PPGEM - Mestrado 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.Master Thesis Avaliação de modelos numéricos para cálculo da transferência de calor na terapia fototérmica(Universidade Federal do Rio Grande do Norte, 2023-12-01) Lucena, Ícaro Kleisson Araújo; Maurente, André Jesus Soares; http://lattes.cnpq.br/8073368791527116; http://lattes.cnpq.br/0575478482366638; Marinho, George Santos; http://lattes.cnpq.br/0490476694313938; França, Francis Henrique RamosCancer has been the focus of researches aimed to improve therapeutic procedures. Among them is hyperthermia, including Interstitial Laser Therapy (ILT) and Plasmonic Photothermal Therapy (PPTT). Models are used for computational simulations of the therapies, and validation of them is crucial to ensure simulation reliability. This study evaluates models for hyperthermia by comparing temperature distributions obtained from simulations with those from a protocol for a real ILT to treat breast cancer. Laser irradiation is administered through an optical fiber in the center of an approximately spherical tumor. The protocol includes devices to control the energy delivered to the tissue, such as a fluid pump, avoiding damage to the optical fiber tip, and probes with thermocouples to measure temperatures. The simulation covers the numerical resolution of the Bioheat Equation (PBHTM) and the Radiative Transfer Equation (RTE), with the divergence of heat flux from RTE serving as the source term in PBHTM. The numerical solution provides temperature distributions in the irradiated region, encompassing tumor and surrounding tissues. Thermophysical and optical properties of tissues were obtained from the literature, while those of the laser were based on a technical manual for the DIOMED DELTA15 lasers. The medium properties were assumed as those of a healthy breast tissue, in a cylindrical computational domain with length of 4 cm and radius of 2 cm. The tip of the optical fiber was located at the domain center. Based on the protocol, irradiation time was 2100 s, considering a semiconductor diode laser with a wavelength of 805 nm, operating at 5 W, and with a light beam diameter of 600 µm. Results were obtained to investigate the sensitivity of temperature field with respect to parameters associated to uncertainties, including laser operational mode (pulsed or continuous), positioning of thermocouples and extent of the cooling region at the tip of the optical fiber. The results obtained from the simulations showed excellent agreement with the experimental data from the protocol, increasing reliability on modeling, adopted hypotheses, and employed codes.Master Thesis Análise dos parâmetros de deposição e nanotribológica de dois líquidos iônicos em um substrato de silício(Universidade Federal do Rio Grande do Norte, 2023-10-30) Fernandes Neto, Felipe; Alves, Salete Martins; https://orcid.org/0000-0002-2659-4746; http://lattes.cnpq.br/8550161853747323; Franceschini Filho, Dante Ferreira; Menezes, Rodrigo PrioliTwo phosphorus-based Ionic Liquids (ILs) were deposited onto a <111> silicon substrate via dip coating. These ILs, trihexylttetradecylphosphonium bis(2,4,4-trimethylpentyl) phosphinate and tetrabutylphosphonium methanesulfonate, are two possible candidates for the lubrication of micro/nanoelectromechanical devices (MEMS/NEMS). To evaluate this, their abilities to form a thin adsorbed film (1 to 100nm) on the silicon surface were studied. Variations were made in deposition parameters such as substrate cleanliness, different concentrations, and deposition speed. The surface was followed by optical microscopy, with the aid of an atomic force microscope (AFM). As a result, it was possible to observe the topography, the variation of the friction force as a function of the applied normal load and the adhesion force between the tip and the film. In addition, a confocal Raman spectroscopy (532 nm laser and 7.2 mW power) was used to observe the presence of ionic liquid in specific regions of interest. Using these tools, it was possible to observe a different behavior in the friction coefficient and in the film formation mechanism on the surface between the two lubricants, which can be attributed to the fact of difference in the size of the cation chain and consequently in its adhesion force.Master Thesis Análise do puncionamento do AHSS Ferrítico-Bainítico (FB590) em temperaturas ambiente e criogênica(Universidade Federal do Rio Grande do Norte, 2023-12-15) Barbosa, Jonas Medeiros de Azevedo; Oliveira, Adilson José de; Costa Júnior, João Carlos Arantes; https://orcid.org/0000-0001-8498-4075; http://lattes.cnpq.br/5028446242533356; https://orcid.org/0000-0001-6104-569X; http://lattes.cnpq.br/3158071963293362; http://lattes.cnpq.br/8078447131788495; Ferreira, Jetson Lemos; Castro, Nicolau ApoenaAdvanced High Strength Steels (AHSS) have been used for vehicular structures aiming for mass reduction with a feasible balance between mechanical resistance and formability in manufacturing processes. Those steels are commonly supplied in thin sheets and must be manufactured typically by forming processes to define the product shape, and punching is one of the critical operations. The AHSS Ferrite-Bainite (FB) stands out for having high local formability, allowing structural reinforcements like flanges to be obtained. Furthermore, processing AHSS involves high strength and plastic elongation values, and the material’s behavior changes during the operation due to processing parameters such as die clearance, punch geometry, and temperature. Models to evaluate the effects of operations above room temperature are available in the literature, but there is a lack of studies at cryogenic temperatures. This research aims to simulate the behavior of the AHSS FB590 material at room and cryogenic temperatures to analyze the ductile-brittle transition effects at the cutting edge. A methodology to obtain values of triaxiality and plastic strain needed for calibration of the constitutive models was developed using digital image correlation (DIC) to determine the fracture moment. The hole expansion simulations showed that an increment of 4.7 mm on the final diameter can be obtained by changing the previous punching operation from room to cryogenic temperature.Master Thesis Avaliação e caracterização de membranas de PLA/ARGILA(Universidade Federal do Rio Grande do Norte, 2023-08-01) Martins, Janiel Lopes; Leite, Amanda Melissa Damião; https://orcid.org/0000-0003-1597-4230; http://lattes.cnpq.br/3077817092155432; http://lattes.cnpq.br/7446017767344657; Nascimento, José Heriberto Oliveira do; https://orcid.org/0000-0001-6804-2854; http://lattes.cnpq.br/7033735079037677; Viana, Kaline Melo de Souto; Carvalho, Nayara BezerraThe advancement of the industry has driven the extensive use of polymers in various applications, due to their specificities and economic advantages. These polymeric materials have a wide range of mechanical and thermal properties, in addition to being lighter and easier to process compared to traditional materials. This work's main objective is to evaluate and obtain membranes using poly (lactic acid) as a polymeric matrix with the addition of 3% and 5% of Cloisite 20A clay fillers, improving permeation properties. The research seeks to investigate the predicted incorporation of clay into PLA and evaluate the impact of this addition on the characteristics and performance of the resulting membranes. Furthermore, to evaluate the influence of filler addition on the polymeric structure and barrier properties of membranes and bionanocomposites, X-ray diffraction (XRD), contact angle, scanning electron microscopy (SEM), water vapor permeation test and apparent porosity test. The XRD diffractograms showed the intercalation of the clay in the polymer matrix that resulted in a semi-crystalline structure, in other words, the crystalline peaks typical of both the polymer and the clay were observed. From the results of the contact angle test, it can be seen that the addition of clay to the polymer matrix caused a change in the surface energy of the bionanocomposites. Analysis of the scanning electron microscopy test showed a dense morphological structure without the formation of visible pores. Based on the results obtained from the water vapor permeation test, it is possible to state that the addition of clay fillers to the polymer matrix resulted in a decrease in the permeability of the membrane, preventing a good interaction between the clay and the polymer. The characterization by the porosity test seemed to show that the bionanocomposite with 5% filler ratified the best results in two time intervals (30 and 45 minutes), meaning an interspersed formation of clay with the polymer. In this way, it was possible to obtain a bionanocomposite with outstanding characteristics and results in permeation properties for application in gas separation and as a filtering material.Master Thesis Fabricação e estudo de um destilador solar de baixo custo com cobertura móvel(Universidade Federal do Rio Grande do Norte, 2023-10-18) Fin, Giovanna Maria de Oliveira; Souza, Luiz Guilherme Meira de; http://lattes.cnpq.br/0801747108308706; http://lattes.cnpq.br/6302192909598072; Aquino, Marcos Silva de; https://orcid.org/0000-0003-4260-3259; http://lattes.cnpq.br/8780485157382325; Batista, Salomão SávioThis work was thoroughly prepared with the aim of developing low-cost technology to reach communities affected by the lack of safe and suitable water for household consumption - the solar distiller with a movable cover. The construction methodology was mentioned, in which market research was conducted to determine the manufacturing cost, and tests were performed with the already-made distiller to obtain its performance and the volume distilled in three main configurations: the conventional one, with the addition of some crushed stones, and with cooling of the glass covers using water. Of the three configurations, the one that showed the highest performance and the greatest volume distilled was the one that used water-based panel cooling, approximately 38.60% and 4.275 liters, respectively.Master Thesis Resultados exergéticos, exergoeconômicos e exergoambientais de uma planta de cogeração com microturbina a gás integrada a uma unidade de destilação com múltiplos efeitos(Universidade Federal do Rio Grande do Norte, 2023-10-30) Santos, Erick Breno Azevedo dos; Cavalcanti, Eduardo José Cidade; https://orcid.org/0000-0002-6880-0122; http://lattes.cnpq.br/3935651748470976; https://orcid.org/0000-0002-0981-4583; http://lattes.cnpq.br/2002401715310002; Lima, Álvaro Augusto Soares; Carvalho, MônicaThe distribution of drinking water is one of the most problems social of humanity, mainly due to scarcity of fresh water in some regions of the world. Hence, desalination has gained more significance, because it is an attractive solution owing to the large volume of seawater. In recent years, technological advances in cogeneration have provided significant improvements in thermal desalination. Nevertheless, the production of desalinated water still has a high operating cost for most countries. Thus, increasing the efficiency of the system components and reducing the costs associated with each one of them become fundamental parts for the improvement of the process. Therefore, this work presents the modeling and evaluation of a 30kW gas microturbine power plant integrated into a multi-effect distillation unit with thermal vapor compression (MED-TVC). The energetic, exergetic, exergoeconomic and exergoenvironmental analyses of the plant were developed by the SPECO method. The plant has presented a production of 29.69 m3/day of desalinated water for 0.04033 kg/s of motive steam, resulting in Gain Output Ratio (GOR) of 8.52. In addition, the exergetic efficiency increased from 13.84% to 23.39% with the use of cogeneration. The exergy destroyed in the desalination unit represented only 18% of the total. The average cost per exergy unit of electricity was 94.73 US$/GJ and the cost of desalinated water produced was 5.6 US$/m3. The exergoeconomic analysis indicated that investments in improvements in generator, effect 1 and regenerator efficiency are fundamental for the economic optimization of the plant. The specific environmental impact of electricity was 13892 mPt/GJ, while that of desalinated water was 14645 mPt/GJ. The environmental results showed that improvements in the regenerator, effect 1, HRSG and generator are crucial for the plant's best environmental performance.Master Thesis Avaliação da produção de biodiesel de algas- análise exergética, exergoeconômica e exergoambiental(Universidade Federal do Rio Grande do Norte, 2023-10-19) Barbosa, Diego dos Santos; Cavalcanti, Eduardo José Cidade; https://orcid.org/0000-0002-6880-0122; http://lattes.cnpq.br/3935651748470976; http://lattes.cnpq.br/9732424366176172; Duarte, Lindemberg de Jesus Nogueira; http://lattes.cnpq.br/6800188552647660; Carvalho, MônicaDue to the environmental impacts caused by fossil fuels, such as air pollution, contributing to climate changes, among others, alternatives to these fuels are needed. Algae biodiesel is a renewable alternative to diesel. Algae promote carbon dioxide capture during production, reproduce quickly and do not compete for land use, indicating that the fuel produced by raw material is environmentally advantageous. In the present work, an algal biodiesel production plant was analyzed from an exergetic, exergoeconomic and exergoenvironmental point of view. The Specific Exergy Costing (SPECO) methodology was utilized to define fuel and products. The cost of biodiesel and glicerin produced was 459.42 $/ton and 331.84 $/ton, respectively. A life cycle analysis (LCA) was developed by applying the eco-indicator 99 method, it was calculated that the environmental impact of biodiesel produced was 182.55 mPt/kg, and the glycerin was 133.84 mPt/kg. The PBR showed the worst exergetic of exergetic efficiency (11.46%) and the highest exergy destruction (2,123.66 GJ). In addition to it, the PBR presented the greatest relative difference in cost (6,706.06%) and environmental impacts (859.62%). The lowest exergoeconomic factor was obtained in mixer #1 (0.18%). The exergoenvironmental factors of the equipment in general were low, indicating that exergy destruction is the dominant factor in the environmental impacts of the plant. The exergetic, exergoeconomic and exergoenvironmental analyses show that there is scope for optimizing the plant in order to minimize its costs and environmental impacts. Thus, the biodiesel produced would have lower cost and environmental impacts. It could turn more viable the production of a fuel, which is accessible, renewable, cleaner than diesel and it could help in climate changing fight.Master Thesis Projeto, construção e avaliação de um dinamômetro para a medição das componentes da força de usinagem no torneamento(Universidade Federal do Rio Grande do Norte, 2022-09-30) Celone, Matteo; Melo, Anderson Clayton Alves de; https://orcid.org/0000-0001-5679-3562; http://lattes.cnpq.br/5242440649066569; http://lattes.cnpq.br/6785802121598987; Oliveira, Adilson José de; https://orcid.org/0000-0001-6104-569X; http://lattes.cnpq.br/3158071963293362; Machado, Álisson RochaMachining is a manufacturing process that plays an important role in the industry, with the turning operation as one of its protagonists. Thus, it is important to perform studies that helps to understand and, consequently, optimize it. In this context, the knowledge of the machining force components in turning is essential to define the best parameters to increase the productivity and reduce the costs. Thus, the measurement of machining force components using piezoelectric dynamometers has been widely used. However, such devices have a high initial price, which often becomes prohibitive for many research laboratories. In this context, this work presents a proposal of a dynamometer able to measure the components of the machining force in turning using uniaxial load cells based on strain gauge transducers, which are usually cheaper than piezoelectric load cells. The proposed instrument was statically calibrated in a universal testing machine from 0 to 1,5 kN and presented metrological characteristics, such as a linearity of 99.3%, 98.14% and 94.8% in the cutting, feed and radial directions, respectively. Furthermore, the use of a calibration matrix reduced the cross sensitivity from 44% to 3%. Finally, turning tests were performed under different cutting conditions to evaluate the functionality of the instrument, forces up to 252 N, 162 N and 141 N were obtained for cutting, feed and thrust forces, respectively; like previous works.Master Thesis Efeito da técnica de preparação de pós de heptamolibdato de amônia e nitrato de cobre na densificação e propriedades dos compósitos Mo-Cu(Universidade Federal do Rio Grande do Norte, 2023-04-12) Morais, Luís Matheus Fernandes de; Costa, Franciné Alves da; http://lattes.cnpq.br/8698567925323942; http://lattes.cnpq.br/2490408879723540; Castro, Nicolau Apoena; http://lattes.cnpq.br/3740711945494961; Gomes, Uilame Umbelino; Araújo Filho, Oscar Olimpio deMo-Cu composite is used in electronic packaging devices, electrical contacts and heat skins. The union of the high electrical and termal conductivity properties of copper with the wear resistance of molybdenum causes strong interest in the electrical and electronics industry. The densification of these Mo-Cu composites via sintering is hampered due to the mutual insolubility of Mo and Cu and the low wettability of Cu to Mo. However, powder metallugy is a viable route to manufacture this composite. In this work, the influence of mechanical mixing (MM) and high energy milling (HEM) techniques, as well as the chemical method of coprecipitation of heptamolybdate (AHM) and copper nitrate (CuN) powders on densification, microstructure and properties of Mo-Cu composite powder compacts was investigated. AHM-CuN powders with 10.8 and 13.9 % by mass of CuN were prepared, respectively, by mechanical (MM and MAE) and chemical coprecipitation methods. The prepared powders were reduced in 750 °C in tubular furnace under H2 atmosphere and a flow of 316 mL/min. The composite Mo-Cu powders with 20 and 25 % by mass of Cu obtained were compacted at 250 MPa and the green compacts produced were sintered at 1.150 °C for 1 h under na atmosphere of H2. The sintered bodies of Mo-Cu powders prepared by coprecipitation and HEM reached a relative density of 96 ± 2.7%, while those prepared by MM reached only 75 %. Said sintered compacts achieved, respectively, a microhardness of 190.7 ± 15.4, 293.3 ± 13.4 and 183.2 ± 18.6 HV, as well as na electrical conductivity of respectively 34, 22 and 15 IACS. The greater homogenization and smaller grain size resulting from the preparation of Mo-Cu powders by coprecipitation and HEM are responsible for obtaining the highest values of density, microhardness and electrical conductivity of the sintered Mo-Cu compacts.Master Thesis Viabilidade de utilização de um forno solar tipo caixa para produzir o assamento de alimentos(Universidade Federal do Rio Grande do Norte, 2023-05-12) Silva, José Weverton Oliveira; Souza, Luiz Guilherme Meira de; http://lattes.cnpq.br/0801747108308706; http://lattes.cnpq.br/0605220281121433; Aquino, Marcos Silva de; https://orcid.org/0000-0003-4260-3259; http://lattes.cnpq.br/8780485157382325; Batista, Salomão SávioThe baking capacity of a box-type solar oven made from wood, with an internal area of around 1.2 m², was studied. Based on the equations that govern the behavior of the device, a thermal balance in its main elements was proposed to determine its thermal efficiency. The solar oven was tested for two configurations: no load and no load. The proposed oven was able to bake nine cakes at once, representing a record in simultaneous baking capacity in the history of more than thirty-five years of studies of solar ovens at the LMHES. The total load of the nine cakes was equivalent to 6.75 kg, which demonstrates the high baking load capacity that this oven is capable of producing, with baking being operationalized in a time of 90 minutes. A load of six 460g pizzas were also baked in the oven in just 25 minutes. The results showed that the absorbing surface and the air reached maximum temperatures of 140°C and 102°C respectively, obtained in the test without load. The viability of the solar oven for the production of several foods simultaneously was demonstrated, and it could be used as a food factory, which could be sold by people with low purchasing power, to generate employment and income.Master Thesis Obtenção e caracterização de nanocatalisadores de WC e Ni suporatados em Al2O3 e MCM-41(Universidade Federal do Rio Grande do Norte, 2023-08-07) Silva, Fernando Erick Santos da; Sousa, Fábio José Pinheiro; Nascimento, Rubens Maribondo do; https://orcid.org/0000-0001-9094-0044; http://lattes.cnpq.br/8671649752936793; https://orcid.org/0000-0002-8381-8806; http://lattes.cnpq.br/9909217959915292; https://orcid.org/0000-0001-6971-6718; http://lattes.cnpq.br/9074860488805508; Lima, Maria José Santos; Raimundo, Rafael Alexandre; Gomes, Uilame UmbelinoThe search for new sources of renewable energy is a global concern for increasingly sustainable development. Among renewable energy sources, hydrogen (H2) is considered an alternative to fossil fuels due to its minimal environmental impact. This study aimed to obtain and characterize nickel (Ni) and tungsten carbide (WC) catalysts supported on alumina (Al2O3) and MCM-41 as potential candidates for hydrogen (H2) production through dry methane (CH4) reforming. Various transition metals such as Co, Pd, Pt, Ru, Rh, Ir, and Ni can be used in the reforming reaction. Tungsten carbide exhibits behavior similar to Pt in various catalytic reactions, resulting from the modification of tungsten's electronic structure through carbon addition. In this context, we successfully synthesized (Ni10%wt.) and (WC10%wt.) catalysts supported on Al2O3 via incipient wetness impregnation with distilled water, as well as (Ni10%wt.), (WC10%wt.), (Ni2%wt.-WC8%wt.), (Ni5% wt.-WC5%wt.), and (Ni8%wt.- WC2%wt.) catalysts supported on MCM-41 via incipient wetness impregnation with ethanol. The (WC) used in the study was produced through carbothermic reduction of ammonium paratungstate (APT). The obtained material was characterized using X-ray diffraction (XRD), X-ray fluorescence, Raman spectroscopy, BET nitrogen adsorption-desorption, and scanning electron microscopy (SEM). Based on the results, it was concluded that the WC synthesis process was efficient, producing nanoscale carbides (15.5nm) with irregular particle shapes and sizes. Incipient wetness impregnation proved to be an effective method for all obtained catalysts, with the nickel phase showing better dispersion on both alumina and MCM-41 supports than the WC phase. However, when both active phases (WC-Ni) were present, the dispersion on the supports improved significantly for the WC active phase. The catalyst (Ni10%wt./Al2O3) exhibited a specific surface area of 3.60 m²/g, while the (WC10%wt./Al2O3) catalyst had a specific surface area of 2.2 m²/g. The Ni10%wt./MCM-41 catalyst had a specific surface area of 588.56 m²/g, whereas the WC10%wt./MCM-41 catalyst showed a surface area of 870.63 m²/g, increasing significantly compared to the nickel active phase (Ni10%p/MCM41).