Artigos
URI permanente para esta coleçãohttps://repositorio.fei.edu.br/handle/FEI/799
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14 resultados
Resultados da Pesquisa
- Synergism between tribological parameters – “micro-abrasive concentration level”, “micro-abrasive particle type”, and “liquid type” of a micro-abrasive slurry composition on the micro-abrasive wear behaviour of Fe-30Al-6Cr (at.%) iron aluminide alloy(2023-07-15) DE PAULA, A. F. M.; BORGES, D. F. L.; DA SILVA F. C.; ROSSINO, L. S.; MANFRINATO, M. D.; VERMA, V.; LUNA-DOMINGUEZ, J. H.; MAGNABOSCO, R.; SCHON, C. G.; Ronaldo Câmara Cozza© 2023 Elsevier B.V.Observing the importance of intermetallic materials in mechanical and metallurgical applications, the present work investigates the micro-abrasive wear behaviour in a model–carbide reinforced iron aluminide system. Fe–30Al–6Cr (at.%) iron aluminide alloy with carbon additions “as cast” specimen was tested. Micrographs revealed a continuous network of eutectic chromium carbides at the interdendritic regions of the D03 ordered aluminide matrix. AISI 52100 bearing steel sphere of diameter 25.4 mm (1″) was used for wear tests as counter body. Micro-abrasive slurries were prepared with micro-abrasive particles of black silicon carbide – SiC or alumina – Al2O3, with distilled water or glycerin, in four possible combinations of materials ⇒ “Al2O3 + H2O distilled”, “Al2O3 + glycerin”, “SiC + H2O distilled” and “SiC + glycerin”. Further, keeping the normal force constant and together with different levels of micro-abrasive slurries compositions and sliding distances, a factorial experiment was designed. Result analysis showed that wear volume increased with an increase in micro-abrasive slurry concentration, independently of the type of micro-abrasive particle and liquid. However, the micro-abrasive slurries prepared with SiC and distilled water provided larger wear volumes than the volumes of wear reported under the micro-abrasive slurries formulated with Al2O3 and glycerin. The reason is attributed to the high hardness of SiC particles resulting in high abrasion, whereas the Al2O3 – glycerin slurry lubrication effect restricted high wear. Wear micrographs revealed a change in worn surface morphology from “grooving micro-abrasion” to “rolling micro-abrasion” due to an increase in sliding distance and micro-abrasive slurry concentration.
- Use of ball-cratering wear test and nanoscratching test to compare the wear resistance of homogeneous and functionally graded titanium nitride thin films(2023-01-05) CARNEIRO DA SILVA F.; DE MATOS MACEDO M.; COSTA MISCIONE J. M.; FONTANA, L. C.; SAGA J. C.; Ronaldo Câmara Cozza; SCHON C. G.© 2022 The Author(s).Homogeneous (HM) and functionally graded (FG) TiN thin films were produced by the grid-assisted magnetron sputtering (GAMS) technique. The joint use of ball-cratering micro-abrasive wear test (BCMA) and nanoscratching (NN) test was proposed and carried out to evaluate the wear resistance of TiN films. The results showed an increase of 33.3% wear resistance in the FG TiN thin film, when compared with the HM TiN thin film. This result was justified by the higher resistance to nucleation and propagation of cracks and higher level of adhesion to the substrate by the FG TiN thin film, validated through the NN tests.
- Assessment of the tribolological behavior of a metallic tribopair: LM25 alloy-Si3N4 composites against EN 31 steel(2022-01-05) AHMAD, Z.; KHAN, S.; Ronaldo Câmara Cozza; PENCHALIAH, R.; VERMA, V.© 2022In the present research work, tribological behavior of hard ceramic silicon nitride (Si3N4) reinforced aluminium alloy LM 25 based composites against EN 31 steel in ambient conditions at various loads (19.60–58.86 N) and sliding distances (1200–2400 m) on pin-on-disk test rig was investigated for commercial purpose of machine components. Three sets of composites were fabricated with 4–12 % of silicon nitride by stir casting technique. SEM Micrographs revealed formation of a homogeneous α-aluminum dendrites network structure developed due to the super-cooling of casting during solidification. EDS showed increased content of hard silicon and nitrogen from 29.04 to 73.96 % and 6.68–14.54 % respectively with 4–12 % reinforcement addition which led to high hardness. Increase in hardness from 58.02 to 63.70 BHN is observed with increase in reinforcement which led to reduction in wear by reducing the actual contact area during sliding whereas strength is reduced on addition of Si3N4. The wear resistance of composite is found greater with 12 % Si3N4 reinforced composite with reduced wear at low sliding distance. Due to continuous sliding, wear debris embedded with the surface forming a layer which resulted in variation in coefficient of friction (COF). COF increased at a high rate up to 1800 m followed at a slow rate up to 2400 m sliding distance with increase of normal load. SEM analysis of worn surfaces revealed removal of surface layer with generation of micro cracks with subsequent sliding in composites reinforced with 4 % and 8 % silicon nitride whereas ploughing mechanism is observed in composite with addition of 12 % Si3N4. The linear increasing trend was observed in wear loss against the dissipated energy for the investigated composites.
- Mechanical and tribological behavior of Al composites containing varying beryllium aluminum silicate and constant CeO2(2021) VERMA, V.; Ronaldo Câmara Cozza; CHEVERIKIN, V.; KONDRATIEV, A.; PENCHALIAH, R.© 2021, The Author(s).Abstract: The main aim of the present work is to see the performance of “Al–Beryl” composites processed via stir casting route with or without CeO2 on their mechanical, wear and corrosive properties for structural applications in heavy machinery and watercrafts. Hardness and ultimate tensile strength increased with 36% and 43%, respectively, with 9% Beryl addition. Further, effect of addition of constant 0.5 wt.% CeO2 in “Al–Beryl” composite was evaluated and remarkably improvement in corrosion resistance was observed. Tribological performance of the composites was investigated by conducting sliding wear tests against steel at different loads in dry and wet conditions. Characteristic features of adhesion, fracture and delamination were observed in SEM micrograph of the worn composite having low beryl content slid in air whereas abrasive wear predominates in water or oil. Addition of increased wt.% of beryl particles led in reduced wear of the composite at all loads. Increase in corrosion resistance by 45% decrease in weight loss with 0.5% CeO2 addition was observed. “Al6061–9% Beryl–0.5% CeO2” composite with high hardness, wear and corrosion resistance is found most promising for structural applications. Article Highlights: (1)An increase of 36% in hardness and 43% in ultimate tensile strength was found in Al composites with 9% Beryl addition;(2)Coefficient of friction was found least for “Beryl–CeO2” added composites in wet sliding conditions;(3)A transition in wear mechanism occurred with adhesion, fracture and delamination of the worn composite with low beryl content slid in air;(4)Corrosion resistance increased by 45% with 0.5% CeO2 addition in Al composites.
- Tribological Characterization of the ASTM F138 Austenitic Stainless-Steel Treated with Nanosecond Optical Fiber Ytterbium Laser for Biomedical Applications(2022-01-05) DE MATOS MACEDO, M.; BERNARDES, G. V. R.; LUNA-DOMINGUEZ, J. H.; VERMA. V.; Ronaldo Câmara Cozza© 2022, Springer Nature Switzerland AG.This study investigated the tribological behavior of the ASTM F138 austenitic stainless-steel – which is generally used in biomedical applications – treated with laser. Metallic biomaterial surfaces were treated under different nanosecond optical fiber ytterbium laser pulse frequencies, with the purpose to increase their surface hardness. Further, ball-cratering wear tests were conducted to analyze their tribological behavior on the basis of their wear volume and coefficient of friction. The obtained results showed that the nanosecond optical fiber ytterbium laser pulse frequency influenced the surface hardness of each specimen and, consequently, on the wear resistance of the ASTM F138 austenitic stainless-steel biomaterial. With an increase of laser pulse frequency, a decrease in the wear volume of the worn biomaterial was observed – which is the main tribological parameter to study the wear resistance of a metallic biomaterial. In contrast, the coefficient of friction values were found to be independent of the laser pulse frequency, surface hardness and the wear volume of the specimen.
- Evaluation of fracture toughness of epoxy polymer composite incorporating micro/nano silica, rubber and CNTs(2020-01-05) Ronaldo Câmara Cozza; VERMA, V.© 2020 Associacao Brasileira de Polimeros. All rights reserved.In engineering applications, fracture toughness is an essential requirement that determines the life of a material. Epoxy polymers are widely used in fibre-reinforced composite materials. Due to their structural efficiency and durability, the use of adhesive and composite materials based on epoxy polymers is widespread in aerospace and automobile industries. In this paper fracture toughness of hybrid epoxy polymer composite with addition of nano/micro figures of silica, rubber and carbon nano tubes (CNTs) is evaluated. It is observed that silica addition promoted nano toughening effect with plastically deformation capability in epoxies. Rubber and multi walled CNTs increased the toughness with negligible reduction in stiffness in epoxies. Future research emphasis can be laid on crucial understanding of stress transfer mechanisms and interfacial bond strength between nano particles – epoxy system and on nanofillers modified epoxies as matrices or interleafs for carbon or glass fiber composites to increase the interlaminar delamination toughness.
- Micro-Abrasive Wear Behavior Study of an Intermetallic Material—Fe–30Al–6Cr (at.%) Under Conditions of Room and Moderate Temperatures: A Comparison(2021-01-13) SILVA, E. K. T. M.; LUNA-DOMINGUES, J. H.; VERMA, V.; Ronaldo Câmara Cozza© 2021, Springer Nature Singapore Pte Ltd.Present work focus on research of tribological resistance of an intermetallic material (Fe–30Al–6Cr—at.%), seeking correlations between wear volume, friction coefficient and temperature. Abrasive experiments were performed with specimens of an iron aluminide alloy against AISI 52100 steel ball and abrasive particles of silicon carbide in glycerin. An individual study was done with respect to their characteristics in terms of SEM-EDS analysis. Different test conditions were defined and the abrasive slurry was, continuously, supplied between the specimen and the ball. Values of tangential force and normal force were acquired simultaneously, for “ball – abrasive particles – specimen” tribological system. Systematic studies of the occurrences of the micro-abrasive wear modes, friction and wear generated during tests were done. Moderate temperature favored a larger degree of plastic deformation than removal of material, reducing the wear rate and decreasing glycerin viscosity, which facilitated the movement of the abrasive particles and, consequently, reduced the friction coefficient. Wear volume presented a rising behavior with increase in sliding distance at room and moderate temperatures. Present research explored the potential of an intermetallic material as structural material subjected to moderate temperatures.
- Assessment of micro-abrasive wear tribological properties of H10 tool-steel under conditions of “constant normal force ⇒ variable pressure” and “constant pressure ⇒ variable normal force”(2021-07-05) MACEDO, M. DE M.; LUNA-DOMINGUES, J. H.; VERMA, V.; SCHON, C. G.; Ronaldo Câmara Cozza© 2021 Elsevier B.V.In industrial applications, tools of H10 tool-steel used in mechanical and metallurgical manufacturing processes, such as rolling, extrusion, forging, sheet metal stamping, milling and turning, frequently present significant levels of micro-abrasive wear, which occurs under specific circumstances of “constant normal force”, resulting in a “variable pressure” physical condition, or “constant pressure”, resulting in a “variable normal force” physical condition. Consequently, results of micro-abrasive wear generated under these tribological conditions can help engineers design materials and tools with a longer working life span when they are working under mechanical and metallurgical manufacturing processes. Observing the relevance of this subject, the purpose of this work is to assess the micro-abrasive wear tribological properties of H10 tool-steel submitted to experimental conditions of “constant normal force ⇒ variable pressure” or “constant pressure ⇒ variable normal force”. Ball-cratering wear tests were conducted on quenched and tempered AISI H10 tool-steel; the counter-body was a quenched and stress-relieved AISI 52100 bearing steel sphere and the abrasive slurries were prepared mixing abrasive particles of silicon carbide with distilled water. During the micro-abrasive wear tests, the abrasive slurry was, continuously, agitated and fed between the sphere and the tested material; values of coefficient of friction were, simultaneously, acquired, as well. After the tests, each wear crater was analyzed by optical microscopy, SEM and CAD software. The results were discussed based on the behavior of the “Steady-State Wear Regime”, “wear volume”, “wear rate”, “micro-abrasive wear modes”, “pitch between grooves”, “coefficient of friction” and, finally, validated by ANOVA. With the attainment of the Steady-State Wear Regime, it was possible to present the following conclusions: (i) wear volume and wear rate increased under conditions of “constant pressure ⇒ variable normal force”, (ii) there was the predominance of “grooving abrasion”, with the action of “micro-rolling abrasion” wear phenomenon, (iii) the pitch between grooves presented, approximately, the same value of the average abrasive particles size and (iv) the coefficient of friction remained in a tribological condition classified, statistically, as “constant”.
- Review: Effect on physical, mechanical, and wear performance of ZrB -based composites processed with or without additives(2020-06-03) VERMA, VIKAS; CHEVERIKIN, VLADIMIR; Ronaldo Câmara CozzaBecause of unique combination of properties, ultra high temperature ceramics (UHTCs) are considered the most suitable material for applications in extreme en-vironments as in hypersonic flights, atmospheric reentry, and rocket propulsion sys-tem. Processing of UHTCs especially ZrB2-based ceramic composites with additives offer advantages in terms of simple processing methodology and excellent proper-ties. Processing route highly controls the ceramic properties. Present review share out systematically and explain the processing strategies of ZrB2-based ceramic com-posites––conventional, hot press or spark plasma sintering and their effect on micro-structure features, physical, and mechanical properties and tribological performance. Present review suggests that it is possible to process full dense ZrB2–SiC ceramic composite with ultrafine or nano size particles via fast sintering technique like spark plasma sintering and gives better mechanical and wear resistant properties.
- Influência da temperatura de resfriamento sobre a variação mássica e resistência mecânica de ABS injetado(2020-06-22) SILVA, FABIANO APARECIDO; Ronaldo Câmara CozzaPeças de ABS injetadas e submetidas a diferentes temperaturas de resfriamento podem apresentar variações em sua massa e diferentes níveis de resistência mecânica. O objetivo deste trabalho é estudar a influência da temperatura de resfriamento sobre a variação mássica e resistência mecânica de peças produzidas em ABS por injeção. Com isso, inicialmente, corpos- -de-prova em forma de engrenagem foram produzidos sob diferentes condições de resfriamento. Em seguida, a variação mássica dos corpos-de-prova foi analisada com o auxílio de uma balança analítica. Para a verificação da resistência mecânica do material estudado, foi projetado e construído um dispositivo mecânico, o qual possibilitou a aplicação de um carregamento ativo entre dois corpos-de-prova. Pelos resultados obtidos, foi possível observar que, com a diminuição da temperatura de resfriamento, houve um aumento de massa e resistência mecânica das peças injetadas.