Em geral, os requisitos essenciais exigidos para uma liga metÃlica utilizada em atividades ligadas à industria petroquÃmica sÃo resistÃncia mecÃnica, tendo em vista os diversos esforÃos aos quais os materiais serÃo submetidos, e resistÃncia à corrosÃo, devido a severidade ambiental ao qual os materiais serÃo expostos. O aÃo inoxidÃvel duplex (AID) vem conquistando cada vez mais espaÃo no setor petroquÃmico justamente por possuir tais requisitos citados acima. Atribuem-se suas altas resistÃncias à corrosÃo e mecÃnica à sua microestrutura balanceada em aproximadamente 50% de ferrita e 50% de austenita. O presente trabalho estudou a influÃncia de diversas condiÃÃes de soldagem sobre o balanÃo de fases de um aÃo inoxidÃvel duplex UNS S31803. Para tanto quatro tÃcnicas de quantificaÃÃes foram utilizadas para medir a fraÃÃo volumÃtrica de ferrita para as diversas condiÃÃes empregadas. AlÃm disso, uma propriedade mecÃnica (dureza) e uma propriedade de resistÃncia à corrosÃo (corrosÃo intergranular) foram avaliadas em funÃÃo da energia de soldagem empregada. Por fim, um estudo qualitativo acerca da precipitaÃÃo de compostos intermetÃlicos oriundos da soldagem foi realizado. Os resultados mostraram que o efeito da energia de soldagem sobre a fraÃÃo volumÃtrica de ferrita foi bem marcante no metal de solda, porÃm para a zona afetada pelo calor (ZAC) e o metal de base este efeito nÃo foi tÃo pronunciado. Ainda em relaÃÃo à fraÃÃo volumÃtrica de ferrita, foi constatado que esta à mais afetado pela largura do corpo de prova que pelo meio de resfriamento pÃs-soldagem. Em geral, tanto a dureza como a resistÃncia à corrosÃo intergranular nÃo sofreram influÃncia quando as diversas condiÃÃes de soldagem foram comparadas. Por fim, apesar de ter ocorrido a precipitaÃÃo de compostos intermetÃlicos, contatou-se que esta foi de pequena intensidade. / In general, the essential requirements for a metal alloy used inactivities are linked to the petrochemical industry mechanical strength, in view of the many efforts to which the materials are subjected, and corrosion resistance due to severe environment to which the materials are exposed. The duplex stainless steel (AID) has been gaining more space in the petrochemical industry precisely because it has such requirements mentioned above. Are attributed to their high resistance to corrosion and its mechanical balanced microstructure by approximately 50% to 50% ferrite and austenite. This work studied the influence of different welding conditions on the balance of phases of a duplex stainless steel UNS S31803. For both techniques of four measurements were used to measure the volume fraction of ferrite for the various conditions employed. Moreover, the mechanical properties (hardness) and corrosion resistance property (intergranular) were measured by the energy welding employed. Finally, a qualitative study about the precipitation of intermetallic compounds derived welding was performed. The results showed that the effect of heat input on the volume fraction of ferrite was well marked in the weld metal, but for the heat-affected zone (HAZ) and base metal this effect was not as pronounced. Still on the volume fraction of ferrite, it was found that this is more affected by the width of the body of evidence by means of cooling after welding. In general, both the hardness and resistance to intergranular corrosion when not influenced by the different welding conditions were compared. Finally, although there was precipitation of intermetallic compounds, is contacted to this was mild.

Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-05-10T20:18:37Z No. of bitstreams: 1 AdrianaLeal.pdf: 1605345 bytes, checksum: 700a558a6725b2db9159b45c403c2cbb (MD5) / Made available in DSpace on 2017-05-10T20:18:37Z (GMT). No. of bitstreams: 1 AdrianaLeal.pdf: 1605345 bytes, checksum: 700a558a6725b2db9159b45c403c2cbb (MD5) Previous issue date: 2016-02-29 / Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão (FAPEMA) / Objectives: To evaluate the effect of airborne-particle abrasion with niobium phosphate bioglass (NbG) microparticles on the bond strength (µTBS) and longevity of an adhesive system to different dentin substrates. Methods and Materials: Caries-free molars were used in this study. The dentin surfaces were evaluated in three groups: (1) Control – Healthy Dentin; (2) Partial removal of carious tissue; (3) complete removal of carious tissue. Half the teeth in each group were submitted to airborne-particle abrasion with NbG microparticles (15s/1cm/5bar). After this, the adhesive Clearfil S3 was applied and composite buildups were constructed incrementally; and specimens were longitudinally sectioned to obtain bonded sticks (1.0 mm2) to be tested in tension (0.5 mm/min) immediately or after 6 months of storage in water. The fracture patterns were evaluated by stereomicroscope (40x) and then by scanning electron microscopy (SEM). The data were analyzed by the Kruskal-Wallis (post-hoc Dunn) and Mann-Whitney tests (α=0.05). Results: Healthy dentin showed the highest bond strength (µTBS). Airborne-particle abrasion with NbG increased the µTBS values in the complete caries removal group. The bond strength values in the 24-hr period were higher than those at 6 months. In the majority of the specimens the fracture mode was adhesive/ mixed. Conclusion: The authors concluded that airborne-particle abrasion on dentin with NbG particles increased the µTBS in the group in which carious dentin was completely removed. / Objetivo: Avaliar o efeito do jateamento de micropartículas de vidro niobofosfato (NbG) na resistência de união (RU) e na longevidade de um sistema adesivo em diferentes substratos dentinários. Dezoito molares extraídos livres de cárie foram usados. As superfícies de dentina foram avaliadas em três grupos: (1) Controle – Dentina Sadia; (2) Remoção parcial do tecido cariado; (3) Remoção total do tecido cariado. Metade dos dentes de cada grupo sofreu um jateamento com partículas de NbG (15s/1cm/5bar). Em seguida o adesivo Clearfil S3 Bond Plus foi aplicado e uma coroa de resina composta foi construída. Os dentes foram seccionados para obtenção dos espécimes (1,0 mm2) e submetidos ao teste de microtração (0,5 mm/min) imediatamente e após 6 meses de estocagem em água. Os padrões de fratura foram avaliados usando estereomicroscópio (40x) e levados ao microscópio eletrônico de varredura (SEM). Os dados foram analisados pelos testes Kruskal-Wallis (pos-hoc Dunn) e Mann-Whitney (α=0.05). Resultados: A dentina sadia apresentou os maiores valores de RU. O jateamento com NbG aumentou os valores de RU no grupo remoção total. Os valores de RU no período de 24h foram superiores ao de 6 meses. A maioria das fraturas dos espécimes foi adesiva/mista. Conclusão: Os autores concluíram que o jateamento à dentina com partículas NbG aumentou a RU no grupo onde a dentina cariada foi totalmente removida.

Esta dissertação desenvolve a idéia de um processo de \"destituição da fala\" de grupos sociais, indígenas, camponeses, ribeirinhos, ameaçados e atingidos por barragens e grupos da sociedade organizada como os sindicatos que representam os trabalhadores das empresas elétricas e organizações não governamentais que discordam da maneira como vem se conduzindo o processo de expansão da oferta de eletricidade através da construção de hidrelétricas. Fazemos dois retrospectos. O primeiro, das lutas sociais por democracia nos últimos 30 anos. O segundo, um histórico da consolidação das empresas elétricas, relacionando-o com a história política brasileira e as relações entre interesses privados e ações de governo. Revela-se uma relação autoritária, pouca participação pública, centralismo decisório e fundamentalmente a prevalência dos interesses capitalistas nos projetos hidrelétricos. O viés autoritário, sendo herança histórica, molda a maneira como até hoje a discussão sobre como a oferta de eletricidade se desenvolve. Os resultados da pesquisa de campo e análise de entrevistas com dirigentes do movimento social organizado, sindicalistas e integrantes da coordenação nacional do Movimento dos Atingidos por Barragens (MAB) revelam a grande distância entre a produção de diagnósticos, reflexões, expectativas das organizações sociais, organizações não governamentais e uma efetiva incorporação desta produção na discussão sobre novos, antigos e futuros projetos hidrelétricos. Há pouco reconhecimento público e institucional das entidades e movimentos sociais que, a despeito de terem propostas e acúmulo de experiências sobre empreendimentos mal sucedidos, reivindicações sobre o passivo social e ambiental das obras já instaladas, não tomam parte dos processos de discussão e decisão. Esta ausência do processo se materializa como elemento de não-reconhecimento e comprometedor da dignidade de ação política destes agrupamentos sociais. A ampliação de espaços de discussão é tratada ao nível teórico e prático a partir da voz dos entrevistados e nos servindo dos estudos das ciências políticas sobre a constituição de esferas públicas, sobre ação comunicativa e sobre a teoria dos movimentos sociais. Dois exemplos internacionais são trazidos para reflexão: o debate público sobre energia no Quebec e o gerenciamento da utilização dos cursos d\'água e das margens dos rios na Holanda. O processo de criminalização dos movimentos sociais é identificado como um obstáculo à idéia de que se crie, na opinião pública, espaço para se discutir de maneira ampla o uso dos rios, das águas e terras ribeirinhas. Conclui-se este trabalho de dissertação apontando algumas oportunidades políticas e frentes de atuação através das quais os movimentos sociais, sindicatos, organizações não governamentais, podem ampliar o espaço de discussão. A participação nos comitês de bacias, exploração das heterogeneidades nos espaços de governo, alianças entre movimento sindical, movimentos sociais e ONGs e a importância dos ciclos de protesto diante de um cenário de criminalização dos movimentos sociais podem, concomitantemente, ampliar espaço e juntar forças para denunciar e se contrapor ao esgotamento dos recursos naturais e à expropriação autoritária e acelerada das terras dos pequenos proprietários, pescadores e moradores ribeirinhos que a instalação de uma quantidade enorme de empreendimentos hidrelétricos vem consolidando. / This Dissertation develops the idea of a process of suppression of the voice of social groups, indigenous peoples, rural workers, riverside populations, those threatened by or victims of Dams construction, and groups of the organized society such as those unions that represent the workers of the electricity companies and non government organizations that disagree with the way how the process of expansion of the electricity supply is being conducted through the construction of hydroelectric plants. We present two retrospective overviews. The first one addresses the social movements in their fight for democracy in the last 30 years. The second one addresses the history of the consolidation of the electricity companies, relating it to the Brazilian politics history and the relationship between private interests and government actions. It is revealed an authoritarian relationship, a small public participation, a centralized decision systems and, essentially, the prevailing of the capitalist interests in the hydroelectric projects. The authoritarian bias, an historic heritage, shapes the way how the discussion on electricity supply developed until the present. The results of the field research and the analysis of the interviews of leaders of the organized social movements, union leaders, and members of the national coordination of the \"Dam Affected People Movement\" - Movimento dos Atingidos por Barragens (MAB), reveal a large gap between the production of diagnostic analysis, expectances of the social organizations and non government organizations, and any substantial incorporation of this production in the discussion of new, previous and future hydroelectric projects. There is little public and institutional recognition of those organizations and social movements, which, in spite of having proposals, experiences on projects with bad outcomes, and demands on the social and environmental liability of the plants already in operation, do not take part in the discussions of the decision making process. The expansion of the discussion arenas is addressed at the theoretical and practical levels, having as base materials the interviews conducted during the field research and political sciences studies on the constitution of public spheres, on the communicative action, and on the theory of social movements. Two international examples are brought to discussion: the public debate on Energy in the Quebec Province, and the management of the use of the riverside space in the Netherlands. The process of criminalization of the social movements is identified as an obstacle to the idea of creating, in the public opinion, spaces for a comprehensive discussion on the use of rivers, of the water, as well as of the river side lands. This dissertation concludes with the identification of political opportunities and directions of action through which the social movements, unions, and non-government organizations can expand the space for discussion. The participation in river basin committees, the exploration of heterogeneous spaces of government, alliances among the unions movement, social movements and NGOs, and the importance of cycles of protest in a scenario of criminalization of social movements can, all together, expand the space and add strengths to make public and to fight against the exaustion of natural resources and the fast and authoritarian expropriation of lands of small rural owners, fishers and riverine inhabitants, which is being consolidated by the large development of hydroelectric enterprises.

O presente trabalho avalia e compara os resultados da tenacidade à fratura da zona termicamente afetada (ZTA) de soldas múltiplos passes por meio de ensaios de CTOD. Para este estudo, foi utilizado um aço alta resistência e baixa liga (ARBL) resistente à corrosão ambiental. As soldas foram realizadas com insumo de calor de 30 e 50 kJ/cm em um chanfro 1/2 K. Os resultados dos ensaios de CTOD mostraram que a solda produzida com maior insumo de calor apresenta tenacidade à fratura mais elevada. A análise microestrutural revelou que as microestruturas de elevada dureza e baixa tenacidade, formadas na ZTA de granulação grosseira, para a condição de 30 kJ/cm, deram lugar às microestruturas de tenacidade mais elevada, para o insumo de calor de 50 kJ/cm. / In this work the fracture toughness results of the heat affected zone (HAZ) in a multiple pass welds using a crack tip opening displacement (CTOD) concept were evaluated and compared. It was used an ambiental resistent high strengh low alloy steel. The welds were carried out using a heat input of 30 and 50 kJ/cm in a bevel preparation 1/2 K. The results of CTOD testing showed that increasing heat input, caused an improvement in the weldments fracture toughness. Microstructural analysis revealed that the high hardness and low toughness microstructures formed at coarse grain HAZ, near fusion line, for welding condition 30 kJ/cm were changed to higher toughness microstructure using a heat input of 50 kJ/cm.

<p>From long ago, rivers have always sustained livelihoods of the peoples through the utilisation of different natural resources available in the basin. All over the world, many rivers have been dammed in the spirit of performing various purposes: agricultural irrigation, domestic water supply and power generation or flood control.</p><p>By the year 2001, the World Commission on Dams brought into focus the debate on damrelated impacts on local economies, societal cultures, livelihoods security and environmental conservation. The outcome of the World Commission on Dams consultation strongly recommended the governments to involve all stakeholders to address appropriately all issues associated with dams.</p><p>The overall focus of this master thesis is the projected Rusumo Falls dam in the Kagera River Basin (East Africa). Based on literature documentation completed by on-ground observations and qualitative interviews at Rusumo, various issues connected with the dam are presented.</p><p>In the first part, the Kagera River Basin background information is provided. It gives an overview of the physical and human characteristics of the Kagera watershed and subcatchments. A brief history and socio-economic indicators are given to enlighten the outsiders about the development challenges of the riparian countries of Burundi, Rwanda, Tanzania and Uganda. Regional frameworks for the development and management of Kagera Basin natural resources are presented: The Kagera Basin Organisation and the Nile Basin Initiative.</p><p>Section two analyses the likely social problems around the Rusumo Hydro Electric Project resulting from the land issue and the electricity needs and posing a dilemma for the governments committed to reverse the poverty and developing the economies. Benefits and drawbacks of the dam as perceived by the beneficiaries are thoroughly listed.</p><p>Based on the overwhelming supports from the Rusumo people, the governments of Burundi, Rwanda and Tanzania together with the international community, a public participation scenario is suggested in the last chapter. It encourages the governments to come together with all interested groups and the affected people of Rusumo and address any matters associated to the dam management process.</p><p>The conclusion of this study draws some strategies and methods to ensure full popular participation in the dam management. It provides some ways to involve all stakeholders to address the related issues. As the Rusumo people perceptions of the dam possible effects might not be realistic, the popular participation can offer them a good opportunity to handle socio-economic problems such as the land issue, the economy restructure and the nature conservation. In this case study, the government of Rwanda is therefore responsible for the establishment of platforms for a broad popular consultation.</p>

Aim This study contends and explains why discrimination in the workforce is a growing problem that has affected thousands of organisations, large and small, operating in today's global marketplace. The research is aimed at describing the perceived experiences of discrimination as well as its effects on employees within the organisation. Method Using a qualitative research design, interviews were used to facilitate the informal sharing of experiences amongst employees. The purpose of this was to understand the different experiences employees had and the impact discrimination had on the individual performance within the organisation. Results Results reveal that employees experience three broad categories of activities that led to experiences of discrimination, namely activities that relates to management and supervision, daily interaction between various groups from diverse backgrounds and unfair general human resource functions. Conclusion The results of the empirical study were discussed according to the themes of Supervision/ Management, Human Resources/ Employee relations and Interactions. It was found that employees were exposed to different types of discrimination, which are explored in the literature review. / Thesis (M.B.A.)--North-West University, Vaal Triangle Campus, 2010.

No description available.

Inconel 738 (IN 738), like other precipitation-hardened nickel-base superalloys that contain a substantial amount of Al and Ti, is very difficult to weld due to its high susceptibility to heat-affected zone (HAZ) cracking during conventional fusion welding processes. The cause of this cracking, which is usually intergranular in nature, has been attributed to the liquation of various phases in the alloy, subsequent wetting of the grain boundaries by the liquid and decohesion along one of the solid-liquid interfaces due to on-cooling tensile stresses. To address the problem of liquation cracking in weldments, recent developments in welding research have resulted in supposedly exclusive solid-state friction joining processes, such as linear friction welding (LFW), for joining crack susceptible structural alloys. The objective of this work was therefore to investigate the weldability of the difficult-to-weld IN 738 superalloy by LFW and to analyze the resulting microstructural changes in the alloy due to the welding process. LFW was performed on Linear Friction Welding Process Development System (PDS) at the Aerospace Manufacturing Technology Centre of the Institute for Aerospace Research, National Research Council (NRC) of Canada. In order to study and decouple the effect of non-equilibrium thermal cycle and imposed compressive stress during the joining, physical simulation of the LFW process was performed by using Gleeble 1500-D Thermo-Mechanical Simulation System at the University of Manitoba. Detailed microstructural study of welded and Gleeble-simulated materials was carried out. Correlation between the simulated microstructure and that of the weldments was obtained, in that, a significant grain boundary liquation was observed in both the simulated specimens and actual weldments due to non-equilibrium reaction of second phase particles, including the strengthening gamma prime phase. These results show that in contrast to the general assumption of LFW being an exclusively solid-state joining process, intergranular liquation, caused by non-equilibrium phase reaction(s), occurred during the process. However, despite a significant occurrence of liquation in the alloy, no HAZ cracking was observed. Nevertheless, the result showed that crack-free welding by linear friction welding is not due to preclusion of grain boundary liquation as has been commonly assumed and reported. Instead, resistance to cracking can be related to the counter-crack-formation effect of the imposed strain and to a concept observed and reported for the first time in this work, which is strain-induced rapid solidification. Furthermore, microstructural evolution during joining cannot be understood without considering the concept of non-equilibrium liquation reaction and strain-induced rapid solidification of the metastable liquid, which are carefully elucidated in this thesis.

In this study, microstructural, micro hardness evaluation and residual stress distribution, of low carbon steel after single pass gas metal arc welding technique (GMAW) were investigated. The goal of this investigation were to reveal the microstructures, micro hardness, residual stress distribution and tensile strength of welded joints by using welding current as varying parameter. In order to realize this objective, welded plate of low carbon steel with thickness of 2.5mm and 250mm long by 200mm wide were welded together with different welding current of 70A, 100A through MIG process. Four different parts of samples were tried. The first part of samples was annealed in a furnace to a temperature of 750 and allowed to cool in air before welding. While the second was not heated, third and fourth trials were heated to a temperature of 200˚C and 580˚C respectively after the welding and allowed cooling in air. Nikon optic microscope and CSM micro hardness testing instrument were used to determine the microstructure of the weld bead and HAZ of the samples, and hardness tests were carried out at different zones of welded joint. Micro hardness behavior was observed by using CSM instrument using 20N load for indentation, which reveals the correlation between hardness, elasticity and plasticity on the heat affected zone (HAZ) and weld bead of the welded plates. The samples were subjected to tensile strength and the distribution of residual stress of the weld. Tensile strength test... [to full text] / Šiame darbe aprašomi mikrostruktūros, mikrokietumo nustatymo bei liekamųjų įtempimų pasiskirstymo tyrimai mažo anglingumo plienuose po lankinio suvirinimo. Tyrimo tiksla - nustatyti suvirintos jungties mikrostuktūros ir mikrokietųmo priklausomybę nuo suvirinimo srovės, kaip kintamo dydžio. Remiantis užduotimi buvo suvirintos 2.5 mm storio, 250 mm ilgio ir 200 mm pločio mažaanglio plieno plokštės, naudojant skirting dydžio (70A ir 100A) suvirininant apsauginių dujų aplinkoje (MIG) srovę. Buvo paruoštos keturios partijos bandinių. Pirmoji partija, proies suvirinant, buvo atkaitinta 750°C temperatųroje, ir ataušintas ore. Tuo tarpu antroji partija nebuvo apdorojama, o trečioji ir ketvirtoji atleista 200 C° ir 580°C temperatūroje ir atvėsinta ore. Suvirinimo vonelės ir erminio poveikio zonos mikrostruktūrai tirti bei mikrokietumui nustatyti buvo naudotas Nicon optinis mikroskopas bei CSM mikrokietumo bandymų įrenginys. Matuojant CSM įrenginiu, 20N įspaudimo apkrova, buvo pastebėtas įdomus kietuvo būvis, kuris atskleidė ryšį tarp kietumo, elastingumo ir plastiškumo esantį suvirintų plokštelių terminio poveikio zonoje bei suvirinimo vonelėje. Buvo matuojamas suvirintų bandinių stiprumas tempiant ir liekamųjų įtempimų pasiskirstymas. Tempimo stiprumo bandymų duomenys parodė ducharakteringus suirimo atvejus – plastiio-elastinio bei trapaus tipo. Liekamųjų įtempimų bandymų rezultati neparodė rėikšmingos liekamųjų įtempimų įtakos pasirinktomis sąlygomis suvirintuose bandiniuose.

Inconel 738 (IN 738), like other precipitation-hardened nickel-base superalloys that contain a substantial amount of Al and Ti, is very difficult to weld due to its high susceptibility to heat-affected zone (HAZ) cracking during conventional fusion welding processes. The cause of this cracking, which is usually intergranular in nature, has been attributed to the liquation of various phases in the alloy, subsequent wetting of the grain boundaries by the liquid and decohesion along one of the solid-liquid interfaces due to on-cooling tensile stresses. To address the problem of liquation cracking in weldments, recent developments in welding research have resulted in supposedly exclusive solid-state friction joining processes, such as linear friction welding (LFW), for joining crack susceptible structural alloys. The objective of this work was therefore to investigate the weldability of the difficult-to-weld IN 738 superalloy by LFW and to analyze the resulting microstructural changes in the alloy due to the welding process. LFW was performed on Linear Friction Welding Process Development System (PDS) at the Aerospace Manufacturing Technology Centre of the Institute for Aerospace Research, National Research Council (NRC) of Canada. In order to study and decouple the effect of non-equilibrium thermal cycle and imposed compressive stress during the joining, physical simulation of the LFW process was performed by using Gleeble 1500-D Thermo-Mechanical Simulation System at the University of Manitoba. Detailed microstructural study of welded and Gleeble-simulated materials was carried out. Correlation between the simulated microstructure and that of the weldments was obtained, in that, a significant grain boundary liquation was observed in both the simulated specimens and actual weldments due to non-equilibrium reaction of second phase particles, including the strengthening gamma prime phase. These results show that in contrast to the general assumption of LFW being an exclusively solid-state joining process, intergranular liquation, caused by non-equilibrium phase reaction(s), occurred during the process. However, despite a significant occurrence of liquation in the alloy, no HAZ cracking was observed. Nevertheless, the result showed that crack-free welding by linear friction welding is not due to preclusion of grain boundary liquation as has been commonly assumed and reported. Instead, resistance to cracking can be related to the counter-crack-formation effect of the imposed strain and to a concept observed and reported for the first time in this work, which is strain-induced rapid solidification. Furthermore, microstructural evolution during joining cannot be understood without considering the concept of non-equilibrium liquation reaction and strain-induced rapid solidification of the metastable liquid, which are carefully elucidated in this thesis.