The effect of hydrogen charging current density and tensile strain rate on the mechanical properties of X80 pipeline steel were investigated by slow strain rate test (SSRT), Charpy impact test, and scanning electron microscopy (SEM) in this thesis. The results show that both the ultimate tensile strength and elongation to failure of X80 steel were deteriorated significantly after charging with hydrogen. With a strain rate of 5 x 10-5 s-1, the relative tensile strength and plasticity loss of X80 steel had no significant change within the range of assumed hydrogen partial pressures at room temperature. At room temperature, X80 steel had no apparent variation in ultimate tensile strength and elongation, except at the strain rate of 10-6 s-1. Specimens obtained the greatest relative tensile strength loss and plasticity loss when strained at 10-6 s-1 with a current density of 4.6 mA/cm2. The fracture morphology of two test groups of X80 steel exhibited significant brittle rupture when tested with dynamic hydrogen charging. The impact energy of X80 was not affected by hydrogen charging. Different current density also had no influence on the results of the impact test.

The effects of weld temperature, travel speed, and backing plate thermal diffusivity on themechanical properties of a weld have been studied. A face centered cubic experiment of designwas completed in which the response variables were yield strength, minimum hardness in the HAZ, and charpy impact toughness. Three models were created from the data gathered usinga stepwise regression in order to see the effects of each parameter. For the yield strength andminimum hardness it was found that only travel speed and backing plate thermal diffusivities werestatistically significant to the properties. The charpy impact toughness saw that all three parameterswere statistically significant to its value. In all three models the travel speed had the greatest affecton the material properties.

Com o decorrer dos anos o consumo de petróleo e seus derivados aumentou significativamente e com isso houve a necessidade de se investir em pesquisas para descobertas de novas jazidas de petróleo como o pré-sal. Porém, não apenas a localização dessas jazidas deve ser estudada, mas, também, sua forma de exploração. Essa exploração e extração, na maioria das vezes, se dão em ambientes altamente corrosivos e o transporte do produto extraído é realizado através de tubulações de aço de alta resistência e baixa liga (ARBL). Aços ARBL expostos a ambientes contendo H2S e CO2 (sour gas) sofrem corrosão generalizada que promovem a entrada de hidrogênio atômico no metal, podendo diminuir sua tenacidade e causar falha induzida pela presença de hidrogênio (Hydrogen Induced Cracking HIC), gerando falhas graves no material. Tais falhas podem ser desastrosas para o meio ambiente e para a sociedade. O objetivo deste trabalho é estudar a tenacidade, utilizando ensaio Charpy, de um tubo API 5L X65 sour após diferentes tempos de imersão em uma solução saturada com H2S. O eletrólito empregado foi a solução A (ácido acético contendo cloreto de sódio) da norma NACE TM0284 (2011), fazendo-se desaeração com injeção de N2, seguida de injeções de H2S. Os materiais foram submetidos a: ensaios de resistência a HIC segundo a norma NACE TM0284 (2011) e exames em microscópio óptico e eletrônico de varredura para caracterização microestrutural, de inclusões e trincas. As amostras foram submetidas a imersão em solução A durante 96h e 360h, sendo que, após doze dias do término da imersão, foram realizados os ensaios Charpy e exames fractográficos. Foram aplicados dois métodos: o de energia absorvida e o da expansão lateral, conforme recomendações da norma ASTM E23 (2012). As curvas obtidas, em função da temperatura de impacto, foram ajustadas pelo método da tangente hiperbólica. Esses procedimentos foram realizados nas duas seções do tubo (transversal e longitudinal) e permitiram a obtenção dos seguintes parâmetros: energias absorvidas e expansão lateral nos patamares superior e inferior e temperaturas de transição dúctil-frágil (TTDF) em suas diferentes definições, ou seja, TTDFEA, TTDFEA-DN, TTDFEA-FN, TTDFEL, TTDFEL-DN e TTDFEL-FN (identificação no item Lista de Abreviaturas e Siglas). No exame fractográfico observou-se que o material comportou-se conforme o previsto, ou seja, em temperaturas mais altas ocorreu fratura dúctil, em temperaturas próximas a TTDF obteve-se fratura mista e nas temperaturas mais baixas observou-se o aparecimento de fratura frágil. Os resultados mostraram que quanto maior o tempo de imersão na solução A, menor é a energia absorvida e a expansão lateral no patamar superior, o que pode ser explicado pelo (esperado) aumento do teor de hidrogênio em solução sólida com o tempo de imersão. Por sua vez, os resultados mostraram que há tendência à diminuição da temperatura de transição dúctil-frágil com o aumento do tempo de imersão, particularmente, as TTDFEA-DN e TTDFEL-DN das duas seções do tubo (longitudinal e transversal). Esse comportamento controverso, que pode ser denominado de tenacificação com o decorrer do tempo de imersão na solução A, foi explicado pelo aparecimento de trincas secundárias durante o impacto (Charpy). Isso indica uma limitação do ensaio Charpy para a avaliação precisa de materiais hidrogenados. / Over the years the consumption of crude oil and its derivatives increased significantly, creating the necessity to invest in research to discover new sources of pre-salt crude oil. However, not only the location of these deposits should be studied, but also its extraction. This exploration and extraction, in most cases, occur in highly corrosive environments and the transport of the extracted product is performed by high strength low alloy steel pipes (HSLA). HSLA steels exposed to environments containing CO2 and H2S (sour gas) suffer general corrosion that promotes the diffusion of atomic hydrogen into the metal structure, which may decrease its toughness and induce cracks by the presence of hydrogen (Hydrogen Induced Cracking - HIC), leading the material to severe failures. Such events can be disastrous for the environment and the society. The objective of this work is to study the toughness using Charpy Impact Tests on an API 5L X65 sour service steel pipe, submitted to different immersion times in a H2S saturated solution. The used electrolyte was the NACE TM0284 (2011) solution A (acetic acid containing sodium chloride), with deaeration by N2 injection followed by H2S injection. The materials were submitted to HIC resistance tests according to NACE TM0284 (2011) standard and examination by optical microscopy and scanning electron microscopy for microstructural inclusions and cracks characterization. The samples were immersed in the solution for 96h and 360h and after twelve days of immersion, Charpy tests and fracture analysis were performed. Two analytical methods were applied to Charpy tests results: the energy absorbed and lateral expansion, as recommended by the ASTM E23 (2012). The obtained curves, that are a function of impact temperature, were adjusted by the hyperbolic tangent method. This procedure was performed in two different orientations in the pipe (transverse and longitudinal) and allowed the determination of the following parameters: energy absorbed and lateral expansion in the upper and lower levels and ductile-to-brittle transition temperatures (DBTT) in its different definitions: DBTTAE, DBTTAE-DN, DBTTAE-FN, DBTTLE, DBTTLE-DN e DBTTLE-FN. Fracture analysis revealed that the material behaved as expected, meaning that at higher temperatures ductile fracture occurred, at temperatures near DBTT it was obtained a mixed fracture and at lower temperatures it was observed the presence of brittle fracture. Results showed that when the immersion time in the solution was higher, the energy absorbed in upper shelf decreases, and also lateral expansion in upper shelf decreases, which may be explained by the (expected) increase of hydrogen level in solid solution, induced by the immersion time. It was found that there is a tendency of the ductile-to-brittle transition temperature to be lower with the increase of immersion time, particularly the DBTTAE-DN and DBTTLE-DN of the two pipe sections (longitudinal and transversal). This controversial behavior, which may be defined as the toughening by the increase of immersion time in the solution A, was explained by the appearance of secondary cracks during impact test (Charpy). This indicates a limitation of the Charpy test for the accurate characterization of hydrogenated materials, concerning toughness.

Made available in DSpace on 2017-07-21T20:42:39Z (GMT). No. of bitstreams: 1 Hudison.pdf: 7678712 bytes, checksum: 77d524c573ba60402f77fbda4e17c5e9 (MD5) Previous issue date: 2013-03-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In the present study was investigated the API 5L X70 steel mechanical behavior through tensile and instrumented impact tests. Results from the instrumented Charpy impact test have allowed quantify the forces, energies and deflections of the specimens. It was used to obtain the fracture mechanics parameters such as the dynamic fracture toughness JId, the stress intensity factor for dynamic loading KId, as also range the ductile brittle transition temperature. Simultaneously was evaluated the mechanisms that induce to the delamination phenomenon as well as the investigation of their influence on the absorbed energy during the impact test. It was also analyzed the microtexture and mesotexture of different samples from the brittle, ductile and mixed regions from the ductile brittle transition temperature curve. Results have shown that the longitudinal direction was slightly superior mechanical properties when compared to the transverse direction. The dynamic fracture toughness JId was higher for the L-T specimen orientation when compared to the T-L orientation and it tends to increase with increasing temperature for both directions. The stress intensity factor values for dynamic loading was close to in both L-T and T-L orientations. The microtexture has revealed that deformation process from the impact test preserves some of its characteristics from the prior processing such as phase transformations and recrystallization components. While the mesotexture feature has shown higher energy values in the ductile brittle transition temperature curve, it is resulted from the formation of deformation substructure. Results obtained by scanning electron microscopy and light microscopy have shown that the main factors that may be contributing to the formation of crack-divider type delaminations are banded microstructure and elongated ferrite grains. While the microtexture from the edges delamination has shown that propagation mechanism is intergranular. Taylor factor mapping has shown that the mechanism responsible for the formation of delamination is accompanied by low plastic deformation. / No presente trabalho foi investigado o comportamento mecânico do aço API 5L X70 através de ensaios de tração e impacto instrumentado. O ensaio de impacto Charpy instrumentado permitiu quantificar as forças, energias e deflexões dos corpos de prova. Com a utilização destes dados foram obtidos parâmetros da mecânica da fratura, tais como, a tenacidade à fratura dinâmica JId, o fator de intensidade de tensão para carregamento dinâmico KId, além da faixa de valores da temperatura de transição dúctil frágil. Concomitantemente foram avaliados os mecanismos que contribuem na formação do fenômeno conhecido como delaminação, bem como a investigação de sua influência sobre a energia absorvida durante o ensaio de impacto. Foram também analisadas a microtextura e mesotextura de diferentes amostras retiradas da região frágil, dúctil e mista, da curva de transição dúctil frágil do material. Os resultados mostraram que o material possui propriedades mecânicas de impacto ligeiramente superiores na direção longitudinal à laminação comparado à direção transversal. Os valores encontrados para a tenacidade à fratura dinâmica JId são superiores para corpos de prova com orientação L-T quando comparados para a orientação T-L, e tendem a aumentar com o aumento da temperatura para ambas orientações. Os valores encontrados para o fator de intensidade de tensão para carregamento dinâmico foram próximos para ambas as orientações L-T e T-L. A microtextura revelou que após a deformação no ensaio de impacto o aço preserva algumas das características do seu histórico de processamento tais como componentes de transformações de fase e recristalização. Enquanto que o estudo da mesotextura mostrou que maiores valores de energia na curva de transição dúctil frágil resultam na formação de uma subestrutura de deformação. Resultados obtidos por microscopia eletrônica de varredura e microscopia ótica mostraram que os principais fatores que podem estar contribuindo para formação de delaminações do tipo trinca divisora são a microestrutura bandeada e grãos alongados de ferrita. Enquanto que a microtextura nas bordas da delaminação mostrou que o seu mecanismo de propagação é intergranular. O mapeamento do fator de Taylor mostrou que o mecanismo responsável pela formação da delaminação é acompanhado por pouca deformação plástica.

Com o decorrer dos anos o consumo de petróleo e seus derivados aumentou significativamente e com isso houve a necessidade de se investir em pesquisas para descobertas de novas jazidas de petróleo como o pré-sal. Porém, não apenas a localização dessas jazidas deve ser estudada, mas, também, sua forma de exploração. Essa exploração e extração, na maioria das vezes, se dão em ambientes altamente corrosivos e o transporte do produto extraído é realizado através de tubulações de aço de alta resistência e baixa liga (ARBL). Aços ARBL expostos a ambientes contendo H2S e CO2 (sour gas) sofrem corrosão generalizada que promovem a entrada de hidrogênio atômico no metal, podendo diminuir sua tenacidade e causar falha induzida pela presença de hidrogênio (Hydrogen Induced Cracking HIC), gerando falhas graves no material. Tais falhas podem ser desastrosas para o meio ambiente e para a sociedade. O objetivo deste trabalho é estudar a tenacidade, utilizando ensaio Charpy, de um tubo API 5L X65 sour após diferentes tempos de imersão em uma solução saturada com H2S. O eletrólito empregado foi a solução A (ácido acético contendo cloreto de sódio) da norma NACE TM0284 (2011), fazendo-se desaeração com injeção de N2, seguida de injeções de H2S. Os materiais foram submetidos a: ensaios de resistência a HIC segundo a norma NACE TM0284 (2011) e exames em microscópio óptico e eletrônico de varredura para caracterização microestrutural, de inclusões e trincas. As amostras foram submetidas a imersão em solução A durante 96h e 360h, sendo que, após doze dias do término da imersão, foram realizados os ensaios Charpy e exames fractográficos. Foram aplicados dois métodos: o de energia absorvida e o da expansão lateral, conforme recomendações da norma ASTM E23 (2012). As curvas obtidas, em função da temperatura de impacto, foram ajustadas pelo método da tangente hiperbólica. Esses procedimentos foram realizados nas duas seções do tubo (transversal e longitudinal) e permitiram a obtenção dos seguintes parâmetros: energias absorvidas e expansão lateral nos patamares superior e inferior e temperaturas de transição dúctil-frágil (TTDF) em suas diferentes definições, ou seja, TTDFEA, TTDFEA-DN, TTDFEA-FN, TTDFEL, TTDFEL-DN e TTDFEL-FN (identificação no item Lista de Abreviaturas e Siglas). No exame fractográfico observou-se que o material comportou-se conforme o previsto, ou seja, em temperaturas mais altas ocorreu fratura dúctil, em temperaturas próximas a TTDF obteve-se fratura mista e nas temperaturas mais baixas observou-se o aparecimento de fratura frágil. Os resultados mostraram que quanto maior o tempo de imersão na solução A, menor é a energia absorvida e a expansão lateral no patamar superior, o que pode ser explicado pelo (esperado) aumento do teor de hidrogênio em solução sólida com o tempo de imersão. Por sua vez, os resultados mostraram que há tendência à diminuição da temperatura de transição dúctil-frágil com o aumento do tempo de imersão, particularmente, as TTDFEA-DN e TTDFEL-DN das duas seções do tubo (longitudinal e transversal). Esse comportamento controverso, que pode ser denominado de tenacificação com o decorrer do tempo de imersão na solução A, foi explicado pelo aparecimento de trincas secundárias durante o impacto (Charpy). Isso indica uma limitação do ensaio Charpy para a avaliação precisa de materiais hidrogenados. / Over the years the consumption of crude oil and its derivatives increased significantly, creating the necessity to invest in research to discover new sources of pre-salt crude oil. However, not only the location of these deposits should be studied, but also its extraction. This exploration and extraction, in most cases, occur in highly corrosive environments and the transport of the extracted product is performed by high strength low alloy steel pipes (HSLA). HSLA steels exposed to environments containing CO2 and H2S (sour gas) suffer general corrosion that promotes the diffusion of atomic hydrogen into the metal structure, which may decrease its toughness and induce cracks by the presence of hydrogen (Hydrogen Induced Cracking - HIC), leading the material to severe failures. Such events can be disastrous for the environment and the society. The objective of this work is to study the toughness using Charpy Impact Tests on an API 5L X65 sour service steel pipe, submitted to different immersion times in a H2S saturated solution. The used electrolyte was the NACE TM0284 (2011) solution A (acetic acid containing sodium chloride), with deaeration by N2 injection followed by H2S injection. The materials were submitted to HIC resistance tests according to NACE TM0284 (2011) standard and examination by optical microscopy and scanning electron microscopy for microstructural inclusions and cracks characterization. The samples were immersed in the solution for 96h and 360h and after twelve days of immersion, Charpy tests and fracture analysis were performed. Two analytical methods were applied to Charpy tests results: the energy absorbed and lateral expansion, as recommended by the ASTM E23 (2012). The obtained curves, that are a function of impact temperature, were adjusted by the hyperbolic tangent method. This procedure was performed in two different orientations in the pipe (transverse and longitudinal) and allowed the determination of the following parameters: energy absorbed and lateral expansion in the upper and lower levels and ductile-to-brittle transition temperatures (DBTT) in its different definitions: DBTTAE, DBTTAE-DN, DBTTAE-FN, DBTTLE, DBTTLE-DN e DBTTLE-FN. Fracture analysis revealed that the material behaved as expected, meaning that at higher temperatures ductile fracture occurred, at temperatures near DBTT it was obtained a mixed fracture and at lower temperatures it was observed the presence of brittle fracture. Results showed that when the immersion time in the solution was higher, the energy absorbed in upper shelf decreases, and also lateral expansion in upper shelf decreases, which may be explained by the (expected) increase of hydrogen level in solid solution, induced by the immersion time. It was found that there is a tendency of the ductile-to-brittle transition temperature to be lower with the increase of immersion time, particularly the DBTTAE-DN and DBTTLE-DN of the two pipe sections (longitudinal and transversal). This controversial behavior, which may be defined as the toughening by the increase of immersion time in the solution A, was explained by the appearance of secondary cracks during impact test (Charpy). This indicates a limitation of the Charpy test for the accurate characterization of hydrogenated materials, concerning toughness.

The thesis deals with the dependence of mechanical characteristics on the anisotropy of polymers Nylon 12 and Ultem 9085 made by a 3D printing technology Fused Deposition Modeling (FDM). The evaluation of the material characteristics was performed on the basis of tensile and non-instrumental impact tests. It was proven that the material characteristics are strongly dependent on anisotropy, i.e. on layer thickness and raster angle for both types of polymers.

This master’s thesis deals with influence of gas content in structure of polymer materials to mechanical properties. Test specimens were prepared by MuCell technology from polyphthalamide reinforced by 50 % of glass fiber content. The theorethical part of this thesis is focused on polymer materials with attention to polyamides and injection moulding technology. In the experimental part, the dependence between the characteristics obtained from the tensile test and the Charpy impact test on the amount of gas in the polymer is examined.

Physical aging of commercially produced polypropylene homopolymers Mosten was studied. The work is focused on monitoring the changes in physical properties of polymer in the time period 90 days from the date of preparation of the test specimen. The aging of polymers was realized at storage temperatures of 23 and 80 °C. The changes in crystallinity, yield strength, modulus, elongation and impact strength using DSC method, tensile tests and impact tests according to Charpy were monitored. Molecular weight distribution was determined by means of GPC at each polymer. Relationships between the changes in physical properties and polymer molecular weight were sought.

The diploma thesis is aimed to assesment of the influence of the specimen orientation during the Small Punch Tests (SPT). Steel ČSN 41 0214, or its equivalent steel RFe80, W.-Nr. 1.104 was chosen for experiments. Resulting records from SPT were evaluated using already known correlations which are reported in literature. The correlation values were compared with values obtained by the standard tests like Charpy impact test and tensile test. The influence of axial, radial and tangential test specimens orientation is discussed in relation to Ductile-to-Brittle fracture behaviour of the steel.

This thesis is focused on application samples with the inner insert used for Charpy impact test. This insert is welded to additional material by electron beam with pre-selected welded parameters. These parameters were chosen from data of performed experiments on homogenous welds. Resulting heterogenous weld was performed of evaluation of the microstructure, chemical composition and microhardness. Experimental materials were used austenitic steel 17 240 and ferritic steel 17 153 used on high-temperature applications.