52 research outputs found
Numerical And Experimental Analysis Of The Microstructural Evolution During Cross Wedge Rolling Of V-ti Microalloyed Steel [análise Numérica E Experimental Da Evolucão Microestrutural Durante A Laminação Transversal Com Cunha De Um Aço Microligado Ao V-ti]
No full textThe improvement of manufacturing processes to assure product quality and reduce the amount of raw material and energy is the main objective of many recent researches. Some of them study cross wedge rolling (CWR) as a substitute to hot upsetting in the manufacture of stepped shafts, pins, eccentric shafts and many other mechanical parts. In this process a cylinder is deformed by two wedge tools assembled on plane plates that move tangentially one against the other. The main objective of this work is to study the thermomechanical behaviour of medium carbon steel during hot CWR by means of a numerical analysis. The numerical results will be compared to the microstructure of microalloyed steel samples which were submitted to CWR experimental tests. The results suggested that dynamic recrystallization was present during CWR and that microstructures in the austenitic region were very refined.624495502Danno, A., Tanaka, T., Hot forming of stepped shafts by wedge rolling with three rolls (1984) Journal of Mechanical Working Technology, 9, pp. 21-35Dean, T.A., Fu, X.P., Past developments, current applications and trends in the cross wedge rolling process (1993) International Journal of Machine Tools and Manufacture, 33 (3), pp. 367-400Gentile, F.C., (2004) Estudo Do Processo De Laminação Cruzada Com Cunha (cross Wedge Rolling) Para Fabricação De Eixos Escalonados, , UNICAMP, agosto de, Tese de DoutoradoJonas, J.J., Dynamic recrystallization-scientific curiosity or industrial tool? (1994) Mat. Scie. and Eng., A184, pp. 155-165McQueen, H.J., Jonas, J.J., Recovery and recrystallization during high temperature deformation (1976) Treatise On Materials Science and Technology, 6, pp. 393-493. , In: ARSENAUT, R. J. (ed.), New York: Academic PressQiang, L.I., Lovell, M.R., Slaughter, W., Tagavi, K., (2002) Journal of Materials Processing Technology, pp. 125-126+248-257Regone, W., Jorge Jr., A.M., Balancin, O., (2000) Metodologia Para Determinar Os Tipos De Amaciamentos Que Atuam Em Processos Termomecânicos, , CBECIMAT, 14.São Pedro - SP, 3 a 6 de dezembro deda Silva, M.L.N., Regone, W., Button, S.T., Microstructure and mechanical properties of microalloyed steel forgings manufactured from cross-wedge-rolled preforms (2005) Scripta Materialia, 54, pp. 213-217Weronski, W., Pater, Z., Selection of geometric parametrs of transverse wedge rolling tools (1992) Journal of Materials Processing Technology, 34, pp. 273-28
Damage evolution during cross wedge rolling of steel DIN 38MnSiVS5
No full textAbstractThe study of variables which influence the formation of central cavities is a constant theme in recent works about Cross Wedge Rolling (CWR). Damage modelling typically used for analysis of cold forming processes, can also be useful for the study of critical conditions in hot forming processes. Varying geometric and process parameters, damage distribution provided important information about the conditions which favor the formation of defects in parts during manufacturing. Using the Hansel-Spittel's rheological law equation, it was studied the behavior of the microalloyed steel DIN 38MnSiVS5 simulated with the finite element method (FE). Tests were carried out in an equipment available at the Metal Forming Laboratory (MFL) to validate the adopted numerical models. In those tests and simulations the stretching angle was kept constant, and three variables were evaluated: forming angle, relative reduction and speed. For this microalloyed steel the high sulfur content associated with a high working temperature determined the formation of large central cavities in the rolled parts which could be also predicted in the simulations
Biological ensilage of fish : optimization of stability, safety and functionality
No full textThis thesis deals with stability, safety, and functionality aspects of biological fish silage (BFS) obtained by lactic acid fermentation. BFS may provide an economically viable, environment friendly way of upgrading fish waste.BFS has been found advantageous when compared to the so-called acid process, since it yielded lower levels of peroxides in the silage oil and led to lower non-protein nitrogen values. Fermentation by lactic acid bacteria (LAB) was shown to efficiently inhibit pathogens such as L. monocytogenes and E. coli O157:H7 as well as some spoilage microorganisms. Histamine degradation by some of the most promising available LAB strains was also tested, as an innovative means of ensuring low levels of this amine in the fermented product. Several potential starter strains were found to degrade histamine as single strain cultures and could find application in fish silage and other fish products in which histamine accumulation might pose a certain risk.Temperatures of 35 - 37°C were regarded as most suitable from the point of view of starter growth and acidification. Strains with a short acidification lag time, such as Lb. plantarum 009, or with very fast growth and good antibacterial properties, such as Lb. curvatus 15.35, are most suitable.Sodium chloride inhibited growth of biogenic amine producing bacteria and additionally decreased non-protein nitrogen and total volatile basic nitrogen values in BFS. Potassium sorbate was shown to inhibit growth and/or acidification by potential starter lactic acid bacteria.</p
Distribuição espacial de crustáceos decápodos e estomatópodos durante o verão no banco de algas calcárias da Ilha do Arvoredo
No full textTCC (graduação) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Curso de Ciências Biológicas
Strengthening Mechanisms of 27MnSiVS6 Microalloyed Steel Deformed by Four Different Forging Processes
No full textAbstractThe demand of automotive industries for parts with high overall quality, low costs and reduced time to market, forced suppliers to search alternative materials and manufacturing processes. Hot forgings with microalloyed steel represent an extensive application in automotive parts. The main objective of this work was to study the microstructures by transmission electron microscopy (TEM) and mechanical properties of 27MnSiVS6 microalloyed steel deformed by ausforming, warm forging and hot forging.Workpieces were heated for 15minutes at 1150°C before hot forging and 800°C before warm forging.Two different ausforming tests were carried out: in the first group workpieces were heated for 15minutes at 1150°C, cooled to 800°C at a cooling rate of 8.7°C/s and then deformed. In the second group the conditions were kept constant except for the heating temperature of 1000°C. All forged products were air cooled after deformed. Ausforming products presented the best mechanical properties. TEM analysis showed that strengthening by vanadium carbonitride precipitates was the main hardening mechanism of both ausformed and hot forged products while warm forgings were strengthened by the higher dislocation density. © 2011 Published by Elsevier Ltd. Selection and peer-review under responsibility of ICM1
Indices de erosividade das chuvas da regiao de Goiânia, GO
No full textThe measure of rainfall erosive potential is becoming object of many studies, since this parameter is indispensable in the studies of models for the prediction of soil losses through hydrical erosion. This study was carried out at EMGOPA/Embrapa-CNPS experimental station, to determine the rainfall erosivity for the Goiania region, GO, Brazil, through rainfall graphical data. The rainfall annual average erosivity for the region was 8353.0 MJ mm/ha/year and 129.8 MJ/ha/year, respectively for EI30 and KE > 25. The correlation coefficients showed that the rainfall and rainfall coefficient allow to estimate the rainfall erosivity in the absence of more complete rainfall data. The erosion critical period, due to the occurrence of erosive rainfalls is from September to February, when 85.70% and 84.05% of the KE > 25 and EI30 annual total, respectively, occurr. In this period, conservation practices are necessary in order to reduce the hydrical erosion, for the maintenance of soil sustainability. (Résumé d'auteur
Sleep, ageing and night work
No full textStudies have shown that the frequency or worsening of sleep disorders tends to increase with age and that the ability to perform circadian adjustments tends to decrease in individuals who work the night shift. This condition can cause consequences such as excessive sleepiness, which are often a factor in accidents that occur at work. The present study investigated the effects of age on the daytime and nighttime sleep patterns using polysomnography (PSG) of long-haul bus drivers working fixed night or day shifts. A total of 124 drivers, free of sleep disorders and grouped according to age (<45 years, N = 85, and ≥45 years, N = 39) and PSG timing (daytime (D) PSG, N = 60; nighttime (N) PSG, N = 64) participated in the study. We observed a significant effect of bedtime (D vs N) and found that the length of daytime sleep was shorter [D: <45 years (336.10 ± 73.75 min) vs N: <45 years (398 ± 78.79 min) and D: ≥45 years (346.57 ± 43.17 min) vs N: ≥45 years (386.44 ± 52.92 min); P ≤ 0.05]. Daytime sleep was less efficient compared to nighttime sleep [D: <45 years (78.86 ± 13.30%) vs N: <45 years (86.45 ± 9.77%) and D: ≥45 years (79.89 ± 9.45%) and N: ≥45 years (83.13 ± 9.13%); P ≤ 0.05]. An effect of age was observed for rapid eye movement sleep [D: <45 years (18.05 ± 6.12%) vs D: ≥45 years (15.48 ± 7.11%) and N: <45 years (23.88 ± 6.75%) vs N: ≥45 years (20.77 ± 5.64%); P ≤ 0.05], which was greater in younger drivers. These findings are inconsistent with the notion that older night workers are more adversely affected than younger night workers by the challenge of attempting to rest during the day.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Universidade Estadual Paulista Departamento de Psicologia Experimental e do TrabalhoUniversidade Federal de São Paulo (UNIFESP) Escola Paulista de Medicina Departamento de PsicobiologiaCentro de Estudo Multidisciplinar em Sonolência e AcidentesUniversidade Estadual Paulista Departamento de Psicologia Experimental e do TrabalhoFAPESP: 98/14303-
Índices de erosividade da chuva, perdas de solo e fator erodibilidade para dois solos da região dos cerrados: primeira aproximação.
No full textOs objetivos deste trabalho foram: testar a adequação de diferentes índices de erosividade das chuvas, comparar duas equações propostas para cálculo da energia cinética das chuvas e estimar o fator K (erodibilidade) da equação universal de perdas de solo (EUPS) para um latossolo vermelho-escuro (LE) álico muito argiloso e um podzólico vermelho-amarelo (PV) álico muito argiloso da região de Sete Lagoas (MG). Não houve diferença significativa entre as duas equações testadas para cálculo da energia cinética das chuvas. O índice EI30 mostrou ser um bom estimador da erosividade da chuva e pode continuar sendo utilizado como fator R (erosividade) da EUPS para a região estudada. Os valores do fator K, para o LE e o PV da região de Sete Lagoas, foram, respectivamente, 0,002 e 0,033 t h (MJ mm)-1
Atributos do solo para predição do escoamento superficil em sub-bacia hidrográfia Brasil
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