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Otimização do processo de soldagem robotizada tandem GMAW do aço ASTM A572 G50
(Universidade Federal de São Carlos, 2018-10-31) Rossini, Luis Felipe Scalet; Spinelli, José Eduardo; https://lattes.cnpq.br/8882038118634925; https://lattes.cnpq.br/3004683472463954
The tandem welding process employs double wire feed in a single torch, providing increased deposition rate and consequent reduction in process times. However, the process complexity increases because the correct combination of parameters is essential to avoid the occurrence of interference between the electric arcs and defects, such as inadequate geometry, accentuated base metal casting, which results in failures under service conditions. The understanding of the TANDEM process and the optimization of the cycle times are the motivations of this work, having as a proposal to analyze the presence of defects and the changes in the microstructure and the mechanical strength through the variation of the modes of metallic transfer, angulation of the welding torch and consequent heat input variation. For all parameter variations, ASTM A572 G50 structural steel test pieces welded with ER70S-6 welding wire have been fabricated using robotic welding stations from a Multinational Company. The volume of the weldments has been the same in all variations of parameters, allowing a comparative analysis of the quality of the joint and presence of defects. The probability of occurrence of defects has been analyzed by the high-frequency acquisition of the values of current, voltage and wire feed speed, while the penetration profile and the dimension of the heat affected zone have been examined through macrographs. The analysis of the microstructure of the molten and heat affected areas has been carried out using an optical microscope, while for the determination of the strength, Vickers micro hardness profiles have been obtained. After different test conditions, the best combination of parameters was found, where the master wire was parameterized in continuous current and the slave wire with pulsed metallic transfer, obtaining a 19,3% higher displacement speed of the robot and no occurrence of anomalies in electrical arcs.
Análise da variação morfológica em Caipirasuchus paulistanus Iori & Carvalho, 2011 e Caipirasuchus montealtensis (Andrade & Bertini, 2008) (Crocodylomorpha: Sphagesauridae)
(Universidade Federal de São Carlos, 2018-10-31) Dias, Willian Alexandre Ferreira; Iori, Fabiano Vidoi; https://lattes.cnpq.br/7623488132403298; Fernandes, Marcelo Adorna; https://lattes.cnpq.br/6709493251686592; https://lattes.cnpq.br/8906511795425295
Caipirasuchus is a genus of Notosuchia that lived during the late Cretaceous in Brazil and, until the present, only found in the Adamantina Formation, Bauru Basin. Within this genus there are the Caipirasuchus montealtensis and the Caipirasuchus paulistanus species, often referred to as taxon brothers due to their morphological proximity. The morphological similarity raises questions about the taxonomy of these species. The main difference between C. montealtensis and C. paulistanus comes from the existence of the pterygoid chamber in C. montealtensis, a chamber that presents intraspecific variation. The main goal of this study was to analyze the morphological variations in the choana region in order to observe whether these variations could mean sexual dimorphism or speciation. Computed tomography has been used to internally explore the choana region and to evaluate the possible communication between the pterygoid structures and the airways in both C. montealtensis and C. paulistanus. The results obtained support the morphological disparities between C. montealtensis and C. paulistanus. It was possible to identify morphological differences in the pterygoid chamber of the C. montealtensis specimens, a complex secondary chamber is present in the paratype and in the juvenile individual and completely absent in the holotype. A communication between the pterygoid chambers and the airways was found in the juvenile C. montealtensis, suggesting possible functions related to vocalization. The new observations expand the knowledge about C. montealtensis and C. paulistanus anatomy, as well as suggesting the possible occurrence of a new species of Caipirasuchus, from the characters found in the juvenile paratype and C. montealtensis. A stratigraphy is important for the taxonomic elucidation of the group and a broader sampling would assist in the taxonomy and understanding the function of the pterygoid chamber.