Programa de Pós-Graduação em Engenharia Mecânica
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Master Thesis Recompressão mecânica de vapor como estratégia de eficiência energética: avaliação termodinâmica de um sistema experimental proposto(Universidade Federal do Rio Grande do Norte, 2025-09-01) Nascimento, Gabriel Cirilo do; Melo, Anderson Clayton Alves de; Barros Neto, Eduardo Lins de; https://orcid.org/0000-0002-1310-7689; http://lattes.cnpq.br/2811639726261017; https://orcid.org/0000-0001-5679-3562; http://lattes.cnpq.br/5242440649066569; http://lattes.cnpq.br/6284103754956875; Silva, Leonardo Chagas da; http://lattes.cnpq.br/9340758076406278; Nascimento, Paula Fabiane Pinheiro do; https://orcid.org/0000-0002-0930-8656; http://lattes.cnpq.br/9568438570514870The rapid growth of the global economy in recent years has led to a high demand for energy sources capable of meeting the needs of large industries. At the same time, there is a growing concern with the search for renewable sources, aiming to reduce greenhouse gas emissions. In this context, one alternative that has gained prominence is energy recovery in thermal processes. It is known that a significant amount of thermal energy is wasted annually worldwide, especially in industries where saturated steam, resulting from heating processes, is released into the environment without being utilized. The recovery of this steam and its reintegration into the production cycle can reduce the total energy consumption of a process and contribute to lowering carbon emissions in industries that rely on fossil fuels for thermal energy generation. A widely used technique to recover this energy is mechanical vapor recompression, which consists of compressing the wasted steam until it becomes superheated and reusing it in the production cycle. Therefore, the objective of this research was to construct a thermal system, using a piston compressor, capable of recovering and superheating water vapor, as well as studying its thermal properties. This allowed for the quantification of energy recovered and saved by the system. The experiments demonstrated an increase of more than 30% in the vaporization rate with the use of the compressor, resulting in an energy recovery of 21.31%.Master Thesis Estudo da usinabilidade de ligas de ferro fundido branco alto-cromo (FFBAC) em condições criogênicas com vistas à fabricação de moldes de injeção de plástico(Universidade Federal do Rio Grande do Norte, 2025-02-04) Almeida Filho, Lélio Goes de; Melo, Anderson Clayton Alves de; Alves, Salete Martins; https://orcid.org/0000-0002-2659-4746; http://lattes.cnpq.br/8550161853747323; https://orcid.org/0000-0001-5679-3562; http://lattes.cnpq.br/5242440649066569; http://lattes.cnpq.br/4364222656575166; Castro, Nicolau Apoena; http://lattes.cnpq.br/3740711945494961; Silva, Flávio José da; https://orcid.org/0000-0002-1430-246X; http://lattes.cnpq.br/2569114755496581High chromium white cast iron (HCWCI) is an abrasion-resistant iron alloy containing 12 to 25% chromium (Cr) and 2 to 3.6% carbon (C) in its composition, in addition to other elements such as silicon (Si), manganese (Mn) and molybdenum (Mo). Its microstructure is composed of M7C3 carbides with high hardness (~1400 HV) and a matrix that can be composed of the following phases: ferritic, pearlitic, bainitic, ausferritic, martensitic, austenitic or a mixture of them. HCWCI is also characterized by its good corrosion resistance and good toughness, presenting excellent performance in a wide range of applications, such as in manufacturing of pump and hydraulic turbines casings. Therefore, it is believed that HCWCI can also be an economical and sustainable alternative for the manufacture of plastic injection molds used in the automotive industry, which are normally made of AISI P20 tool steel, which has a high market value, in addition to being produced in batches. In the case of HCWCI, the blocks where the various shapes of a mold are machined could be produced to order in medium-sized foundries, with the main mold preforms already ready. However, it is known that conventional machining of hard and abrasive alloys such as HCWCI is a big challenge. Therefore, this work had as its main objective to investigate the machinability of four HCWCI alloys with different chemical compositions and microstructures, called 19Cr-Eut, 19Cr-Hipo, 26Cr-Eut and 26Cr-Hipo. Face milling tests assisted by liquid nitrogen (LN2) were performed on the four alloys to obtain the cutting tool wear curves. The same was also done on a quenched and tempered AISI P20 steel block for comparison. At the end of these first tests, in order to demonstrate the technical feasibility of using HCWCI as a raw material for manufacturing plastic injection molds for the automotive industry, a U-shaped cast preform was machined on the opposite side of the block whose alloy resulted in the longest cutting tool life in the first face milling tests. In addition to measuring the flank wear of the cutting tools, their worn areas were analyzed by scanning electron microscopy.Master Thesis Obtenção e estudo do comportamento dos filmes finos multicamadas TiSiN/TiSiC depositados em aço AISI 4340 usando a técnica de deposição por plasma em cilindros catódicos(Universidade Federal do Rio Grande do Norte, 2025-06-02) Linhares, Álvaro Albueno da Silva; Feitor, Michelle Cequeira; Silva, Kesia Karina de Oliveira Souto; https://orcid.org/0000-0002-9705-6750; http://lattes.cnpq.br/4712628443097348; https://orcid.org/0000-0002-4850-9493; http://lattes.cnpq.br/4011909474871656; http://lattes.cnpq.br/5592695591704324; Sousa, Rômulo Ribeiro Magalhães de; https://orcid.org/0000-0003-2062-6505; http://lattes.cnpq.br/3246869695770169; Costa, Thercio Henrique de Carvalho; https://orcid.org/0000-0001-7429-4273; http://lattes.cnpq.br/3647710047561421Thin films are layers applied to enhance substrate properties, such as resistance and durability. The plasma treatment technique in cathodic cylinders (CCyPD) is innovative, but there are no records in the literature regarding the application of multilayer thin films with this technique, making this study pioneering in exploring this approach. In this context, the objective of this study was to obtain and characterize TiSiN/TiSiC multilayer thin films, deposited on AISI 4340 steel substrate by the CCyPD method. The plasma treatment was carried out using titanium (Ti) and silicon (Si) cylinders, applying a fixed potential while varying the time, temperature, and gas ratio for each deposited layer. After treatment, the samples were analyzed using characterization techniques, including: X-ray diffraction (XRD) with grazing incidence, Raman spectroscopy, Field Emission Scanning Electron Microscopy (FESEM) coupled with Energy Dispersive Spectroscopy (EDS), microhardness and tribological tests (friction coefficient and wear volume), and profilometry analysis to evaluate surface roughness. The results showed that the deposited layers exhibited the typical composite phases of multilayers, with the corresponding vibrational bands detected by Raman spectroscopy. FEG-SEM confirmed that the coating consisted of alternating TiSiN/TiSiC layers, with good adhesion to the substrate. The EDS analysis revealed the elemental composition of the multilayers, containing Ti, Si, N, and C. The mechanical properties indicated a significant increase in hardness in the coated samples, while in terms of tribological performance, the multilayer films exhibited low friction coefficients and reduced wear compared to the uncoated substrate. The results demonstrated that the multilayers exhibited high hardness, low friction coefficient, and increased wear resistance compared to the uncoated substrate. It is concluded that the CCyPD technique was effective in depositing multilayer thin films, showcasing its potential to enhance substrate properties and contribute to the development of high-performance coatings.Master Thesis Síntese e caracterização de filmes finos de Ti-Cr-Si-N sobre aço aisi 4340: aumento de dureza e da resistência ao desgaste(Universidade Federal do Rio Grande do Norte, 2025-04-22) Neves, Igor Bruno Alves; Feitor, Michelle Cequeira; Souza, Ivan Alves de; https://orcid.org/0000-0001-7381-6025; http://lattes.cnpq.br/0708410440290223; https://orcid.org/0000-0002-4850-9493; http://lattes.cnpq.br/4011909474871656; http://lattes.cnpq.br/1676152210873593; Nascimento, Igor Oliveira; http://lattes.cnpq.br/8924715510520920; Costa, Thercio Henrique de Carvalho; https://orcid.org/0000-0001-7429-4273; http://lattes.cnpq.br/3647710047561421; Aires, Michelle de Medeiros; http://lattes.cnpq.br/0109757587437841; Sousa, Romulo Ribeiro Magalhães de; https://orcid.org/0000-0003-2062-6505; http://lattes.cnpq.br/3246869695770169The aim of this work is the synthesis and characterization of Ti-Cr-Si-N thin films obtained by the cathode roller method. Thin films are layers of material between nanometers and micrometers thick that are deposited on a substrate to modify its surface properties. These properties can be optical, chemical, electrical, mechanical, magnetic and thermal, depending on the type of film and the application. In the field of mechanics, thin films can increase the wear and corrosion resistance of materials, so the substrate used in the research was AISI 4340, due to its importance in mechanical manufacturing. The cylinders used as cathode targets were made from a mixture of titanium, chrome and silicon powders pressed in a compaction matrix. The nitriding reactor with the modified cathodic cage method or cathodic cylinders (CCyPD) was used to carry out the deposition treatments. The depositions were made at two types of potential: cathodic and floating, at temperatures of 300, 350, 400 and 450 °C. In the cathodes with two proportions of gases (N2-H2): 80-20% or 20-80%. Subsequently, the films deposited on the treated samples were characterized by X-ray diffraction (XRD) and Raman spectroscopy. A hardness test was carried out. The dry pin-disc wear test, SEM with EDS, and profilometry to evaluate the wear track were also carried out. The results showed that the type of treatment potential (cathodic or floating) influenced the formation of some phases. The diffractogram showed that the crystallinity of the phases increased with the treatment temperature in the samples analyzed. XRD and Raman showed the synthesis of nitrides on the surface of the substrate. The hardness tests showed that the hardness increased by at least 70% compared to the substrate at a ratio of 20-80% (N2-H2). The formation of nitrides, which are very hard materials, on the surface of the samples explains this increase in surface mechanical properties. The wear track region generated by the tribological pin-disk test was analyzed in terms of the profile on the surface of the samples. Compared to the untreated substrate, the treated samples showed greater roughness and greater resistance to pin wear. The cathodic samples showed higher hardness values and lower wear track depth values, particularly the 400°C treated sample, which showed 2349HV and 2.5μm.Master Thesis Influência e uso do inibidor nitrito de sódio no combate à corrosão na armadura do concreto(Universidade Federal do Rio Grande do Norte, 1996-10) Muniz, Cláudia Virgínia de Souza; Silva, Djalma Ribeiro da; http://lattes.cnpq.br/2791074318745945; Gentil, Vicente; Alves Júnior, Clodomiro; http://lattes.cnpq.br/7441669258580942; Scatena Júnior, Hélio; http://lattes.cnpq.br/6975073327732548The influence of sodium nitrite on the process of corrosion inhibition of steel inserted in concrete was studied. Steel contents (relative to cement mass) used in this work were 0, 4, 6, 8, 10%. Marine atmosphere was mimicked by immersing the samples in 3,5% aqueous NaCl Solutions. The inhibitor effect a the compressive strength, water uptake, electrical resistivity, and Tafel parameters was monitored. Regarding corrosion analysis, Tafel parameters were obtained for test specimens with all the mentioned inhibitor contents by simulation. In the case ofiCOr, it enabled one to verifv what was the inihibitor contribution to the corrosion kinetics. It was found that the effectiveness of inhibition increases when inhibitor concentration was increased, being 6% the limit concentration for corrosion inhibition in this particular case. Water uptake and electrical resistivity were independent onthe amount of inhibitor. Conversely, compression strength decreased 30% for test specimens with 6% ofinhibitor. It was concluded that the addition ofNaNCh to concrete can be a simple altemative for retarding corrosion caused by chloride ions, improving structure durability, provided that, in conjunction with the inhibitor, additives which enhance compression strength are used. Measurements ofi^ from potentiostatic polarization were reprodulible, as long as the analyzed test specimens underwent conditioning to laboratory environment and were adequately protected.Master Thesis Estudos energético, exergético, exergoeconômico e exergoambiental (4E) de um Sistema de Produção de Hidrogênio Verde com Células de Eletrólise de Óxido Sólido (SOEC)(Universidade Federal do Rio Grande do Norte, 2025-01-17) Rufino, Cleydson Tiago Ferreira; Cavalcanti, Eduardo José Cidade; Lima, Álvaro Augusto Soares; http://lattes.cnpq.br/4673751198892295; https://orcid.org/0000-0002-6880-0122; http://lattes.cnpq.br/3935651748470976; Carvalho, Mônica; Macedo, Thiago de OliveiraA utilização do hidrogênio verde como vetor de energia é uma das ações em busca da descarbonização do planeta, redução das emissões de gases de efeito estufa (GEE), além de ser uma fontes de energias limpas,. As células eletrolisadoras são as mais utilizadas mundialmente para produzir hidrogênio através da água. Entre elas, a célula de eletrólise de sólido óxido (SOEC) possui a maior eficiência de conversão de energia, pois opera na faixa de temperatura entre 600 até 1200°C. O objetivo geral dessa dissertação é realizar a análise energética, exergética, exergoeconômica e exergoambiental (4E) de um sistema de produção de hidrogênio verde com células de eletrólise de óxido sólido. As hipóteses do modelo foram 60 módulos de eletrolisadores em paralelo, a célula opera a 950°C com densidade de corrente de 2500 A/m2. O sistema de armazenamento de sal fundido e as baterias permitem que as células operem num período de 9 horas. Tem-se como resultado capacidade produção de 1,88 kg/h de hidrogênio por módulo. Cada módulo consome 19,77 kg/h de água. O campo solar supre uma taxa de calor constante de 853 kW com 3307 heliostatos. Cada módulo é suprido por 52,55 kW de eletricidade através de 163 módulos fotovoltaicos com 83 baterias de 220 Ah. A tensão operacional da SOEC é 1,043 V. O maior erro relativo do modelo foi de 2,76%. A eficiência exergética global do sistema é de 19,19%. As menores eficiências exergéticas foram no sistema fotovoltaico e baterias, de 18,06%, e no trocador de calor #1, com 24,14%. O custo total de aquisição dos equipamentos foi de 22,811 MUS$. O campo solar de torre e os heliostatos tiveram o maior custo do sistema, sendo igual a 13,397 MUS$. O LCOH do sistema foi igual a 8,40 US$/kg. O custo do hidrogênio produzido é de 68,21 US$/GJ. O custo da eletricidade gerada nos painéis com baterias foi de 26,92 US$/GJ. O componente com pior desempenho sobre o ponto de vista exergoeconômico foi o conjunto de painéis fotovoltaicos com baterias com maior taxa de destruição de exergia de 22,93 US$/h e fator exergoeconômico de 18,07%. O componente com menor valor do fator exergoeconômico é o trocador de calor #1 com f = 3,73 %. O componente com maior potencial de melhoria com menor esforço é o campo solar de torre e heliostatos, cuja diferença relativa de custo é de 4686,42. A maior taxa de impacto ambiental associado ao componente foi do campo solar de torre e heliostatos sendo igual a 7974 mPt/h.Master Thesis Análise do comportamento sobre impacto de compósitos de fibra de vidro-epóxi aditivados com agente de reparo(Universidade Federal do Rio Grande do Norte, 2024-12-10) Silva Júnior, Francisco de Assis da; Freire Júnior, Raimundo Carlos Silvério; Barbosa, Ana Paula Cysne; https://orcid.org/0000-0002-9510-4851; http://lattes.cnpq.br/3718650566004689; https://orcid.org/0000-0003-0920-7916; http://lattes.cnpq.br/1042806990155996; Cioffi, Maria Odila HilárioPolymeric glass-epoxy composites are widely recognized for their versatility, primarily due to their outstanding mechanical properties. However, when subjected to loads, service conditions, and environmental factors, they may develop microcracks that compromise these properties. The literature suggests that the addition of a thermally activated self-healing thermoplastic, such as polyethylene-co-methacrylic acid (EMAA), can help extend the service life of these laminates. It is worth considering the replacement of conventional glass fiberepoxy composites with thermoset matrices by self-healing composites, especially in conditions where they demonstrate superior practical performance. Thus, with the aim of contributing to academic research, this study analyzed the influence of EMAA in glass-epoxy prepreg laminates, investigating interlaminar shear strength (ILSS), damage propagation under low-velocity impact (drop-weight type), and post-impact ILSS, comparing the mechanical properties at 0% and 10% of the self-healing agent. The tests were conducted according to ASTM D 2344M (2022) and ISO 14130 (1997) standards for ILSS, and ASTM D 7136 (2020) for dropweight impact. Experimental results indicated that ILSS strength in samples with the self-healing agent remained practically unchanged, showing a reduction of only 3.6%, with a strength of (26.57 ± 0.37) MPa. Regarding the damage data, the samples without EMAA exhibited significant degradation of mechanical properties, with a 52.4% reduction in shear strength after 20 impacts, along with considerable damage propagation, reaching a delamination area of 1495 mm². In contrast, the samples with the self-healing agent showed better performance, with only a 26.2% reduction in shear strength, even after multiple impact cycles. The delamination area was drastically smaller, with values of 309 mm² after repair. The normalization analyses of residual strength indicated that the samples repaired with EMAA retained about 77% of the original strength, while the samples without the agent exhibited pronounced degradation. These results confirm that EMAA showed to be effective in limiting damage propagation and restoring some of the mechanical properties of fiberglass laminates.Master Thesis Desenvolvimento da instrumentação para um protótipo de sistema flexível de manufatura(Universidade Federal do Rio Grande do Norte, 2024-10-28) Batista, Lucas Damasceno de Araújo; Oliveira, Adilson José de; Souza, Thiago Cardoso de; https://orcid.org/0000-0001-6104-569X; http://lattes.cnpq.br/3158071963293362; https://orcid.org/0000-0002-0547-3718; http://lattes.cnpq.br/3258161610687398; Santana Júnior, Orivaldo Vieira de; Santos, Tiago Felipe de AbreuIndustry 4.0 concept enables the manufacturing of several products by integrating traditional processes to information technologies. This concept applies to Flexible Manufacturing Systems (FMS), which consist of automated sets of several machine tools, typically controlled by numerical controls (CNCs), and interconnected by a system for transporting, handling and storing products. A centralized system for decision-making is responsible for controlling this grouping. The FMS may have a digital twin for operational tests. The main objective of this study was to develop a prototype FMS composed of a conveyor belt and a robotic manipulator with 6 degrees of freedom, instrumented with transducers for localization and recognition of objects (color, shape, and QR Code). Computer vision routines were developed to recognize visual attributes of the objects contained on the conveyor belt. A control based on inverse kinematics by the algebraic method aimed to manipulate these recognized objects on the conveyor belt to predefined locations and based on these visual attributes. A camera and a laser transducer associated with a MyRIO 1900 microcontroller instrumented the prototype. The LabVIEW® software allowed the development of the computational routines described; and the Unity® software, the implementation of a Digital Twin for the prototype. The laser transducer identified the presence of objects in 76% of the cases and activated and deactivated the computer vision routines in specific situations. The manipulation of objects followed a path defined by a 4th-order Bézier parametric equation. The Digital Twin moved the virtual system based on data received from the physical system of the FMS prototype via LAN communication in less than 2 ms and without loss of information.Master Thesis Produção de filmes DLC via deposição por plasma com cilindros catódicos(Universidade Federal do Rio Grande do Norte, 2024-06-13) Araújo, Anthunes Íkaro de; Costa, Thercio Henrique de Carvalho; https://orcid.org/0000-0001-7429-4273; http://lattes.cnpq.br/3647710047561421; http://lattes.cnpq.br/1828899248242526; Libório, Maxwell Santana; https://orcid.org/0000-0003-1579-8775; http://lattes.cnpq.br/1840848773429843; Costa, Tharsia Cristiany de CarvalhoThis study involves the deposition of diamond-like carbon (DLC) thin films on AISI 4340 steel by thermochemical treatment, using the plasma deposition technique with cathodic cylinders (CCyPD) in a plasma reactor. This technique involves using a support cage for the compacted powder cylinders, developed as a new variation of the cathodic cage deposition technique. The objective is to produce DLC films through the CCyPD technique with high hardness and good tribological behavior to enhance the resistance and lifespan of AISI 4340 steel. The cathodic cylinder was produced with graphite powder and compacted with a load of 2 tons in a hydraulic press. Treatments were performed using different proportions of argon (Ar) and acetylene (𝐶2𝐻2) gases for a period of 4 hours, under floating potential, using an alumina disc. The characterizations of the deposited films were studied by X-ray diffraction (XRD) to determine the phases, and Raman spectroscopy for the chemical composition of the film. To quantify the surface hardness and coefficient of friction, Vickers microhardness and pin-on-disk tests were performed. After the pin-on-disk test, a portable roughness meter was used to profile the wear track. The results showed adequate DLC film characteristics, such as the presence of carbon and diamond phases in XRD, D and G bands in Raman spectroscopy, high surface hardness, and low coefficient of friction, contributing to the increased lifespan of AISI 4340 steel.Doctoral Thesis Efeito da técnica de preparação de pó e da adição de Nb na densificação e microestrutura dos compósitos WC-Cu-Nb sinterizados com fase líquida(Universidade Federal do Rio Grande do Norte, 2023-03-20) Coelho, Renan Sávio de Almeida; Costa, Franciné Alves da; http://lattes.cnpq.br/8698567925323942; http://lattes.cnpq.br/4429205296751509; Silva, Angelus Giuseppe Pereira da; Dias, Avelino Manuel da Silva; https://orcid.org/0000-0001-8974-5137; http://lattes.cnpq.br/1142442322601442; Mashhadikarimi, Meysam; Araújo Filho, Oscar Olimpio de; Gomes, Uilame UmbelinoWC-Cu composites are used as electrical contacts in high power circuit breakers and electrical resistance welding electrodes. This is due to the high thermal and electrical conductivity and excellent workability of copper associated with the high resistance to wear and erosion by electric arc of tungsten carbide. However, the low wettability of liquid copper on tungsten carbide particles and the mutual insolubility of the constituents make it difficult to densify this composite. This work investigates the effect of adding 5 and 10% by mass of Nb to the WC-20%Cu composite and the influence of the powder preparation technique on the microstructure, densification and properties of WC-Cu-Nb composites sintered in liquid phase. The crystallite size of the WC-20%Cu- 5%Nb composite powders ground for 5 h in an attritor mill reached 11.0, 11.2 and 26.9 nm for the respective WC, Cu and Nb phases. In contrast, the crystallite size of the same composite powders milled for 10 h in a planetary mill reached only 15.0 and 16.3 nm for the respective WC and Cu phases, but the Nb phase amorphizes or goes into solid solution in Cu. Although the attrition mill produced a greater reduction of crystallites and greater dispersion of the hard WC phase in the soft Cu and Nb phases, contamination by Fe, from the grinding body and chromed steel container, promoted less densification of the powder compacts of the composite. WC-20%Cu-5%Nb, as the compacts of these composite powders ground for 5 h in an attritor mill reached a density of only 71.39 ± 3.38% of the theoretical density, while the compacts of the same composite powders ground for 10 h in a planetary mill, also with chrome steel grinding bodies, reached a density of 81.43 ± 2.7% of the theoretical density. On the contrary, when grinding was carried out in a planetary mill with carbide grinding media, no contamination was detected and the density reached 93.25 ± 3.16%. The addition of Nb contributes to the densification of the WC-Cu composites, as the powder compacts of the WC-20%Cu composite with zero, 5 and 10% by mass of Nb prepared in a planetary mill reached a density, respectively, 77.62 ± 1, 0.65%, 81.43 ±2.70%, 84.34 ± 1.37% of theoretical density when sintered at 1150 °C for 1 hour. Furthermore, the microstructure of the sintered compacts of WC-20%Cu powders with a higher amount of Nb exhibit smaller grain size, confirming their efficiency in inhibiting the grain growth of the sintered composites. Brinell hardness increases with milling time reaching values of 101 HB and decreases with decreasing WC mass. The electrical conductivity increases with the addition by mass of Nb, reaching 2.27% IACS when the amount of 10% by mass of Nb is added to the WC-20%Cu composite.