Torneamento assistido por ultrassom de materiais cerâmicos em verde e pré-sinterizados

• Ano de defesa: 2019
• Autor(a) principal: Gonçalves Júnior, Marcos
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual Paulista (Unesp)
• Palavras-chave em Português: Advanced ceramics; Green machining; Pre-sintered machining; Ultrasonic assisted turning; Design of experiments; Cerâmica avançada; Usinagem em verde; Usinagem pré-sinterizada; Torneamento assistido por ultrassom; Planejamento de experimentos
• Link de acesso: http://hdl.handle.net/11449/181510

The advanced ceramic machining in green and pre-sintered states aims to minimize the machining step after sintering, in order to reduce the high cost of the process. Such methods provide a considerable advantage in the production of components with complex geometry in terms of surface finishing, economic efficiency and flexibility, as it allows obtaining near-netshape dimensions. However, it is easy to introduce damages and/or chipping due to its low mechanical resistance, mainly, in the use of inadequate cutting parameters. In order to improve the machining performance of hard and brittle materials, ultrasonic assisted machining can be employed. Applications of this technique have demonstrated that the process can greatly improve the machining performance. In this thesis, we investigated the application of ultrasonic assisted turning (UAT) in green and pre-sintered ceramic materials. For this purpose, components have been developed for the appropriate assembly of the test bench, with emphasis the flexure hinge support. In order to carry out the process, design of experiments (DOE) with fractional factorial and response surface modeling were performed and analysis of variance (ANOVA) was applied in some obtained data. The machining forces were measured by a dynamometer and correlated with the cutting parameters and the surface finishing. The results showed that the UAT method provided better surface finishes and reduced roughness in relation to the conventional turning (CT), as well as minimized the introduction of excessive surface damage under some conditions. It was verified that, the machining forces did not change between the CT and UAT methods using the same cutting parameters. In the tool wear analysis, the UAT method provided a reduction of 34% and 28.1% flank wear in the green and pre-sintered condition respectively, as well as, reduced the change of the original tool tip geometry and, consequently, the reduction in the forces generated