http://hdl.handle.net/11422/91 Fri, 10 Apr 2026 14:46:55 GMT 2026-04-10T14:46:55Z http://hdl.handle.net/11422/28506 Title: Colheita de energia de vibração a partir de sistemas inteligentes e adaptativos utilizando interações magnéticas Author(s)/Inventor(s): Savi, Pedro Vieira Advisor: Savi, Marcelo Amorim Abstract: This work investigates the vibration-based energy harvesting from smart and adaptive devices with magnetic interaction. The conversion of the mechanical vibration energy is promoted by smart materials, specifically a magnetostrictive material. It is exploited nonlinearities induced by magnetic interactions that confer multistability characteristics of the system. Magnetic interactions are described by a novel model that represents the magnets by multiple points, improving the usual description of the method of the equivalent magnetic dipole point. Based on the modeling of the magnetic interaction, it is presented a dynamical system associated with an adaptive energy harvesting device composed by a cantilever beam with basis excitation that represents the energy source of external vibration. The system has a magnet at the beam end that interacts with other three magnets. The system adaptability is associated with a degree of freedom of one of the three magnets, modifying system multistability aspects. A dynamical investigation shows the feasibility to enhance energy harvesting capacity changing the magnet position. Results show that the nonlinear dynamics perspective is capable to define the best characteristics of the device according to external conditions Publisher: Universidade Federal do Rio de Janeiro Type: Dissertação Sat, 01 Oct 2022 00:00:00 GMT http://hdl.handle.net/11422/28506 2022-10-01T00:00:00Z http://hdl.handle.net/11422/27481 Title: Avaliação do Método SPB utilizado na determinação do crescimento estável de trinca em testes de fratura Author(s)/Inventor(s): Delgado Ramirez, Egon Rolf Advisor: Kotik, Héctor Guillermo Abstract: Since its proposal for the evaluation of stable crack growth, the Spb method has been successfully applied in the evaluation of fracture toughness of metallic and polymeric materials. However, some points of the methodology have not been studied indepth, such as the applicability in standardized geometries in which ηpl depends on the a/W ratio, as well as the choice of the a/W ratio for the specimen used as a reference. To discuss this and other aspects, theoretical analyzes of the Spb method and experimental tests were carried out. The theoretical analysis revealed that considerable differences can be achieved in the C(T) and SE(T) geometries when the same ηpl factor is used in the specimens with blunt and pre-cracked notches. To minimize these differences, it was proposed to use a more general expression of the Spb method, together with the ηpl factors provided by the standards for geometries, where ηpl changes with a/W. As well as some a/W ratios are recommended for the reference specimen, which were determined according to the useful plastic displacements that each specimen can achieve. The proposed experimental methodology, based on the load separation and the ηpl factors provided by the standards, proved to be adequate for the C(T) geometry, while for the SE(T) geometry the results indicate that further research is needed.Também disponível on-line Publisher: Universidade Federal do Rio de Janeiro Type: Tese Sun, 01 May 2022 00:00:00 GMT http://hdl.handle.net/11422/27481 2022-05-01T00:00:00Z http://hdl.handle.net/11422/27480 Title: Desenvolvimento e avaliação de nanocompósitos de EVA :argilominerais e compósitos de EVA: dendrímero como redutores de ponto de fluidez e otimizadores da garantia de escoamento de sistemas parafínicos e de petróleo Author(s)/Inventor(s): Alves, Bruna Frugoli Advisor: Lucas, Elizabete Fernandes Abstract: During production, transport, and logistics activities of crude oil, it is necessary to use methods to prevent operational problems caused by waxes precipitation. To overcome this problem polymeric additives can be used, and polymeric composites are a promising alternative. In this work, poly(ethylene-co-vinyl acetate) (EVA) containing 10 mol% vinyl acetate was used as a load of EVA:clay minerals nanocomposites and EVA:dendrimer composites. All nanocomposites were able to reduce the pour point, while EVA had no effect. Among nanocomposites, the EVA:palygorskite were the most efficient pour point depressants for both model system and oils. Besides reducing the pour point, the EVA:dendrimer composites also significantly reduced the viscosity of the systems and induced the formation of a differentiated waxy crystal morphology. In general, both nanocomposites and composites were more efficient than pure EVA and acted by modifying the waxy crystals' morphology and improving the flow. When compared, EVA:clay minerals nanocomposites performed better than EVA:dendrimer composites in improving the flow assurance of waxy systems Publisher: Universidade Federal do Rio de Janeiro Type: Tese Thu, 01 Dec 2022 00:00:00 GMT http://hdl.handle.net/11422/27480 2022-12-01T00:00:00Z http://hdl.handle.net/11422/27479 Title: Transient modeling and simulation of piston devices moving through single-phase and two-phase flows in pipes applied to pigs and plungers Author(s)/Inventor(s): Viggiano Neves de Freitas, Raphael Advisor: Rachid Bodstein, Gustavo Cesar Abstract: The passage of piston devices through pipes is commonly used in the oil and gas industries for the purposes of cleaning, monitoring, and increasing production efficiency. These devices are not self-driven and require their interaction with the flow entailing a pressure discontinuity across the piston body that drives it along the pipe. To ensure the proper operation of such devices it is crucial to predict the dynamics of the piston and its effects on the flowline. In this work, two modeling approaches are studied for pigs, and one model is proposed for a plunger upstroke. The pig model is applied to single-phase flow, and two-phase flow, including the bypass flow through the piston body. The plunger upstroke model includes the effects of liquid fallback and the gas slippage through the plunger body. In addition, a new methodology is proposed for the coupling of the piston models with the transient one-dimensional flow models. For the two-phase flow models, two two-fluid models are tested with different numerical methods, with the combinations of model-method being validated through benchmarking. The results obtained with the pig model are compared with results from the literature under single-phase and two-phase stratified flow. The results obtained with the plunger upstroke model are also validated with data from the literature, and with experimental data acquired during this work Publisher: Universidade Federal do Rio de Janeiro Type: Tese Fri, 01 Jul 2022 00:00:00 GMT http://hdl.handle.net/11422/27479 2022-07-01T00:00:00Z