Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-21T11:56:39Z No. of bitstreams: 0 / Made available in DSpace on 2017-11-21T11:56:39Z (GMT). No. of bitstreams: 0 / O processo de soldagem por fricção e mistura (FSW) tem despertado grande interesse nos últimos anos e tornou-se uma alternativa para unir materiais de baixa soldabilidade, como as ligas de alumínio das séries 2XXX e 7XXX, as quais são empregadas na estrutura das aeronaves, por possuírem elevada relação resistência/peso. O processo FSW, todavia, causa mudanças microestruturais nos materiais soldados, particularmente na zona misturada (ZM) e nas zonas termicamente (ZTA) ou termomecanicamente (ZTMA) afetadas. Estas mudanças geralmente interferem no desempenho frente à corrosão das ligas soldadas. No presente estudo, a resistência à corrosão das ligas de alumínio 2024-T3 e 7475-T761, unidas pelo processo FSW foi investigada em solução 10 mM de NaCl. Ensaios de visualização em gel ágar-ágar e de imersão associados a técnicas microscópicas foram realizados para investigar o efeito do acoplamento galvânico na corrosão das diferentes regiões da junta soldada. Os resultados do ensaio de visualização em gel mostraram que, quando acopladas, a liga 2024 atua como cátodo e a 7475 como ânodo. Os ensaios de imersão revelaram acoplamento galvânico entre as ligas na zona misturada (ZM). A região mais afetada pela corrosão foi a ZTMA da liga 7475, com corrosão intergranular desde as primeiras horas de imersão. A influência do processo de soldagem na resistência à corrosão das duas ligas de alumínio foi investigada por ensaios eletroquímicos. Os ensaios eletroquímicos adotados foram medidas de potencial de circuito aberto (PCA) em função do tempo de exposição ao meio corrosivo, espectroscopia de impedância eletroquímica (EIE) e curvas de polarização potenciodinâmica. Os ensaios de polarização mostraram elevada atividade eletroquímica na zona de mistura indicada pelos altos valores de densidade de corrente em comparação com as demais zonas testadas. Os resultados de EIE globais mostraram que nas primeiras horas de exposição ao eletrólito o processo de corrosão foi predominantemente controlado pela liga 7475; todavia, com o tempo de exposição ao eletrólito, a corrosão passou a ser controlada pela liga 2024. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP

Os aços inoxidáveis austeníticos são os mais utilizados em situações onde é indispensável resistência à corrosão e excelentes propriedades mecânicas. O níquel costuma ser o principal elemento de liga utilizado na estabilização da fase austenítica, e nos últimos anos seu valor, de acordo com a London Metal Exchange, sofreu variações abruptas de preço, desestabilizando o mercado do aço inoxidável. Nesse contexto os aços da série 200, também conhecidos como aços Cr-Mn-Ni, que substituem parte do níquel por manganês para manter a estabilidade da fase austenítica, tiveram sua produção incrementada. O objetivo do presente trabalho foi comparar a resistência à corrosão por pite de dois aços inoxidáveis austeníticos, aço 17Cr-6Mn-5Ni (designado como aço 298, não normalizado) e o aço UNS S30403. Para tanto, foram estudadas duas variáveis: o efeito da temperatura de solubilização e da composição química do eletrólito, a qual foi constituída por soluções aquosas com teor fixo de 0,6M NaCl e adições progressivas de Na2SO4 visando verificar o efeito inibidor do íon sulfato nos diferentes aços com os diferentes tratamentos de solubilização (1010°C, 1040°C, 1070°C e 1100°C). A corrosão por pite foi determinada através de ensaios de polarização potenciodinâmica cíclica e os resultados obtidos foram discutidos através das variações microestruturais encontradas. Foram empregadas técnicas de microscopia ótica e eletrônica de varredura, análises por dispersão de energia, difração de raios X, medidas magnéticas com ferritoscópio e análise de imagem para quantificação da fase ferrita. Primeiramente, constatou-se que, na maioria das condições de composição química de eletrólito e tratamento térmico, em geral o aço UNS S30403 apresenta maior potencial de pite do que o aço 298. Mais detalhadamente, os resultados mostraram que a adição de íon sulfato aumenta a resistência à corrosão por pite em meio contendo cloreto dos aços 298 e UNS S30403 em todas as condições de tratamento térmico, sendo que o efeito benéfico da adição de sulfato é mais acentuado para o aço 298. O tratamento de solubilização teve pouca influência sobre a resistência à corrosão por pite do aço UNS S30403 (considerando-se cada eletrólito isoladamente); por outro lado, o aço 298 apresentou forte dependência com o tratamento térmico: na ausência de sulfato (0,6M NaCl) os tratamentos de solubilização diminuíram o potencial de pite; já na presença de sulfato, teores crescentes de Na2SO4 tiveram um efeito benéfico, cada vez mais forte, chegando ao ponto de atingir, para as concentrações de 0,6M Na2SO4 nas condições de tratamento térmico a 1070°C e 1100°C, potenciais de pite mais elevados do que os respectivos para o aço UNS S30403. Foi detectada a presença de uma segunda fase (ferrita, enriquecida em cromo) em ambos os aços (UNS S30403 e 298), e a presença de precipitados ricos em manganês no aço 298. Os distintos comportamentos foram explicados através da solubilização dos precipitados ricos em manganês. Concluiu-se que a dissolução, de tais precipitados, permitiu o aumento do teor de manganês na matriz austenítica do aço 298, sendo que a consequência disso, para o eletrólito puro em NaCl, foi a diminuição do potencial de pite desse aço, enquanto que na presença de sulfato, o efeito inibidor desse íon foi potencializado devido a maior afinidade química entre o íon sulfato e o elemento manganês - agora em solução sólida comparativamente àquela do íon cloreto e este elemento. Como o aço UNS S30403 não apresenta manganês como elemento de liga, nem consequentemente os precipitados ricos nesse elemento, o efeito deletério da solubilização, não foi observado em NaCl, e o efeito benéfico da adição de Na2SO4, sobre a resistência à corrosão por pite, não foi significativo para esse aço em função da temperatura de solubilização. / Austenitic stainless steels are widely used when both high corrosion and mechanical resistance are essentials. In general, nickel is added to stainless steels to stabilize the austenite phase. During the last decade, the nickel price fluctuated considerably; unstabling the stainless steel global market. The 200 series stainless steels, also known as Cr-Mn-Ni stainless steels, emerged as an alternative for traditional austenitic steels. In these steels, manganese replaces a fraction of nickel content, maintaining stable the austenitic phase. Consequently, the production of stainless steel containing manganese has increased notoriously. The present study has the aim to compare the pitting resistance corrosion, between the 17Cr-6Mn-5Ni (designated as 298) and UNS S30403 austenitic stainless steels. The effect of solution heat treatment temperature, and the chemical composition of environment aqueous solution were evaluated (the electrolytes used are constituted for aqueous solution with 0,6M NaCl fixed and Na2SO4 progress additions) verifying the inhibitor effect of sulfate ion in both steels on distinct temperature ranges (1010°C, 1040°C, 1070°C and 1100°C) defined for the solution heat treatments. The pitting corrosion resistance was determined by means of cyclic potentiodynamic polarization, and the answers obtained were discussed through the microstructural variations found. Optical and electron microscopy technique, X ray diffraction analysis, magnetic measurements using the ferritoscope and image analysis to ferrite phase quantification were used during this investigation. In most conditions examined, the UNS S30403 steel show highest pitting potential that 298 steel. In more detail, the results showed that addition of sodium sulfate increased the pitting corrosion resistance in media containing chloride ions of both UNS S30403 and 298 steels, in all heat treatment conditions, being more pronounced in 298 steel. The solution heat treatment had little influence on pitting resistance corrosion of UNS S30403 steel (considering separately each electrolyte); on the other hand, the 298 steel showed a strong dependence with the heat treatments: in absence of sulfate (0,6M NaCl) the heat treatments decreased the pitting corrosion resistance, but in presence of sulfate, the gradual increment of Na2SO4 concentration had a beneficial effect, each time more strong, reaching, for 0,6M NaCl+0,6M Na2SO4 condition in heat treatment temperatures 1070°C and 1100°C, higher pitting potential values than UNS S30403 steel. The presence of a chromium-rich second phase (chromium ferrite) in both steels (UNS S30403 and 298) and manganese-rich precipitates in 298 steel were detected. The different behaviors were explained through annealing solution of manganese-rich precipitates found in 298 steel. It is concluded that after heat treatments, the dissolution of these precipitates increased the manganese content in solid solution in 298 steel. Consequently decreasing the pitting potential values for 0,6M NaCl electrochemical condition (environment without Na2SO4). On the other hand, in presence of Na2SO4 the inhibitor effect is potentialized due to highest chemical affinity between ion sulfate and manganese (now in solid solution) compared to that between chloride ion and manganese. The UNS S30403 stainless steel does not contain manganese as alloying element, nor manganese-rich precipitates, deleterious effect in 0,6M NaCl was not observed, and the beneficial effect on pitting corrosion resistance due the sulfate additions was not significantly different in this steel when the annealing solution temperature is changed.

En raison de leurs excellentes propriétés mécaniques, couplées à une bonne résistance à la corrosion par piqûres et à un coût modéré (basse teneur en nickel et en molybdène), les aciers inoxydables austéno-ferritiques (dits aciers inoxydables duplex) sont largement utilisés dans de nombreux secteurs industriels. Les aciers inoxydables duplex ont une microstructure complexe composée à proportion équivalente d’austénite et de ferrite. L’austénite ayant une composition chimique différente de celle de la ferrite, un film hétérogène se forme à la surface des aciers inoxydable duplex. Par ailleurs, les deux phases métalliques ayant des propriétés mécaniques différentes, un champ de contraintes hétérogènes est généré dans les grains. Sous certaines conditions, l’existence de gradients de contraintes peut conduire à des hétérogénéités du film passif. Dans cette étude, l’effet d’un vieillissement de longue durée dans un milieu contenant des chlorures sur la composition chimique du film passif a été tout d’abord étudié. Le comportement en corrosion de certains alliages duplex a été ensuite déterminé à partir d’essais TCP (détermination de la température critique de piqûration). Les résultats ont été analysés en tenant compte des informations obtenues précédemment. Après vieillissement, l’épaisseur du film passif et le rapport Cr/Fe ont significativement augmenté. La distribution des chlorures dans le film passif est hétérogène. Cette distribution a été reliée à la microstructure du matériau et au champ de contraintes résiduelles. Il a été montré qu’elle influence le comportement électrochimique du matériau. Le comportement en corrosion est ensuite analysé à l’aide des courbes de polarisation locales. Des critères métallurgiques ont été proposés pour l’amorçage de piqûres. / Duplex stainless steels (DSS) are highly important engineering materials, due to their generally high corrosion resistance combined with high strength and moderate alloy cost (lower nickel and molybdenum content). They are widely used in various industrial sectors. DSS have a complex microstructure with comparable volume of austenite and ferrite. Due to differences in chemical composition between austenite and ferrite, a heterogeneous passive film is formed on both phases. In addition, due to differences in mechanical properties, a heterogeneous stress field may be generated in metallic grains. Under certain conditions, these differences may also yield formation of a heterogeneous passive film. In this work, the influence of long-term ageing in chloride-containing media by on the chemical composition of the passive film was first studied by means of XPS and Auger at the microscale. The corrosion behaviour of some duplex stainless steels was then determined from CPT tests (determination of the critical pitting temperature). Results were analysed taking into account information obtained previously. After ageing, the thickness and the ratio Cr/Fe are significantly increased. The chloride distribution in the passive film was heterogeneous. It was related to the microstructure and the residual strain field. It was shown that this distribution modifies the electrochemical behaviour of samples. The corrosion behaviour was then analysed from local polarization curves and CPT tests. Metallurgical criteria for pitting were proposed.

This graduation thesis dwells on a worm gear design for an elevator mechanism in an already existing wheel case with actuator unit S3 for elevator type BOV 320/0,63. The work includes dimensional and control calculation for the worm gear and as an attachment you will find spiral worm and worm gear drawing documentation, including its specific location.

This thesis deals with problems with manufacturing of high frequency elliptic and hyperbolic optic mirrors, which makes one of the most important functional parts of parabolic satellites made for biggest and highest placed international astronomical radio-telescope in the world - ALMA, which is built on Chajnantor plateau in Chille in South America. Individual chapters are designed in the flow of technological process of manufacturing, containing theoretical and practical analysis of the problems. Content of the thesis leads especially to description and clarification of individual causes of problems during manufacturing.

The thesis deals with vibrations caused by geometric defect and fatigue damage of rolling element bearing. Hardware for vibration measurement is tested on 25 new pieces of NJ 304. Second part of the thesis examines if measuring of bearing vibration can help to detect a geometric defect. Geometric defects are detected according to a spectrum of vibration but the results are not absolutely exact. The possibility to detect geometric defects by measuring vibration has not been proven. The end of project tests diagnostic methods for rolling element bearings. The bearing defect was simulated to demonstrate bearing failure frequencies, envelope method and vibration spectrum.

The corrosion resistance under elevated temperature of additively manufactured 316L stainless steel made by directed energy deposition was studied. Test samples were prepared in a hybrid additive manufacturing machine using standard deposition parameters recommended by the manufacturer. Control samples were cut from wrought material to compare the results. The test was performed under a corrosive atmosphere with a solution of water with 3.5 % in weight of salt (NaCl). The total duration of the test was 635 hours, divided in five stages of 12, 24, 48, 226, and 325 hours to analyze the samples between each stage. The samples were analyzed quantitatively measuring weight loss and surface topography, and qualitatively by macroscopic inspection with digital photography, and microscopic inspection with optical and scanning electron microscopy. The results show a higher corrosion rate for the additively manufactured samples compared to the control samples. An evident increase in the size of pits initially present on the samples was observed and quantified on the additively manufactured. Although the additively manufactured samples were more aggressively attacked by corrosion, they still presented a shiny surface finish at the end of the test, reinforcing the idea of the formation of a passive oxide layer and suggesting that the corrosion was focalized in the surface defects by pitting and crevice corrosion mechanisms.

Many medical devices have been shifting to personal platforms such as smartphones due to its ubiquitous availability, variety of included sensors, robust communication, and user-friendliness. By utilizing smartphones as a medical sensing device should improve the early detection of abnormalities and the long-term monitoring of health conditions. Tissue abnormalities will be detected by touch sensation due to mechanical property changes within the tissue. However, touch sensation is unquantifiable and subjective. We integrate the smartphone with a tactile sensor to build a portable and personalized tissue assessment device based on changes in mechanical properties. The Smartphone Tactile Imaging Probe (STIP) is developed to quantify the mechanical properties of the tissue. The proposed system has a dual-sensing mode: compression-based sensing (STIP-C) and indentation-based sensing (STIP-I). STIP–C is designed to detect and measure the size and hardness of the inclusion. It assesses mechanical property changes caused by the tumor inside the tissue. STIP–I is designed to measure the pitting parameters and viscoelastic properties of the tissue. This system will assess the viscoelasticity changes caused by fluid retention within the tissue. STIP estimates mechanical and viscoelastic behavior changes in the tissue and provides the risk evaluation of an underlying health problem. Breast cancer risk assessment and edema severity level classification are the main applications of STIP. We estimate the breast cancer risk by incorporating the patient’s personal risk value into the STIP-C data associated with the tumor mechanical properties to improve the risk assessment accuracy. To classify the edema severity level, the STIP-I measures the pitting parameters and viscoelastic properties of the tissue. From these parameters, we build a Viscoelastic Pitting Recovery (VPR) model. The model illustrates the changes in tissue viscoelastic behavior associated with the edema severity level. Using the VPR model, we use the thresholding method to classify the edema cases. We also developed customized phantoms representing the different amounts of fluid retention in the tissue. The experimental result found a relationship between the amounts of pitted depth from STIP-I and the fluid amount of a phantom. In this dissertation, we developed and tested a portable tissue mechanical property estimation system. The interchangeable dual-mode STIP sensing probe and risk assessment methods were developed for the breast tumor malignancy and edema severity applications. / Electrical and Computer Engineering

Duplex stainless steel (DSS) that developed in the 1930’s is a type of steel that consists of bothaustenite and ferrite phases in an almost equal proportion. It inherits properties of both ferriticand austenitic stainless steel and so it has good mechanical and corrosion resistance propertiesthat makes it suitable material in different industries with aggressive environment. There aredifferent approaches that used to evaluate the susceptibility of stainless steels to pitting corrosionlike Pitting Resistance Equivalent Number (PREN) and electrochemical methodologies. In thisstudy, focus is on the potentiodynamic (AL 101 5170) and potentiostatic (ASTM G150) testmethods as laboratory evaluations in which standard DSS (2205) is exposed to the differentchloride concentrations 0.1 M and 1 M respectively. In these methods parameters like PittingPotential (Ep) and Critical Pitting Temperature (CPT) can be measured respectively and used topredict the susceptibility of DSS to pitting corrosion. DSS owes its good corrosion resistance tothe oxide film that protects the metal from corrosion. Pitting can be initiated as a result of anyheterogeneities on the metal surface which act as a passive film defect like non-metallicinclusions and intermetallic precipitations such as sigma phase when metal is exposed toaggressive environment and high temperature. The aim of the present work is to make acomparison between two electrochemical methods besides finding how inclusions andmicrostructure can have impact on their results and on pitting corrosion. The results of theexperiment shows that there is a positive linear relation only in longitudinal direction betweenCPT and Ep. Also, among two test methods only ASTM G150 can detect sigma phase existence(<3%). Based on investigations in this experiment, inclusion characteristics such as numberdensity and composition has compatible results in both methods so that samples with big sizeinclusions (>8 μm) have negative effect on corrosion resistance and in terms of composition,samples with nitride inclusions has lower CPT and Ep compared with those with only oxide oroxide/sulfide inclusions. It is also discovered that phase arrangement is not the same in allspecimens that produced by different production methods and samples with finer phases havehigher CPT values in both longitudinal and transvers directions. However, this shape ofmicrostructure only affect the Ep in longitudinal directions but not transvers.

<p> Inland degradational trends of coastal dolomite pavements (on the Amabel formation near Tobermory Ontario Map 1) were examined in three wave energy settings: passive, intermediate, and active shores. </p> <p>Six pavement property trends were examined to determine the effect of low fetch lengths (7-10 km - Ford 83) and long shallow wave approach (Map 1) on the break-up of passive coastal pavements (south-west Bear's Rump Island): vegetation cover , grike dimensions, fracturing, pitting, shattering and flaking, and soil and rubble depths. </p> <p> Detailed analysis of small scale surface solution features, "karren", was undertaken at five 1 m sample grids on the intermediate average fetch 70-90 km -Grosset 85) Cyprus Lake provincial park pavements. </p> <p> / Thesis / Bachelor of Arts (BA)