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Orientador: Sergio Tonini Button / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-13T02:45:42Z (GMT). No. of bitstreams: 1 Santaella_MauricioLopez_M.pdf: 4037016 bytes, checksum: 0e06e55364f0ff6351af1956d5dda499 (MD5) Previous issue date: 2009 / Resumo: Uma faixa significativa do preço final de produtos forjados é proveniente de custos referentes a re-trabalho de ferramental devido a falhas superficiais nas matrizes de conformação. Na busca de uma empresa por maior competitividade em termos de preço e tempo, surge a necessidade de entender-se os mecanismos de falha das matrizes de modo a aumentar sua vida útil, evitando situações de risco para a matriz e uma possível falha, diminuindo custos referentes ao re-trabalho e diminuindo tempos de manutenção e set-ups, tendo por fim um aumento de produtividade. Além de mudanças conhecidas para o aumento da vida útil das matrizes como, por exemplo, temperatura e velocidade de forjamento, lubrificação e alterações metalúrgicas superficiais nas matrizes, pode-se aumentar a vida útil das matrizes com mudanças geométricas do desenho do forjado. Neste trabalho foi estudado como a modificação dos valores do raio de boca, largura do patamar de rebarba, maior profundidade de cavidade, raio superior da haste, espessura de rebarba e temperaturas de forjamento e de matrizes influenciam no processo de desgaste de matrizes de pré-forma no forjamento de bielas automotivas na região da haste. Através de simulação numérica e análise estatística pôde-se verificar que os parâmetros que mais influem no processo de desgaste são os mesmos que influem na profundidade de cavidade de matriz que por sua vez influem diretamente na largura total de rebarba que escoa pelo patamar de rebarba, sendo assim a largura de rebarba uma medida comparativa do desgaste. Foi analisado também o processo de forjamento na região da haste de bielas, podendo-se verificar quatro etapas distintas para a evolução do desgaste, da tensão normal e do carregamento. Nessa avaliação verificou-se que o processo de escoamento durante o forjamento difere do observado em referências bibliográficas disponíveis, podendo-se verificar um processo de recalque na haste ou de escoamento radial das cabeças do laminado em direção à haste, o que tende a aumentar o diâmetro do tarugo que por sua vez com diâmetros maiores da haste, aumentam também o processo de desgaste, portanto sendo um importante fator a ser considerado em projetos de bielas. Da análise dos gráficos da força necessária para forjar a região da haste pôde-se verificar também que a curva gráfica de carregamento se distingue quando há falha de preenchimento de cavidade quando comparado com um processo sem falha. Por fim através da construção de gráficos de mapeamento do processo ou sobre-posição de gráficos de contorno para os parâmetros com os quais houve falha de preenchimento para o desgaste e carregamento, podem-se verificar regiões otimizadas, sem falhas, com menores valores de desgaste, com aumento da vida útil das matrizes, garantia de qualidade do produto e possivelmente, redução de matéria-prima. / Abstract: A significant part of forgings prices is due to costs from reworks of forging dies because of superficial failures on their surfaces. In quest of a higher competitiveness in terms of prices and production times, it is necessary to understand the mechanisms of die failure to increase its working life, avoiding risk situations and a possible total failure of the tools, and also decreasing costs of reworks, and maintenance and set-ups, achieving a higher productiveness. Besides known changes to increase forging die life such as forging temperature, stroke speed, lubrication (friction) and superficial metallurgical modification on dies surfaces, it is possible to increase die life trough geometrical changes of the die sketch. In this work it has been studied how the modification of the corner radius, flash land width, depth of cavity, radius of the upper stem, flash thickness and temperatures of forging dies and workpiece influence the wear of the forging of connecting rods in the stem region from the preform dies. Through numerical simulation and statistical analysis it was found that the parameters that most influence the process of die wear are the same that affect the die cavity volume which also influence directly the overall width of flash of the forged part. Therefore, the width of a flash is a comparative measure of abrasive wear. It was also analyzed the process of forging in the stem region from connecting rods and it could be verified four distinct stages in the evolution of the abrasive wear, normal stress and forging load. Through this validation it was found that the material flow during the process differs from the observed in available bibliographies and it could be also verified a process of upsetting in the rods stem or a radial flow of the rolled workpiece heads toward the rods stem, which tends to increase the diameter of the workpiece stem. Larger diameters increase the process of abrasive wear, therefore being an important factor to be considered in the design of connecting rods dies. From the analysis of the necessary load to forge the stem region of the rod it was verified that the loading pattern is different when the cavity is not completely filled. Finally through the construction of processing maps it can be determined optimized regions without filling defects, with lower values of wear and thereby increasing die life, keeping the product quality and possibly reducing raw material. / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

As operações de usinagem compreendem uma parcela significativa do universo da manufatura sendo que atualmente algumas tendências bem definidas, como a usinagem de peças já endurecidas, vêm ganhando espaço no campo da fabricação de moldes e matrizes, em especial, mas também na indústria automotiva e de construção de máquinas. O torneamento e o fresamento de materiais, nesta difícil condição de usinagem, já estão estabelecidos na indústria. Assim, a conversão do processo de produção atual de materiais em estado mole para endurecido só será possível com todas as operações de usinagem incluídas. Devido a isso, a demanda por furação e roscamento de peças endurecidas está em constante crescimento. Essas operações apresentam dificuldades muito maiores do que as de torneamento e fresamento, daí a importância de ferramentas especificamente projetadas para elas. Dessa forma, este trabalho teve como objetivo estudar o processo de desgaste sofrido pelas ferramentas durante a furação e roscamento de aços AISI D2 e AISI H13 com a utilização de diferentes velocidades de corte. As forças de corte e o torque também serão medidos durante o processo para avaliar seus comportamentos com o aumento da velocidade. Com os resultados obtidos verificou-se que na furação e roscamento de aços endurecidos de baixa usinabilidade, como no caso do aço AISI D2, o desgaste da ferramenta é muito acentuado, podendo tornar o processo inviável economicamente caso não sejam empregadas velocidades de corte extremamente reduzidas. De uma forma geral, a furação e o roscamento do AISI H13 pode ser viável, pois o número de furos/roscas obtidos dentro dos critérios especificados mostrou-se muito superior ao esperado. Os principais mecanismos de desgastes que atuaram nos machos de corte durante o processo de roscamento de ambos os aços (AISI D2 e AISI H13) foram abrasão nas superfícies de folga e adesão nas superfícies de saída de forma acentuada nos três primeiros filetes. / The cutting processes compose a huge part of the manufacturing universe and, nowadays, some well-defined trends, like cutting hardened materials, are increasing not only in die molding production but also in automotive and machine industries. The turning and milling processes of materials, in this difficult condition of cutting, are already applied in the mechanical industries. Therefore, the total conversion of the present production process of regular materials into hardened ones can only be reached when all the cutting processes are included. Because of that, the demands of drilling and tapping hardened materials have increased constantly. These operations require tools specifically designed for them, because they have proven themselves to be much more difficult than the turning and milling processes. In that way, this work aimed to study the wear process of drills and taps used to machining the AISI D2 and AISI H13 hardened steels with different cutting speeds. The cutting forces and the torque generated were also acquired during the cutting process to evaluate its behavior with the speed increase. After analyzing the results, a very aggressive tool wear was confirmed in the drilling and tapping process of hardened steels with bad machinability, like the AISI D2 steel, and this can make the process economically unfeasible if an extremely reduced cutting speed is not used. Generally, the drilling and tapping process of the AISI H13 can become economically viable, because the number of holes/threads achieved in accordance with the specified criteria was superior to the expected ones. In the cutting process of both materials (AISI D2 and H13), the main wear mechanism observed on the taps were abrasion, on the clearance surface, and adhesion, on the rake surface. This was severe for the first three threads of the tap.

A retificação representa o processo mais utilizado na usinagem de peças para obtenção de altos níveis de qualidade superficial, dimensional e produtividade. Uma importante etapa da retificação consiste na preparação e condicionamento do rebolo para o corte, a dressagem. Durante a dressagem, a superfície da ferramenta de corte é alterada para obtenção de arestas cortantes de acordo com as especificações desejadas. O objetivo deste trabalho é desenvolver um método para inscrição de texturas na superfície do rebolo que proporcionem melhores condições de corte durante a retificação e, também, possibilite utilizar a retificação como processo para texturização superficial de peças. O método desenvolvido consiste em alterar controladamente a profundidade de dressagem utilizando um excitador eletromecânico fixado na base do dressador de uma retificadora cilíndrica CNC. A movimentação é controlada por um software desenvolvido para sincronizar o deslocamento longitudinal do dressador com ondas senoidais enviadas ao amplificador operacional do excitador. Desta forma, o dressador proporciona inscrição de texturas no rebolo durante a dressagem. O método foi experimentalmente avaliado e sua funcionalidade foi comprovada. Texturas diversas foram inscritas na superfície do rebolo, com até 15 \'mü\'m de profundidade. Com o uso da texturização de rebolos foi possível obter redução de até 20% da potência específica de corte, sem perda representativa da qualidade final da peça (rugosidade e cilindricidade) e mantendo a vida da ferramenta de corte, em comparação com retificação convencional. Em complemento, o método possibilitou criação de diversos padrões de texturas nas superfícies de peças retificadas, possibilitando utilizar a retificação como um processo de usinagem para este fim. / Grinding represents the most applied machining process to achieve best combination of surface and dimentional quality, also productivity. One important stage of the grinding process is to prepare and condition the grinding wheel surface for the cutting, the dressing operation. During the dressing, wheel surface is changed to acquire cutting specification required for the operation. The objective of this work is develop a method to texturing the grinding wheel surface for better grinding performance and, also, texturing of surfaces through normal grinding cutting. The method controlled changes the dressing depth using an electro-mechanical actuator fixed to the dressing tool base of a CNC grinding machine. The displacement of the dressing tool is controlled using the developed software. It is able to synchronize the longitudinal movement with generated sine waves sent to the operational amplifier of the actuator. Through this movement and control, the dressing tool is able to texture the grinding wheel. The method was experimentally evaluated and its functionally proved. It is possible to inscribe different texturing patterns in the wheel surface, with depth up to 15 \'mü\'m. Using texturized wheels, is possible to reduce up to 20% the grinding power, without representative losses with the machined workpiece quality (roughness and roundness) and tool life, compared to regular grinding. In addition, it is possible to transfer different textures patterns to the workpiece surface while cutting, enabling grinding s a machining process to produce workpiece patterns.

O objetivo deste estudo foi avaliar o possível efeito da saliva in situ, associada ou não ao flúor, sobre a recuperação da estrutura dentária do esmalte desmineralizado, que recebeu profilaxia utilizando jato de bicarbonato de sódio. Para isso, foram utilizados 40 blocos de esmalte de dente bovino de 4x4 mm, os quais foram submetidos a um processo de desmineralização in vitro para a formação de lesões artificiais de cárie. Sobre a superfície destes blocos, foi aplicado o jato de bicarbonato de sódio, simulando a realização de uma profilaxia profissional. Após essa etapa, os blocos foram divididos em dois grupos (GI e GII) e montados em dispositivos intra-bucais, os quais foram utilizados por 10 voluntários, durante dois períodos experimentais de quatro horas. Os blocos do GI foram expostos diretamente à saliva in situ, enquanto os do GII, foram expostos à saliva associada ao flúor sob forma de bochecho com solução de NaF a 0,2%, durante o minuto inicial. No primeiro período experimental, metade dos voluntários fez parte do GI e a outra metade do GII, havendo uma inversão dos grupos no segundo período. As possíveis alterações ocorridas na superfície do esmalte após as etapas do experimento, foram avaliadas através de testes de microdureza Knoop (25g/5s) e da quantificação do desgaste com o auxílio de um rugosímetro. Para a comparação dos valores de microdureza e de desgaste entre os grupos, e entre as etapas de cada grupo, foi aplicada a Análise de Variância a dois Critérios (ANOVA) e o teste de Tukey, adotando-se um nível de significância de 5% (p<0,05). Os resultados do teste de microdureza mostraram uma diminuição, estatisticamente significante, nos valores de microdureza superficial do esmalte após a etapa de desmineralização (183,7KHN), quando comparada à microdureza superficial inicial (342KHN). Em seguida, após a simulação da profilaxia, houve um aumento significante da microdureza (337,3KHN), não havendo diferença estatisticamente significante entre o valor inicial. Quanto ao desgaste, a simulação da profilaxia promoveu um desgaste no esmalte desmineralizado da ordem de 0,709µm. Após a etapa de remineralização, o valor da microdureza diminuiu um pouco em relação ao valor inicial (303,7KHN), embora tenha sido próximo ao mesmo. Em relação ao valor do desgaste, foi observada uma diminuição estatisticamente significante (0,476 µm), o que representa uma diminuição de quase um terço do valor inicial. Não houve diferença estatisticamente significante entre os resultados dos grupos I e II em todas as etapas do experimento. De acordo com as condições e com a metodologia adotadas na presente pesquisa, foi possível concluir que após 4 horas de remineralização in situ houve recuperação de parte da estrutura dentária perdida devido à aplicação do jato de bicarbonato de sódio sobre o esmalte desmineralizado, apesar de a realização de um bochecho adicional com solução fluoretada não ter promovido aumento no ganho mineral em relação à ação somente da saliva. / The aim of this study was to evaluate the effect of saliva in situ, in the recovery of the superficial structure of the demineralized tooth enamel in which a sodium bicarbonate jet was applied. The effect of an additional mouthrinsing with a NaF solution was also evaluated. A total of 40 specimens of bovine enamel (4x4 mm) were processed in vitro to obtain artificial caries lesions were utilized for this study. A jet of sodium bicarbonate was applied on the surface of the specimens simulating a prophylaxis procedure. The specimens were divided in two groups(GI and GII). They were mounted in an intra-oral model used by 10 volunteers for two fourhour experiments. During the first four-hour experiment, the specimens of GI were directly exposed to saliva in situ. Those of GII were exposed to one minute mouthrinsing with 0.2% NaF. In the second four-hour experiment, the volunteers were crossed-over to the opposite experimental treatment group. The changes on the enamel surface were analyzed by the superficial microhardness test (Knoop, 25g/5s) and perfilometry, using a rugosimeter to determine the superficial dental wear. In order to compare the degree of microhardness and wear, among groups in the different experimental phases, the ANOVA and the Tukey test were used with an acceptable significance of 5% (p<0.05). The microhardness test showed a significant decrease of the initial value from 342 KHN to 183.7KHN after the demineralization phase. In the prophylaxis simulation, the microhardness value increased to 337 KHN, while a 0.709 µm wear was detected. After the remineralization procedure, there was a mild decrease on the degree of superficial microhardness to 303.7 KHN. Considering the superficial wear, it was detected a significant decrease (0.476 µm) comparing to the value found after the prophylaxis. There were no statistical differences between GI and GII in all phases of the experiment. After a four-hour period of an in situ remineralization, we concluded that it is possible to have a partial recovery of the dental structure, initially lost due to the use of sodium bicarbonate on the demineralized enamel. The performance of an additional mouthrinsing with fluoridate solution did not lead to an increase in the mineral gain.

M.Ing. / Sound pressure levels exceeding acceptable limits are being generated by trains travelling on the 1000 m radius curved railway line past the town of Elands Bay. Unacceptable sound levels are attributed mainly to top of rail wheel squeal. Top of rail wheel squeal belongs to the family of selfinduced vibrations and originates from frictional instability in curves between the wheel and the rail under predominantly saturated lateral creep conditions. In small radius curves, saturated lateral creep conditions occur due to the steering of railway wheelsets with large angles of attack. Given the large curve radius and the utilisation of self-steering bogies on the Sishen-Saldanha Iron Ore railway line, curve squeal is a highly unexpected result for the 1000 m radius curved railway line. This is because curving of bogies in large radius curves are achieved without high wheelset angles of attack leading to saturated creep conditions. An experimental and analytical investigation was carried out to identify the mechanisms influencing the generation of wheel squeal in large radius curves. Simultaneous measurement of sound pressure and lateral wheel-rail forces were made during regular train service in one of the two 1000 m radius curves at Elands Bay to characterise the bogie curving behaviour for tonal noise due to wheel squeal occurring in the large radius curve. The lateral force curving signature not only reveals the levels of lateral wheel-rail forces required for bogie curving, but also whether the bogie is curving by means of the creep forces generated at the wheel-rail interface only or if contact is necessitated between the wheel flange and rail gauge corner to help steer the bogie around the curve. The test set-up consisted of two free field microphones radially aligned at equivalent distances towards the in – and outside of the curve in line with a set a strain gauge bridges configured and calibrated to measure the lateral and vertical forces on the inner and outer rail of the curve. This test set-up allowed the squealing wheel to be identified from the magnitude difference of the sound pressures recorded by the inner and outer microphones in combination with comparing the point of frequency shift of the squeal event due to the Doppler Effect with the force signals of the radially aligned strain gauge bridges. From the experimental phase of the investigation, it was found that wheel squeal occurring in the 1000 m radius curve at Elands Bay is characteristic of empty wagons and is strongly related to the squealing wheel’s flange/flange throat being in contact with the gauge corner of the rail. Here high levels of spin creepage associated with high contact angles in the gauge corner lead to high levels of associated lateral creepage necessary for squeal generation. This is in contrast to lateral creepage due to high wheelset angles of attack being the key kinematic parameter influencing squeal generation in small radius curves. Furthermore, the amplitude of wheel squeal originating from the passing of empty wagons was found to be inversely proportional to the level of flange rubbing on the squealing wheel i.e. increased flange contact on the squealing wheel brings about a positive effect on squeal control. Contrary to the empty wagons which are characterised by tonal curve squeal, loaded 4 wagons requiring contact between the wheel flange and rail gauge corner in the 1000 m curve was characterised by broadband flanging noise. It was concluded from measurements that flange contact occurring under high lateral forces for steady state curving of loaded wagons provides the complete damping necessary for squeal control. The curve squeal noise that originated from the passing of empty wagons in the Elands Bay curve could further be classified according to the frequency at which the squeal event manifested itself in the curve, i.e. low frequency audible (0 – 10 kHz), high frequency audible (10 – 20 kHz) and ultrasonic squeal (> 20 kHz). The vast majority of low frequency audible squeal events recorded in the 1000 m Elands Bay curve occurred at approximately 4 kHz and originated from the low rail/trailing inner wheel interface, whilst the vast majority of high frequency audible squeal events occurred in the frequency range between 15 and 20 kHz and originated from both the high rail/leading outer wheel and low rail/trailing inner wheel interfaces.

The main purpose of this research project was to determine the fatigue-life behaviour of AISI 1008 sheet steel which has been mechanically formed to a radius of curvature of 120mm and then to correlate the fatigue-life behaviour to that of the parent or “as manufactured” material. During the forming process it was felt important to induce plastic strain through stretch-bending by clamping the sides of a plate sample’s (width) edges in the bending fixture before being bent by a single acting mechanical press. It was determined through actual testing that there was a decrease in fatigue-life when the mechanical formed data was compared to fatigue data of the parent material. Standard fatigue mathematical models were used to relate the actual fatigue data. Due to the material being cold formed to a radius of curvature of 120mm, residual stresses induced during the forming process played an essential role during the fatigue-life prediction calculations. The maximum relieved stress in the parent material was compressive in nature having a magnitude of 11percent of the “as manufactured” yield strength (265 MPa). For the mechanical formed material compressive residual stresses were measured on the outer surface while tensile stresses were measured on the inner surface. The difference between actual number of cycles to failure to that calculated using the standard mathematical models for the parent material, ranged between 48 percent and 18 percent and for the mechanical formed samples between 35 percent and 1percent, depending on the strain amplitude used. An important aspect of this study was to determine the criteria required for mathematical modelling of the parent material as testing occurred between the limit of proportionality and yield point. Although this aspect requires further investigation the mathematical results obtained during this study were considered to be acceptable.

Polymers as construction material are common in the industry. Although more recently the use of polymer composites in more demanding applications has increased, requiring more of them mechanically, tribologically and thermally. To enhance the properties various fillers are used, from common glass fibers to more advanced nanoparticles. For this study three types of base polymers have been studied: poly-amide (PA), poly-phenylene-sulphide (PPS) and poly-ether-ether-ketone (PEEK). They have been filled with glass fibers, carbon fibers, poly-tetra-fluoro-ethylene (PTFE), graphite and thermally conductive modifier in various combinations. Fibers are used to increase the mechanical properties, PTFE and graphite are added as lubricating additives to reduce the friction, and the thermally conductive modifier to increase the thermal conductivity. Five general groups of polymer composites were studied. Pure PEEK PPS, PA and PEEK filled with fibers PPS, PA and PEEK filled with fibers and lubricating additives PA filled with lubricating additives PEEK filled with fibers and additives for lubrication and thermal conductivity The polymer composites have been tribologically tested in a reciprocating sliding test set-up. Friction, wear and surface damage have been studied. Three types of counter surfaces have been used: ball bearing steel balls, stainless steel cylinders and anodized aluminum cylinders. Load, surface temperature of the polymer composites and number of cycles were varied to study any changes in friction and wear. The wear marks on the polymer composites were studied using an SEM. Cross sections of some tested samples were prepared to study any subsurface damage. From the tests the polymer composites showed similarities in friction. Lubricating additives gave lower friction, often around 0.05-0.15, while pure and only reinforced gave higher, often around 0.4-0.5. The wear was also less for polymer composites with lubricating additives. There was no clear influence of temperature but for most tests an increase in temperature gave lower friction. The only influence of load was that higher load gave wider wear tracks. Since no cross sections were prepared to compare subsurface damage due to different loads there might be a possibility that there were some differences below the surface as well. Otherwise cross sections showed that polymer composites with only fibers had cracks and cracked fibers below the surface due to the high stresses the polymer composite had been subjected to. With lubricating additives there was no large subsurface damage and it seems as if the lubricating additives formed a protective tribofilm in the wear track, giving both lower friction and wear. The presence of such a tribofilm was confirmed by XPS analysis that showed a surface layer containing F from PTFE. The conclusions are that the tribological properties of a polymer composite are strongly dependent on its fillers. Lubricating additives form a tribofilm that lowers friction and wear. Elevated temperatures might drastically change the tribological behavior of a polymer composite why it is important to do tests at higher temperatures. Cross sections can give information about subsurface damage and might help to understand the wear mechanisms and deformation of polymer composites better. More microscopy and mechanism studies are required in order to further understand the tribological behavior of polymer composites.

Abstract This study concentrates on developing and tuning various oil analysis methods to meet the requirements of modern industry and environmental analytics. Oil analysis methods form a vital part of techniques used to monitor the condition of machines and may help to improve the overall equipment effectiveness value of a factory in a significant manner. Worm gears are used in various production machines, and their breakdowns may cause significant production losses. Wearing of these gears is relatively difficult to monitor with vibration analysis. Analysis of two indicator metals, copper and iron, may reveal wearing phenomena of worm gears effectively, and savings can be significant. Effective wear metal analysis requires good tools. ICP-OES with kerosene dilution is widely used in wear metal analysis, but purchasing and using of ICP-OES is expensive. A cheaper FAAS technique with similar pre-treatment of oil samples was tested and it proved to be useful especially in analyzing small amounts of samples. The accuracy of FAAS was sufficient for quantitative work in machine diagnostics and waste oil characterization. Solid debris analyses are useful in oil contamination control as well as in detection of wearing mechanisms. Membrane filtration, optical microscopy, SEM and automatic particle counting were applied in analysis of rolling and gear oils. Particle counting is an effective way to detect oil contamination, but in the studied cases even larger particles than those detected in normal ISO classes would be informative. However, membrane filtration and optical microscopy may reveal the wearing machine element exactly. Additives provide oils with desired properties thus they should be monitored intensively. A FTIR method for quantitative analysis of fatty alcohols and fatty acid esters in machinery oils was developed during this work. It has already been used successfully in quantitative and qualitative analysis of machinery oil samples. Various kinds of oils may be spilled into the soil during use and in accident situations, and they can migrate to groundwater layers. Biodegradation of oils can remove them from the soil or water completely or at least diminish the amount of harmful substances. An automatic, respirometric BOD OxiTop method was used to evaluate the biodegradability of various oils in water and soil media. The biodegradation of certain bio and mineral hydraulic oils was evaluated in groundwater, where bio oils usually biodegraded more effectively than mineral oils. The use of oils in machines weakened especially the biodegradability of bio oils. Biodegradability of bio oils was also studied in standard conditions of OECD 301 F and bio oils usually biodegraded moderately good in these conditions. The biodegradation of forestry chain oils and wood preservative oils was evaluated in forest soils. Linseed oil biodegraded moderately, but certain experimental wood preservatives biodegraded more effectively. Widely used creosote oil biodegraded in a lesser degree. Rapeseed oil-based chain oils biodegraded more effectively than corresponding tall oil.

Ces travaux de thèse concernent l'étude du contact à grande vitesse pouvant intervenir entre le pied de l'aube et l'alvéole du disque (tous deux en Ti6Al4V) de la soufflante du turboréacteur CFM56. Le comportement et les modes d'endommagement associés à ce type d'événements restent méconnus et peu traités dans la littérature. L'utilisation d'un tribomètre spécifique adapté sur un banc balistique, d'un thermocouple feuille-pièce et de modélisations numériques (éléments finis) ont permis d'étudier les liens existants entre vitesse, pression, température et efforts de frottement. Les endommagements induits ont ensuite été analysés en étudiant l'usure et l'évolution de la microstructure en sous surface (MEB, Imagerie 3D et EBSD). Une modélisation semi-analytique basée sur le cisaillement adiabatique des aspérités a été développée pour étudier l'évolution de la taille de la surface réelle de contact. En associant ce modèle à deux essais expérimentaux, des enveloppes inférieures et supérieures de l'évolution du coefficient de frottement pour une large gamme de vitesse de glissement ont été calculées. Ce travail de thèse est le fruit d'une collaboration entre la société Snemca, le LaBPS (Laboratoire de mécanique, Biomécanique, Polymères et Structure) et le LEM3 (Laboratoire d'étude des Microstructures et de Mécanique des Matériaux) / In case of exceptional events in aircraft engines (bird ingestion or blade disassembly), blade motions induce sliding at the interlock between the blade root and the slot of the fan rotor. The interface then undergoes quasi-instantaneous sliding under high normal pressure. This thesis work was initiated to investigate this phenomena and deals therefore with extreme sliding interactions for a Ti6Al4V tribopair (aircraft engine CFM56). Interface behavior and wear modes associated to these extreme thermomechanical loads remain poorly studied in literature. Links between velocity, pressure, temperature and friction force have been investigated by using a specific tribometer adapted on a ballistic bench, a foil-workpiece thermocouple and finite elements analysis. Induced damage were then analyzed by studying wear and microstructure evolutions (SEM, nanotomography and EBSD). A semi-analytical model, based on adiabatic shearing of asperities, has been proposed to evaluate the evolution of the real area of contact. By associated the latter with two experimental tests, upper and lower estimations of the mean friction force for a large velocity range can be calculated. This work is the result of collaboration between aircraft manufacturer Snecma, the LaBPS (Laboratory of Mechanics, Biomechanics, Polymers and Structures) and the LEM3 (Laboratory of Microstructure and Mechanics of Materials)