Revestimento superficial em componente fundido de máquina agrícola

A necessidade de desenvolver o processo de manufatura para aplicação de revestimento superficial em peças fundidas de máquinas agrícolas viabilizou a realização deste trabalho junto à indústria. A análise das principais variáveis do processo produtivo foi considerada levando-se em conta recursos necessários, tais como, ferramental e equipamentos, material de adição (arame de soldagem), inspeção das características macroscópicas e, principalmente, as especificações de engenharia do item. A revisão bibliográfica ressaltou os problemas normalmente existentes quando da soldagem de peças fabricadas de ferro fundido, assim como esclareceu os principais cuidados necessários para obtenção de revestimentos superficiais com qualidade. Para definição e aprovação do processo de soldagem a ser usado, foram realizados testes simulando uma soldagem automatizada, controlando os principais parâmetros de soldagem. A análise da qualidade do cordão de solda, sob o ponto de vista de aparência geral, geometria, presença de descontinuidades (porosidade e inclusões de escória), foi feita através de inspeção visual. Devido a necessidade de estruturar o processo de solda afim de possibilitar fornecimento continuada de peças para a linha de montagem, foi analisado e proposto um conceito de gabarito de soldagem. Os ensaios de micrografia mostraram a penetração e aspectos internos do depósito de solda. O exame micrográfico mostrou também que a trinca transversal que ocorre no material não avança para dentro do metal base. Os resultados dos testes e ensaios proporcionaram os subsídios para permitir a aprovação do método proposto a fim de dar continuidade na estruturação do processo de soldagem para revestimento superficial das peças fundidas.

Metodologia de análise e diagnóstico de fratura em um componente automotivo sujeito a cargas cíclicas alternadas

The competitiveness of the trade generated by the higher availability of products with lower quality and cost promoted a new reality of industrial production with small clearances. Track deviations at the production are not discarded, uncertainties can statistically occur. The world consumer and the Brazilian one are supported by the consumer protection code, in lawsuits against the products poor quality. An automobile is composed of various systems and thousands of constituent parts, increasing the likelihood of failure. The dynamic and security systems are critical in relation to the consequences of possible failures. The investigation of the failure gives us the possibility of learning and contributing to various improvements. Our main purpose in this work is to develop a systematic, specific methodology by investigating the root cause of the flaw occurred on an axle end of the front suspension of an automobile, and to perform comparative data analyses between the fractured part and the project information. Our research was based on a flaw generated in an automotive suspension system involved in a mechanical judicial cause, resulting in property and personal damages. In the investigations concerning the analysis of mechanical flaws, knowledge on materials engineering plays a crucial role in the process, since it enables applying techniques for characterizing materials, relating the technical attributes required from a respective part with its structure of manufacturing material, thus providing a greater scientific contribution to the work. The specific methodology developed follows its own flowchart. In the early phase, the data in the records and information on the involved ones were collected. The following laboratory analyses were performed: macrography of the fracture, micrography with SEM (Scanning Electron Microscope) of the initial and final fracture, phase analysis with optical microscopy, Brinell hardness and Vickers microhardness analyses, quantitative and qualitative chemical analysis, by using X-ray fluorescence and optical spectroscopy for carbon analysis, qualitative study on the state of tension was done. Field data were also collected. In the analyses data of the values resulting from the fractured stock parts and the design values were compared. After the investigation, one concluded that: the developed methodology systematized the investigation and enabled crossing data, thus minimizing diagnostic error probability, the morphology of the fracture indicates failure by the fatigue mechanism in a geometrically propitious location, a tension hub, the part was subjected to low tensions by the sectional area of the final fracture, the manufacturing material of the fractured part has low ductility, the component fractured in an earlier moment than the one recommended by the manufacturer, the percentages of C, Si, Mn and Cr of the fractured part present values which differ from the design ones, the hardness value of the superior limit of the fractured part is higher than that of the design, and there is no manufacturing uniformity between stock and fractured part. The work will contribute to optimizing the guidance of the actions in a mechanical engineering judicial expertise

Engenharia de microestrutura em varistor à base de ZnO: evidências de homogeneidade e correlação com reações químicas

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Morphological analysis of the corneal endothelium in eyes of dogs using specular microscopy

Foram estudados 20 olhos de 10 cães sem raça definida, machos e fêmeas com 6 anos de idade. A morfologia das células do endotélio da córnea foi analisada utilizando-se microscópio especular de contato. Foram estudadas as regiões central e periférica da córnea. de cada região da córnea foram realizadas três micrografias. de cada micrografia foram analisadas no mínimo 100 células endoteliais. Foram obtidos os valores do polimegatismo e pleomorfismo. O endotélio corneano de cães caracterizou-se por uma monocamada de células poligonais uniformes em tamanho e forma. A forma predominante das células endoteliais foi hexagonal. O índice de polimegatismo foi 0.22. Este estudo demonstrou que a morfologia das células do endotélio da córnea de cães é semelhante à observada em humanos.

Utilização de processos oxidativos avançados baseados em ozônio como pré-tratamento para bagaço de cana-de-açúcar, e hidrólise do bagaço pré-tratado com combinado enzimático dos fungos Penicillium viridicatum RFC3 e Trichoderma reesei QM9414

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influência dos elementos de liga nos parâmetros de processo de fundição de ferros fundidos especiais

Pós-graduação em Engenharia Mecânica - FEG

Caracterização de Bacteriófagos Infectando Isolados Clínicos de Pseudomonas aeruginosa Armazenados em uma Coleção de Cultura

To isolate, to concentrate and to purify bacteriophages from isolates of P. aeruginosa; To observe the capacity of bacteriophages to infect isolates of P. aeruginosa susceptible and multiresitant to antimicrobial; To caractherize bacteriphages by electronic microscopy techniques. 10 isolates of Pseudomonas aeruginosa from LEMC culture collection were submitted to the experiments of ideal temperature for the lyse region appearance in the MaConkey culture plate and 2 extraction methods for the concentration of the phages, clorophorm (Silankorva) and filtration plus centrifugation (Bergan). Three infected clinical isolates of multiresistant P. aeruginosa an one susceptible isolate ( PA01) were evaluated by 3 transmission electron microscopy techniques to caractherize phages morphologically (“on grid”, “on drop” and direct extraction from the lyse region of the culture plate). The ideal temperature to obtain lyses region was 37°C. The stock solutions, obtained through the methodologies of Sillankorva and Bergan, had satisfactory results in infecting the multiresistant isolate and the negative control. Among the 3 techniques of electronic microscopy tested the direct from the lyse plate was the best to obtain the micrography of the phages

Efeito do Estrôncio (Sr) no tratamento de modificação do eutético da liga Al-1%Si

This study aimed to analyze the cooling curves, micro and macrograph alloy Al-1 %Si without the addition of strontium modifier and with the addition of the same. One of the ways of improving mechanical properties of alloy Al -Si is through the modification process. For the experiments two billets of the alloy Al-1%Si cast iron mold in a billet with addition of 0.02% strontium by weight, and the other billet without the addition of modifier were fused. In the solidification process of billet temperature was monitored and recorded every second for later plotting in Origin 8 program and analyzes the cooling curves obtained. The billets were cut and passed by grinding and polishing to perform the macrograph and micrographs. The results concerning the macrograph indicated that billet without the addition of Strontium particle size obtained was more refined than the billet where the strontium modifier was added. Regarding the micrograph, photos stemmed from the optical microscope didn´t show the expected modification effect by the addition of Strontium. This suggests that the low amount of silicon (1 %) present in the alloy used in this study interfered in the change process, because according to the literature review, Strontium 0.022 % by weight is sufficient to fully modify an alloy with 7% Silicon. The results from the cooling curve showed that both the eutectic temperature and the solidification time remained unchanged with the addition of strontium

Análise macro e micrográfica da liga AA-356 conforme a taxa de resfriamento

The present work aims to study the characteristics of the alloy Al - 7 % Si - 0 , 3Mg ( AA356 ) , more specifically characterize the macrostructure and microstructure and mechanical properties of the alloy ingots AA356 obtained in metal molds and sand molds for power studying the structures through the difference of cooling rates . This alloy is explained by the fact of referring league has excellent combination of properties such as low solidification shrinkage and good fluidity, good weldability , high wear resistance , high strength to weight ratio, has wide application in general engineering , and particularly in the automotive and aerospace engineering . In this work we will verify this difference in properties through two different cooling rates . We monitor the solid solidification temperatures by thermocouples building with them the cooling curve as a tool that will aid us to evaluate the effectiveness of the grain refining because it achieved with some important properties of the alloy as the latent heat of solidification fraction the liquid and solid temperatures, the total solidification time, and identify the presence of inoculants for grain refinement. Thermal analysis will be supported by the study of graphic software “Origin “will be achieved where the cooling curve and its first derivative that is the cooling rate. Made thermal analysis, analysis will be made in macrographs ingots obtained for observation of macrostructures obtained in both types of ingots and also analysis of micrographs where sampling will occur in strategic positions ingots to correlate with the microstructure. Finally will be collecting data from Brinell hardness of ingots and so then correlating the properties of their respective ingots with cooling rate. We found that obtained with cast metal ingots showed superior properties to the ingots obtained with sand mold

Caracterização estrutural da Liga Al-1% Si

The aim of this study is to characterize the macrostructure and microstructure of Al - 1%Si alloy obtained in sand and metallic molds. Aluminium has good mechanical properties, but adding silicon, even in small quantities, can change the microstructure and improves mechanical behavior. Workpieces were castings in metallic and sand molds and one can see a difference in their cooling curve, macroscopic and microscopic structures. The sand mold casting has lower cooling rate and so its grains are larger. Due to the lower concentration of grain boundary, the hardness is lower compared to that found in metallic molds, which has smaller grains and a higher hardness. Therefore, it can be concluded that the cooling rate and alloying elements affect the final microstructure of the workpiece

Micropartículas contendo nanopartículas de quitosana usando sulfato e genipina para liberação modificada da triancinolona: obtenção, caracterização e estudo em células tumorais

Chitosan is a polymer biocompatibility and biodegradability widely used in drug delivery systems. The co-crosslinking of chitosan with sodium sulfate and genipin, to form particulate systems is related of making them more resistant to acidic pH and to modulate the release kinetics for the oral route. Triamcinolone is a glucocorticoid with anti-inflammatory and immunosuppressive actions. The nanoparticles were prepared by co-crosslinking and characterized for particle size, PDI, zeta potential, crosslinking degree, encapsulation rate, morphology, infrared spectroscopy, thermal analysis, release kinetics and cells studies. The nanoparticles were prepared initially without genipin with sodium sulphate and the particles parameters were monitored in function of different ratio of drug / polymer, different concentrations of sodium sulfate and polysorbate 80 and the drip mode of crosslinkers on polymers. After optimizing conditions, the chosen system parameters without genipin included mean diameter of 312.20 ± 5.70 nm, PDI 0.342 ± 0.013 and zeta potential of 20.18 ± 2.28 mV. The genipin was introduced into the system analyzing different concentrations (0.5, 1.0 and 2.0 mM) and crosslinking times (3, 6, 12 and 24 h). Evaluating crosslinking time with genipin (0.5 mM) it was showed that varying the genipin reaction time the systems size ranged from 235.1 to 334.4 nm, the PDI from 0.321 to 0.392 and zeta potential 20.92 to 30.39 mV. The crosslinking degree that coud vary from 14 to 30 %. Nanoparticles without genipina, 6 h and 24 h crosslinking time were dried by spray-drying method. Analysis by scanning electron micrograph (SEM) revealed that the microparticles showed spherical morphology. The encapsulation rate was 75 ± 2.3 % using validated HPLC methodology. The infrared analysis showed chemical interactions between the components of the formulation. Thermal analysis showed that systems with a higher degree of crosslinking had a higher thermal stability. On release kinetics, increasing the degree of crosslinking was able to decrease the concentration and rate of release of triamcinolone. In studies with liver cancer cells (HepG2) and colon (HT-29), the microparticulate prepared with triamcinolone and 24 h of crosslinking with genipin showed a potential for antitumor activity in hepatic cell line HepG2. Therefore, a new delivery system for triamcinolone on polymeric nanoparticles of chitosan cocrosslinked with genipin and sodium sulfate was obtained with hepatic antitumor potential.