https://repositorio.unifei.edu.br/jspui/handle/123456789/55 Thu, 01 Oct 2026 23:09:44 GMT 2026-10-01T23:09:44Z https://repositorio.unifei.edu.br/jspui/handle/123456789/3173 Título: Aquisição e validação de sinal de ruído eletroquímico Abstract: Corrosion is a global problem, which implies costs in industrialized countries of up to 4.5% of GDP, with either economic, but also social and environmental impacts. In the case of Brazil, the waste of water supply networks due to leaks loss is quite significant and much of it is caused by network degradation, indicating that corrosion control should be promoted whenever possible. This study proposes a corrosion monitoring system, in system subject to the use of inhibitor, with the approach of passive technique for monitoring corrosion by electrochemical noise (EN), in which the classification of events in a corrosion sensor by EN is part of methodological study for structural integrity (or “health”) monitoring system (SHM). Due to very dynamic and stochastic nature of the signal, this study and analysis of EN measurements (ENM) considers numerical and graphic characteristics of two corrosion systems both in saline aqueous solution: carbon steel and stainless steel. These experiments are repeated for accumulating data, which allow the generation of several graphs in time and frequency domains, from which at least one characteristic is extracted, which has a good correlation with data from corrosion processes. Then, based on a supervised machine learning system, the training data allows the model to be calibrated. From the test data, the correctness rate of the model above 50% is verified. Tipo: Dissertação Thu, 17 Feb 2022 00:00:00 GMT https://repositorio.unifei.edu.br/jspui/handle/123456789/3173 2022-02-17T00:00:00Z https://repositorio.unifei.edu.br/jspui/handle/123456789/4474 Título: Study on multi-modal dynamic vibration absorbers applied to helicopters Abstract: Vibration control is a critical challenge in helicopter engineering, where high-amplitude structural vibrations accelerate component wear and fatigue while degrading crew performance and comfort. Conventional Dynamic Vibration Absorbers (DVA) are widely used in helicopters, as an evolution of the DVA, there is the Multi-Modal Vibration Absorber (MMDVA), which can suppress several rotor harmonics simultaneously with a single device. This study implements a finite element method (FEM) based design methodology for MMDVAs tailored to the main and tail rotor frequencies of a Brazilian Navy Lynx helicopter, utilizing carbon fiber leaf springs integrated with steel inertial masses. Experimental vibration analysis using flight test accelerometer data informed target frequency selection, revealing that while the dominant excitation frequencies are governed by main rotor and tail rotor harmonics, their relative amplitude distribution varies significantly between pilot and co-pilot locations and across flight conditions. From this analysis, four target frequencies were selected for each MMDVA to attenuate. A two-stage optimization routine based on a genetic algorithm was implemented: the first stage aligns the isolated natural frequencies of the MMDVAs with the target frequencies using modal analysis, and the second stage refines its geometry through coupled harmonic analysis to account for damping and interaction with the host structure. Two candidate geometries were proposed, taking advantage of multiple vibration mode shapes like flexion and torsion. The first geometry comprises two mass blocks, each contributing with two vibration modes, generating two antiresonances per block. The second geometry comprises three mass blocks, whose combined motion contributes to four vibration modes of the structure, generating four antiresonances. By generating multiple antiresonances with a single device, the proposed MMDVAs achieve broader vibration suppression than conventional single-mode absorbers, making more efficient use of absorber weight compared to adding multiple independent devices to the structure. Tipo: Dissertação Fri, 10 Jul 2026 00:00:00 GMT https://repositorio.unifei.edu.br/jspui/handle/123456789/4474 2026-07-10T00:00:00Z https://repositorio.unifei.edu.br/jspui/handle/123456789/4473 Título: Impacto socioeconômico da liberalização do mercado de eletricidade no Brasil: previsão e análise otimizada de tarifas Abstract: The Brazilian electricity sector is undergoing a major transformation, following the growth of the deregulated market. Similar to several countries around the world, Brazil is restructuring its power market and adopting measures to expand the participation of low-voltage consumers in the Free Contracting Environment (ACL). Technical Note No. 10/2022-SRM/ANEEL proposes a gradual migration of consumers from the regulated to the free market until 2026. Within this context, this thesis evaluates the effects of this proposal on the regulated market, analyzing the impact of migration across 13 Brazilian concession areas based on a combination of an optimized tariff model and forecasting models. Specifically, the study examines how market opening influences the behavior of the regulated agents, considering both the socioeconomic welfare of the consumers who remain in the regulated market and the financial performance of the distribution companies. According to the results, the market opening proposal led to a reduction in both the financial-economic balance of the utilities and social welfare. Furthermore, there was an increase in tariffs that could directly impact household budgets, requiring higher spending on electricity. As a consequence, a potential reduction in consumers' purchasing power is observed, since a larger portion of their income is spent on higher electricity bills, limiting the consumption of other goods and services. This tariff increase stems from legacy contracts, which were established in the past to serve a larger number of consumers, as well as the need to ensure the financial-economic equilibrium of the distributors. With free migration, the clients who stay in the regulated market are penalized by these contracts because, as more people leave the Regulated Contracting Environment, the remaining fixed cost is divided among fewer people. In conclusion, the proposal from NT No. 10/2022-SRM/ANEEL affects each concession area differently. Therefore, regulatory adjustments are essential to prevent long-term tariff increases, making it crucial to align the schedule for opening the free market with the reduction of legacy contracts. Finally, it is worth noting that although the proposed methodology is applied to the Brazilian scenario, it can be adapted and used by any country undergoing electricity market liberalization, provided it respects local rules and regulations. Tipo: Tese Fri, 10 Jul 2026 00:00:00 GMT https://repositorio.unifei.edu.br/jspui/handle/123456789/4473 2026-07-10T00:00:00Z https://repositorio.unifei.edu.br/jspui/handle/123456789/4472 Título: Design, optimization, and real-time structural health monitoring using embedded 3d-printed piezoresistive sensors in composite structures Abstract: Structural Health Monitoring (SHM) is an essential strategy for ensuring the safety and longevity of critical infrastructure and advanced composite structures. While embedded sensors offer a transformative approach to real-time monitoring by enabling in-situ damage detection, their widespread adoption is hindered by challenges at the sensor-material interface, unoptimized geometric designs, and a critical lack of system-level validation in complex load-bearing components. This thesis presents a comprehensive ”Experiment- Model-Optimize-Validate” framework for the development, optimization, and system-level integration of additively manufactured piezoresistive strain sensors. Through a systematic review of the state-of-the-art, the predominance of carbon-based piezoresistive sensors manufactured via Fused Deposition Modeling (FDM) was established, alongside the critical need to balance sensor sensitivity with the mechanical integrity of the host structure. To address this inherent trade-off, a rigorous computational and experimental methodology was developed. A Design of Experiments (DoE) evaluated the influence of geometric parameters (trace width, inter-trace distance, thickness, and end-loops) on sensor performance. Utilizing Gaussian Process Regression (GPR) and a Multi-Objective Particle Swarm Optimization (MOPSO) algorithm, optimal geometries were identified. Experimental validation demonstrated that fully embedded configurations achieved exceptional piezoresistive sensitivity (Gauge Factor ≈ 59), while a geometrically scaled variant successfully restored the host structure’s stiffness to near-native levels (≈ 2.18 GPa) without significant loss of sensitivity. To bridge the gap between laboratory-scale coupon testing and field-ready deployment, the optimized sensing architectures were integrated into a geometrically complex aerospace pylon structure using multi-material FDM. Sensor placement was strategically guided by Finite Element Analysis (FEA) to target critical strain hotspots, and a redundant sensing network was implemented to ensure fault tolerance. System-level testing, validated by full-field Digital Image Correlation (DIC), proved that the embedded sensors exhibited high-fidelity temporal synchronization with mechanical deformation, capturing transient structural events with negligible viscoelastic lag. Furthermore, the redundant architecture successfully maintained monitoring capabilities and diagnosed asymmetrical loading anomalies. Ultimately, this research provides a highly scalable and robust methodology for transitioning 3D-printed embedded sensors from isolated component optimization to integrated, self-sensing structural systems, advancing the technological readiness of real-time SHM in aerospace and civil engineering applications. Tipo: Dissertação Wed, 01 Jul 2026 00:00:00 GMT https://repositorio.unifei.edu.br/jspui/handle/123456789/4472 2026-07-01T00:00:00Z