Estudo do mecanismo de corrosão por pites em água do mar de aços inoxidáveis supermartensíticos microligados com Nb e Ti

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influência do aporte térmico da soldagem GTAW no balanço de fases Ferrita/Austenita do Aço Inoxidável Duplex UNS S32205

Pós-graduação em Engenharia Mecânica - FEIS

Ganho de peso de novilhas mestiças submetidas ou não à esterilização pela introdução intrauterina de esferas inoxidáveis e ao uso ou não de modificador orgânico

Avaliou-se o ganho de peso de novilhas mestiças, 1/4 Simental e 3/4 Nelore, empregando-se o método experimental de esterilização, que consiste na introdução intrauterina de esferas inoxidáveis. Foram utilizadas 100 novilhas nulíparas, destinadas ao abate, com idades entre 12 e 24 meses e com média de peso de 275kg. Todos os animais receberam o mesmo manejo alimentar, em sistema de pastejo em Brachiaria brizantha, com água e sal mineral ad libitum, e pesagens a intervalos de 28 dias, obedecido o jejum prévio de 16 horas. Os animais foram distribuídos aleatoriamente em quatro grupos (G) experimentais: G1 - composto por 25 novilhas testemunhas; G2 - por 25 novilhas esterilizadas e aplicação de um modificador orgânico; G3 - por 25 novilhas esterilizadas; e G4 - por 25 novilhas não esterilizadas e aplicação de um modificador orgânico. Foram introduzidas 12 esferas de aço inoxidável, previamente esterilizadas, no útero de cada novilha. Houve maior ganho de peso total e diário entre os animais do G2, 140,50kg e 0,578g/dia vs 108,58kg e 0,447g/dia (G1), 103,73kg e 0,427g/dia (G3), 102,68kg e 0,423g/dia (G4), respectivamente. Esta técnica pode ser recomendada aos criadores.

Value of ultrasonographic contrast in duplex scanning of leg arteries - Comparison with conventional duplex scanning and arteriography

Aim. Duplex scanning has been used in the evaluation of the aorta and proximal arteries of the lower extremities, but has limitations in evaluating the arteries of the leg. The utilization of ultrasonographic contrast (USC) may be helpful in improving the quality of the image in these arteries. The objective of the present study was to verify whether the USC increases the diagnostic accuracy of patency of the leg arteries and if it diminishes the time needed to perform duplex scanning.Methods. Twenty patients with critical ischemia (20 lower extremities) were examined by standard duplex scanning, duplex scanning with contrast and digital subtraction arteriography (DSA). The 3 arteries of the leg were divided into 3 segments, for a total of 9 segments per limb. Each segment was evaluated for patency in order to compare the 3 diagnostic methods. Comparison was made between standard duplex scanning and duplex scanning with contrast in terms of quality of the color-coded Doppler signal and of the spectral curve, and also of the time to perform the exams.Results. Duplex scanning with contrast was similar to arteriography in relation to patency diagnosis (p>0.3) and even superior in some of the segments. Standard duplex scanning was inferior to arteriography and to duplex scanning with contrast (p<0.001). There were improvements of 70% in intensity of the color-coded Doppler signal and 76% in the spectral curve after the utilization of contrast. The time necessary to perform the examinations was 23.7 minutes for standard duplex scanning and 16.9 minutes for duplex scanning with contrast (p<0.001).Conclusion. The use of ultrasonographic contrast increased the accuracy of the diagnosis of patency of leg arteries and diminished the time necessary for the execution of duplex scanning.

Extrinsic compression of popliteal artery in asymptomatic athlete and non-athlete individuals - A comparative study using duplex scan (color duplex sonography)

Aim. Extrinsic compression of the popliteal artery and absence of surrounding anatomical abnormalities characterize the functional popliteal artery entrapment syndrome (PAES). The diagnosis is confirmed to individuals who have typical symptoms of popliteal entrapment and occlusion or important stenosis of the popliteal artery with color duplex sonography (CDS), magnetic resonance imaging (MRI) or arteriography during active plantar flexion-extension maneuvers. However, variable result findings in normal asymptomatic subjects have raised doubts as to the validity of these tests. The purpose of this study was to compare the frequency of popliteal artery compression in 2 groups of asymptomatic subjects, athletes and non-athletes.Methods. Forty-two individuals were studied. Twenty-one subjects were indoor soccer players, and 21 were sedentary individuals. Physical activity was evaluated through questionnaires, anthropometric measurements, and cardiopulmonary exercise test. Evaluation of popliteal artery compression was performed in lower limbs with CDS, ankle-brachial index (ABI) measurements and continuous wave Doppler of the posterior tibial artery.Results. The athletes studied fulfilled the criteria of high level of physical activity whereas sedentary subjects met the criteria of low level of activity. Popliteal artery compression was observed with CDS in 6 (14.2%) studied subjects; 2 of whom (4.7%) were athletes and 4 (9.5%) were non-athletes. This difference was not statistically significant (p=0.21). Doppler of the tibial arteries and ABI measurements gave good specificity and sensibility in the identification of popliteal artery compression.Conclusion. The frequency of popliteal artery compression during maneuvers in normal subjects was 14.2% irrespective of whether or not they performed regular physical activities. Both Doppler and ABI showed good agreement with CDS and should be considered in screening popliteal arteries in individuals suspected of PAES.

Correlation between the intensity of venous reflux in the saphenofemoral junction and morphological changes of the great saphenous vein by duplex scanning in patients with primary varicosis

Aim. One of the major causes of chronic venous disease is venous reflux, the identification and quantification of which are important for diagnosis. Duplex scanning allows for the detection and quantification of reflux in individual veins. Evaluation of the great saphenous vein in primary varicosis is necessary for its preservation. Objective of the study is to evaluate a possible correlation between the intensity of reflux at the saphenofemoral junction, diameter alterations of the incompetent great saphenous vein and the practical effect of such correlation. Also to compare the clinical severity of the CEAP classification with such parameters.Methods. Three hundred limbs were submitted to duplex evaluation of their insufficient saphenous veins. Vein diameter was measured on five different points. Velocity and flow at reflux peak and reflux time were determined. The saphenous vein's diameters were correlated with velocity, flow and time. The three latter parameters and diameters were compared with clinical severity according to CEAP.Results. Correlation was found between the saphenous vein's diameters, velocity and flow. No correlation was observed between time and diameter in the thigh's upper and middle thirds. When comparing diameter, velocity and flow with CEAP clinical severity classification, an association was observed. The correlation between reflux time with clinical severity was weak.Conclusion. Reflux time is a good parameter for identifying the presence of reflux, but not for quantifying it. Velocity and peak flow were better parameters for evaluating reflux intensity as they were correlated with great saphenous vein alterations, and were associated with the disease's clinical severity. [Int Angiol 2010;29:323-30]

Avaliação da resistência à corrosão de aços inoxidáveis com Nb endurecíveis por precipitação

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação da resistência ao desgaste de aços inoxidáveis endurecíveis por precipitação nitretados

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Aging behaviour of 25Cr-17Mn high nitrogen duplex stainless steel

The precipitation behaviour of a nickel free stainless steel containing 25% chromium, 17% manganese and 0.54% nitrogen, with duplex ferritic-austenitic microstructure, was studied using several complementary techniques of microstructural analysis after aging heat treatments between 600 and 1 000 degrees C for periods of lime between 15 and 6 000 min. During aging heat treatments, ferrite was decomposed into sigma phase and austenite by a eutectoid reaction, like in the Fe-Cr-Ni duplex stainless steel. Chromium nitride precipitation occurred in austenite, which had a high nitrogen supersaturation. Some peculiar aspects were observed in this austenite during its phase transformations. Chromium nitride precipitation occurred discontinuously in a lamellar morphology, such as pearlite in carbon steels. This kind of precipitation is not an ordinary observation in duplex stainless steels and the high levels of nitrogen in austenite can induce this type of precipitation, which has not been previously reported in duplex stainless steels. After chromium nitride precipitation in austenite, it was also observed sigma phase formation near the cells or colonies of discontinuously precipitated chromium nitride. Sigma phase formation was made possible by the depletion of nitrogen in those regions. Time-temperature-transformation (precipitation) diagrams were determined.

Propriedades mecânicas e de corrosão de dois aços inoxidáveis austeníticos utilizados na fabricação de implantes ortopédicos

ASTM F 138 austenitic stainless steel is extensively used as an orthopedic implant material. However, some aspects, such as low strength in the annealed condition and susceptibility to localized corrosion, limit wider use of this kind of steel. Recently, a high-nitrogen austenitic stainless steel, specified in the standard ISO 5832-9, has been indicated as an alternative to ASTM F 138 steel for more severe loading and permanent application inside the human body. In this work, microstructure, mechanical properties, corrosion resistance and fatigue behavior of both steels were determined and compared. ISO 5832-9 steel displayed better mechanical and corrosion behaviors than did ASTM F 138 steel The combination of these features lead ISO steel to enhanced fatigue performance in both neutral and aggressive environments. Analyzed were the role of nitrogen in solid solution, combined with niobium in the Z-phase, and the factors that led to superior ISO 5832-9 properties.

A influência da microestrutura e dos tratamentos superficiais na vida em fadiga de aços inoxidáveis martensítico e austenítico usados na fabricação de válvulas para motores a combustão interna

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estudo da microestrutura e da resistência à corrosão integranular em chapas soldadas de aços inoxidáveis austeníticos série 304L após goivagem ao arco elétrico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Análise morfológica de pites em aços inoxidáveis austeníticos ABNT 304 e 310S submetido à nèvoa salina

Pós-graduação em Engenharia Mecânica - FEG

Ganho de peso e características de carcaça de novilhas cruzadas submetidas ou não à esterilização pela introdução intra-uterina de esferas inoxidáveis

Pós-graduação em Medicina Veterinária - FMVZ

Microstructural and electrochemical characterization of friction stir welded duplex stainless steels

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)