Avaliação da integridade estrutural em um tubo de aço API 5L X70 através da propagação de trincas por fadiga

Pós-graduação em Engenharia Mecânica - FEG

Um estudo sobre o endurecimento, o processamento e propriedades mecânicas de uma liga de alumínio da série 3XXX tipo AA 3104 com adições de zinco

Modificações na composição química e no processamento termomecânico têm sido algumas das várias alternativas estudadas, para melhorar o desempenho de ligas de alumínio tradicionais. Neste trabalho foi modificada a composição de uma liga Al-Mn-Mg do tipo AA 3104, endurecível por deformação, adicionando-se diversos teores de zinco, transformando-a numa liga Al-Mn-Mg(Zn), endurecível por precipitação. O objetivo foi estudar e quantificar os efeitos do zinco sobre o processamento termomecânico e as propriedades mecânicas da liga modificada. Ligas com teores de zinco entre 0,03 a 1,52% foram fundidas e processadas obtendo-se um encruamento semelhante a condição H-19 industrial, denominada rota R. Ligas com teores de zinco entre 1,14 a 2,17% foram fundidas e processadas segundo três diferentes rotas: na rota S, o recozimento da rota R foi substituído por solubilização antes da laminação a frio; nas rotas E3H e E6H, as tiras laminadas a frio foram envelhecidas em dois estágios: 121°C por três horas para as duas rotas, mais três horas para a rota E3H e seis para a rota EH a 163°. A tensão de escoamento (SIGMA IND E) e a resistência à tração (SIGMA IND T) para a rota R aumentaram da ordem de 18% e 19% respectivamente, com o aumento do teor de zinco, enquanto o alongamento (E) permaneceu em torno de 4,5%. As propriedades mecânicas (SIGMA IND E SIGMA T E ) AUMENTARAM EM TORNO DE 25%, 31% E 27%, respectivamente, para a rota S. Considerando concentrações aproximadamente iguais de zinco, não foram verificadas diferenças significativas para (SIGMA E SIGMA T), entre as rotas R E S, no entanto, a rota S apresentou alongamento médio maior que a rota R da ordem 44%. Os menores valores de (SIGMA IND E SIGMA IND T) e os maiores valores de E foram obtidos para a rota E6H.

Avaliação da eficácia de primers para metal na resistência ao cisalhamento da união entre cimentos resinosos e metais não nobres. Efeito do armazenamento em água

O sucesso das restaurações metálicas indiretas depende, dentre outros fatores, de uma união eficaz entre a estrutura metálica e o cimento dentário empregados. Sabe-se que os primers para metal atuam com comprovada eficácia na resistência adesiva dos cimentos resinosos às ligas nobres. Entretanto, pouco foi estudado sobre o efeito de tais materiais em ligas não nobres. O propósito deste estudo foi avaliar a eficácia de primers para metal na resistência ao cisalhamento da união entre cimentos resinosos e metais não nobres. Discos (9 mm de diâmetro e 3 mm de altura) foram fundidos em liga de NiCr (n=80) e em titânio comercialmente puro (Ti c.p.) (n=80) e foram incluídos em anel de PVC com resina acrílica quimicamente ativada. As superfícies dos discos foram regularizadas com lixas de carbeto de silício de granulação 320, 400 e 600 e jateadas com partículas de óxido de alumínio de 50 µm. Espécimes de cada metal foram divididos em quatro grupos (n=20). Uma matriz metálica bi-partida (5 mm de diâmetro interno e 2 mm de altura) foi posicionada na superfície do espécime. As áreas adesivas receberam um dos seguintes tratamentos: 1) Panavia F; 2) Alloy Primer e Panavia F; 3) Bistite DC e 4) Metaltite e Bistite DC. Para evitar a exposição dos cimentos à luz, estes foram espatulados e inseridos na matriz dentro de uma câmara de revelação radiográfica. Quarenta minutos após a confecção, os espécimes foram armazenados em água destilada a 37ºC por 24 horas e então termociclados (1.000 ciclos, 5ºC e 55ºC, 30 segundos cada banho). Após a termociclagem, os espécimes foram armazenados novamente nas mesmas condições descritas anteriormente por um período de 24 horas (n=10) ou de 6 meses (n=10) antes do ensaio de cisalhamento em uma máquina de ensaios mecânicos (Material Test System 810).

Estudo da fragilização ao revenido em aço liga de 2,25CR-1MO através do ensaio de indentificação instrumentada

2,25Cr-1Mo alloy steels are widely used in petrochemical plant equipments working in high temperature conditions because of their good mechanical proprieties in these conditions. Although, when exposed for a long time at high temperature, in the rage of 343 °C to 593 °C, may present the temper embrittlement phenomenon. The component named stripper of assembly converter of fluid catalytic cracking unit (UFCC) of studied plant is manufactured using this material, which is subject to temper embrittlement. The phenomenon of temper embrittlement refers to progressive lose of toughness, making the material brittle. With embrittlement, equipaments manufactured with this material are under risks to suffer brittle fracture in the cool down and start-up situations of them, which can cause catastrophic failures. By this reason, this research studies presence of temper ebrittlement phenomenon on this material. To verify the toughness of the material is conventionally used charpy V-notch test. However, this test requires the removing of samples of the material to make specimens. This fact becomes critical when talk about structural components of an equipment. So, this research also studies a non-destructive test that can be executes in-situ, known as instrumented indentation, as an alternative detection of the phenomenon at the component stripper, by comparative of the mechanical proprieties obtained by conventional tests in similar samples

Determinação experimental da tenacidade à fratura em baixas temperaturas de tubos de aço API 5L X70

Because of the great metallurgical advances, the welded tubes by HF / ERW (High Frequency / Electrical Resistance Welding) have played a more active role in the oil and gas, gradually replacing tubes produced by other processes (UOE, SAW, and others) to deep water applications, in high and extremely low temperatures, highpressure conditions and in highly corrosive environments. However, studies have revealed that defects in the welded joints are in one of main causes of failures in pipelines. Associated with damage external and the stringent requirements of this sector, the welded joints become particularly critical for his toughness and the determination of this particular property is fundamental. This study aims to evaluate the toughness of the HF / ERW pipes in HSLA steel API X70 class, used in pipelines transport systems of gas and oil from data obtained with CTOD tests (Crack Tip Opening Displacement). The main objectives of this project are: mechanical and microstructural characterization of steels API X70 manufactured in Brazil; and evaluation of the toughness of weld process by HF / ERW steel API X70 national. After having the tests done, mechanical, chemical and metallurgical, we have the conclusion that those pipe are in agreement to API 5L 42ª edition for X70MO and the toughness behaves like the expected

Lean six sigma como estratégia para o aumento de eficiência em laminação de alumínio

This study aims to assess the implementation of Lean Six Sigma in the preparation of plates and hot lamination process for a company of aluminum rolled products, to improve the quality, productivity and process efficiency. As a basis for achieving these goals, the DMAIC methodology and various quality tools such as Cause Effect Diagram, Process Flow, SIPOC, Pareto, FMEA and Control Chart were used, trying to propose improvements to processes and increase their efficiency. The results were significant and were the basis for the continuation of a continuous improvement project throughout the factory

Estudo do envelhecimento da liga AA 7075 encruada

Aluminum alloys are widely used in industry, because they combine different mechanical properties according to the alloying elements used in addition to thermal and mechanical treatments performed, resulting in materials with good weight/resistance relation. The 7XXX series alloys are worked heat treatable alloys commonly used in the aerospace industry, especially due to their high mechanical properties obtained after aging heat treatment, which increases the interest around 7075 alloy. Some studies with alloys which can be aged show that it is possible that cold word processes affect the results of aging. Thus, this study was intended to verify the influence of the aging process of AA 7075 alloy. There were three routes of aging with specimens previously treated thermally. In the first route T6 treatment was performed with a annealed specimen and other in solid solution. The second was the natural aging in a annealed specimen. In the last route was done aging by steps with a annealed specimen and other in solid solution with the intention to reduce the effects of natural aging. The results show that the routes 1 and 3 had similar hardness for all the samples, showing that the validity of Route 3 as an alternative and also the hardening did not affect the hardness at the end of the process, significantly reducing the time required for the highest hardness. Finally, natural aging was less effective in increasing hardness

Efeitos da contaminação in situ por níquel em peixes da espécie Oreochromisniloticus (Cichlidae)

A contaminação de rios com metais pesados vêm aumentando nas últimas décadas em resposta ao crescimento do setor industrial e seus dejetos, que frequentemente são despejados no ambiente sem que o tratamento adequado seja realizado. As implicações ambientais da contaminação dos ecossistemas naturais de água doce com níquel ainda são mal compreendidas, entretanto, a demanda global por este metal e as descargas antrópicas provenientes do setor industrial só aumentam. Embora o níquel não seja considerado altamente tóxico como outros metais, ele tem a capacidade de ser bioacumulativo e é, portanto, potencialmente perigoso para os peixes. Assim, é importante que seja desenvolvida uma compreensão mais profunda da fisiologia básica do níquel em peixes, tanto como um nutriente essencial quanto como um agente tóxico. Desse modo, o presente estudo teve como objetivo a análise do potencial genotóxico e mutagênico do níquel em peixes da espécie Oreochromis niloticus (Cichlidae), e a comparação das concentrações utilizadas deste metal nos bioensaios com a concentração limite, estabelecida pelo Conselho Nacional do Meio Ambiente (CONAMA). A resolução 357/05 do CONAMA, para controlar e taxar os limites máximos de contaminantes na água define que o limite máximo da concentração total de níquel permitida em corpos de água doce é de 0,025 mg/L Ni. Assim, os organismos-teste foram expostos a três diferentes concentrações de cloreto de níquel diluído, sendo que, a primeira concentração foi de 0,0125 mg/L, ou seja, metade da concentração máxima definida pelo CONAMA. A segunda concentração utilizada, 0,025 mg/L é o próprio limite de concentração estabelecido pela resolução. Por fim, a terceira concentração utilizada foi de 0,050 mg/L, que consiste no dobro da concentração máxima total de níquel permitida em corpos de água doce... (Resumo completo, clicar acesso eletrônico abaixo)

Estudo e modelagem 3D de um cabeçote para um motor monocilíndrico, 400cc, 4 T

The cylinder head contains the combustion chamber for the air-fuel mixture and the intake and exhaust valves, the valve guide and the valve seat. The cylinder head also is a support for the camshaft and valve rocker. The holes where the spark plugs are connected are designed to fit the better place in the combustion chamber. The cylinder heads often are manufactured using materials such as aluminum and cast iron. The cooling fins located in the outside of the cylinder head are designed for a good heat transfer and therefore their dimensions and positioning are important. This work aims the calculation for a cylinder head to be installed in a 400 cc displacement, gasoline powered, four stroke, single cylinder engine. According to the displacement it will be analyzed the combustion chamber, the intake and exhaust valves, as well as the camshaft and rocker arms. This also a work to help to accomplish the design of a single cylinder engine, where the alternatives parts, cylinder block and crankcase are all already machined and assembled in this campus

Análise microestrutural de tubos API P110, para prospecção de petróleo e gás, soldados pelo processo HF/ERW

On the grounds of the great advances achieved over recent years, the process HF/ERW (High-Frequency/Electric Resistance Welding)welded pipe have played an active role in the oil and gas industry for deep water applications, at high and extremely low temperatures, under high pressure and in highly corrosive environments, gradually replacing manufactured pipes by other processes. However, studies have shown that defects in the welded joints are a the leading causes of pipelines failures, which has required the determination of toughness values in this region, in compliance with the strict recommendations of the codes and standards with manufacturers and construction companies, on the oil and gas sector. As part of the validation process required toughness values, this research project focuses on a microstructural analysis in HF / ERW tubes microalloyed, steel grade API 5CT P110, designed to explore oil and gas in deep waters, the subject of strategic relevance to the country because of the recent discoveries in the Santos mega fields: Tupi and Libra (pre-salt). In this scientific work will be presented and discussed the results of mechanical tensile and Charpy, a few CTOD tests curves (showing the trend of toughness values to be obtained), and the microstructures of the base material obtained by optical microscopy, with special emphasis on the formation of nonmetallic inclusions in the welded joint

Tratamento de modificação de eutético da liga AA356

Alloy Al-7%Si-0,3Mg (AA356), having an excellent combination of properties such as low solidification shrinkage and good fluidity, good weldability, high wear resistance, high strength to weight particularly in the automotive and aerospace engineering. The refinement of the structure aluminum silicon eutectic alloy is a fairly common practice in the casting, through the treatment knows as modification. You can get the modification for the addition of chemicals and rare earths, these have the ability to modify the structure of the eutectic, but only sodium and strontium produce a strong action modifier when used in low concentrations. The modifying effect of silicon grain turns into a fibrous form branched and enveloped by the metal matrix in the form of a composite structure that has the highest limit of tensile strength, ductility and machinability. This work will be obtained AA356 alloy ingots using two different types of molds: metal mold and sand mold. Macrographs will be made in ingots obtained for observation of the macrostructures obtained in both types of ingots. Will be sampled at strategic locations of the ingots to correlate microstructure and cooling rate. The results showed that the material of the ingot has a strong influence on the resulting micro-andmacrostructure

Estudo da propagação de trinca por fadiga sob carregamento de amplitude variável

For engineering projects that require high reliability levels, is often not enough know only physical and chemical material properties. It’s necessary understand the failure mode of these materials in operation to ensure security level in the project and establish more stringent criteria in the analysis of structural integrity. Due to this need, aircraft industry has been using aluminum alloys in their designs and projects. “Currently more than 70% of aircraft structures are built of high strength aluminum alloys among which stand out 7075-T6 and 2024-T3 alloys, which are considered basics for being used in the new alloys development.” (PASTOUKHOV & VOORWALD, 1995). Some years ago ALCOA develops Al 2524 alloy that has emerged as refinement of Al 2024 (Al, Cu. Mg) alloy, with purpose of improve fracture toughness and fatigue resistance on structural components. The present research addresses testing of fatigue crack propagation under variable amplitude loading for Al 2024 alloy, observing the interaction effects from application of overhead blocks and plastic zone at the crack tip and makes an analysis of fracture surface images

Geografia dos movimentos socioterritoriais no Brasil de 2000 à 2012

The struggle for land is not a recent theme in Brazilian history. Since colonization, people have fought and resisted against oppression and injustice in the countryside, as can be evidenced by the highwaymen, peasant leagues and the war of Canudos. More recently, the struggle for land and agrarian reform can be evidenced by the struggles of the MST, CONTAG, CPT and other movements. For these movements, denominated as socioterritorial movements, land/territory is an essential condition for their existence and for the maintenance of their territoriality. The present paper examines the geography of socioterritorial moviments: the construction of the concept of socioterritorial movements and their forms of action and scales of actuation in the period 2000 to 2012, focusing on the movements that have been most active. These movements are studied through as analysis of data of the Land Struggle Data Base (Banco de Dados da Luta pela Terra –DATALUTA), print and digital media reports and a bibliographic survey of the literature. The action of socioterritorial movements can be studied through the forms of land occupations and demonstrations in the countryside which are the principal means of the struggle against large landholders, agribusiness and the State. These actions question the model of development which privileges agribusiness and, as such, are viewed by some as a hindrance to the development of the country. Over the years, the number of socioterritorial moviments, and their actions have oscillated due to a series of factors, such as repression (criminalization of members and violence against them), policies adopted by Brazilian governments and the contradictions inherent in very process of the spacialization of the struggle for land. These actions can be analyzed according to the scale of the struggle of the movements – municipal, micro-regional, state, macro-regional, and national

Analise do sistema de medição em peças aeronaúticas através do estudo de R&R (repetibilidade e reprodutibilidade)

The Measurement System Analysis (MSA - Measurement System Analysis) is a statistical methodology developed to study and analyze the behavior of the measurement systems, and, therefore, allow the increased of the confidence readings performed by measuring instruments. It’s widely used in the automotive industry since the 90’s and is a mandatory requirement for the approval of the parts according to ISO Standard of the automotive sector. However, the aerospace industry doesn’t require this type of Study, once which the vast majority of aeronautics parts have characteristics (dimensions) with very tight tolerances, closed, ie, at the home of microns. This work aims to create lists of recommendations for definitions of measuring instruments in developing of control plans, which correlates tolerances fields of characteristics for different settings and acceptance of the instrument, classified as optimum, recommended and not recommended, through of the study of R&R (Repeatability and Reproducibility) in aeronautics parts. Every methodology of the experimental part was based on modern strategy of continuous improvement, the DMAIC (Define Measure Analyze Implant Control), in order to achieve better measurement method used in the control of milling aeronautics parts, identifying and reducing the variations of the measurement process. The results of the R&R Study in large part of measuring instrument manuals were considered acceptable and/or recommended, ie with values of %P/T and %RR lower than 30%, providing statistical data which have enabled the elaboration of tables of recommendations, which, from this work, have turned into very important documents and aid for Process Engineering, having in their hands a technical study able to identify which is the most appropriate instrument to get a more robust dimensional... (Complete abstract click electronic access below)

Avaliação da toxicidade do cloreto de níquel utilizando Allium cepa como organismo teste

O impacto das atividades antropogênicas sobre o meio ambiente é um tema de grande relevância atualmente, atraindo a atenção da comunidade científica em geral, visto que essas atividades têm causado alterações significativas na qualidade da água, do solo e do ar. Dentre a ampla gama de poluentes resultantes das atividades humanas, merece destaque a classe dos metais pesados, os quais possuem propriedades tóxicas e genotóxicas, constituindo fatores de risco para o desenvolvimento de desordens neurodegenerativas, artrite e câncer nas populações expostas a estes contaminantes, bem como alterações nos ecossistemas contaminados. Neste sentido, o presente trabalho teve por objetivo avaliar o potencial citotóxico, genotóxico e mutagênico do níquel como contaminante, utilizando Allium cepa (Liliaceae) como organismo-teste, a fim de detectar possíveis efeitos deletérios em seu material genético. Estas avaliações foram feitas por meio da exposição de sementes de A. cepa a três soluções, com diferentes concentrações de níquel. Os resultados obtidos no primeiro biensaio e na repetição estão apresentados na forma de artigo científico, a ser submetido para revista especializada. O estudo dos efeitos do níquel em A. cepa foram importantes, uma vez que os dados da avaliação dos danos induzidos neste organismo modelo podem ser utilizados para a comparação com modelos animais, sendo possível assim, a inferência dos perigos aos ecossistemas e à população que está exposta a esse contaminante