorecida quando as chapas são produzidas por laminação convencional devido ao surgimento de uma textura do tipo cubo {100}<100> de forte intensidade após tratamentos térmicos de recristalização. O objetivo do trabalho foi investigar se processos com componentes de cisalhamento podem melhorar esta propriedade. Para este trabalho foram selecionados dois processos de deformação plástica que introduzem tensões de cisalhamento: Extrusão em canal angular (ECA) e Laminação assimétrica (LA); esses processos foram comparados à laminação convencional. Na laminação convencional a deformação resulta principalmente de esforços de compressão. No processo ECA o cisalhamento é imposto na intersecção de dois canais de mesma geometria que se interceptam formado um ângulo &#61542;. Na laminação assimétrica o esforço de cisalhamento é introduzido devido à variação de velocidade entre os cilindros de laminação. Partiu-se de chapas de alumínio AA1050 produzidas pelo processo Caster. As deformações foram executadas basicamente em 4 esquemas: i) Laminação convencional com 70% de redução; ii) ECA rota A de 1 a 8 passes; iii) ECA rota A de 1 a 4 passes seguido por laminação convencional com redução de 70% e iv) LA com reduções variando de 30 a 50%. Foi realizada a caracterização mecânica e microestrutural do estado deformado e foi estudada a conformabilidade após tratamento térmico de recozimento. Na deformação por ECA foi observado a redução do tamanho de grão, que medido por EBSD e por microscopia eletrônica de transmissão foi de cerca de 1 &#956;m. A evolução da deformação equivalente comparada com o aumento da dureza indicou uma estabilização do tamanho de grão/célula a partir de 4 passes. Após 8 passes a fração de contornos de alto ângulo ultrapassou a de contornos de baixo ângulo, ou seja, ocorreu recristalização dinâmica durante a deformação. A textura após um passe de ECA se aproximou da textura ideal para matriz ECA de 120°. Mas para deformações com quatro e oito passes, a textura evoluiu para uma dispersão das orientações contendo os {111} paralelos à superfície da chapa (fibra &#61543;), o aparecimento de orientações do tipo cubo rodado (100)<011> e de Goss rodado {110} <110>. A laminação convencional após ECA provocou o retorno às orientações típicas de laminação: latão, cobre e Goss. A deformação por laminação assimétrica com uma diferença de velocidade tangencial de 1,2 impôs esforços de cisalhamento, porém foi necessário diminuir a redução por passes de 10% para 5% para que o cisalhamento adicional modificasse sensivelmente a textura. Comparando a estampabilidade dos materiais deformados, observou-se que a deformação ECA aumentou a profundidade da penetração no ensaio Erichsen, enquanto que a laminação diminuiu o índice Erichsen. A laminação assimétrica reduziu a intensidade de textura e destruiu a simetria das orientações cristalográficas. Esta amostra encruada apresentou estampabilidade superior à das amostras laminadas. Após o recozimento, as amostras de laminação convencional, com ou sem pré-deformação ECA apresentaram texturas típicas de material laminado recozido com alto índice de textura tipo cubo. Nas amostras ECA a fibra &#61543; não ficou estável e teve sua intensidade reduzida. Embora a intensidade de textura total tenha permanecido baixa, o aumento de deformação ECA antes do tratamento térmico reforçou a orientação Goss {110}<001>. Já a amostra de laminação assimétrica houve dispersão das orientações na fibra <100>//ND e tanto orientações cubo como cubo rodado estavam presentes. O menor índice de anisotropia planar foi obtido na amostra de 4 passes ECA recozida (representando uma menor tendência ao orelhamento) e um índice de penetração no ensaio Erichsen da mesma ordem de chapas laminadas convencionalmente. Demostrou-se que tanto a deformação ECA quanto a laminação assimétrica podem modificar significantemente a textura de deformação e de recozimento e melhorar as características de conformabilidade da liga de alumínio 1050. Esta etapa de processamento deve estar localizada no final do processo de conformação mecânica, antes do recozimento final.