O objetivo deste trabalho foi de otimizar o processo de fabricação da placa reforçadora de solo, fabricada pelo processo de injeção sob baixa pressão em liga de alumínio. Atualmente, a liga utilizada no processo é a SAE 305 (AA 413) e problemas de falha do componente em campo tem sido reportados pelos clientes. As peças estudadas referem-se às placas acessórias utilizadas para fornecer sustentação durante a entrada e saída de vaus por carros de combate do Exército Brasileiro, anteriormente adquiridas no mercado internacional e agora produzidas internamente. O estudo focou na alteração da composição química da liga, baseado na liga de alumínio da peça importada, tratamento de banho com modificação do silício, refino de grão e modificação no projeto do molde permanente. Adquiriu-se junto ao fornecedor a liga de Al9Si0,3Mg visando a fabricação das peças com tratamento térmico T6. Para obtenção das propriedades mecânicas foram realizados ensaios de tração, dureza Brinell e impacto. Para caracterização metalúrgica foram realizados ensaios metalográficos com auxílio de microscopia óptica. Verificou-se que a presença de magnésio na liga Al-Si exclusivamente com tratamento térmico T6, alterou o comportamento mecânico da peça melhorando seus resultados. O tratamento de banho com modificador de silício a base de sódio não produziu resultados significativos. Finalmente, realizou-se simulação do preenchimento da molde via software CAE Click2Cast, modo injeção de baixa pressão, para caracterização dos defeitos e sugestões de melhoria no sistema de alimentação. Deste trabalho, conclui-se que as melhores propriedades mecânicas de resistência a tração e dureza foram obtidas com a alteração da liga SAE 305 para a liga Al9Si0,3Mg com tratamento térmico T6 e que para atingir melhores resultados deve-se introduzir ao processo um novo molde permanente com refrigeração e alimentação adequada da peça. / The objective of this research was to optimize the manufacturing process of the reinforcing plate of soil, manufactured by the injection process under low pressure in Al-Si alloy. Currently, the alloy used in the process is SAE 305 (AA 413) and mechanical resistance problems, when used in the field, have been reported by customers. Currently, the alloy used in the process is SAE 305 (AA 413) and field component failure problems have been reported by customers. The studied pieces refer to the accessory plates used to provide support during the entry and exit of vats by tanks of the Brazilian Army, previously acquired in the international market and now produced internally. The study focused on the alteration of the chemical composition of the alloy, based on the aluminum alloy of the imported part, bath treatment with silicon modification, grain refining and modification in the permanent mold design. The Al9Si0.3Mg alloy was purchased from the supplier to manufacture the T6 heat treated parts. To obtain the mechanical properties tensile tests, Brinell hardness and impact were performed. For metallurgical characterization, metallographic tests were performed with the aid of light microscopy. It was verified that the presence of magnesium in the Al-Si alloy exclusively with T6 heat treatment, altered the mechanical behavior of the part improving its results. Bath treatment with sodium silicon modifier did not produce significant results. Finally, the mold filling simulation was carried out using CAE Click2Cast software, low pressure injection mode, to characterize the defects and suggestions for improvement in the feed system. From this work, it was concluded that the best mechanical properties of tensile strength and hardness were obtained with the change of the SAE 305 alloy to the Al9Si0.3Mg alloy with T6 thermal treatment and that to achieve better results a new permanent mold with cooling and proper feeding of the part.

Aluminum alloy 6061-T6 is a common engineering material used in aerospace, automotive, structural applications. Despite its wide use, little has been published about the effects of damage from surface corrosion on its fatigue life. An investigation was performed where 6061-T6 extrusions were exposed to a 3.5% NaCl solution at pH 2 for 2 days and 24 days. The length of time and pH were chosen in order to create distinct surface flaws. The effect of these flaws on the fatigue life was then investigated and analyzed using scanning electron microscopy (SEM) and Weibull statistics. It was determined that samples corroded for both 2-days and 24-days exhibit fatigue lives that can be described using a 3-parameter Weibull distribution. The result of which was the determination of a threshold value for fatigue as well a general understanding of flaw geometry.

[EN] The friction stir welding (FSW) is a joining process that uses a non-consumable tool generates frictional heat (without reaching the melting point) and plastic deformation in the weld line as it rotates and moves the tool, so that a welded joint is obtained in solid state. This technique is capable to join many engineering materials but was initially focused on high strength aluminum alloys (series 2XXX, 6XXX and 7XXX) due to two main approaches: because they are difficult to weld by conventional welding processes fusion for their applications in key sectors such as automotive, aviation, aerospace, shipbuilding and other manufacturing industries due to high strength/weight ratio. FSW parameters as rotational speed, welding speed, weld pitch ratio (WPR), tool profile, among others, are responsible for obtaining sound welds (flawless), of the microstructural changes, of the mechanical and technological properties of welded joints. Therefore, it is important to study the parameters-microstructure-property relationship to maintain the quality of welded joints. In this work we have studied the influence of some FSW processing parameters (rotation speed, welding speed, weld pitch ratio and joint configuration) on the microstructural changes, mechanical and technological properties to a rolling sheet of aluminum alloy AA6082-T6 of 5mm thick. For the four configurations obtained it has been characterized the microstructure with various techniques, such as optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and differential scanning calorimetry (DSC) to identify major phases, dispersoids, second phases, dissolution, precipitation, and re-precipitation of phases, sub-structure, crystallographic texture, etc. in each welding zone and for each configuration. Also it has been obtained mechanical properties through microhardness tests, tensile and fatigue tests, and technological properties through accelerated corrosion tests. The results of the experiments indicate that it can to obtain sound welds, i.e. defect-free with different processing parameters, and they greatly influence in the microstructure and therefore on the mechanical and technological properties. Similarly, it found that it can get better mechanical properties (tensile strength and hardness) with a low weld pitch ratio (WPR [mm/rev]<2, "cold condition") and single-pass butt joint, while the best fatigue properties are obtained for high weld pitch ratio (WPR [mm/rev]>4 "hot condition") and single-pass butt joint. In comparison, the base metal has better mechanical properties and worse corrosion properties than the four configurations studied and in any case the double-pass butt joint never were one revulsive option to single-pass butt joint. / [ES] La soldadura por fricción-agitación (FSW) es proceso de unión que utiliza una herramienta no consumible que genera calor por fricción (sin llegar al punto de fusión) y deformación plástica en la línea de soldeo a medida que rota y avanza la herramienta, con lo que se obtiene una unión soldada en estado sólido. Esta técnica es capaz de unir muchos materiales de ingeniería pero se ha centrado inicialmente en las aleaciones de aluminio de alta resistencia (series 2XXX, 6XXX y 7XXX) debido a dos enfoques principales: porque son difíciles de soldar por procesos de soldadura por fusión convencionales y por sus aplicaciones en sectores claves como automoción, aeronáutico, aeroespacial, construcción naval y otras industrias de fabricación, debido a la alta relación resistencia/peso. Los parámetros de FSW como velocidad de rotación, velocidad de avance, relación de soldeo (WPR), perfil de la herramienta, entre otros, son responsables de la obtención de soldadas sanas (sin defectos), de las transformaciones microestructurales, de las propiedades mecánicas y tecnológicas de las uniones soldadas. Por lo tanto, es importante estudiar la relación parámetros-microestructura-propiedades para mantener la calidad de las juntas soldadas. En este trabajo se ha estudiado la influencia de algunos parámetros de procesado FSW (velocidad de avance, velocidad de rotación, relación de soldeo, configuración de junta) en las modificaciones microestructurales, propiedades mecánicas y tecnológicas para una chapa laminada de aleación de aluminio AA6082-T6 de 5 mm de espesor. Para las cuatro configuraciones obtenidas se han caracterizado a profundidad la microestructura con varias técnicas, tales como, microscopia óptica (MO), microscopía electrónica de barrido (MEB), microscopía electrónica de transmisión (MET), difracción de electrones retrodispersados (EBSD) y calorimetría diferencia de barrido (DSC) para identificar fases, dispersoides, segundas fases, disolución y precipitación de fases, sub-estructura, textura cristalográfica, etc., en cada zona de soldadura y para cada configuración. También se han obtenido las propiedades mecánicas a través de ensayos de microdureza, tracción y fatiga, y propiedades tecnológicas a través de ensayos de corrosión acelerada. Los resultados de la experimentación indican que se pueden obtener cordones sanos, es decir, libres de defectos con diferentes parámetros de procesado, y que éstos influyen en gran medida en la microestructura y por ende en las propiedades mecánicas y tecnológicas. Igualmente, encontramos que se pueden obtener mejores propiedades mecánicas de tracción y dureza para una relación de soldeo (WPR) con bajo aporte térmico y soldadura por una cara, mientras que las mejores propiedades a fatiga se obtienen para la configuración con alto aporte térmico y soldadura por una cara. En comparación, el metal base tiene mejores propiedades mecánicas y bajas propiedades a corrosión con respecto a las cuatro configuraciones estudiadas y, en ningún caso las soldaduras por ambas caras fueron una opción revulsiva de las soldaduras por una cara. / [CAT] La soldadura per fricció-agitació (FSW) és un procés d'unió que utilitza una eina noconsumible que genera calor per fricció (sense arribar al punt de fusió) i deformació plàstica en la línia de soldadura a mesura que gira i avança l'eina, amb el que s'obté una unió soldada en estat sòlid. Aquesta tècnica és capaç d'unir molts materials d'enginyeria però s'ha centrat inicialment en els aliatges d'alumini d'alta resistència (sèries 2xxx, 6xxx i 7XXX) a causa de dos enfocaments principals: perquè són difícils de soldar per processos de soldadura per fusió convencionals i per les seves aplicacions en sectors claus com automoció, aeronàutic, aeroespacial, construcció naval i altres indústries de fabricació, degut a l'alta relació resistència/pes. Els paràmetres de FSW com velocitat de rotació, velocitat d'avanç, relació de soldadura (WPR), perfil de l'eina, entre d'altres, són responsables de l'obtenció de soldadures sanes (sense defectes), de les transformacions microestructurals, de les propietats mecàniques i tecnològiques de les unions soldades. Per tant, és important estudiar la relació paràmetres-microestructura-propietats per mantenir la qualitat de les juntes soldades. En aquest treball s'ha estudiat la influència d'alguns paràmetres de processat FSW (velocitat d'avanç, velocitat de rotació, relació de soldadura, configuració de les juntes) en les modificacions microestructurals, propietats mecàniques i tecnològiques per a una xapa laminada d'aliatge d'alumini AA6082- T6 de 5 mm de gruix. Per a les quatre configuracions obtingudes s'han caracteritzat a profunditat la microestructura amb diverses tècniques, com ara, microscòpia òptica (MO), microscòpia electrònica de rastreig (MER), microscòpia electrònica de transmissió (MET), difracció d'electrons retrodispersats (EBSD) i calorimetria diferèncial d'escombrat (DSC) per identificar fases, dispersoides, segones fases, dissolució i precipitació de fases, sub-estructures, textura cristal-logràfica, etc., a cada zona de soldadura i per a cada configuració. També s'han obtingut les propietats mecàniques a través d'assajos de microduresa, tracció i fatiga, i propietats tecnològiques a través d'assaigs de corrosió accelerada. Els resultats de l'experimentació indiquen que es poden obtenir cordons sans, és a dir lliures de defectes, amb diferents paràmetres de processat, i que aquests influeixen en gran mesura en la microestructura i per tant en les propietats mecàniques i tecnològiques. Igualment, trobem que es poden obtindre millors propietats mecàniques de tracció i duresa per una relació de soldadura (WPR) amb baix contingut tèrmic i soldadura per una cara, mentre que les millors propietats a fatiga s'obtenen per a la configuració amb alta aportació tèrmica i soldadura per una cara. En comparació, el metall base té millors propietats mecàniques i baixes propietats a corrosió pel que fa a les quatre configuracions estudiades i, en cap cas les soldadures per ambdues cares van ser una opció revulsiva de les soldadures. / Martínez Díaz, E. (2016). INVESTIGACIÓN DE LAS MODIFICACIONES MICROESTRUCTURALES Y PROPIEDADES MECÁNICAS EN UNA ALEACIÓN DE ALUMINIO AA6082-T6 SOLDADA CON LA TÉCNICA DE FRICCIÓN-AGITACIÓN (FSW) [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/62161 / TESIS

Fatigue is one of the critical design aspects with immense significance where thefatigue life of a material can be stated as the number of cycles that a componentcan withstand under a particular type of loading without failure. The design processhas to include fatigue analysis in order to predict failure due to fatigue. This helpsin maintenance and servicing of a component reducing the chance of failure duringoperation of the component. Increased efficiency of predictive maintenance improvesthe life of the component.This thesis aims to study the relationship between the experimental, analytical andnumerical solutions of two high strength aluminium alloys and one steel alloy fortheir life in aircraft applications covering the effects of geometrical irregularities. Italso aims to answer convergence between the numerical and the analytical methodwhen compared with each other. The simulations are carried out for three materialsamong many used in aircraft and industrial applications (Al 7050-T7451, Al 7075-T6 and AISI 4340 Steel) for a pre-defined set of geometries. The stress field andthe stress concentration factor variations are also studied to identify their effects onfatigue life.The results from this work forms a strong background for the future research alongside SAAB or any other industries using these materials for their structures to findout the failure or predicting it accurately. Also, integral structures can be analysedin detail using this thesis as a base.

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This thesis is titled "A Framework for Enhancing the Accuracy of Ultra Precision Machining." In this thesis unwanted relative tool / workpiece vibration is identified as a major contributor to workpiece inaccuracy. The phenomenon is studied via in situ vibrational measurements during cutting and also by the analysis of the workpiece surface metrology of ultra precision diamond face turned aluminum 6061-T6. The manifestation of vibrations in the feed and in-feed directions of the workpiece was studied over a broadband of disturbance frequencies. It is found that the waviness error measured on the cut workpiece surface was significantly larger than that caused by the feed marks during cutting. Thus it was established that unwanted relative tool / workpiece vibrations are the dominant source of surface finish error in ultra precision machining. By deriving representative equations in the polar coordinate system, it was found that the vibrational pattern repeats itself, leading to what are referred to in this thesis as surface finish lobes. The surface finish lobes describe the waviness or form error associated with a particular frequency of unwanted relative tool / workpiece vibration, given a particular feed rate and spindle speed. With the surface finish lobes, the study of vibrations is both simplified and made more systematic. Knowing a priori the wavelength range caused by relative tool / workpiece vibration also allows one to extract considerable vibration content information from a small white light interferometry field of view. It was demonstrated analytically that the error caused by relative tool / workpiece vibration is always distinct from the surface roughness caused by the feed rate. It was also shown that the relative tool / workpiece vibration-induced wavelength in the feed direction has a limited and repeating range. Additionally, multiple disturbance frequencies can produce the same error wavelength on the workpiece surface. Since the meaningful error wavelength range is finite given the size of the part and repeating, study then focussed on this small and manageable range of wavelengths. This range of wavelengths in turn encompasses a broadband range of possible disturbance frequencies, due to the repetition described by the surface finish lobes. Over this finite range of wavelengths, for different machining conditions, the magnitude of the waviness error resulting on the cut workpiece surface was compared with the actual relative tool / workpiece vibrational magnitude itself. It was found that several opportunities occur in ultra precision machining to mitigate the vibrational effect on the workpiece surface. The first opportunity depends only on the feed rate and spindle speed. Essentially, it is possible to force the wavelength resulting from an unwanted relative tool / workpiece vibration to a near infinite length, thus eliminating its effect in the workpiece feed direction. Further, for a given disturbance frequency, various speed and feed rate combinations are capable of producing this effect. However, this possibility exists only when a single, dominant and fixed disturbance frequency is present in the process. By considering the tool nose geometry, depth of cut, and vibrational amplitude over the surface finish lobe finite range, it was found that the cutting parameters exhibit an attenuating or filtering effect on vibrations. Thus, cutting parameters serve to mitigate the vibrational effect on the finished workpiece over certain wavelengths. The filter curves associated with various feed rates were compared. These filter curves describe the magnitude of error on the ultra precision face turned workpiece surface compared with the original unwanted tool / workpiece vibrational magnitude. It was demonstrated with experimental data that these filter curves are physically evident on the ultra precision diamond face turned workpiece surface. It was further shown that the surface roughness on the workpiece surface caused by the feed rate was reduced with relative tool / workpiece vibrations, and in some cases the feed mark wavelength was changed altogether. Mean arithmetic surface roughness curves were also constructed, and the filtering phenomenon was demonstrated over a broadband of disturbance frequencies. It is well established that a decrease in the feed rate reduces the surface roughness in machining. However, it was demonstrated that the improved surface finish observed with a slower feed rate in ultra precision diamond face turning was actually because it more effectively mitigated the vibrational effect on the workpiece surface over a broadband of disturbance frequencies. Experimental findings validated this observation. By only considering the effect of vibrations on the surface finish waviness error, it was shown that the workpiece diamond face turned with a feed rate of 2 {tm / rev has a mean arithmetic surface roughness, Ra , that was 43 per cent smaller than when a feed rate of 10 μm / rev was used. / Thesis / Doctor of Philosophy (PhD)

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The purpose of this project was to show the updated procedures and to make additions to the computer program called Tmin designed by E. I. DuPont De Nemours and Company. This program is used as a screening tool for determining the largest of the minimum pipe-wall thicknesses in a piping system. This project involved several additions that will be released in the next version of the Tmin computer program. The first major additions to be implemented are four alternating Stress-to-Number of cycles curves: Aluminum 1100, Aluminum 3003-0, Aluminum 6061-T6, and Nickel 200. In addition, procedures of the ASME for fatigue curve analysis and implementation of fatigue data were investigated. These four stress-to-number of cycles (S-N) fatigue curves were added to Tmin's internal Microsoft Access® database. Next, a 2-D vertical piping span configuration was incorporated. Finally, DuPont required a Microsoft Word® document output of the pipe-wall thickness data including the piping span model information. Other user-friendly additions were included. Since this computer program was to be American Society of Mechanical Engineers (ASME) compliant, a study of the ASME Pressure Vessel and Piping standards and codes was made to determine how pipe-wall thickness calculations were to be processed. The 2-D vertical piping span calculation procedures were investigated. Once the 2-D vertical piping span analysis was complete, the largest pipe-wall thickness value calculated were passed to a Microsoft Word® document. The last implementation is the inclusion of help files. Help file button additions in all input boxes allowed for the user to know exactly what was needed before a data entry was made. / Master of Science

Made available in DSpace on 2017-07-21T20:43:45Z (GMT). No. of bitstreams: 1 Luis Otavio Ribas Lima.pdf: 8124964 bytes, checksum: d16bc8c64f9e15d57f770b1b271d6b3b (MD5) Previous issue date: 2014-06-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Aluminum alloys have been the primary material of choice for the aircraft due to their properties such as low density, high mechanical and corrosion resistance. Commercial aircraft apply aluminum alloys for the fuselage, wings and supporting structure due to the extensive knowledge in design and production of aluminum components, and most importantly, aluminum alloys continue to be developed, keeping it highly competitive. A great development happen with the heat-treatable alloys, which allow improvement of the mechanical properties. Among this alloys stand out the Al-Zn-Mg-Cu series, known for high strength, toughness and corrosion resistance. The improvement of those alloys occurs by the precipitation of nanometric particles MgZn2, called η phase. This study’s aim was to promote an interrupted heat treatment T6I4-65 in an AA7050 aluminum alloy, with fatigue crack growth resistance as priority. Interrupted heat treatments’ goal is optimizing the consumption of solute atoms during process of nucleation and growth of precipitates as a finely dispersion. The T6I4-65 condition obtained was analyzed by differential scanning calorimetry, DSC, optical and electronic microscopy, mechanical tests as hardness, tensile and fatigue crack growth. The T6I4-65 treatment results in a microstructure with a fine dispersion of precipitated phase η’, about 75% smaller than those resulting from in current use, T7451. This microstructure resulted in a reduction of up to 24% in fatigue crack growth rate compared to that resulting from T7451 treatment, keeping the ductility of 17% of area reduction and yield strength higher than 400MPa. / Ligas de alumínio são o principal material de uso na indústria aeronáutica devido a suas propriedades como baixa densidade, alta resistência mecânica e a corrosão. Aeronaves comerciais utilizam ligas de alumínio em sua fuselagem, asas e na estrutura de suporte devido ao extenso conhecimento no projeto e produção de componentes em alumínio, e mais importante, as ligas de alumínio continuam a serem desenvolvidas, mantendo-se altamente competitivas. Ocorreu um grande avanço com o desenvolvimento das ligas tratáveis termicamente, que permitiram a otimização das propriedades mecânicas. Entre estas ligas tratáveis, destaca se a família Al-Zn-Mg-Cu, conhecidas pela alta resistência mecânica, tenacidade e resistência a corrosão. O aperfeiçoamento destas ligas ocorre pela precipitação de partículas nanométricas de MgZn2, conhecida como fase η. O objetivo deste trabalho foi obter um tratamento térmico interrompido T6I4-65 em uma liga de alumínio AA7050 com prioridade ao aumento de resistência à propagação de trinca por fadiga. Tratamentos interrompidos tem por objetivo otimizar o consumo de átomos de soluto durante os processos de nucleação e crescimento dos precipitados endurecedores na liga na forma de dispersão finamente dispersa. A condição T6I4-65 obtida foi analisada por meio de calorimetria diferencial de varredura, DSC, microscopia ótica e eletrônica de varredura e transmissão, ensaios mecânicos dureza, tração e propagação de trinca por fadiga. Este tratamento resultou em uma microestrutura com uma dispersão de finos precipitados de fase η’, cerca de 75% menores que os resultantes de tratamentos de uso corrente, T7451. Esta microestrutura promoveu a redução de até 24% na taxa de propagação de trinca por fadiga em comparação à resultante do tratamento T7451, mantendo grande ductilidade, até 17% de redução de área e limite de escoamento superior a 400MPa.