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Abotaleb, Ahmed. "Advanced modeling and optimization of the friction stir welding process : applications to Inconel 718 and high-performance alloys." Electronic Thesis or Diss., Strasbourg, 2024. http://www.theses.fr/2024STRAD024.
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Cette thèse porte sur le soudage par friction-malaxage (FSW) appliqué à l'Inconel 718 et au soudage dissemblable avec le Ti-6Al-4V. Un modèle thermomécanique, développé sous COMSOL Multiphysics v5.3 et validé pour l’aluminium 6061-T6, a été adapté à l’Inconel 718. Une analyse paramétrique, incluant vitesse de rotation, vitesse de soudage, force axiale, dimensions de l’outil, refroidissement actif et préchauffage par induction, a été réalisée via des méthodes comme Taguchi, ANOVA et régression non linéaire. Les résultats montrent que la force axiale et la vitesse de rotation influencent fortement le procédé, tandis que le préchauffage et le refroidissement améliorent la dissipation thermique et la structure des grains. Enfin, des stratégies PID et MPC sont proposées pour optimiser le contrôle thermique, offrant des avancées pour le FSW des alliages haute performanceThis study investigates friction stir welding (FSW), a solid-state joining technique for similar and dissimilar metallic materials, focusing on Inconel 718 and its dissimilar welding with Ti-6Al-4V. Using a thermomechanical model developed in COMSOL Multiphysics v5.3, validated with 6061-T6 Aluminum data and extended to Inconel 718, key parameters—rotational speed, welding speed, axial force, tool dimensions, active cooling, and induction preheating—were optimized through parametric study, Taguchi analysis, ANOVA, and non-linear regression. Results show axial force and rotational speed critically affect FSW, while induction preheating and active cooling enhance heat dissipation and grain structures. PID and MPC strategies are proposed for thermal control, advancing FSW optimization for high-performance alloys
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Mas, Fanny. "Solidification and phase transformations in a dissimilar steel weld 18MND5/309L/308L : evolution of microstructure and mechanical properties." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI076/document.
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Les liaisons bimétalliques entre acier faiblement allié et acier inoxydable sont nombreuses au sein des réacteurs nucléaires français où elles assurent la connexion entre les principaux composants et les tuyauteries du circuit primaire. Le revêtement interne de cuve réalisé par soudage feuillard-flux est un autre cas de soudure dissimilaire dont le rôle est d'assurer une bonne protection contre la corrosion. Ce travail de thèse a notamment pour but de comprendre la genèse des microstructures complexes se formant à l'interface entre les deux aciers pendant le soudage. Il étudie d'autre part leur évolution durant le traitement thermique post-soudage à 610°C ainsi que les conséquences de ces transformations sur le comportement mécanique du joint soudé. Partant du métal de base, on rencontre successivement une fine bande de martensite, une zone purement austénitique puis la microstructure biphasée δ/γ de l'acier inoxydable. Des techniques de microscopie (MEB, EDS, EBSD) combinées à des calculs thermo-cinétiques (modèle de Scheil-Gulliver, surfusion en pointe de dendrite) ont permis d'expliquer le gradient de microstructure et les raisons des transitions de phases observées. Au cours du traitement thermique de détensionnement à 610°C, le gradient de potentiel chimique du carbone à travers l'interface de fusion cause la dissolution de la cémentite et la croissance des grains du côté faiblement allié. On observe également la diffusion du carbone à travers l'interface et la précipitation de carbures riches en Cr dans le liseré martensitique et la zone austénitique. Une caractérisation détaillée des profils de composition et de la précipitation a été réalisée à différentes échelles (depuis le millimètre jusqu'au niveau atomique). Un modèle mésoscopique, s'appuyant sur des bases de données thermodynamiques et cinétiques, a été développé pour coupler la diffusion à longue distance dans un milieu multi-constitué à la germination et croissance des précipités (approche de type Kampmann-Wagner). Il a permis de prévoir la teneur en carbone ainsi que la fraction volumique et la distribution de taille des précipités en fonction de la distance à l'interface. Les conséquences de la forte variabilité de microstructure sur le comportement mécanique local ont été analysées dans la dernière partie de ce travail, en particulier les aspects de déformation localisée et de rupture ductile. Des lois de comportement élasto-plastique ont été déterminées pour chacune des régions de l'assemblage à l'état détensionné. L'étude des mécanismes de rupture ductile dans les zones les plus faibles de la soudure, c'est-à-dire le métal de base décarburé et les couches de revêtement austénitique a donné lieu à des observations in-situ et une modélisation de l'endommagementDissimilar welds between low-alloy steel and stainless steel are numerous within the French nuclear power plants where they enable connecting the main components to the primary circuit pipes. The internal cladding (in stainless steel) of the pressure vessel (in bainitic steel) made by submerged arc welding is another case of dissimilar weld whose goal is the protection against corrosion. This PhD work aims at understanding the complex microstructures which form at the interface between both steels during welding together with their evolution during the post-weld heat-treatment at 610°C and their consequences on the mechanical behavior of the welded assembly. Starting from the base metal, one meets successively a thin layer of martensite, a fully austenitic zone and the two-phase δ/γ microstructure of the stainless steel. Microscopy techniques (SEM, EDS, EBSD) combined with thermo-kinetics calculations (Scheil-Gulliver model, dendrite tip undercooling) have allowed explaining the graded microstructure and the reasons for the observed phase transitions. During the post-weld heat-treatment, the large gradient of carbon chemical potential across the fusion line leads to cementite dissolution and grain growth on the low-alloyed side. Carbon diffusion through the interface and Cr-rich carbides precipitation in both the martensitic layer and the austenitic weld have also been observed. An in-depth characterization has been performed at different scales (from the millimeter to the atomic level) to quantify the extent of carbon diffusion and carbides precipitation during the phase transformations. A mesoscopic thermodynamic and kinetic model based on Calphad databases has been developed to fully couple long-range diffusion in a multi-component system with precipitates nucleation and growth (Numerical Kampmann-Wagner approach). It allowed a prediction of the carbon content, volume fraction and size distribution of the precipitates at any distance from the fusion line. The consequences of the high variability of microstructures on the local mechanical behavior have been examined in the last part of this work, in particular the localization of deformation and the ductile failure. Elasto-plastic constitutive laws were determined for each region of the dissimilar weld in the heat-treated state. Ductile failure mechanisms in the weak zones of the weld, namely the decarburized base metal and the stainless steel cladding layers, were investigated through in-situ observations and damage modeling
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Mirim, Denilson de Camargo. "Investigação da tensão residual na soldagem laser entre o aço carbono AISI 1010 e o aço inoxidável AISI 304." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-17062011-152023/.
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Um dos mais críticos problemas encontrados na união de materiais distintos é a formação de tensões residuais, que ocorre principalmente pelo fato desses materiais possuírem coeficientes de expansão térmica e condutividades térmicas diferentes. Neste trabalho foi estudada a técnica de soldagem laser entre o aço carbono AISI 1010 e o aço inoxidável AISI 304. Os materiais foram unidos por solda autógena de topo com um laser de Nd:YAG contínuo. O principal objetivo do estudo foi a identificação da influência dos parâmetros de soldagem, pela análise das tensões residuais na zona termicamente afetada (ZTA). Foi executado um planejamento fatorial de três fatores a dois níveis com uma réplica, em que foram variadas a potência, a velocidade de soldagem e a posição focal do feixe laser. Na superfície da amostra foram realizadas medidas de tensão residual pela técnica de difração de raios X, para estudar sua variação em função dos parâmetros investigados. O método do furo cego foi também utilizado para avaliar a tensão residual ao longo da profundidade das amostras até a profundidade de 1 mm. Além das medidas de tensão residual, os cordões de solda foram avaliados por microscopia óptica e eletrônica de varredura (MEV), que tiveram como objetivos determinar a geometria do cordão e mudanças na microestrutura, também foram feitas medidas de microdureza Vickers para se avaliar a extensão da ZTA. Para se avaliar as propriedades mecânicas da união foram realizados ensaios de tração e fadiga. O software MINITAB 15 foi utilizado para a análise das tensões residuais nas diferentes profundidades da ZTA obtidas pelo método do furo cego. Foi utilizada também a regressão estatística baseada nas diferentes influências da entrada e combinação dos fatores na tensão residual geradas nessa união. Os resultados indicam que o desenvolvimento de modelos pode prever as respostas satisfatoriamente e fornecer aos usuários um guia para definir os melhores parâmetros de união.The dissimilar materials union has the residual stress formation as one of the most critical problems, which occurs mainly because these materials have both different thermal expansion coefficients and thermal conductivities. In this study, it was investigated the laser welding technique between steels, AISI 1010 and AISI 304. The materials were joined by butt autogenous welding with a continuous Nd:YAG laser. The main objective was to identify the welding parameters influence by the residual stresses analysis in the heat affected zone (HAZ). It was executed a factorial design with three-factor at two levels with a replica, which were varied power, welding speed and focal position of the laser beam. Residual stress measurements by the diffraction of X-rays were performed on the sample surface, to study their variation as a function of the parameters investigated. The blind hole method was also used to evaluate the residual stress along the samples depth, up to depth of 1mm. Besides residual stress measurement, weld seams were evaluated by optical and scanned electron microscopy, which were aimed to determine the weld geometry and changes in the microstructure. It was also made Vickers hardness measurements to evaluate the extent of HAZ. To evaluate the mechanical properties of the union were performed tensile and fatigue test. The MINITAB 15 software was used to analyze the residual stresses obtained by the blind hole method at different depths of the HAZ. It was also used statistical regression based on both the influences different and the combination of this input factors, in the residual stress of union. The results indicate that the models can satisfactorily predict the responses and provide users a guide to better define the welding parameters.
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Silva, Sandro Luz da [UNESP]. "Análise de juntas soldadas de aços dissimilares AISI 304 e SAE 1020 com metais de adição ER 309L e ER 70S3 pelo processo GTAW." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/146732.
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Atualmente os processos de soldagem de juntas dissimilares são muito utilizados na indústria petrolífera e nuclear, caracterizada pela união entre diferentes materiais. No presente trabalho, será estudada a possibilidade da união entre o aço inoxidável AISI 304 e aço carbono SAE 1020. Os quais são largamente utilizados em linhas de vapor em plantas de energia, em reatores nucleares, plantas petroquímicas, devido suas diferentes propriedades mecânicas e resistência à corrosão. Este trabalho tem por objetivo principal, estudar profundamente, as propriedades mecânicas, físicas e químicas, com o auxílio de testes e equipamentos específicos: ensaios de Microdureza Vickers, ensaio de tração, de interpretação das macrografias e micrografias utilizando microscopia ótica e também análise da difração de raios x das juntas soldadas. Foram executadas pesquisas bem fundamentadas, para verificar e discutir os resultados obtidos, justificando a substituição das varetas de aço inoxidável AWS ER 309L, por varetas de aço carbono AWS ER 70S3 como metal de adição, utilizando processo de soldagem manual GTAW (Gas-Shielded Tungsten Arc Welding), objetivando a redução de custo no processo de soldagem e viabilizando um bom investimento para pesquisas futuras.
Nowadays the welding processes of dissimilar joints are widely used in the oil and nuclear industry, characterized by the union of different materials. In the present work, will be studied the possibility of union between stainless steel AISI 304 and carbon steel SAE 1020. Which are widely used in steam lines in power plants, nuclear reactors, petrochemical plants, due to their different mechanical and corrosion resistance properties. The main objective of this work is to study deeply the mechanical, physical and chemical properties, evaluated by specific tests and equipments: Vickers hardness tests, tensile tests, interpretation of macrographs and micrographs utilizing the optical microscope and also analysis of x-ray diffraction applied to the welded joints. Well-founded research have performed to verify and discuss the results. Justifying the replacement of stainless steel rods AWS ER309L, carbon steel rods AWS ER70S3 as filler metal, using manual welding process GTAW (Gas-Shielded Tungsten Arc Welding), aiming the cost reduction in welding and process, making a possible good investment for future research.
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Dawson, Karl. "Dissimilar metal welds." Thesis, University of Liverpool, 2012. http://livrepository.liverpool.ac.uk/7373/.
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This dissertation details the findings of experimental investigations of welds made between ferritic creep resistant steels that differ in chromium content. Analysis of the microstructural evolution during the application of post weld heat treatments is reported. Particular attention was paid to the key alloy strengthening mechanisms and the manner in which they were affected by carbon redistribution which takes place when these welds are exposed to high temperatures. The fusion interface regions of transition joints, made between P91 parent alloy and P22, P23 and P24 type weld consumables, were analysed in as received and post weld heat treated conditions. Carbon redistribution from the low to higher alloyed material, which resulted in its depletion from weld alloy adjacent to the fusion line, was confirmed in all weld systems subsequent to post weld heat treatment (PWHT). The effect of tempering treatments, carried out at 730°C for two and eight hour durations, on carbide populations in partially decarburised weld alloy was explored. The consequential microstructural changes, which were affected by the dissolution of M23C6 and M7C3 carbides, were compared to those observed in regions of weld alloy unaffected by carbon depletion. High resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM) were used extensively in the analysis of weld metal and heat affected zone (HAZ) microstructures. Electron diffraction and x-ray energy dispersive spectroscopy were exploited in the crystallographic and chemical characterisation of precipitates. Their evolution as a function of thermal exposure is presented for each alloy. Chemical signatures for each precipitate species, which enabled their identification, were determined for carbides in the different alloys. However, due to variations in the compositions of fusion interface M23C6 carbides, some permutations of which overlapped with compositions of M7C3, satisfactory identification demanded classification of their crystal structure. A significant difference between the microstructures of P23 and P24 alloys, in the weld specimens tested, was observed. Although vanadium and niobium carbonitrides (MX) were identified in both alloys, their distributions were not the same. Retention of carbonitride particles within partially decarburised P23 and P24 weld materials, subsequent to 8 hours post weld heat treatment, has been substantiated. Diffraction intensity distributions in Debye-Scherrer ring patterns, which were generated from MX precipitation, indicated lattice parameters varied. Microanalysis revealed that MX precipitates were present over a wide range of compositions. A combination of the composition analysis and diffraction studies indicated that MX precipitation was stable over a range of compositions in the carbon depleted regions of P24 alloy. Recrystallisation of the bainitic P22 weld alloy adjacent to the fusion line, which was accompanied by a loss of material hardness, was observed in 2 and 8 hour PWHT P91/P22 welds. It has been shown that the microstructural stabilisation of carbon depleted T/P23 and T/P24 alloys was conferred by a dispersion of MX precipitates. Retention of these stable particles, which in many cases are less than 10 nm in diameter, in carbon depleted material, resulted in the complete avoidance of any recrystallisation in 2 hour post weld heat treated T/P23 and T/P24 welds and only isolated occurrences in 8 hour tempered specimens. Subgrain size distributions were determined from electron channeling contrast images of various regions of the dissimilar metal welds. Results showed that, although recrystallisation of MX forming alloys did not occur, destabilisation of lath boundaries, due to the dissolution of M23C6 and M7C3 carbides, results in a coarser subgrain microstructure in carbon depleted P24 weld alloy. The loss of resistance to plastic deformation as a result of recrystallisation, which has been shown to take place in decarburised P22 alloy, was not observed in the alloys which precipitated the MX phase.
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BANGASH, MUHAMMAD KASHIF. "Joining of Dissimilar Materials." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2711296.
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Material manufacturers and engineering structure designers are currently focusing new ways to exploit the benefits of light-weight, hybrid materials with improved properties at a low cost. The ability to join dissimilar materials is enabling the design engineers to develop light-weight and efficient automobiles, aircraft and space vehicles.
The objective of this PhD research study was to produce alternative and efficient joining solutions for automotive and aerospace applications. The joining of dissimilar material was experimented to obtain light-weight Fibre Reinforced Polymer (FRP) sandwich composites, Al-foam sandwich (AFS) composites, hybrid dynamic FRP epoxy/polyurethane composites and the joining of Ti6Al4V alloy with and without surface modification to Ceramic Matrix Composite (CMC) and itself.
The joining of Al-foam and Al-honeycomb to FRP skins was performed. The experimental results show that higher flexural properties can be achieved by replacing Al-honeycomb with low-cost Al-foam as a core material in the sandwich structures. Compared to FRP-honeycomb sandwich panels, FRP-Al foam sandwich panels display ~25 % and ~65 % higher flexural strength in a long and short span three-point bending tests respectively.
AFS composites with complete metallic character, to withstand high-temperature application conditions, were produced by soldering/brazing techniques using Zn-based and Al-based joining alloys. A post-brazing thermal treatment was designed to recover the mechanical properties of AFS composites, lost during the soldering/brazing process. The microstructural analysis of the Al-skin/Al-foam interface revealed that the diffusion of joining materials into the joining substrates (Al-sheet and Al-foam) was achieved. Around 80% higher bending load before failure was observed when the AFS specimens produced with Zn-based joining alloys were subjected to flexural load compared to those produced with Al-based joining alloys.
Hybrid dynamic Carbon Fibre Reinforced Polymer (CFRP) composites with enhanced impact properties were produced by exploiting the reversible cross-linking functionalities of dynamic epoxy and dynamic PU resin systems. By joining dynamic CFRP-epoxy and dynamic CFR-PU laminates, hybrid dynamic composite in three different configurations and a non-hybrid composite were obtained. The four dynamic composites were characterised for structural, thermal, flexural and impact properties. The damage initiation upon impact was observed at around 95% higher energy level in the hybrid configuration (CFRP-4), compared to the non-hybrid configuration. The hybrid configuration CFRP-3 responded with around 55% higher perforation threshold energy compared the non-hybrid configuration.
Preliminary work on Adhesive joining of the Ti6Al4V alloy to itself was performed to analyse the effect micro-machining on adhesion and the effect of shape/design of micro-slots on an adhesive joint strength. Three types of micro-slots: V, semi-circle and U-shaped micro-slots were produced on Ti6Al4V sheet surface by using an in-house developed Micro-Electro-Discharge Machining (Micro-EDM) setup. Ti6Al4V alloy specimens with and without micro-machined surfaces were bonded together using a commercial epoxy adhesive. The Single Lap Offset (SLO) shear test results revealed that the micro-slot oriented perpendicular to the applied load displayed ~23 % higher joining strength compared to when the micro-slots were oriented parallel to the applied load. U-shaped micro-slots configuration displayed ~30 % improvement in the joint shear strength compared to the specimens with un-modified surfaces. The fractured surfaces analysis revealed mix (adhesive-cohesive) with cohesive dominated failure in bonded specimens with micro-machined surfaces compared to the as-received where pure adhesive failure was observed.
The joining of CMCs (C/SiC and SiC/SiC) to Ti6Al4V alloy was experimented using active brazing alloy (Cusil-ABA) and Zr-based brazing alloy (TiB590) in a pressure-less argon atmosphere. The CMC-Ti6Al4V joint strength was further improved by modifying the surface of Ti6Al4V alloy using an in-house built Micro-EDM setup. Around 40% higher joining strength was recorded when the Zr-based brazing alloy was used as a joining material compared to the conventional active brazing alloy, Cusil-ABA. Improvement in the joining strength was noticed when the Ti6Al4V surface was modified prior to joining.
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Gonçalves, Vitor Manuel Martins. "Soldadura laser de ligações dissimilares." Phd thesis, Instituições portuguesas -- UTL-Universidade Técnica de Lisboa -- IST-Instituto Superior Técnico, 1998. http://dited.bn.pt:80/5.
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Stenhouse, Henry G. "Direct bonding dissimilar optical materials." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/420653/.
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This thesis presents the work conducted during this project on direct bonding of dissimilar optical materials at the Optoelectronics Research Centre, University of Southampton. It covers the history and background of the art, before progressing to the development of unique bonding processes used during the research detailed. During this project, direct bonding using chemical and plasma activation is successfully conducted on both amorphous and crystalline materials. Bonding of borosilicate glass is demonstrated in the production of planar structured fibre preforms to be caned. Development of Nd:YAG to sapphire bonds is reported, producing bonds of remarkable resilience, capable of surviving dicing and polishing procedures. Zinc selenide to diamond and sapphire bonding is presented using a plasma activated approach along with investigation of the resulting bond’s limits, demonstrating the heat spreading benefits of a bonded diamond layer.
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Shukla, Nitin. "Heat Transport across Dissimilar Materials." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/27820.
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All interfaces offer resistance to heat transport. As the size of a device or structure approaches nanometer lengthscales, the contribution of the interface thermal resistance often becomes comparable to the intrinsic thermal resistance offered by the device or structure itself. In many microelectronic devices, heat has to transfer across a metal-nonmetal interface, and a better understanding about the origins of this interface thermal conductance (inverse of the interface thermal resistance) is critical in improving the performance of these devices. In this dissertation, heat transport across different metal-nonmetal interfaces are investigated with the primary goal of gaining qualitative and quantitative insight into the heat transport mechanisms across such interfaces. A time-domain thermoreflectance (TDTR) system is used to measure the thermal properties at the nanoscale. TDTR is an optical pump-probe technique, and it is capable of measuring thermal conductivity, k, and interface thermal conductance, G, simultaneously.
The first study examines k and G for amorphous and crystalline Zr47Cu31Al13Ni9 metallic alloys that are in contact with poly-crystalline Y2O3. The motivation behind this study is to determine the relative importance of energy coupling mechanisms such as electron-phonon or phonon-phonon coupling across the interface by changing the material structure (from amorphous to crystalline), but not the composition. From the TDTR measurements k=4.5 W m-1 K-1 for the amorphous metallic glass of Zr47Cu31Al13Ni9, and k=5.0 W m-1 K-1 for the crystalline Zr47Cu31Al13Ni9. TDTR also gives G=23 MW m-2 K-1 for the metallic glass/Y2O3 interface and G=26 MW m-2 K-1 for the interface between the crystalline Zr47Cu31Al13Ni9 and Y2O3. The thermal conductivity of the poly-crystalline Y2O3 layer is found to be k=5.0 W m-1 K-1. Despite the small difference between k and G for the two alloys, the results are repeatable and they indicate that the structure of the alloy plays a role in the electron-phonon coupling and interface conductance.
The second experimental study examines the effect of nickel nanoparticle size on the thermal transport in multilayer nanocomposites. These nanocomposites consist of five alternating layers of nickel nanoparticles and yttria stabilized zirconia (YSZ) spacer layers that are grown with pulsed laser deposition. Using TDTR, thermal conductivities of k=1.8, 2.4, 2.3, and 3.0 W m-1 K-1 are found for nanocomposites with nickel nanoparticle diameters of 7, 21, 24, and 38 nm, respectively, and k=2.5 W m-1 K-1 for a single 80 nm thick layer of YSZ. The results indicate that the overall thermal conductivity of these nanocomposites is strongly influenced by the Ni nanoparticle size and the interface thermal conductance between the Ni particles and the YSZ matrix. An effective medium theory is used to estimate the lower limits for the interface thermal conductance between the nickel nanoparticles and the YSZ matrix (G>170 MW m-2 K-1), and the nickel nanoparticle thermal conductivity.Ph. D.
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Race, Julia Margaret. "Carbon diffusion across dissimilar steel welds." Thesis, University of Cambridge, 1992. https://www.repository.cam.ac.uk/handle/1810/221881.
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Xiao, Kaida. "Colour appearance assessment for dissimilar sizes." Thesis, University of Derby, 2006. http://hdl.handle.net/10545/312310.
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The colour size effect is an important aspect of colour appearance phenomenon, in which the colour appearance is changed according to different sizes of the same colour stimulus. Although colour appearance has been actively researched over the last 20 years and models have been developed capable of predicting the colour appearance under a wide range of viewing conditions, the colour size effect was not taken into account due to lack of reliable colour appearance data for colours with various sizes. This lead to great difficulty for industry for faithfully reproducing colours between dissimilar sizes. In this study, it is intended to accumulate colour appearance data for various sizes, to analyse the size effect and develop a model to predict size effect in purpose of accurate colour appearance reproduction across dissimilar sizes. Colours in six sizes, including the size of a real room, were divided into two groups and were assessed by a panel of observers. The techniques of magnitude estimation and asymmetric colour matching (by using CRT and physical colours) were applied. Totally, there were 4920 assessments conducted for various field sizes by using different scaling techniques under different viewing conditions. The colour appearance of the room was investigated in two aspects: size effect and mixed illuminant based upon both physical measurement and psychophysical visual experimental results. For the former, colour appearance between the room and 10° size were compared and modelled. For mixed illuminant prediction, a mathematical model was developed to predict the adopted white for a room with any wall colour. Finally, a model for predicting colour appearance for room colours was derived including three parts: the illumination prediction, colour appearance model (CIECAM02) and size effect correction. The size effect was further investigated using the visual results from all different six SIZ es. Based upon the CIB recommended 2° and 10° standard colorimetric observers, the colour appearances of object samples were predicted. The changes of colour appearance for those colour samples from one size to another were analysed. Most importantly, the relative changes of colour appearances of six dissimilar size colours were also revealed based upon proposed experimental results. A clear trend was found that colour appears lighter and more colourful with the increase of stimulus size, there is however little change in hue.Finally, colour appearance models that are capable of predicting colour size effect for any sizes of colours were developed. They were firstly derived based upon both CIELAB uniform colour space and CIECAM02 colour appearance model, which were named as size effect correction model. Another model, named as size effect transform model, was also developed based on human cone response functions. By using those size effect models, the colour appearance for dissimilar sizes can be predicted incorporate with colour appearance model . These models can also successfully predict the visual results.
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Wang, Tianhao. "Friction Stir Welding of Dissimilar Metals." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1404577/.
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Dissimilar metals joining have been used in many industry fields for various applications due to their technique and beneficial advantages, such as aluminum-steel and magnesium-steel joints for reducing automobile weight, aluminum-copper joint for reducing material cost in electrical components, steel-copper joints for usage in nuclear power plant, etc. The challenges in achieving dissimilar joints are as below. (1) Big difference in physical properties such as melting point and coefficient of thermal expansion led to residual stress and defects. (2) The miscibility issues resulted in either brittle intermetallic compound layer at the welded interface for miscible combinations (such as, aluminum-steel, aluminum-copper, aluminum-titanium, etc.) or no metallurgical bonding for immiscible combinations (such as magnesium-copper, steel-copper, etc.). For metallurgical miscible combinations, brittle intermetallic compounds formed at the welded interface created the crack initiation and propagation path during deformational tests. (3) Stress concentration appeared at the welded interface region during tensile testing due to mismatch in elastic properties of dissimilar materials. In this study, different combinations of dissimilar metals were joined with friction stir welding. Lap welding of 6022-T4 aluminum alloy/galvanized mild steel sheets and 6022-T4 aluminum alloy/DP600 steel sheets were achieved via friction stir scribe technology. The interlocking feature determining the fracture mode and join strength was optimized. Reaction layer (intermetallic compounds layer) between the dissimilar metals were investigated. Butt welding of 5083-H116 aluminum alloy/HSLA-65 steel, 2024-T4 aluminum alloy/316 stainless steel, AZ31/316 stainless steel, WE43/316 stainless steel and 110 copper/316 stainless steel were obtained by friction stir welding. The critical issues in dissimilar metals butt joining were summarized and analyzed in this study including IMC and stress concentration.
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Chen, Hui-Chi. "Fibre laser welding of dissimilar materials." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/fibre-laser-welding-of-dissimilar-materials(de9ec14d-4201-4e65-b4f8-9a40bfd7a883).html.
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Joining technology has played an important role in manufacturing since the industrial revolution. Welding methods are under constant development in response to real demands. Laser welding is considered an effective joining method that can provide high quality and cost effective results to bring economical benefits to industry. Nowadays, fibre lasers have the capability to fill some of the roles of the CO2 and Nd:YAG lasers in industrial welding applications because of their excellent characteristics such as higher energy density and superior beam quality. However, up to now, few quantitative evaluations of its performance against more traditional lasers have been conducted in laser material processing. This thesis presents an investigation into the fibre laser welding of dissimilar materials processes. The challenges in the welding of dissimilar materials are mainly related to the large differences in the physical and chemical properties of the welding materials. These differences readily cause residual stresses, intermetallic phases and chemical composition gradients. The aim of this work is to understand and explain mechanisms occurring in single mode fibre laser welding of dissimilar materials. The first part of this work addressed fibre laser butt welding of Ti-6Al-4V titanium alloy to Inconel 718 nickel alloy. Here, the weld quality was evaluated in terms of the weld geometry, microstructures, hardness distributions and the formation of intermetallic phases. Results showed that the offset position of the laser beam was an important factor affecting the weld quality. Furthermore, the thermal history of the weld was simulated using analytical modelling analysis and this was used to identify a parameter window for crack-free welding. The second part of this work focused on fibre laser lap welding of Zn-coated steel to Al alloy with different laser power delivery modes (pulsed wave and continuous wave). The relationship between the weld quality and process parameters, such as: pulse frequency, laser power, welding speed, the shielding gas type and number of welding passes, were investigated. The mechanical properties, metallurgical effects and corrosion performances of welds were analysed. Results showed that the shielding gas type and the number of welding passes were key factors in controlling the weld quality in the fibre laser welding of Zn-coated steel to Al alloy process. Finally, the common features, characteristics and the potential of fibre laser welding of dissimilar materials are presented.
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Patsikas, Dimitrios. "Track score processing of multiple dissimilar sensors." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Jun%5FPatsikas.pdf.
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Thesis (M.S. in Applied Physics and M.S. in Electrical Engineering)--Naval Postgraduate School, June 2007.Thesis Advisor(s): Phillip E. Pace, Murali Tummala, Gamani Karunasiri. "June 2007." Includes bibliographical references (p. 57-58). Also available in print.
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Peel, Matthew J. "Friction-stir welding of dissimilar aluminium alloys." Thesis, University of Manchester, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488339.
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Zywicz, Edward. "On elastic-plastic cracks between dissimilar media." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14401.
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Grant, James Philip. "Non-Contact Lap Splices in Dissimilar Concretes." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/56585.
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Non-contact lap splices placed within a single concrete placement are often used and have been studied in previous research projects. However, non-contact lap splices used with each bar in a different concrete placement such that there is a cold joint between the bars, have not been investigated. This situation is found in the repair of adjacent box beam bridges and in the construction of inverted T-beam systems, among others. It is vital to understand whether the same mechanisms are present across a cold joint with two different types of concrete as are present in traditional non-contact lap splices.
In this research, eight T-beam specimens with non-contact lap splices were tested. The spacing between the bars, the splice bar blockout length, and presence of transverse bars were varied to study the effectiveness of the splices. The beams were tested in four point bending so that the splice region was under constant moment and the tension forces in the spliced bars were constant. End and midspan deflections were measured along with surface strain measurements at midspan and at the quarter span points, top and bottom. Gap openings were also measured at the ends of the blockouts.
The main conclusions found from this research are that beams containing non-contact lap splices were able to develop nominal capacity with the bar spacing less than or equal to 4 in. and the blockout between 17 and 20 in. long. Extending the blockouts and adding transverse bars underneath the splices did not add to the capacity.Master of Science
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Donatus, Uyime. "Corrosion protection and microstructure of dissimilar materials." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/corrosion-protection-and-microstructure-of-dissimilar-materials(b419af19-3459-4218-9aff-b1b857a36cb4).html.
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Corrosion Protection and Microstructure of Dissimilar Materials. A thesis submitted to The University of Manchester for the degree of Doctor of Philosophy by Uyime, Donatus on the 30th of July, 2015.Investigations on the micro- and macro-galvanic corrosion mechanisms in un-coupled AA2024-T3 alloys, AA2024-T3 coupled with mild steel (with and without the influence of cadmium and under varying solution temperatures), dissimilar friction stir welds of AA5083-O and AA6082-T6 alloys and a friction stir welded AA7018 alloy have been carried out. Selected methods of preventing and / or minimising the investigated corrosion phenomena were also investigated. The investigation of the corrosion behaviour of the uncoupled AA2024-T3 alloy revealed that there are two distinct stages of polarization during the galvanostatic polarization of AA2024T3 alloy in de-aerated 3.5% NaCl solution. From the first stage, the relationships between the pitting incubation time, pitting potential and applied current density for AA2024T3 alloy in the de-aerated condition were established. Whilst studying the in situ corrosion phenomena on the uncoupled AA2024-T3 alloy using the scanning vibrating electrode technique (SVET),three distinct stages in the variation of the recorded current density values with time were revealed. Attempts were made to correlate these stages with the corrosion behaviour of the alloy. The study of the galvanic interactions between AA2024-T3 and mild steel revealed that AA2024-T3 is anodic to mild steel at room temperature, but polarity reversal of the couple starts (from a temperature as low as 35 oC upwards) when the couple is introduced into the solution above ambient temperature. Importantly, AA2024-T3 is clearly cathodic to mild steel at 60 oC, although with very low measured galvanic current values. Cadmium coating (at ambient temperature) on the mild steel reduced the galvanic corrosion of the couple by as much as 20 µA/cm2 because of the formation of a CdO/Cd(OH)2 layer on mild steel. In the study of the dissimilar friction stir welds of AA5083-O and AA6082-T6 alloys, it was observed that material flows (pushes but does not mix) more from the advancing side into the retreating side and that the mixture of materials is far from complete. Two welding speeds were compared; the welding speeds have no clear influence on the microhardness, but affected the mixing proportions in the flow arm and in the nugget stem. The faster welding speed resulted in increased susceptibility to corrosion because of the reduced tool rotation per weld length for heat generation and the mixing of materials. The heat affected zones of both alloys and the transition regions between the AA5083-O alloy and the AA6082-T6 alloy rich zones have been identified to be the regions that are most susceptible to corrosion. Anodizing the weld in order to minimise corrosion showed that the AA5083-O alloy rich zones materials, in the weld, oxidizes more during anodizing compared with the AA6082-T6 alloy rich zones. Sputtering deposition prior to anodizing, promotes the formation of a uniform oxide film across the entire weld zones and prevents the boundary dissolution that occurs when the dissimilar weld of AA5083-O and AA6082-T6 alloys is anodized in 4 M H2SO4 solution at 15 V at ambient temperature. The investigation of the corrosion susceptible regions in friction stir welded AA7018 alloy, which was based on the use of ISO 11846 immersion test and the potentiodynamic polarization technique in naturally aerated 3.5 % NaCl solution, revealed intergranular, crystallographic and second phase particle influenced mode of attack. The heat affected zone was found to be the most susceptible to corrosion.
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Leskovar, Michael. "The stability of interfaces between dissimilar materials /." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/9728.
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Chow, Khin Choong. "Fusion of images from Dissimilar Sensor systems /." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FChow.pdf.
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Thesis (M.S. in Combat Systems Technology)--Naval Postgraduate School, Dec. 2004.Thesis Advisor(s): Monique P. Fargues, Alfred W. Cooper. Includes bibliographical references (p. 73-75). Also available online.
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Rodrigues, Juliana Aparecida. "Estudo da soldabilidade entre o aço austenítico alto manganês de efeito TRIP com o aço microligado ARBL pelo processo de soldagem TIG." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18158/tde-16102014-152401/.
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Tendo em vista a tendência mundial de se buscar a diminuição de peso de estruturas metálicas de veículos, o desenvolvimento de aços de resistência mecânica superior apresenta-se como um importante fator para a competitividade e sustentabilidade da indústria brasileira, além da segurança do usuário. No setor automobilístico, as reduções no peso e no consumo de combustível requerem não somente a pesquisa de novos aços, mas também a utilização de componentes híbridos, resultantes, entre outros, da união entre os aços austeníticos inovadores de alta liga e baixo custo (TRIP) e aços ferríticos comerciais (ARBL). Na presente dissertação foram investigadas as propriedades mecânicas microestruturais, antes e após o processo de soldagem TIG, dos aços TRIP e ARBL utilizados pela indústria automotiva. O principal objetivo do trabalho foi avaliar possíveis estruturas e modificações nas propriedades das juntas soldadas de acordo com parâmetros de soldagem pré-determinados. Primeiramente, verificaram-se as extensões da zona termicamente afetada dos corpos de prova soldados. Os perfis de microdureza indicaram que não houve uma alteração significativa de dureza na zona termicamente afetada do aço de efeito TRIP, enquanto que para o aço ARBL observa-se um considerável aumento. Os limites de escoamento determinados pelos ensaios de tração realizados permitiram a obtenção dos níveis de resistência mecânica das juntas soldadas. Através dos ensaios de microscopia eletrônica de varredura e microscopia ótica foi possível observar a influência do aporte térmico na zona termicamente afetada do aço ARBL. A análise de EDX nas juntas dissimilares permitiu observar a presença de zonas parcialmente diluídas na zona fundida do lado do metal de base ARBL, a caracterização da composição química nas interfaces entre os metais de base e o metal de solda e prever a microestrutura destas regiões. As fases presentes nos metais de base e na zona fundida foram caracterizadas também pela difração de raios x. Por meio da estereologia quantitativa caracterizou-se as fases presentes na zona fundida e determinou-se suas proporções em função do aporte térmico.In view of the global trend of searching for the weight reduction of metal frames in vehicles, the development of superior mechanical resistance steels presents itself as an important factor for the competitiveness and sustainability of the Brazilian industry, as well as to user safety. In the automotive industry, the reductions in vehicle weight and fuel consumption not only require research of new types of steel but also the use of hybrid components, which result, amongst other things, between the union of austenitic innovative high alloy and low cost (TRIP) with commercial ferritic steels (HSLA). This dissertation analyses the microstructural mechanical properties before and after the TIG welding process, the TRIP steel, and HSLA used by the automotive industry. The main objective of this study was to evaluate possible phase changes in steel structures and transformation in the properties of the welded joints according to pre-determined welding parameters by analyzing extensions of the heat-affected and melted zones of welded specimens. The micro hardness profiles showed no significant changes in hardness in the heat affected HSLA steel, while the TRIP steel showed considerable increase. Additionally, the yield point determined by the traction tests performed, allowed the obtainment of the mechanical resistance levels of the welded joints. Through the tests of scanning electron and optical microscopy was observed the influence of heat input on heat affected zone of HSLA steel. EDX analysis allowed us to observe the presence of molten zones partially diluted in the side of the base metal HSLA, characterization of the chemical composition at the interface of the base metal and weld metal and predicting the microstructure in these regions. The phases present in the base metal and weld zone were characterized too by x-ray diffraction. By quantitative stereology characterized by the phases present in the weld zone and their proportions were determined as a function of heat input.
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Pinheiro, Pedro Helton MagalhÃes. "Efeitos da temperatura de interpasse sobre as alteraÃÃes metalÃrgicas e propriedades mecÃnicas de juntas dissimilares do aÃo ASTM A182-F22 soldadas com ligas de nÃquel." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=12096.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoAs ligas de nÃquel podem ser utilizadas na uniÃo de juntas dissimilares de aÃos carbono baixa liga. Uma das finalidades desta uniÃo à evitar a formaÃÃo de trincas induzidas pelo hidrogÃnio. Existe uma limitaÃÃo por norma que impÃe a temperatura de interpasse mÃxima de 150ÂC para soldagem com ligas de nÃquel. Contudo, a temperatura de interpasse baixa reduz a produtividade e consequentemente aumenta os custos de fabricaÃÃo. Um estudo que avalia como a temperatura de preaquecimento/interpasse na soldagem dissimilar influencia as alteraÃÃes metalÃrgicas e propriedades mecÃnicas à oportuno. Desta forma, o objetivo geral deste trabalho à avaliar o efeito do aumento da temperatura de interpasse nas alteraÃÃes metalÃrgicas e nas propriedades mecÃnicas de juntas dissimilares soldadas do aÃo ASTM A182-F22 com diferentes ligas de nÃquel. Foram realizadas soldagens MIG/MAG automÃtica em juntas do aÃo (ASTM A182-F22) utilizando diferentes ligas de nÃquel como metal de adiÃÃo e diferentes temperaturas de interpasse (35ÂC, 150ÂC e 350ÂC). A energia de soldagem foi mantida constante (1,0 kJ/mm). Baseado nos resultados obtidos o aumento da temperatura de preaquecimento tende a reduzir a fraÃÃo de precipitados, decorrente do aumento da diluiÃÃo. O coeficiente de distribuiÃÃo do Mo e Nb diminuem com o aumento do teor de ferro na solda. Isto, por sua vez, torna mais forte a segregaÃÃo destes elementos. A temperatura de interpasse tendeu a reduzir a dureza da (ZTA-GG), por conta da reduÃÃo da velocidade de resfriamento. Nos ensaios de traÃÃo os corpos de prova romperam na regiÃo referente ao metal de base. Houve uma reduÃÃo no limite de escoamento nas condiÃÃes soldadas com temperatura de 350ÂC, sendo uma possÃvel causa a precipitaÃÃo de carbonetos devido ao preaquecimento e aos multipasses. Os ensaios de Charpy-V indicaram que, de uma forma geral, o aumento da temperatura de interpasse reduziu a tenacidade na zona fundida. A energia absorvida na interface sofreu reduÃÃo com o aumento da temperatura de interpasse, decorrente do aumento da descarbonetaÃÃo. O tempo de soldagem foi reduzido de forma considerÃvel com o aumento de temperatura de interpasse, entretanto, deve-se avaliar as alteraÃÃes na ZTA e ZF.
Nickel alloys can be used to weld dissimilar joints of low alloy carbon steels. One of the purposes of this union is to avoid the formation of hydrogen induced cracking. According codes and standard there is a limitation that imposes the maximum interpass temperature at 150ÂC for welding using nickel alloys. However, the low interpass temperature reduces productivity and increases manufacturing costs. A study that evaluates effect of the preheating and interpass temperature of dissimilar welds on the metallurgical changes and mechanical properties is of great relevance. In this way, the general objective of this study is to assess the effect of interpass temperature on metallurgical changes and mechanical properties of dissimilar welded joints among ASTM A182-F22 steel and different nickel-based alloys. GMAW were carried out on joints of steel (ASTM A182-F22) using different nickel-based alloys as filler metal and different interpass temperatures (35ÂC, 150ÂC and 350ÂC). The heat input was kept constant (1.0 kJ/mm). Based on the results obtained it was observed that increasing preheating temperature there is a tends to reduce the precipitates content, because of dilution. The distribution coefficient of Mo and Nb decrease with the increase of iron content in the fusion zone, making stronger the segregation of these elements. Interpass temperature tend to reduce the HAZ hardness, due to the in cooling rate reduction caused by increase interpass temperature. In the tensile tests failure in the base metal. There was a reduction in yield strength for welds produced with 350ÂC preheat temperature, being a possible cause the precipitation of carbides due to preheating and multipasses. The Charpy-V tests indicated that, generally, the increase in interpass temperature reduced the toughness in the fusion zone. The absorbed energy by the interface dropped when interpass temperature increase. The welding time was considerably reduced with the interpass temperature increase, however, it should be to considerate changes in HAZ and fusion zone.
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Turek, Gabriella. "Multiple scattering from submerged bodies dissimilar acoustical properties." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/17056.
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Knapp, Steven. "Mechanical Properties of an Inconel Dissimilar Metal Weld." Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31126.
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A pipe consisting of Inconel 600 welded to grade 106-B Carbon-Steel using Inconel 182 weld filler is used to transport heavy water in nuclear reactors. A confidential report concluded that cracking is one of the problems these pipes are currently facing. Before cracking can be fully understood the mechanical properties of the weld must be determined.
This thesis analyzed the pipe at various length-scales using optical microscopy, micro-hardness testing, small and large scale tensile testing and digital image correlation (DIC). This thesis successfully achieved it goals of determining the mechanical properties and creating a model of the Inconel dissimilar metal weld. It partially met the goal of observing fracture mechanisms as it was able to observe fracture in tensile samples but was not able to successfully track crack growth.
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Bäck, Mimmi. "Welding of dissimilar metals in different welding positions." Thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-184241.
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The three boiling water reactors (BWR) in Oskarshamn produce about 10 % of the electrical power in Sweden. The combination of intense radiation fluxes and high temperatures in nuclear reactors creates an extraordinary environment. Therefore, a number of material challenges arise at a nuclear power plant that needs to be solved in order to maintain the nuclear power production, safety and reliability. Dissimilar metal welds can be found at a lot of places in nuclear power plants and due to reparations or replacement some dissimilar metal welds need to be welded on site. The technical regulations for the Swedish nuclear power plants specifies that welding of dissimilar joints shall be made with gap of at least 1.5 mm and in horizontal position. Welding a dissimilar joint on site makes it difficult to follow the technical regulations, therefore, the aim with this study is to determine if different welding positions of dissimilar metal welds affect the structure and composition of the weld metal in a negative way and to investigate the importance of a gap in the root. In this study six samples were welded in three different welding positions, horizontal, vertical and reversed vertical with or without a gap of 1.5 mm in the root. The samples were evaluated by non-destructive testing, optical microscopy, chemical analysis, tensile testing, bend testing and hardness measurements. The results shows that two of the samples welded without gap failed the transverse root bend test, the same samples did also have high hardness values in the root bead. The conclusions are that the welding position, horizontal, vertical or reversed vertical does not affect the weld negative in a noticeable way. However, the gap and a good dilution with the filler metal are important.
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Marte, Judson Sloan. "Codeformation Processing of Mechanically-Dissimilar Metal/Intermetallic Composites." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/27463.
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A systematic and scientific approach has been applied to the study of codeformation processing. A series of composites having mechanically-dissimilar phases were developed in which the high temperature flow behavior of the reinforcement material could be varied independent of the matrix. This was accomplished through the use of a series of intermetallic matrix composites (IMCs) as discontinuous reinforcements in an otherwise conventional metal matrix composite.
The IMCs are produced using an in-situ reaction synthesis technique, called the XDâ ¢ process. The temperature of the exothermic synthesis reaction, called the adiabatic temperature, has been calculated and shown to increase with increasing volume percentage of TiB2 reinforcement. Further, this temperature has been shown to effect the size and spacing of the TiB2, microstructural features which are often used in discontinuous composite strength models.
Study of the high temperature flow behavior of the components of the metal/IMC composite is critical to the development of an understanding of codeformation. A series of compression tests performed at 1000° to 1200°C and strain-rates of 10-3 and 10-4 sec-1. Peak flow stresses were used to evaluate the influence of material properties and process conditions. These data were incorporated into phenomenologically-based constitutive equations that have been used to predict the flow behavior. It has been determined that plastic deformation of the IMCs occurs readily, and is largely TiB2 independent, at temperatures approaching the melting point of the intermetallic matrices.Ph. D.
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Lee, Genevieve W. "Advanced Characterization of Solid-State Dissimilar Material Joints." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492794418438023.
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Sorensen, Daniel David. "Dissimilar Metal Joining in the Medical Device Industry." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1494157928729494.
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Ali, Khaled Yousif. "Friction Stir Welding Between Similar and Dissimilar Materials." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1513857047779233.
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BERRETTA, JOSE R. "Solda laser em materiais dissimilares com laser de Nd:YAG pulsado." reponame:Repositório Institucional do IPEN, 2005. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11293.
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Made available in DSpace on 2014-10-09T12:50:23Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:02:52Z (GMT). No. of bitstreams: 1 10892.pdf: 82299221 bytes, checksum: dceed1e4106bebec1654b10d9cef9110 (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Fazzolari, Correa Elisa. "La réduction dissimilative du nitrate en ammonium dans les sols." Lyon 1, 1989. http://www.theses.fr/1989LYO10056.
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La reduction dissimilative du nitrate en ammonium est mise en evidence dans dix sols agricoles, et represente 3,7 a 35,8% de la quantite d'azote nitrique apporte. L'etude de l'effet de plusieurs niveaux de c-glucose/n-nitrate (2,5; 5; 10) sur cette reaction, ainsi que sur la denitrification, a ete realisee dans des echantillons de sol standardides physiquement et soumis a differentes pressions partielles en oxygene (0; 0,5; 1,0; 2,0 kpa). Cette etude demontre que, malgre une production importante de n::(2)o (denitrification) dans tous les traitements, la production dissimilative d'ammonium est favorisee par des rapports c/n eleves et que, dans ces conditions, elle semble etre moins sensible a l'action de l'oxygene que la denitrification (. . . )
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McDonald, Patrick Edward. "Wicking in Multi-Ply Paper Structures with Dissimilar Plies." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14082.
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The wicking properties of multi-ply paper samples with dissimilar plies were investigated. These materials exhibit wicking performance in excess of either of their individual plies. Samples were produced from a ply of softwood pulp and a ply of hardwood pulp of equal caliper and basis weight. The softwood sample possessed a larger average pore size, a fact verified via porometry. Samples of a single ply were also produced for comparison. The samples were tested using both upward and downward gravimetric wicking tests. There was no saturation gradient observed, however there was a variation in the degree of bulk expansion during wicking. Capillary pressure and permeability for the various sample types were determined from the results of these tests and compared. It is shown that the wicking performance of the two ply sample is comparable to that of a theoretical material with the capillary pressure of the hardwood ply but the permeability of the softwood ply. Wicking in two-ply samples was also observed in an NMR apparatus. This was used to determine that the hardwood ply leads during wicking, and observe the rate of saturation as well as bulk expansion. A third type of experiment tracked the transport of dyed water from one ply to the other, establishing the direction of fluid transport during wicking to be from the softwood ply to the hardwood ply. The theory is proposed, based on these results, that wicking in this type of material consists of a smaller pored leading ply that draws water from a more permeable larger pored material that acts as a moving reservoir.
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Maldonado-Zepeda, Cuauhtemoc. "The effect of interlayers on dissimilar friction weld properties." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ59028.pdf.
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Chan, Ray Tai-Chi. "Modelling of beach profile evolution for dissimilar sized sediments." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286601.
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Bible, Timothy N., and Sean M. Hevey. "Transforming army general purpose forces for simultaneous dissimilar operations." Thesis, Monterey, California. Naval Postgraduate School, 2008. http://hdl.handle.net/10945/3794.
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Approved for public release; distribution is unlimitedPreparedness for operations in both the Irregular Warfare (IW) and Major Combat Operations (MCO) environments is essential given a tumultuous and unpredictable Contemporary Operational Environment (COE). This thesis is an effort to provide a solution to the U.S. Army's emerging trend toward uni-focused operations fixated on IW. In this thesis, we propose recommendations for change to the current Army force structure centered on the Brigade Combat Team (BCT) and the Army Force Generation (ARFORGEN) model through which these units are cycled for refit, training, and deployment. These recommended modifications are intended to optimize the Army for its role as a deterrent force, and to assist the Army in its ability to proficiently conduct operations in the IW and MCO environments either consecutively or simultaneously.
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Long, Eric J. "Cost valuation: a model for comparing dissimilar aircraft platforms." Monterey, California. Naval Postgraduate School, 2006. http://hdl.handle.net/10945/10086.
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MBA Professional ReportThe purpose of this MBA Project was to investigate and provide an overview of current cost valuation methods used to compare aircraft and then determine if the current methods were satisfactory for comparing dissimilar aircraft platforms. The goal of the project was to develop a model using OandS and procurement cost inputs together with aircraft inventory and utilization data in order to produce a cost per unit hour for any given aircraft. A demonstration of the modelb2ss validity using aircraft and cost data from the Predator UAV and the F-16 was then performed to illustrate how it can be used to aid comparisons of dissimilar aircraft platforms that perform similar missions.
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Rafols, Juan Carlos. "Corrosion of Post-Tensioned Tendons Repaired with Dissimilar Grout." UNF Digital Commons, 2012. http://digitalcommons.unf.edu/etd/354.
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A failure associated with steel corrosion was identified in early 2011 in a bridge external post-tensioned tendon, approximately eight years after construction. Large voids in the grout and pockets of non-homogeneous material were identified. The non-homogeneous grout was characterized by high moisture content, and in most cases, the chloride content was lower than conservative threshold values. The non-homogeneous grout also had high pH and high content of sulfates (approximately in the range of 10,000-ppm). As a result, there was an interest in the study of possible corrosion development in repaired systems in which the affected tendons have been re-grouted with dissimilar grouts. The presence of two distinct grouting materials, manifested by the existing/simulated base grout and a newly introduced repair grout, provided the dissimilar grout condition studied. Corrosion activity was monitored in un-stressed mock up assemblies, in sections retrieved from the failed tendon, and in samples immersed in simulated pore solution. Corrosion activity was monitored through macrocell current, linear polarization resistance, open circuit potential, potentiodynamic scans, and electrochemical impedance spectroscopy. Samples in simulated pore solutions were studied at various pH levels and constituent concentrations. All samples were repaired or built with commercially available grouts. After analysis, no evidence of corrosion development was found when both existing and repair grout were free of material deficiencies. Corrosion activity was noted in the presence of nonhomogeneous grout and an increase in rate was observed due to macrocell coupling with sections containing normal grout. Results suggest that early exposure to sulfate to hydroxyl ion ratio as low 0.35 may prevent steel passivation and result in early high corrosion rates. Otherwise, sulfate to hydroxyl ratios as high as three may not be sufficient to initiate corrosion after formation of passive layer.
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Dinsley, Christopher Paul. "Fatigue properties of dissimilar metal laser welded lap joints." Thesis, Sheffield Hallam University, 2004. http://shura.shu.ac.uk/19561/.
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This work involves laser welding austenitic and duplex stainless steel to zinc-coated mild steel, more specifically 1.2mm V1437, which is a Volvo Truck Coiporation rephosphorised mild steel. The work investigates both tensile and lap shear properties of similar and dissimilar metal laser welded butt and lap joints, with the majority of the investigation concentrating on the fatigue properties of dissimilar metal laser welded lap joints. The problems encountered when laser welding zinc-coated steel are addressed and overcome with regard to dissimilar metal lap joints with stainless steel. The result being the production of a set of guidelines for laser welding stainless steel to zinc-coated mild steel. The stages of laser welded lap joint fatigue life are defined and the factors affecting dissimilar metal laser welded lap joint fatigue properties are analysed and determined; the findings suggesting that dissimilar metal lap joint fatigue properties are primarily controlled by the local stress at the internal lap face and the early crack growth rate of the material at the internal lap face. The lap joint rotation, in turn, is controlled by sheet thickness, weld width and interfacial gap. Laser welded lap joint fatigue properties are found to be independent of base material properties, allowing dissimilar metal lap joints to be produced without fatigue failure occurring preferentially in the weaker parent material, irrespective of large base material property differences. The effects of Marangoni flow on the compositions of the laser weld beads are experimentally characterised. The results providing definite proof of the stirring mechanism within the weld pool through the use of speeds maps for chromium and nickel. Keywords: Laser welding, dissimilar metal, Zinc-coated mild steel, Austenitic stainless steel, Duplex stainless steel, Fatigue, Lap joint rotation, Automotive.
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Dolloff, Paul A. "An improved bus protection technique with dissimilar current transformers." Thesis, Virginia Tech, 1995. http://hdl.handle.net/10919/46432.
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Yee, Abigail K. "Using Group Transmissibility Concepts to Compare Dissimilar Vehicle Platforms." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1250525222.
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Kuo, Min. "Dissimilar friction welding of titanium alloys to alloy 718 /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487846354483177.
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Stewart, Jeffrey. "Temper Bead Welding for Dissimilar Metal Welds and Overlays." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574840746589766.
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Reese, Gregory A. "Dissimilar Friction Stir Welding Between Magnesium and Aluminum Alloys." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc955097/.
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Joining two dissimilar metals, specifically Mg and Al alloys, using conventional welding techniques is extraordinarily challenging. Even when these alloys are able to be joined, the weld is littered with defects such as cracks, cavities, and wormholes. The focus of this project was to use friction stir welding to create a defect-free joint between Al 2139 and Mg WE43. The stir tool used in this project, made of H13 tool steel, is of fixed design. The design included an 11 mm scrolled and concave shoulder in addition to a 6 mm length pin comprised of two tapering, threaded re-entrant flutes that promoted and amplified material flow. Upon completion of this project an improved experimental setup process was created as well as successful welds between the two alloys. These successful joints, albeit containing defects, lead to the conclusion that the tool used in project was ill fit to join the Al and Mg alloy plates. This was primarily due to its conical shaped pin instead of the more traditional cylindrical shaped pins. As a result of this aggressive pin design, there was a lack of heat generation towards the bottom of the pin even at higher (800-1000 rpm) rotation speeds. This lack of heat generation prohibited the material from reaching plastic deformation thus preventing the needed material flow to form the defect free joint.
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Clark, John William Gordon. "Investigating chemical and microstructural evolution at dissimilar metal welds." Thesis, University of Nottingham, 2015. http://eprints.nottingham.ac.uk/30664/.
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Dissimilar metal welds (DMWs) are widely used in steam vessels in thermal power stations to join low-temperature alloys, such as steels, to high temperature alloys, such as nickel-based alloys. This provides a cost-effective manufacturing solution. However, there is a history of DMWs failing due to creep in service environments. Many investigations have been performed on weld systems and failures in the traditional 2.25Cr-1Mo (P22) steels, but fewer have been performed on newer 9Cr-1Mo steels, such as P91 and P92. Failures involving these newer steels continue to occur, for reasons which are not thoroughly understood. The factors involved are believed to include system stresses, differences in thermal expansion and microstructural evolution due to interdiffusion across the weld interface. The overall aim of this research was to investigate the chemical and microstructural stability of a range of DMWs involving P91 and P92 steels. Much of the work is centred on a 3-bead manual metal arc weld of nickel alloy 625 onto a P92 substrate. This was subjected to tempering (760 °C for 2 hours) and furnace ageing (625 °C for 32 and 125 days). The as-welded and aged states were characterised by a range of techniques, including SEM, TEM, EDX and microhardness testing. Site-specific TEM samples were extracted from the weld interfaces using focussed ion beam (FIB) methods. EDX measurements show iron-enrichment in the weld metal (WM) up to 30 wt%, and a partially mixed zone (PMZ) up to 50 microns from the weld. TEM analysis of the as-welded state reveals the presence of a 1 – 2 micron wide band separating the two alloys, and of different crystallographic orientation to both. Following ageing, diffusion of carbon takes place from the P92 to the WM, leading to a carbon denuded zone (CDZ) in the former and an enriched zone (CEZ) in the latter. Precipitates in the CDZ (M23C6 and MX) dissolve to supply this diffusion, while Nb-rich MX phases have formed on grain boundaries in the CEZ. Additionally, carbides are found to form along the interface between the band and the P92. EDX measurements confirm that the aged WM is enriched in carbon near the interface. Microhardness measurements reveal slight softening of the P92 in response to ageing, and pronounced hardening of the WM. The thermodynamics of the alloys were modelled using the software Thermo-Calc, while diffusion across the interface was modelled using DICTRA. The findings support the trends of the experimental results in terms of diffusion behaviour and phase changes. An industrial case study, ex-service P91 – alloy 625 pressure vessel welds exposed to c. 565 °C for c. 40,000 hours, has also been undertaken. Creep failure occurred during service near the weld interface. SEM showed that the creep crack tip was advancing through the CDZ. Microstructural changes were similar to those in the P92 – alloy 625 system, only more pronounced; the CDZ was found to be almost entirely devoid of standard M23C6 and MX precipitates, having been replaced by a band of carbonitrides (either M23X6 or M6X) of unusual chemistry, parallel to the weld interface. A second industrial case study involved a weld between P91 and P92 steels using the P87 filler metal, recently developed by EPRI, which is designed to minimise interdiffusion. This system, in contrast to those involving alloy 625, shows evidence for only minimal interdiffusion after ageing at 649 °C for 131 days, with no CDZ being observed. These observations are supported by Thermo-Calc and DICTRA calculations. Therefore, systems of this type may be resistant to creep failure in long-term service.
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Hevey, Sean M. Bible Timothy N. "Transforming army general purpose forces for simultaneous dissimilar operations." Monterey, Calif. : Naval Postgraduate School, 2008. http://edocs.nps.edu/npspubs/scholarly/theses/2008/Dec/08Dec%5FHevey.pdf.
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Thesis (M.S. in Defense Analysis)--Naval Postgraduate School, December 2008.Thesis Advisor(s): Gustaitis, Peter. "December 2008." Description based on title screen as viewed on January 30, 2009. Includes bibliographical references (p. 89-91). Also available in print.
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Dolloff, Paul D. "An improved bus protection technique with dissimilar current transformers /." This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-12302008-063159/.
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Mani?oba, Robson Hebraico Cipriano. "Estudo do acoplamento entre superf?cies seletivas de frequ?ncia assim?tricas em estruturas de multicamadas." Universidade Federal do Rio Grande do Norte, 2012. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15185.
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Previous issue date: 2012-06-18Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
This work presents the development of new microwaves structures, filters and high gain antenna, through the cascading of frequency selective surfaces, which uses fractals D?rer and Minkowski patches as elements, addition of an element obtained from the combination of the other two simple the cross dipole and the square spiral. Frequency selective surfaces (FSS) includes a large area of Telecommunications and have been widely used due to its low cost, low weight and ability to integrate with others microwaves circuits. They re especially important in several applications, such as airplane, antennas systems, radomes, rockets, missiles, etc. FSS applications in high frequency ranges have been investigated, as well as applications of cascading structures or multi-layer, and active FSS. In this work, we present results for simulated and measured transmission characteristics of cascaded structures (multilayer), aiming to investigate the behavior of the operation in terms of bandwidth, one of the major problems presented by frequency selective surfaces. Comparisons are made with simulated results, obtained using commercial software such as Ansoft DesignerTM v3 and measured results in the laboratory. Finally, some suggestions are presented for future works on this subject
Este trabalho apresenta o desenvolvimento de novas estruturas de micro-ondas, filtros multi-banda ou banda larga, atrav?s do cascateamento de superf?cies seletivas em frequ?ncia, que usa patches fractais de D?rer pentagonal e Minkowski como elementos, al?m de um elemento obtido a partir da combina??o de outros dois mais simples que s?o o dipolo em cruz e a espira quadrada. Superf?cies seletivas em frequ?ncia (FSS) abrangem uma grande ?rea das Telecomunica??es e t?m sido largamente utilizadas devido a seu baixo custo, peso reduzido e possibilidade de se integrar com outros circuitos de micro-ondas. Elas s?o especialmente importantes em diversas aplica??es, como avi?es, sistemas de antenas, radomes, foguetes, m?sseis, etc. Aplica??es de FSS em faixas de frequ?ncia elevadas t?m sido investigadas, assim como aplica??es destas estruturas em cascata ou multicamadas, FSS ativas. Nesse trabalho, s?o apresentados resultados simulados e medidos para as caracter?sticas de transmiss?o de estruturas cascateadas (multicamadas), com intuito de investigar o comportamento do funcionamento em termos de largura de banda, um dos grandes problemas apresentados por superf?cies seletivas em frequ?ncia. S?o feitas compara??es entre resultados simulados, obtidos utilizando software comercial como Ansoft DesignerTM v3 e resultados medidos em laborat?rio. S?o apresentadas, ainda, sugest?es de continuidade do trabalho
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CAMARGO, MARIA SILVIA DE SOUZA. "MILK OF THE DOG: NOVEL EXPERIENCES FROM SIMILARS AND DISSIMILARS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=34145@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
O romance Leite de Cadela trata de momentos-chave na vida de uma família, narrados sob o ponto de vista de seus quatro membros. A trama começa com um acidente sofrido pelo pai e a partir daí, mãe e dois filhos se debatem em torno de temas como doença e saúde; educação e infância; experiência e teoria; medicina tradicional e alternativa. Para constituir-se como dissertação acadêmica, os capítulos do romance são interrompidos e comentados por dezenove ensaios breves. Estes integram o trabalho fazendo jogo de afinidades e contrastes, semelhanças e estranhamento com o enredo desdobrado, de modo a iluminar aspectos, na maioria secundários, mas que discutem questões do cotidiano atual. No diálogo da ficção com os miniensaios, evocam-se experiências da autora quando jornalista, como observadora crítica de cinema, teatro, literatura e artigos de informação científica. Busca-se trazer a encenação ficcional, centrada na medicina homeopática para um confronto com tensões e impasses característicos do presente.
The novel Milk of the Dog deals with key-moments in the life of a family, narrated from the point-of-view of its four members. The plot begins with an accident, suffered by the father, and the resulting struggles of the mother and her two children. The story explores the reality of theory vs. experience in issues like health, illness, education, childhood, medicine and therapy. To support the dissertation, the chapters are interrupted and commented on, in nineteen brief essays. They mirror the fiction by reflecting affinities and contrasts, similarities and differences with the unfolding plot. The essays illuminate mostly secondary aspects, but urgent contemporary questions. In the dialogue between fiction and essay, the author s experiences as a journalist and critic are examined, as well as observations about movies, plays, literature and scientific information. We seek to bring fiction, centered on homeopathic therapy, into juxtaposition with currentday tensions and obstacles.
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Peck, Jackson. "Design Factors in Laser Driven Impact Welding." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1556879640891786.
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Barros, Isabel Ferreira de. "Soldagem dissimilar do aço inoxidável ferrítico AISI 444 e do aço inoxidável austenítico AISI 316L por meio do processo TIG autógeno utilizando corrente pulsada." reponame:Repositório Institucional da UFC, 2014. http://www.repositorio.ufc.br/handle/riufc/11959.
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BARROS, I. F. Soldagem dissimilar do aço inoxidável ferrítico AISI 444 e do aço inoxidável austenítico AISI 316L por meio do processo TIG autógeno utilizando corrente pulsada. 2014. 197 f. Dissertação (Mestrado em Ciências de Materiais) – Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2014.Submitted by Marlene Sousa (mmarlene@ufc.br) on 2015-05-08T16:03:35Z No. of bitstreams: 1 2014_dis_ifbarros.pdf: 11649143 bytes, checksum: f4e6ad321a3ef82f5badd87ce9859e52 (MD5)
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The use of stainless steels has intensified with the industrial demand growing, which extends its application for various sectors such as the oil and gas, desalination equipment in industry, sugar industry, among others. In that context, the use of ferritic stainless steels has grown in recent years on account of its excellent relationship between corrosion resistance and cost, and a great option in substitution of austenitic stainless steels. Intending to study the connection of dissimilar stainless steels by means of a welding process, this paper will lay the submit the ferritic stainless steel AISI 444 and AISI 316L austenitic stainless steel with TIG welding autogenous (without filler metal) with pulsed current. That union seeks to get a fused zone with better mechanical properties together with the correction of possible related to welding those steels problems, such as grain growth in ferritic steels, to which its refinement is possible through the use of pulsed current during the procedure. The choice of these two materials was based on the characteristics of each one separately for they possess closest properties, despite having different classifications, allowing the combined use of both, and thus ferritic act in order to partially replace the austenitic stainless steel in situations where the combination of high corrosion resistance and mechanical strength are not relevant. That action combined, and does not affect the characteristics of the set of negative way is to use lower cost benefit, because the presence of nickel austenitic stainless steels by more expensive finishes them. Thus, it is expected to provide, through this work, further deepening the respect of dissimilar welding between stainless steel AISI 444 ferritic and austenitic stainless steel AISI 316L, evaluating operational parameters such as the pulse of current and heat input on obtained microstructure and mechanical properties
A utilização dos aços inoxidáveis tem se intensificado juntamente com a crescente demanda industrial, em que sua aplicação se estende pelos mais variados setores, como por exemplo, na indústria de petróleo e gás, em equipamentos de dessalinização, na indústria sucroalcooleira, entre outros. Neste contexto, o uso de aços inoxidáveis ferríticos tem crescido nos últimos anos devido a sua excelente relação entre resistência à corrosão e custo, sendo uma ótima opção em substituição aos aços inoxidáveis austeníticos. Objetivando estudar a união de aços inoxidáveis dissimilares por meio de um processo de soldagem, o presente trabalho submeterá o aço inoxidável ferrítico AISI 444 e o aço inoxidável austenítico AISI 316L à soldagem TIG autógeno (sem metal de adição) com corrente pulsada. Essa união visa obter uma zona fundida com melhores propriedades mecânicas juntamente com a correção dos possíveis problemas relacionado à soldagem desses aços, como por exemplo, o crescimento de grão nos aços inoxidáveis ferríticos, em que seu refinamento se torna possível através da utilização de corrente pulsada durante o procedimento. A escolha desses dois materiais baseou-se nas características inerentes a cada um separadamente e também por possuírem propriedades muito próximas, apesar de possuírem classificações diferentes, permitindo a utilização combinada de ambos e dessa forma o aço inoxidável ferrítico atuará de forma a substituir parcialmente o aço inoxidável austenítico nas situações em que a combinação de elevada resistência à corrosão e resistência mecânica não são tão relevantes. Essa utilização combinada, além de não afetar as características do conjunto de maneira negativa tem como benefício reduzir custos, visto que a presença de níquel nos aços inoxidáveis austeníticos acaba por encarecê-los. Dessa forma, espera-se fornecer através deste trabalho um maior aprofundamento a respeito da soldagem dissimilar entre o aço inoxidável ferrítico AISI 444 e o aço inoxidável austenítico AISI 316L, avaliando os parâmetros operacionais, como a pulsação da corrente e a energia de soldagem sobre a microestrutura obtida, bem como as propriedades mecânicas