Orientador: Kátia Lucchesi Cavalca Dedini / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-22T11:25:08Z (GMT). No. of bitstreams: 1 Radaelli_GustavoZarpelon_M.pdf: 6785468 bytes, checksum: 07019edf34b966c552330056d686bd33 (MD5) Previous issue date: 2013 / Resumo: Os mancais possuem um papel expressivo dentre os componentes de um sistema rotativo, tendo o suporte de um elemento rotativo como sua principal função. Por trabalharem na interface entre elementos fixos e rotativos, os mancais constituem a origem de grande parcela das falhas ocorrentes em um sistema. Dentre estes, os mancais de rolamento de contato angular estão entre os mais utilizados, principalmente pela indústria automobilística. Apesar da ampla gama de aplicações, esses mancais usualmente estão sujeitos a falhas por fadiga de superfície, o que torna imprescindível um estudo aprofundado dos esforços e das velocidades aplicados às esferas e, consequentemente, às pistas interna e externa. A descrição dos esforços e das velocidades nas esferas é um desafio considerável, uma vez que as esferas estão sujeitas a uma lubrificação elastohidrodinâmica, que por sua vez, depende integralmente dos esforços e das velocidades das esferas para ser modelada, gerando assim um processo iterativo. O principal objetivo deste trabalho é analisar o rolamento de esferas de contato angular, com embasamento teórico na literatura clássica para, em seguida, iniciar o equacionamento do equilíbrio de forças nas esferas e no mancal, o qual por sua vez, resulta na força de contato associada à condição de lubrificação. Para tanto, um programa computacional para simulação numérica das análises cinemáticas e dinâmicas foi desenvolvido e seus resultados comparados com a literatura. Após realizar a validação inicial do modelo com a literatura, uma solução mais completa é proposta para reproduzir de uma forma mais detalhada o que se encontra em aplicações práticas. Os resultados encontrados pelas diversas simulações foram condizentes com os resultados encontrados na literatura clássica, atestando que o programa computacional desenvolvido é consistente / Abstract: The bearings are of great importance and its major function is to support a rotating element. Due to the mandatory role of these components in the interface between fixed and rotating elements, the bearings are the source of a great percentage of the possible faults on a system. The rolling bearings of angular contact are one of the most utilized, mainly by the automotive industry. In spite of the great applications field, these bearings are usually subject to damage by superficial fatigue, which makes of great significance the detailed study of the efforts and the velocities on the spheres and, consequently, on the external and internal railways. The description of the efforts and velocities acting on the spheres is a considerable challenge, once the spheres are subject to an elastohidrodynamic lubrication that fully depends on the efforts and velocities of the spheres, generating an iterative process. The main objective of this work is to analyze the rolling bearings of angular contact, under theoretical bases, in order to accomplish the forces balance for the balls and for the bearing, which in turn results in the contact forces associated to the lubrication condition. The analysis requires the development of a computational program to numerically simulate the kinematic and dynamic conditions and, then, some of the results can be compared with the literature. After the initial validation of the model with the literature, a more complete solution is proposed to make it closer to practical applications. Results obtained by several simulations are compatible with those found in theoretical bases, attesting that the computational program developed is consistent / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Des travaux scientifiques récents ont ouvert de nouveaux champs d’application aux traitements mécaniques tels que le grenaillage. Il a été montré que de tels traitements, réalisés avant un traitement de nitruration à la surface d’alliage ferreux, permettaient d’abaisser les températures de traitement et d’augmenter significativement les cinétiques de diffusion. Nous avons entrepris de tester les performances de cette combinaison de traitements mécanique et thermochimique sur des aciers inoxydables et des alliages à base nickel austénitiques. Des essais ont été réalisés à partir d’une technique de grenaillage mécanique appelée « Surface Mechanical Attrition Treatment » (SMAT). Des billes en métal ou en céramique sont introduites dans l’enceinte et mises en mouvement par la sonotrode. Les billes percutent et introduisent donc une déformation plastique à la surface des échantillons. Après cette étape, les échantillons subissent un traitement thermochimique de nitruration assisté plasma. La comparaison des résultats obtenus après nitruration sur des échantillons traités mécaniquement avec ceux n’ayant pas été pré-traités mécaniquement a permis de quantifier les effets des traitements combinés. Les analyses par diffraction des rayons X, les mesures de microdureté, les observations au microscope optique/électronique à balayage/électronique en transmission, les analyses de texture par EBSD (Electron BackScatered Diffraction) et la mesure des profils de concentration en azote par SIMS (Secondary Ion Mass Spectrometry) et SDL (Spectroscopie à Décharge Luminescente) ont montré l’importance de la nature de la couche transformée mécaniquement sur la diffusion de l’azote / Recent scientific work has opened new fields of application to mechanical treatments such as shot blasting or peening. Indeed, it has been shown that this treatment, performed before a nitriding treatment on the surface of ferrous alloy, lowers processing temperatures and significantly increases the diffusion kinetics. We undertook to test this combination of mechanical and thermochemical treatments on stainless steels and nickel-based alloys. The mechanical treatments were done by Surface Mechanical Attrition Treatment (SMAT). This method is implemented in a box where metal or ceramic balls were introduced and set in motion by an ultrasound system in order to impact the surface of the pieces. The treated samples were then nitrided at low temperature by using a remote plasma. The comparison of the results obtained after nitriding treatments on mechanically treated samples and those not mechanically treated allows quantifying the effects of the combined treatments. Analyses by X-ray diffraction, microhardness measurement, observations by optical and scanning and transmission electron microscopy, texture analysis by EBSD (Electron Diffraction BackScatered) and measurement of nitrogen concentration profiles by SIMS (Secondary Ion Mass Spectrometry) show the importance of the nature of the deformed layer