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Cho, Min Hyun. "Numerical simulation of arc welding process and its application." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1155741113.
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Nekouie, Esfahani Mohammadreza. "Laser welding of dissimilar carbon steel to stainless steel 316L." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/19760.
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Laser welding of metals and alloys is extensively used in industry due to its advantages of controlled heating, narrow weld bead, low heat affected zone (HAZ) and its ability to weld a wide range of metals and dissimilar metals. Laser welding of dissimilar metals such as carbon steels and stainless steel is still a challenging task, particularly due to the formation of brittle phases in the weld, martensitic formation in the HAZ and solidification cracking in the fusion zone. These issues can significantly deteriorate the strength of the welded joint. The aim of this work is to investigate the fundamental phenomena that occur inside the dissimilar weld zone and their effect on weld quality. In order to establish the key process variables, an initial study concentrated on the effect of different laser process parameters on dissimilar weld quality. In the second part of the work, a comprehensive study was performed to understand and subsequently control the alloying composition in laser dissimilar welding of austenitic stainless steel and low carbon steel. A dissimilar weld that is predominantly austenitic and homogeneous was obtained by controlling the melt pool dynamics through specific point energy and beam alignment. The significance of dilution and alloying elements on joint strength was established. A coupled CFD and FEM numerical model was developed to assist in understanding the melt pool dynamics and transportation processes of alloying elements. The model has been validated by a series of laser welding experiments using various levels of specific point energy. The laser welding characteristics in terms of geometric dimensions, surface morphology, alloying concentration, and dilution, were compared, and it is concluded that the specific point energy and laser beam position are the key parameters that can be controlled to obtain a weld bead with characteristics most suitable for industrial applications. In the third part of the work, a comparative study was performed to understand the significance of cooling rate, and alloying composition on the microstructure and phase structure of the dissimilar weld zone. Results show that the HAZ within the high carbon steel has significantly higher hardness than the weld area, which severely undermines the weld quality. A new heat treatment strategy was proposed based on the results of the numerical simulation, and it is shown to control the brittle phase formation in HAZ of high carbon steel. A series of experiments was performed to verify the developed thermo-metallurgical FEA model and a good qualitative agreement of the predicted martensitic phase distribution is shown to exist. Although this work is presented in the context of dissimilar laser welding of mild steel to stainless steel, the concept is applicable to any dissimilar fusion welding process.
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Evdokimov, Anton [Verfasser]. "Numerical laser welding simulation of dissimilar Steel-Aluminum overlap joints / Anton Evdokimov." Düren : Shaker, 2020. http://d-nb.info/122416816X/34.
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Wu, Tong Combescure Alain. "Experiment and numerical simulation of welding induced damage stainless steel 15-5PH /." Villeurbanne : Doc'INSA, 2008. http://docinsa.insa-lyon.fr/these/pont.php?id=wu.
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Wu, Tong. "Experiment and numerical simulation of welding induced damage : stainless steel 15-5PH." Lyon, INSA, 2007. http://theses.insa-lyon.fr/publication/2007ISAL0091/these.pdf.
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The objective of this study is the prediction of damage and residual stresses induced by hot processing which leads to phase transformation in martensitic stainless steel. This study firstly concerns the modelling of the damage of material induced by a complex history of thermoelastoplastic multiphase in heat-affected-zone (HAZ) of welding. In this work, a two-scale mode of elastoplastic damage multiphase was developed in the framework of thermodynamatics of irreversible process. The constitutive equations are coupling with ductile damage, elasoplasticity, phase transformation, and transformation plasticity. The experiments of 15-5PH were implemented for the identification of phase transformation, transformation plasticity and damage models. Tests of flat notched specimen were designed to provide the validation of damage model and strain localization using three dimensional image correlation technologies. In addition, microscopic analysis was performed to provide microstructure characterization of 15-5PH and to discover the damage mechanism. Finally the numerical simulation was performed in the code CAST3M® of CEA. We used the two-scale model including phase transformation, transformation plasticity and damage to simulate the level of residual stresses of a disk made of 15-5PH metal heated by laser. The internal variables, such as strain, stress, damage, were successfully traced in the simulation of two-scale model. The simulation results showed the transformation plasticity changes the level of residual stresses and should not be negligible; damage decreases about 8 percent peak value of residual stresses on upper surface of diskL’objectif de cette étude est la prédiction du dommage et des contraintes résiduelles induites par des procédés haute température conduisant à une transformation de phase martensitique. On s’est intéressé plus premièrement à la modélisation du dommage induit par une histoire thermomécanique complexe, comme peuvent en produire les Zones Affectées Thermiquement de soudage. Nous proposons dans ce travail un modèle à deux échelles développé dans le cadre de la thermodynamique des processus irréversibles. Les équations de ce modèle couplent plasticité, endommagement, transformation de phase et plasticité de transformation. Nous avons réalisé de nombreux essais sur le 15-5PH en vue de l’identification des transformations de phase et des lois de comportement thermomécaniques. Les essais sur les éprouvettes entaillées ont été conçus pour valider les modèles d’endommagement ainsi que la localisation des déformations en utilisant la stéréo corrélation d’images. Les simulations numériques ont été effectuées avec le code CAST3M du CEA dans lequel nous avons implanté le méso modèle. Nous avons calculé l’état de contraintes résiduelles dans un disque de 15-5PH induites par un chauffage laser. En sus des contraintes, on peut suivre au cours du calcul les variables internes telles que l’endommagement ou les déformations anélastiques. Les simulations montrent que la plasticité de transformation modifie le niveau des contraintes résiduelles et peut ne pas être négligeable. Quand à l’endommagement, celui-ci fait décroître les valeurs maximales de contrainte résiduelles jusqu’à huit pourcent dans les zones les plus sollicitées
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Kiranmayi, Abburi Venkata. "Characterising high energy beam welding in structural steels with numerical simulation and validation." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.683553.
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Welding has been one of the most extensively used joining processes for engineering applications and is the most frequently used process in nuclear power plants. Welding involves complex thermal, mechanical and metallurgical phenomena, affecting the microstructure of the material and generating internal or residual stresses and distortions in the process. Residual stresses are locked up stresses resulting from the thermal and/or mechanical processing of the parts. Residual stresses are inevitable and usually detrimental to the service life of a component often resulting in collapse or total structure failure. Numerous welding techniques have been developed over the past decades with the aim to reduce the residual stresses and enhance the performance of the component. These techniques need to be thoroughly studied and understood before implementing them in actual service. Electron beam welding and laser beam welding are two emerging techniques that are most promising because of many favourable features, including narrow fusion width to depth ratio, high welding speeds and capability to join metals that are dissimilar without any filler material. However to understand the full capability of these methods, it is essential to study the processes and their consequences on the joint. This dissertation presents the development of numerical and experimental approach to analyse electron beam welding and laser beam welding in a modified 9Cr-lMo (P91) butt welded plate. Modified 9Cr-lMo steel is used in nuclear power plants because of its high desirable properties such as strength and creep resistance at high temperatures. A number of simulation procedures using sequentially coupled thermo-mechanical analysis of the welding process are developed to study the welding process and the generation of residual stresses. The model incorporates the sol id-state phase transformation, exhibited by P9l steel during rapid cooling stage, which is the critical factor in the final residual stress field. The finite element models are validated using neutron diffraction measurements. The validated models are then used to study the influence of material properties, hardening models, annealing temperature and the boundary conditions on the final residual stress distribution . Also post-weld heat treatment used for relaxing the residual stresses due to welding is simulated and the extent of relaxation is studied. Uniaxial cross-weld creep tests are conducted on electron-beam welded samples to investigate the creep life. With the experience gained from modelling electron beam welding on P91 plates, an attempt has been made to develop a finite element model to simulate the electron beam welding of dissimilar metal welds in a butt plate made of P91 and AISI 316LN SS steels. The developed model is evaluated based on neutron diffraction experiments. Significant amount of effort has been directed towards developing an accurate and reliable numerical model to simulate the complex phenomena and severe non-linearity associated with welding processes such as temperature dependent material properties, hardening models, boundary conditions and solid-state phase transformation, which is the main purpose of this research. The residual stresses are predicted successfully. It is shown that the major contributor towards the residual stress profile is the volume change associated with the solid-state phase transformation during the cooling stage. Other factors such as temperature dependent thermo-mechanical properties, material hardening properties and boundary conditions have relatively less influence on the residual stresses.
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Lindgren, Lars-Erik. "Deformations and stresses in butt-welding of plates : numerical simulation and experimental verification." Doctoral thesis, Luleå tekniska universitet, Material- och solidmekanik, 1985. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26528.
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Deformation and stresses in butt-welding of plates were studied. The work includes numerical simulation and experimental verification. The simulations were performed by use of the finite element method. Temperature dependence of material properties and phase transformations were considered. A thermo-elastoplastic material model was used. Plane stress conditions were assumed. Automatic butt-welding of plates without backing needs close tolerances of joint geometry. The thermally induced deformations and stresses are of great importance for joint geometry during welding. Therefore the change of gap width in front of the moving arc has been of special interest in these studies. The residual stresses, which may affect inservice behaviour of welded plates, were also calculated and measured. The tack-welds were found to influence the change in gap width in front of the moving arc. A proper tack-welding procedure is important in order to avoid large changes in gap width during butt-welding. The tack-welds should be made as soon after each other as possible. The sequence in which the tack-welds are made also affect the change in gap width. The gap width increased during the last part of the butt-welding in the simulations performed in this work. This increase was larger for wide plates than for narrow plates. Residual stresses close to the weld were large. The effective stress reached the yield limit of the material in the weld line.Godkänd; 1985; 20070424 (ysko)
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Zhang, Kaiwen. "IN-SITU MEASUREMENT AND NUMERICAL SIMULATION OF LINEAR FRICTION WELDING OF Ti-6Al-4V." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1578051567375844.
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Robe, Hugo. "Apports à la compréhension du soudage FSW hétérogène d’alliages d’aluminium par une approche expérimentale et numérique." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEE005/document.
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L’allègement des structures est actuellement un enjeu industriel majeur. L’utilisation de certains alliages d’aluminium couplés à de nouveaux procédés d’assemblages est une bonne réponse à cette problématique. Le procédé de soudage FSW permet notamment la réalisation d’assemblages multi-matériaux en s’affranchissant des problèmes de fusion. Cette étude, réalisée au sein de l’entreprise TRA-C industrie, s’est intéressée plus particulièrement au cas du soudage FSW hétérogène d’alliages d’aluminium des séries 2xxx (Al-Cu-Mg-Ag) et 7xxx (Al-Zn-Mg), dans une large gamme de paramètres industriels. Les caractérisations des assemblages ont pu mettre en avant de fortes hétérogénéités microstructurales et mécaniques au travers des cordons. Ainsi la présence d’une zone faible, adoucie dans la ZAT du côté de l’alliage 7xxx, amène à favoriser la rupture en traction. Une évolution métallurgique importante déclenchée par le cycle thermique généré explique principalement ce phénomène. D’autre part, cette étude expérimentale a été couplée à des travaux de simulation numérique du procédé en configuration homogène. Le modèle éléments finis intègre, pour la première fois, la géométrie réelle et complexe (filetage, facettes, …) de l’outil de soudage utilisé expérimentalement et est couplé à l’utilisation d’une technique de maillage mobile. Cette technique numérique a permis de s’affranchir intégralement des distorsions de mailles conséquentes souvent rencontrées, ainsi que de décrire fidèlement les effets thermomécaniques engendrés par l’outil de soudage. Une étude de sensibilité aux paramètres de soudage ainsi qu’aux matériaux soudés a démontré une excellente corrélation entre les cinétiques thermiques expérimentales et numériques tout en démontrant l’aspect prédictif du modèleThe lightweight structures optimisation is one of the main topics in transportation industry. It can be achieved by optimisation of materials as well as induced assembly process. As a solid-state process, Friction Stir Welding (FSW) allows to produce dissimilar materials joining while avoiding fusion defects. This work focused on the dissimilar welding of aluminium alloys from 2xxx (Al-Cu-Mg-Ag) and 7xxx (Al-Zn-Mg) series in an industrial context. Joints characterizations were conducted at multiple scales to understand parameters impact on material flow, joint morphology, and performances. They have shown large heterogeneities in the microstructure as well as the global and local mechanical behaviour. Whatever the welding parameters used, good mechanical performance has been reached. A specific softened zone has been detected in the 7xxx alloy’s HAZ which caused fracture during transverse tensile test. Significant metallurgical evolution induced by thermal cycles mainly explains these phenomena.On the other hand, simulation works were also conducted to simulate the welding process in similar material configuration. The finite elements model integrates, for the first time, the real and complex tool design (thread, flats…). Complex geometry can be used by coupling with a specific moving mesh technique. This numerical development completely overcomes the consequent mesh distortion often encountered in FSW simulation. The current model presents good sensitivity and robustness for several welding conditions and materials. It also demonstrates an excellent correlation between experimental and numerical thermal fields while revealing the predictive aspect of the model
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Ehlen, Georg [Verfasser]. "Transient Numerical Simulation of Complex Convection Effects during Solidification in Casting and Welding / Georg Ehlen." Aachen : Shaker, 2004. http://d-nb.info/1170537685/34.
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Kaars, Jonny, Peter Mayr, and Kurt Koppe. "Determining Material Data for Welding Simulation of Presshardened Steel." MDPI AG, 2018. https://monarch.qucosa.de/id/qucosa%3A31829.
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In automotive body-in-white production, presshardened 22MnB5 steel is the most widely used ultra-high-strength steel grade. Welding is the most important faying technique for this steel type, as other faying technologies often cannot deliver the same strength-to-cost ratio. In order to conduct precise numerical simulations of the welding process, flow stress curves and thermophysical properties from room temperature up to the melting point are required. Sheet metal parts made out of 22MnB5 are welded in a presshardened, that is, martensitic state. On the contrary, only flow stress curves for soft annealed or austenitized 22MnB5 are available in the literature. Available physical material data does not cover the required temperature range or is not available at all. This work provides experimentally determined hot-flow stress curves for rapid heating of 22MnB5 from the martensitic state. The data is complemented by a comprehensive set of thermophysical data of 22MnB5 between room temperature and melting. Materials simulation methods as well as a critical literature review were employed to obtain sound thermophysical data. A comparison of the numerically computed nugget growth curve in spot welding with experimental welding results ensures the validity of the hot-flow stress curves and thermophysical data presented.
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Pavlyk, Vitaliy [Verfasser]. "Modelling and Direct Numerical Simulation of Dendritic Structures under Solidification Conditions during Fusion Welding / Vitaliy Pavlyk." Aachen : Shaker, 2004. http://d-nb.info/1170545319/34.
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Noori, Rahim Abadi Seyyed Mohammad Ali. "Investigation of Melt Pool Thermo-hydrodynamic Behaviour inLaser Beam Welding ofTi-6Al-4V through Numerical Simulation." Licentiate thesis, Högskolan Väst, Avdelningen för svetsteknologi (SV), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-17410.
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Laser is an efficient and widely used heat source in metal processing suchas welding and additive manufacturing. It has some great advantages compared to the other conventional heat sources like electron beam and arc namely: ability of handling complicated joint geometries and producing large components. Laser beam welding encompasses many complex physical phenomena such asheat transfer, metal melting, flow and solidification, free surface deformation, evaporation and possibly vaporization. The aim of this research work istwo-fold: gain deeper process understanding and improve the model reliability. Deeper process understanding is sought on the effect of beam shaping on themelt pool. To achieve improved model reliability, a good support consists in using qualitative experimental data representing the process. Thus, 3D validation of the melt pool geometry is performed while it was usually 2D inprevious research works. Furthermore, a new calculation procedure for laser absorption is introduced. To conduct this research work, a Computational Fluid Dynamics approach is used. A solver, capable of tracking the deformation of the melt free surface, is developed in OpenFOAM. Concerning beam shaping, it is found that not only the melt pool size as previously known but also the melt flow pattern is modified through elongating the beam shape.This last result could not be revealed by former studies as the non-transparent media hinders optical observation. New in-process quantitative measurements performed by a project partner are used to test the model. Weaknesses of the former absorptivity models are highlighted, as well as the limitations of the proposed model. Finally, the results show that the proposed absorptivity model function of local surface conditions leads to much better agreement with experimental results compared to the former constant absorptivity model. The maximum discrepancy compared to the experimental measurement, which is observed for the melt pool depth, can indeed be reduced to about 10%.Laser är en effektiv och allmänt använd värmekälla vid svetsning och additiv tillverkning. Den har några viktiga fördelar jämfört med andra konventionella värmekällor såsom elektronstråle och elektrisk ljusbåge, nämligen: den kan ofta användas till komplicerade svetsgeometrier, och den kan producera stora komponenter. Lasersvetsning involverar olika sammansatta fysikaliska fenomen såsom värmeöverföring, metallsmältning, flöde, stelning, ytdeformation, avdunstning och i vissa fall förångning. Syftet med mitt forskningsarbete är tvåfaldigt: att få en djupare processförståelse och att förbättra modellens tillförlitlighet. Fördjupad processförståelse eftersträvades för att förstå hur formen på laserstrålen påverkar svetssmältan. För att uppnå förbättrad modellsäkerhet behövs experimentella data av hög kvalitet som representerar processen. Således utfördes 3D-validering av smältgeometrin medan det vanligtvis var 2D i tidigare forskningsarbeten. Dessutom har en ny modell för laserabsorption föreslagits. I forskningen har numerisk strömningssimulering (Computational Fluid Dynamics) använts för att simulera processen och en numerisk lösare, som kan spåra deformationen av den rörliga smälta ytan, är utveckladi programvaran OpenFOAM. Beträffande laserstrålens utbredning visar resultaten att svetssmältans storlek och även svetssmältansflöde modifieras genom att laserstråleformen förlängs. Medan den förra är känd från tidigare experimentella studier upptäcktes den senare inte före denna studie eftersomdet icke-transparenta mediet hindrar optisk observation. Nya (in-process) kvantitativa mätningar utförda av en projektpartner har använts för att testa modellerna. Svagheter i den tidigare absorptionsmodellen framhävdes, liksom begränsningarna i den föreslagna modellen. Slutligen visade resultaten att den föreslagna modellen där laserabsorptionen är en funktion av lokala ytförhållanden ledde till en bättre overensstämmelse med mätningar jämfört med den tidigare modellen med konstant laserabsorbtion. Den maximala avvikelsen jämfört med experimentell mätning, som observerades med avseende på smältbassängsdjupet, kunde reduceras till cirka 10%.
Till licentiatuppsats hör 2 inskickade artiklar, som inte visas nu.
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NAKAMURA, Takashi, 達也 長谷川, Tatsuya HASEGAWA, 雄一郎 高井, Yuichiro TAKAI, 晋太郎 土井, Shintaro DOI, 隆. 中村, 知宏 前田, and Tomohiro MAEDA. "レーザによる熱可塑性プラスチックのラップ接合 (第3報, 数値シミュレーションによる接合条件の検討)." 日本機械学会, 2002. http://hdl.handle.net/2237/9093.
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Ahn, Joseph. "Experimental characterisation and numerical simulation of fibre laser welding of AA 2024-T3 and Ti-6Al-4V." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/53827.
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The aircraft industry has long recognised the importance of climate protection and the benefits of reducing weight for the production of cost effective and fuel efficient aircraft structures. Fibre laser welding provides advantages over conventional riveting, mainly in terms of weight reduction and time saving. However, significant changes in microstructure, metallurgical state and associated mechanical properties occur in welded joints. Such changes can result in residual stresses, distortions and defects formation in the welded structure, thus significantly influencing the performance and service life. In order to maintain structural integrity of welded structures, the relationship between welding process and performance of the structure needs to be fully assessed. In this thesis, comprehensive relationships between materials, welding process, microstructure and mechanical properties of welded joints were established. Welding parameters including power density, laser power, welding speed, focal position, filler metal feed rate and shielding gas composition were optimised to produce high quality full penetration welds. Solidification cracking was found to be a critical issue in AA 2024-T3 when welding without filler metal. The addition of filler metal reduced its crack sensitivity but it was also necessary to provide the optimum feed rate to avoid welding defects and keyhole instability. Sufficiently high laser power and low welding speed were required for full penetration and also to minimise welding defects. Both argon and helium shielding gases were found to be effective since only weakly ionised laser induced vapour plume was formed rather than strongly ionised plasma. Softening in AA204-T3 deteriorated the plastic straining capacity of the weld due to confined plasticity development within the weld. A poor weld quality resulted in a mixed mode of brittle and ductile failure and contained micro porosities and hot cracks, whereas, a good weld quality led to a ductile mode with significantly less welding defects. In the case of Ti-6Al-4V, the strength was the greatest in the weld as a result of martensitic microstructure formed during fast cooling rates. Local plastic deformation was the lowest in the weld and therefore, failed in the parent material but at the cost of reduced ductility relative to the unwelded parent tensile specimens. The residual stresses and distortions due to time dependent and localised heating imposed during fibre laser welding were numerically simulated with thermal and mechanical boundary conditions integrated in the finite element models including post weld heat treatment, mechanical stress relieving treatment and various clamping arrangements. Mechanical boundary conditions had relatively small influence on residual stresses in thin sheets of butt welded specimens, whereas, greater restraints led to higher residual stresses and lower restraints led to lower residual stresses in T-joint specimens. Non-isothermal diffusional and diffusionless phase transformations in Ti-6Al-4V were modelled and their influence on residual stresses and distortions was examined. Phase transformations only had a small influence on the magnitude and distribution of residual stresses and distortions because the level of internal stresses due to phase transformation remained low unlike other materials which exhibit greater differences in the specific volumes between phases. Post weld heat treatment (PWHT) induced diffusional phase transformations via decomposition of martensite into α. It also decreased the magnitude of y stresses to the yield strength of Ti-6Al-4V at the treatment temperature by releasing the locked-in stresses. Mechanical stress relieving was also studied for reducing residual stresses and distortions, by means of plastic deformation applied during as well as after welding. When the load reached more than 50% of its yield strength, the stresses became compressive. Residual stresses were experimentally measured using X-ray and neutron diffraction techniques They were found to be dependent on the crystallographic hkl plane due to the presence of microscopic stresses. In the case of Ti-6Al-4V, the reflections were weak and only few times larger than the background due its highly incoherent cross-section. In addition, texture in Ti-6Al-4V weld also contributed to lower intensity counts observed during measurements. As a result, only certain peaks were detected in certain orientations. The Y residual stresses in the welding direction were very high but not as high as the yield strength of the material at room temperature for both AA 2024-T3 and Ti-6Al-4V. They were largely tensile in nature only within the weld and tended to be weakly compressive in the rest of the specimen. Comparative analyses between experimental and numerical results showed good agreements, proving the robustness of the finite element models.
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Vaněk, Mojmír. "Predikce deformací svarových spojů pomocí počítačové simulace." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230286.
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In this master’s thesis there are set down dependencies of distortion of T-joints on the size of heat input and welding speed. Dependencies were found for single- and double-fillet welds, for single- and multiple-pass welding. The computer simulations were carried out in programs Visual-Weld and SYSWELD. The size of the melted zones, stress fields, material structure and hardness of the weld specimens were specified. Simulation results were compared with experimentally detected values.
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Hanna, Farah. "A thermo-metallurgical-mechanical model for the numerical simulation of multipass GTA welding of martensitic X10CrMoVNb9-1 steel." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066416/document.
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En raison de sa stabilité microstructurale l'acier martensitique 'X10CrMoVNb9-1' est considéré comme un des candidats pour plusieurs futurs composants des réacteurs à hautes températures 'Very High Temperature Reactor' (VHTR). Ces épais composants (200 mm) sont assemblés par soudage TIG multi-passe. Ce procédé de soudage génère des cycles thermiques et thermomécaniques complexes au niveau de la Zone Affectée Thermiquement (ZAT). Cette thèse est la suite de celle de G.-M. Roux. Ce travail de six ans a pour but de prédire l'état microstructural après soudage dans la ZAT. G.-M. Roux a déjà développé une première version d'un modèle Thermo-Métallurgico-Mécanique (TMM) et a été validée en termes de contraintes résiduelles sur des essais de soudage simples mono-passe. Dans cette thèse une nouvelle version du modèle TMM est proposée, permettant d'améliorer les prévisions en termes de l'état microstructural post soudage dans la ZAT, et les contraintes résiduelles engendrées par l'opération de soudage.Cette thèse s¿appuie sur une approche de modélisation fine des transformations de phases, à savoir la modélisation de la transformation matériau de base - austénite lors d'un chargement anisotherme complexe, la modélisation de la transformation austénite - martensite et finalement la modélisation du revenu de la martensite. Sans oublier la caractérisation du comportement mécanique de chaque phase et l'étude du comportement multi-phasique. La simulation numérique avec le code éléments finis Cast3M de plusieurs procédés de soudage permet de comparer les modèles aux résultats expérimentauxDue to its microstructural stability, the martensitic steel 'X10CrMoVNb9-1 is considered a candidate for several future high temperatures reactor components. These thick components (200 mm) are assembled by GTA multi-pass welding. This welding process generates complex thermal and thermomechanical cycles in the Heat Affected Zone (HAZ). This thesis is following that of G.-M. Roux. This work of 6 years aims to predict the microstructural state after welding in the HAZ. A first version of a Thermo-Metallurgical-Mechanical model (TMM) has been developed and validated in terms of residual stresses on single-pass welding simple tests. In this thesis a new version of the TMM model is proposed to improve the forecasts in terms of the microstructural state and residual stresses post welding in the HAZ. The main improvements of this model TMM its capabilities to take into account the successive heating and cooling cycles, characterizing the multi-pass welding process. This thesis is based on a detailed modeling approach for phase transformations, namely modeling the transformation base material - austenite during anisothermal complex loadings, modeling transformation austenite - martensite and finally the martensite tempering modeling. Not to mention the characterization of the mechanical behavior of each phase and the study of multiphase behavior. Numerical simulation with the finite element code Cast3M of several welding processes was used to compare models with experimental results
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Karki, Utsab. "Experimental and Numerical Study of High-Speed Friction Stir Spot Welding of Advanced High-Strength Steel." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5521.
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With the desire to lighten the frame while keeping or increasing the strength, Advanced High-Strength Steels (AHSS) have been developed for use in the automotive industry. AHSS meet many vehicle functional requirements because of their excellent strength and acceptable ductility. But joining AHSS is a challenge, because weldability is lower than that of mild steels. Friction stir spot welding (FSSW) is a solid state joining process that can provide a solution to the weldability issues in AHSS, but FSSW has not been studied in great detail for this application. In this work, Si3N4 tools were used for FSSW experiments on DP 980 steel with 1.2mm thickness. Joint strength was measured by lap shear tension testing, while thermocouples were used for the temperature measurements. A finite element model was developed in order to predict material flow and temperatures associated with FSSW. Since a 3D model of the process is very time consuming, a novel 2D model was developed for this study. An updated Lagrangian scheme was employed to predict the flow of sheet material, subjected to the boundary conditions of the fixed backing plate and descending rotating tool. Heat generation by friction was computed by including the rotational velocity component from the tool in the thermal boundary conditions. Material flow was calculated from a velocity field while an isotropic, viscoplastic Norton-Hoff law was used to compute the material flow stress as a function of temperature, strain and strain rate. Shear stress at the tool/sheet interface was computed using the viscoplastic friction law. The model predicted welding temperatures to within 4% of the experiments. The welding loads were significantly over predicted. Comparison with a 3D model of FSSW showed that frictional heating and the proportion of total heat generated by friction were similar. The position of the joint interface was reasonably well predicted compared to experiment.
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Locatelli, Fabio Renck. "Modelagem do campo de temperaturas e distorções de uma junta do tipo T soldada pelo processo GMAW." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/103840.
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O elevado fluxo de calor envolvido no processo de soldagem de componentes favorece o aparecimento de tensões residuais, cujo alívio propicia o surgimento das distorções. Uma vez que essas distorções podem comprometer a utilização dos componentes, tornam-se relevantes pesquisas a respeito dos parâmetros, mensuração e previsão das distorções. Este trabalho tem como objetivo analisar as distorções na soldagem GMAW de uma junta tipo T, através do estudo termoestrutural em um modelo numérico pelo método dos elementos finitos com validação experimental. Para isso, o trabalho foi dividido em duas etapas sequenciais, sendo a primeira destinada à validação do modelo numérico e a segunda à elaboração de casos numéricos para análise. O modelo numérico utiliza elementos finitos tridimensionais para a obtenção do campo de temperaturas e distorções. Para a aplicação do fluxo de calor à peça utilizou-se a equação de Goldak como modelo de aporte de calor na análise térmica transiente. A dependência da temperatura na variação das propriedades físicas e mecânicas dos materiais foi considerada. A parte experimental da primeira etapa permitiu definir duas velocidades de soldagem mantendo a mesma energia do processo, originando dois conjuntos de parâmetros denominados como principais e alternativos. Na segunda etapa foram analisados oito casos, definidos através da combinação de três variáveis: variação da velocidade, sequência de soldagem e tempo de resfriamento entre filetes. O campo de temperaturas transiente é verificado pela medição de temperaturas em oito pontos, enquanto o campo de distorções é verificado utilizando um sistema de medição por coordenadas. Dentre os casos analisados, a menor distorção foi observada no caso 6 (velocidade mais rápida, sequência “vai-volta” e com intervalo de resfriamento) onde a distorção máxima foi de 4,31 mm, enquanto a maior distorção foi apresentada pelo caso 4 (velocidade mais lenta, sequência “vai-vai” e com intervalo de resfriamento) com distorção máxima de 6,41 mm.The high heat flow involved in the component’s welding process favors the appearance of residual stress, which alleviation provides the appearance of distortions. Once these distortions can impair the use of the components, become relevant searches about the parameters, measurement and prediction of distortions. This work aims to analyze the distortions in GMAW welding of a T-type joint, through thermo-structural study in a numerical model by finite element method with experimental validation. For this, the work was divided in two sequential stages, the first aimed to the numerical model’s validation and the second to the development of numerical cases to analysis. The numerical model uses three-dimensional finite elements for obtainment the temperature field and distortions. For the application of heat flow to the part was used the Goldak’s equation as a model of heat input in transient thermal analysis. The temperature dependence in the variation of physical and mechanical properties of the materials was considered. The experimental part of the first stage allowed to define two welding speeds while keeping the same process energy, originating two sets of parameters called principal and alternative. In the second stage, eight cases were analyzed, defined by the combination of three variables: speed variation, sequence of welding and cooling time between fillets. The transient temperature field is checked by measuring temperatures in eight points, while the distortion field is checked using a coordinate measuring system. Among all cases analyzed, the lowest distortion was observed in case 6 (fastest speed, "going-back" sequence and cooling interval) in which the maximum distortion was 4.31 mm, while the largest distortion was presented by the case 4 (slower speed, "go-go" sequence and cooling interval) with maximum distortion of 6.41 mm.
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Awang, Draup Awang Jefri. "Numerical simulation of the structural response of friction stir welded aluminium 2139-T8 alloy subjected to complex loading configurations." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/numerical-simulation-of-the-structural-response-of-friction-stir-welded-aluminium-2139t8-alloy-subjected-to-complex-loading-configurations(a840bd28-102d-4c15-be6c-b4e72631e875).html.
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Friction stir welding (FSW) and aluminium alloy 2139-T8 are currently being considered for use in future military vehicles. However, stringent regulations on weld integrity under extreme loading conditions limit the adoption of new technologies. Moreover, current finite element (FE) based methods do not give reliable predictions of strain distribution in welds, which makes it difficult to assess the performance of structures. Therefore, an extensive research program was carried out to develop a generalised finite element (FE) based methodology to predict the response of welded structures under complex loading configurations. The methodology enables the complex distribution of mechanical properties arising from welding, which is linked to microstructural variation, to be incorporated into a macro scale structural model. The method is general, and is applicable for any heat treatable aluminium alloy under a range of joining processes. To achieve this, the microstructure of 2139-T8 alloy was characterised at a range of length scales, with particular emphasis on the size and distribution of strengthening Omega precipitates. 2139-T8 was subjected to bead on plate FSW to enable characterisation of the effects of processing on the local microstructure. In addition, kinetic data for 2139-T8 was generated, allowing a simple softening model to be developed; this allowed the post-weld strength distribution to be predicted. The model was also used to recreate bulk specimens of 2139-T8 with equivalent local weld microstructure, which was verified by transmission electron microscopy. Material with equivalent microstructure was used to estimate the local mechanical property distributions across the weld, including the initial yield stress and plastic response; the mechanical properties of 2139-T8 are known to be representative of 2139-T84. From observations of this combined data, a methodology was developed to enable the estimation of the complex mechanical property distributions arising during welding. Furthermore, an automated computer program was written to implement the property distributions into FE based models. The methodology was verified using data generated for 2139-T8 and was used to simulate the response of FSW 2139-T8 loaded in uniaxial tension. The simulations were verified experimentally using digital image correlation (DIC) and the methodology was shown to demonstrate increased accuracy and reliability over existing FE methods, with respect to strain predictions. In addition, the method eliminates the need to calibrate the structural model to a particular loading configuration. Theoretically, the models are insensitive to loading and this property was tested by extending the model to simulate the strain distribution of large scale welded panels subject to explosive blast loading. The simulations were verified against blast tests where FSW 2139-T84 panels were subjected to blast loading from the detonation of plastic explosive. The results indicate that the modelling methodology developed is capable of producing accurate and reliable predictions of strain distribution in welded structures under complex loading configurations.
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Zain-ul-abdein, Muhammad. "Experimental investigation and numerical simulation of laser beam welding induced residual stressed and distorsions in AA 6056-T4 sheets for aeronautic application." Lyon, INSA, 2009. http://theses.insa-lyon.fr/publication/2009ISAL0069/these.pdf.
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The effort is made in this work to experimentally measure and numerically simulate the residual stresses and distortions induced by laser beam welding with industrially used thermal and mechanical boundary conditions on the thin sheets of an aluminium alloy AA 6056-T4. Several small scale experiments were carried out with various instrumentations like thermocouples and LVDT sensors, which were used to record the temperatures and displacements during welding, respectively. Infra-red camera was also used to qualify the evolution of weld pool temperature as a function of time. Measurements of in-plane and out-of-plane displacements were achieved by stereo image correlation technique. Micrography was carried out to measure the dimensions of fusion zone. The database so prepared served as benchmark for the validation of numerical simulation results. Thermo-mechanical characterisation of 6056-T4 was also performed in order to identify the material properties to be used during numerical simulation. Finite element (FE) simulations are performed with the commercial FE software Abaqus and the volumetric heat source models with Gaussian distribution of flux are programmed in Fortran. The industrially used thermal and mechanical boundary conditions are integrated in the numerical models. Heat transfer analyses are performed first in order to achieve the required weld pool geometries and temperature fields. Mechanical analyses are performed next so as to predict the distortion and the residual stress state. The material is assumed to follow elasto-plastic and/or elasto-viscoplastic law with isotropic hardening (von Mises plasticity model). The comparative analyses between the experimental and simulation results have shown good agreements. Finally, the residual stress and strain states are evaluated through simulationsCe travail se concentre sur les mesures expérimentales et les simulations numériques des contraintes résiduelles et des distorsions induites par le soudage laser utilisant les conditions aux limites mécaniques et thermiques, appliquées dans le milieu industriel sur des plaques minces d’un alliage d'aluminium AA 6056-T4. Plusieurs expériences de petites échelles ont été réalisées avec différents instruments, comme des thermocouples et des capteurs LVDT qui ont été utilisés pour enregistrer, respectivement, les températures et les déplacements pendant le soudage. La caméra infrarouge a été aussi utilisée pour qualifier l’évolution de la température de bain fondu en fonction du temps. Les mesures de déplacements dans le plan et hors-plan ont été obtenues par stéréo-corrélation d’images. Une micrographie a été réalisée pour mesurer les dimensions de la zone de fusion. La base de données ainsi préparée a servi de point de référence pour la validation des résultats de simulation numérique. La caractérisation thermomécanique du 6056-T4 est également effectuée pour identifier les propriétés des matériaux à utiliser lors de la simulation numérique. Les simulations par éléments finis sont effectuées avec le logiciel commercial Abaqus et les modèles de source de chaleur volumétrique avec distribution Gaussienne du flux sont programmés en Fortran. Les conditions aux limites thermiques et mécaniques utilisées dans l’industrie sont intégrées aux modèles. Les analyses thermiques sont effectuées en premier pour atteindre la géométrie de zone de fusion et les champs de température souhaitées. Les analyses mécaniques sont effectuées ensuite pour prédire la déformation et l’état de contraintes résiduelles. La loi de comportement du matériau est considérée élasto-plastique / élasto-viscoplastique avec écrouissage isotrope (modèle de plasticité de von Mises). Les analyses comparatives entre les résultats expérimentaux et les simulations présentent une bonne concordance des valeurs. Enfin, les états de contraintes et déformations résiduelles sont évaluées par calcul
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Dinh, Trong Tuan. "Modèles hyper-réduits pour la simulation simplifiée du soudage en substitut de calcul hors d’atteinte." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEM023/document.
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Le soudage multipasse est mis en œuvre pour recharger des tuyauteries présentant localement des sous-épaisseurs. La simulation numérique facilite le choix des nombreux paramètres de soudage. La réduction des modèles permet d'accélérer ces choix. Dans ce travail, nous nous sommes intéressés aux cas pour lesquelles il est difficile de réaliser intégralement la simulation du soudage, faute de temps ou par manque de moyens de calcul. Ce sont des simulations hors d'atteintes. Or, les prévisions manquantes ne permettent pas la mise en œuvre d'une méthode de décomposition orthogonale aux valeurs propres pour extraire une base réduite de modes empiriques à partir des données produites par simulation numérique. Nous proposons donc soit un modèle directionnel bien adapté au soudage, soit une étape d'extrapolation des données de simulations par décalage spatial des prévisions calculées. Ces deux approches sont complémentaires de la méthode d'hyper-réduction, dans laquelle les équations de bilan sont restreintes à un maillage réduit. Ces méthodes permettent de démarrer une simulation numérique du soudage avec un modèle éléments finis, puis de poursuivre cette simulation par un modèle hyper-réduit. Cela évite d'avoir à réaliser de nombreuses études paramétriques et permet de traiter des simulations qui sont hors d'atteintes. Ce mémoire se termine par un chapitre traitant du cas de rechargement d'un tube, pour lequel EDF a mis en œuvre un essai instrumentéMulti-pass welding is used to recharge pipes with local sub-thickness. Numerical simulation facilitates the selection of many welding parameters. Reducing the order of models speeds up these choices. In this work, we were interested in cases where it is difficult to carry out the entire welding simulation due to time constraints or lack of calculation means. These computations are called out of reach simulations. However, the missing forecasts do not allow the implementation of a orthogonal decomposition method to extract a reduced basis of empirical modes from the data produced by numerical simulations. To overcome this difficulty, we propose either a directional model well adapted to welding, or a step of extrapolation of the simulation data by spatial shift of the already calculated forecasts. These two approaches are complementary to the hyper-reduction method, in which the balance equations are restricted to a reduced mesh size. These methods allow to start a numerical simulation of welding with a finite element model, then to continue this simulation with a hyper-reduced model. This avoids the need for numerous preliminary parametric studies and allows simulations that are out of reach. This manuscript ends with a chapter dealing with the case of reloading a tube, for which EDF has carried out an instrumented test
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Gastebois, Sabrina. "Simulation numérique du soudage FSW à l'aide d'une formulation ALE." Thesis, Paris, ENMP, 2015. http://www.theses.fr/2015ENMP0040/document.
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Depuis l'invention du soudage par frottement malaxage (FSW) en 1991 par The Welding Institute (TWI), l'industrie aéronautique envisage de remplacer l'assemblage par rivetage des tôles par ce procédé. L'objectif est d'alléger les structures, plus particulièrement les panneaux des structures d'aéronefs qui sont souvent raidis avec des lisses et des profilés assemblés à la peau extérieure. La qualification du procédé FSW dans l'aéronautique requiert de produire des joints de très haute qualité avec une longue durée de vie des outils. Ceci nécessite un réglage fin des paramètres procédé tels que la géométrie de l'outil (dimensions de l'épaulement et du pion, filetage) et les vitesses d'avance et de rotation. Le but de ce travail est d'accompagner la conception du procédé par la simulation numérique. Il comporte trois parties: (1) le développement de la formulation arbitrairement lagrangienne ou eulérienne (ALE) dans la version parallèle du logiciel Forge® pour l'adapter au FSW, (2) la modélisation du procédé FSW et (3) la calibration du modèle EF et la validation des résultats numériques suite à la réalisation d'essais FSW en configuration par recouvrement.Ce travail est basé sur la formulation ALE parallèle développée dans Forge® afin de modéliser les différents défauts caractéristiques du FSW (bavures et trous). L'algorithme de transport des champs continus, indispensable au caractère eulérien, est affiné afin de considérer les particularités de l'écoulement du procédé (nœud du plan d'entrée, en contact avec l'outil ou dans les bavures et sortant du domaine d'étude). Un nouveau schéma d'intégration temporelle basée sur les coordonnées cylindriques plus adapté à ce procédé fortement rotationnel est introduit. Enfin, un filetage sur l'outil est modélisé par l'introduction d'une nouvelle loi de frottement à l'interface outil / matière.Cette formulation ALE générale et parallèle a montré sa robustesse pour modéliser le procédé FSW. Les résultats thermomécaniques sont en accord avec de précédents résultats validés par l'expérience. De plus l'outil numérique obtenu a montré ses capacités pour la modélisation des bavures ou des pertes de contact derrière le pion.Finalement la configuration de soudage par recouvrement industrielle a été étudiée. Pour cela des essais expérimentaux ont été réalisés pour divers paramètres du procédé et divers types de joints de recouvrement. Puis les mesures de forces et du couple dans l'outil et de la température dans l'outil et la tôle ont permis de calibrer les paramètres du modèle (frottement, loi de comportement, coefficients thermiques) et de valider les résultats EFSince the invention of Friction Stir Welding (FSW) in 1991 by The Welding Institute (TWI), aeronautics industry has been investigating the possibility to use this process instead of riveting with the objective to lighten its structures and more particularly the aircrafts structure panels. Aircraft panels are often straightened with stringers and profiles which are joined to the outer skin. The qualification of FSW process in aeronautics requires producing very high quality joints with the longevity of tools, which requires fine tuning of process parameters such as the geometry of the welding tool (shoulder and pin dimensions, threads on pin and shoulder) and the advancing and rotating speeds. The aim of this work is to support the design of the process by numerical simulation. It has three parts: (1) developing an efficient and accurate Arbitrary Lagrangian or Eulerian (ALE) formulation within the parallel version of Forge® software, (2) modelling the FSW process and (3) calibrating the F.E. model and validating simulation results thanks to FSW experiments on lap joints.This work is based on the parallel ALE formulation developed in Forge® to model the different possible defects taking place in FSW (flashes and worm holes). The transport algorithm of continuous fields, required by the Eulerian frame, is enhanced to take the special characteristics of the FSW's flow into account (nodes located in input plan or flashes or in contact with the tool). A new time integration scheme based on cylindrical coordinates, which are best suited for this process, is introduced. Finally, the pin and shoulder threads are modelled by introducing a new friction law at the tool / material interface.This general and parallel ALE formulation is robust enough to model the FSW process. Thermomechanical results obtained are in agreement with previous results validated by experiences. And the numerical tool demonstrated its ability to model flashes formation and losses of contact behind the pin. Finally industrial welding lap joints configuration was studied. Experimental tests were conducted with several process parameters and type of lap joint. And measure of torque and forces in tool, and temperature in tool and sheet metal allowed to calibrate model parameters (friction, behavior law, thermal coefficients) and to validate FE results
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Richter, Tomáš. "Svařování rotorových materiálů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230289.
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Master’s thesis titled Welding of turbine rotor materials discusses evaluation of welding parameters by numerical simulation in software SYSWELD and Visual - WELD. Base material 23 CrMoNiWV 8-8 is welded by submerged arc welding technology. Used flux is F 26G and electrode is flux-cored wire TOPCORE 838 B. Material structures, hardness, values of residual stresses and distortion of weldment for this process are calculated by using the numerical analysis.
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Vaněk, Mojmír. "Vývoj modelů chování Al slitin pro aplikace v numerických simulacích svařování a tepelného zpracování." Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-364598.
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The thesis deals with methodology for computational approaches for numerical simulations of welding and heat treatment of aluminium alloys. The thesis describes improvement of the current methodology for metallurgical part of the numerical analysis of welding, which is important mainly for prediction of dimensions of the heat affected zone (and deformations). The improvement was carried out based on CHD diagram that describes precipitation and dissolution of phases during continuous heating. The thesis also describes carried material measurements (measurement of chemical composition, dilatometric tests, tensile tests of several conditions of materials at temperatures up to 500 °C and measurement of aging curves), which allowed to significantly refine analysis results for the alloys EN AW-5083 and EN AW-6082. Based on an evaluation of the measurements, several conclusions were made. They can be useful for creation of material databases of other aluminium alloys. The thesis also describes quantification of dependence between tensile strength and yield strength on the Vickers hardness for different conditions of EN AW-6082. There is also methodology for numerical simulation of the heat treatment process of heat treatable Al alloys in the dissertation. The methodology is completely new approach which has never been published so far. Application of this method is based on user changes of the material database in software Sysweld after relatively easy measurement of aging curves. Therefore, the methodology can be considered as promising for application in industrial practice.
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Graf, Marcel, Sebastian Härtel, and André Hälsig. "Numerische Auslegung des Mehrlagenschweißens als additives Fertigungsverfahren." Universitätsbibliothek Chemnitz, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-225946.
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Die additiven Fertigungstechnologien erleben seit einigen Jahren einen enormen Zuspruch bei der Herstellung von Einzelteilserien mit komplexen, endkonturnahen Geometrien und der Verarbeitung von Sonder- oder hybriden Werkstoffen. Prinzipiell lassen sich die Verfahren gemäß VDI- Richtlinie 3404 in drahtbasierte und pulverbasierte unterteilen. Eine weitere Unterteilung erfolgt hinsichtlich der Ausschmelztechnologie. Allen Verfahren ist gleich, dass schichtweise der Grundwerkstoff an den Stellen aufgetragen wird, wo er gemäß Endkontur benötigt wird. Damit ist ein immer wiederkehrender Wärmeeintrag verbunden, der somit Einfluss auf die Mikrostruktur der Bauteile und gleichzeitig auch auf die mechanischen Endeigenschaften ausübt. Die so erzeugten Komponenten sollten wenig Verzug oder Eigenspannungen als auch keine Porosität aufweisen, um die Gebrauchseigenschaften nicht negativ zu beeinflussen. Das Ziel ist es mittlerweile, diese verschiedenen Technologien numerisch abzubilden, um die Bauteileigenschaften vorherzusagen und ggf. Optimierungspotenziale zu eruieren.
Der untersuchte Prozess ist das drahtbasierte Mehrlagenschweißen mittels des Metallschutzgasschweißens, bei dem neben der Simulation auch die Validierung im Fokus hinsichtlich Geometrie und Gefügeausbildung in den Schweißlagen stand. Diesbezüglich wurden im vorliegenden Fall zum einen alle, für die numerische Simulation notwendigen Materialparameter (mechanische und thermophysikalische Kenngrößen) des Schweißzusatzwerkstoffes G4Si1 bestimmt und in ein kommerzielles FEM-Programm (MSC Marc Mentat) implementiert. Zum anderen erfolgt zukünftig die wissenschaftliche Analyse der Verbesserung der Bauteileigenschaft, in dem die Schweißnaht unter Ausnutzung der Schweißhitze warmumgeformt wird. Erste Ergebnisse numerischer Simulationsergebnisse zeigen positive Effekte. Diese zeigen mikrostrukturelle Veränderungen (Kornfeinung durch Rekristallisation) und führten letztendlich zur Steigerung der mechanischen Eigenschaften. Der Vorteil dieser Verfahrenskombination ist außerdem die Kompensation des Verzuges durch die gezielte Umformung und einem gleichzeitigen „Richten“.
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Tirand, Guillaume. "Etude des conditions de soudage laser d'alliages à base aluminium par voie expérimentale et à l'aide d'une simulation numérique." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14482/document.
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Le développement du soudage laser dans divers secteurs industriels particulièrement dans l’aéronautique au cours de la dernière décennie, a nécessité bien des études encore insuffisantes en nombre pour bien comprendre et contrôler les conditions de soudage laser que ce soit au niveau interaction laser/matière, au niveau des transferts thermiques ou au niveau métallurgique. La démarche suivie dans cette étude consiste (1) à mettre en évidence expérimentalement la problématique du soudage laser d’alliage base aluminium, c'est-à-dire le couplage des effets entre les différents paramètres de soudage, (2) à décrire l’histoire thermique d’une opération de soudage laser à partir d’une modélisation et d’une simulation numérique et (3) à exploiter la connaissance de l’évolution thermique d’un assemblage encours de soudage pour optimiser les performances mécaniques de l’assemblage en terme de résistance statique, de résistance à la fissuration à chaud, de tenue à la fatigue et de résistance à la corrosion. Les déficits de performance par exemple en terme de résistance sont principalement attribuable à des vitesses de refroidissement trop faibles au cours du soudage comparativement à des trempes ce qui justifie l’efficacité d’un traitement de mise en solution post soudage préalablement à un traitement de durcissement par précipitationThe development of laser welding in various branches of industry particularly in the aeronautics during the last decade, required many studies still insufficient in number to understand and control the conditions of laser welding concerning laser / material interaction,as well as thermal transfers or metallurgical aspects. The approach followed in this study consists (1) to bring to light experimentally the problem of laser welding of aluminium based alloy, that is the coupling of the effects between the various welding parameters, (2) to describe the thermal history of an operation of laser welding from a modelling and from a numerical simulation and (3) to exploit the knowledge of the thermal evolution of an assembly all along welding operation to optimize the mechanical performance of the assembly in term of static resistance, resistance to hot cracking, fatigue and corrosion resistance. The deficit of performance for example in term of tensile resistance is mainly related to too low speeds of cooling during welding compared with quenching. It justifies the efficiency of a post welding solution heat treatment before a precipitation hardening treatment
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Timesli, Abdelaziz. "Simulation du soudage par friction et malaxage à l'aide de méthodes sans maillage." Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0111/document.
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Le procédé de soudage par friction et malaxage est un procédé récent qui a été développé au sein de l'institut de soudure britannique "The Welding Institute" au début des années 90. Ce procédé, utilisé généralement en aéronautique, est sans apport de matière et permet de souder principalement des alliages d'aluminium difficilement soudables par les procédés classiques de soudage. Il consiste à malaxer le matériau de base à l'aide d'un outil constitué d'un pion et d'un épaulement frottant sur les faces supérieures des tôles à souder. La modélisation de ce procédé est très complexe puisque ce dernier implique des couplages entre des phénomènes mécaniques, thermiques et métallurgiques. Le malaxage dans le procédé de soudage FSW est difficile à simuler à l'aide de la méthode des éléments finis (en lagrangien) puisque la zone proche de l'outil de soudage est le siège de grandes déformations. Donc le remaillage est nécessaire. Cependant, le remaillage est cher et très difficile pour les problèmes tridimensionnels. Par ailleurs, après un remaillage, il est nécessaire d'interpoler les champs (vitesses, contraintes,...) correspondant à la solution courante, ce qui peut introduire des erreurs supplémentaires dans le calcul (on parle de diffusion numérique). Nous proposons dans ce travail des modèles basés sur la méthode sans maillage dite "Smoothed Particle Hydrodynamics SPH" et la méthode des moindres carrés mobiles (Moving Least Square MLS) pour la simulation de ce procédé. Ces modèles sont formulés dans le cadre lagrangien et utilisent la forme forte des équations aux dérivées partielles. Le premier modèle basé sur SPH considère la zone de soudure comme un fluide non newtonien faiblement compressible et dont la viscosité dépend de la température. Ce modèle est proposé pour la simulation numérique du comportement thermomécanique d'un matériau soudé par le procédé FSW. Dans le deuxième modèle, un algorithme itératif implicite de premier ordre a été proposé, pour simuler le malaxage de la matière dans le cas d'un matériau viscoplastique, en utilisant la méthode MLS et la technique de collocation. Le troisième modèle est un algorithme implicite d'ordre élevé basée sur le couplage de la méthode MLS et la Méthode Asymptotique Numérique MAN. Cet algorithme permet de réduire le temps de calcul par rapport à l'algorithme itératif implicite de premier ordre. La validation de ces trois modèles proposés a été faite par le code industriel FluentFriction stir welding is a recent process that has been developed by the British Welding Institute TWI "The Welding Institute" since 1990s. This process, generally used in aerospace, does not need additional material and allows mainly joining plates of aluminum alloys which are difficult to weld by the classical welding processes. It consists in mixing the base material using a tool comprising a pin and a shoulder which heats the plates to be welded by friction. The modeling of this process is very complex since it involves the coupling between mechanical, thermal and metallurgical phenomena. The mixing in welding process FSW is difficult to simulate using finite element method in lagrangian framework since the area near the welding tool is submitted to large deformations. So remeshing procedure is often required. However, remeshing can be very expensive and difficult to perform for three-dimensional problems. Moreover, after remeshing step, it is necessary to interpolate the fields (velocities, constraints ...) corresponding to the current solution, which may lead to additional errors in the calculation (called numerical diffusion). We propose in this work models based on meshless methods called "Smoothed Particle Hydrodynamics SPH" and Moving Least Square method for the simulation of this welding process. These models are formulated in lagrangian framework and use the strong form of partial differential equations. The first model based on SPH considers the welding zone as a weakly compressible non-newtonian fluid and whose viscosity depends on the temperature. This model is proposed for the numerical simulation of thermo-mechanical behavior of a welded material by FSW process. The second model is a first order implicit iterative algorithm proposed to simulate material mixing in the case a visco-plastic behavior using the MLS method and the collocation technique. The third model is a high order implicit algorithm based on the coupling of MLS method and Asymptotic Numerical Method (ANM). This algorithm allows reducing the computation time by comparison with the first order implicit iterative algorithm. The validation of these three proposed models was done by the industrial code Fluent
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Mackwood, Andrew. "Numerical simulations of thermal processes and welding." Thesis, University of Essex, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272572.
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Bezerra, Alexandre Campos. "Simulação numérica da soldagem com aplicação à caracterização do comportamento dinâmico de estruturas soldadas." Universidade Federal de Uberlândia, 2006. https://repositorio.ufu.br/handle/123456789/14774.
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Fundação de Amparo a Pesquisa do Estado de Minas GeraisNowadays, welded structures are widely employed in engineering design. Generally, these structures have internal stresses (residual stresses) generated by the thermal cycle to which these parts are submitted during welding process. In many cases, these stresses are not minimized by means of thermal treatment. Thus, one must take into account the residual stresses in the design of welded components. However, computation of residual stress field is not an easy task and, besides, it is important to evaluate the quality of welded components. Therefore, by using the advantage of the fact that the stress state influences the mechanical behavior of components and structures (stress stiffening effect), it was proposed to evaluate the viability of a methodology to control the quality of welded components, by means of dynamic responses. This way, it was verified experimentally the sensitivity of vibrating natural frequencies to welding residual stress in different structures. It was confirmed that thin structures are more sensitive to the stress stiffening effect. To evaluate this effect numerically, a procedure to simulate welding was validated by using experimental data from literature. This procedure was used to obtain the residual stress field. This stress field is included in a modal analysis to verify the modifications of natural frequencies. Numerical results were compared to experimental results obtained here, showing a good agreement. It was also proposed to use the electromechanic impedance technique to evaluate the stress stiffening effect. An analysis of the results shows the possibility of use the stress stiffening effect to implement a methodology for quality control of welded components.
Atualmente, estruturas soldadas encontram-se amplamente aplicadas em projetos de engenharia. Normalmente, estas estruturas apresentam tensões internas (residuais) devidas ao ciclo térmico ao qual são submetidas durante a soldagem. Em muitos casos, estas tensões não são minimizadas por meio de tratamento térmico, havendo assim a necessidade de inclusão destas em projeto. Entretanto, a determinação do campo de tensões residuais não é tarefa fácil e, no caso de uma produção em série, é importante avaliar a qualidade do componente confeccionado. Sendo assim, aproveitando o bem conhecido fato de o comportamento mecânico de componentes e estruturas sofrer influência do estado de tensão (enrijecimento por tensão), propõe-se avaliar a viabilidade de uma metodologia de controle de qualidade de peças soldadas por meio de respostas dinâmicas. Desta forma foi verificada experimentalmente a sensibilidade das freqüências naturais de vibração ao estado de tensões residuais de soldagem em diferentes estruturas. Confirmou-se que estruturas esbeltas são mais sensíveis ao enrijecimento por tensões residuais de soldagem. Com a finalidade de avaliar este efeito numericamente, um procedimento para simulação da soldagem foi validado utilizando-se dados experimentais da literatura. Na seqüência, utilizou-se tal procedimento para, após a determinação das tensões residuais de soldagem, realizar uma análise modal e avaliar as alterações nas freqüências naturais de vibração (e conseqüentemente o efeito do enrijecimento por tensão). Os resultados numéricos foram confrontados com os resultados experimentais obtidos neste trabalho, apresentando uma boa concordância. Finalizando o trabalho, propõe-se utilizar a técnica da impedância eletromecânica para avaliar o enrijecimento por tensão. Uma avaliação dos resultados mostra ser possível utilizar o enrijecimento por tensão para implementar uma metodologia para controle de qualidade de componentes soldados.
Doutor em Engenharia Mecânica
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Nguyen, Minh Chien. "Modélisation et simulation multiphysique du bain de fusion en soudage à l'arc TIG." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM4749/document.
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Au cours de ce travail, un modèle physique et numérique 3D du procédé de soudage à l’arc TIG (Tungsten Inert Gas) a été développé dans l’objectif de prédire, en fonction des paramètres opératoires, les grandeurs utiles au concepteur d’assemblages soudés.Le modèle développé, à l’aide du code de calcul aux éléments finis Cast3M, traite les phénomènes physiques agissant dans la pièce et, plus particulièrement, dans le bain de soudage, l’arc étant traité comme une source. Pour ce faire, les équations non-linéaires de la thermohydraulique couplées à celles de l’électromagnétisme sont résolues en régime stationnaire avec un modèle prenant en compte la surface libre déformable du bain de soudage.Une première étape du développement a porté sur la modélisation des phénomènes électromagnétiques par deux méthodes numériques différentes, à comparer les résultats numériques obtenus avec ceux de la littérature. Ensuite, afin de valider le pouvoir prédictif du modèle, des simulations de différentes configurations de soudage d’intérêt ont été étudiées, en variant la composition chimique du matériau, la vitesse de défilement, la pression d’arc imposée et, plus particulièrement, la position de soudage. Des comparaisons avec des expériences et des modèles numériques de la littérature confirment les bonnes tendances obtenues. Enfin, une approche de la modélisation de l’apport de matière a été abordée et des résultats de cette approche ont été montrés. Notre modèle complet constitue donc une base solide pour le développement de modèles de simulation numérique du soudage (SNS) 3D totalement couplés avec l’arc dans le futur et sera intégré dans le logiciel métier WPROCESSIn this work, we develop a 3D physical and numerical model of the GTA (gas tungsten arc) welding process in order to predict, for given welding parameters, useful quantities for the designer of welded assembly.The model is developed in the Cast3M finite element software and takes into account the main physical phenomena acting in the workpiece and particularly in the weld pool, subject to source terms modeling the arc part of the welding process. A steady solution of this model is thought for and involves the coupling of the nonlinear thermohydaulics and electromagnetic equations together with the displacement of the deformable free surface of the weld pool.A first step in the development consisted in modeling the electromagnetic phenomena with two different numerical methods, in comparing the numerical results obtained with those of the literature. Then, in order to assess the predictive capability of the model, simulations of various welding configurations are performed : variation in the chemical composition of the material, of the welding speed, of the prescribed arc pressure and of the welding positions, which is a focus of this work, are studied. A good agreement is obtained between the results of our model and other experimental and numerical results of the literature. Eventually, a model accounting for metal filling is proposed and its results are discussed. Thus, our complete model can be seen as a solid foundation towards future totally-coupled 3D welding models including the arc and it will be included in the WPROCESS software dedicated to the numerical simulation of welding
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Le, Gloannec Brendan. "Modifications microstructurales sous sollicitations thermomécaniques sévères : application au soudage par résistance des gaines de combustibles en aciers ODS." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0367/document.
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Les aciers renforcés par dispersion d’oxydes (ODS) sont des matériaux candidats pourconstituer les gaines de combustibles des réacteurs nucléaires de IVème génération refroidis au sodium(RNR-Na). Le soudage par résistance en bout de ces gaines est étudié dans ce travail, avec pourobjectif la détermination et la compréhension des effets du procédé sur l’évolution de la microstructuredes aciers ODS à 9 % et 14 % de chrome à l’échelle des grains et des oxydes nanométriques. Uneapproche couplant caractérisations microstructurales sur soudures, simulation numérique et simulationphysique du procédé, à l’aide d’un simulateur thermomécanique Gleeble 3500, est adoptée. Le soudagepar résistance en bout impose localement des conditions de sollicitations sévères en termes dedéformation, vitesse de déformation et température. Ces sollicitations induisent un affinement de lamicrostructure dont l’origine peut être attribuée à un mécanisme de recristallisation dynamique (acier à14 % de chrome) ou à l’association de la recristallisation dynamique et des transformations de phase(acier à 9 % de chrome). Les conditions d’occurrence de la recristallisation dynamique sont étudiéessur ces matériaux. On montre notamment la possibilité d’une transition entre recristallisation dynamiquecontinue et discontinue sur l’acier à 14 % de chrome en fonction des conditions de sollicitation. Il estégalement observé que ces sollicitations thermomécaniques sévères induisent une augmentation de lataille des oxydes nanométriques associée à une diminution de leur fraction volumiqueOxide dispersion strengthened (ODS) steels are considered as candidate materials for thedevelopment of fuel cladding for sodium-cooled fast reactors (SFR). Resistance upset welding of thecladding is studied in this work. The aim is to determine and to understand the process effects on themicrostructure of ODS steels with 9% and 14% of chromium at the scales of the grains and thenanometric oxides. An approach coupling microstructural characterization of welds, numericalsimulation and physical simulation of the process, using a thermomechanical simulator Gleeble 3500,is proposed. Resistance welding locally imposes severe thermomechanical conditions in terms of strain,strain rate and temperature. Refinement of the microstructure is noted and correspond to a dynamicrecrystallization mechanism (14 % Cr steel) or the combination of dynamic recrystallization and phasetransformations (9 % Cr steel). The conditions of occurrence of dynamic recrystallization are studied.The possibility of a transition between continuous and discontinuous dynamic recrystallization is shownfor the 14 % Cr steel according to the loading conditions. Such severe thermomechanical conditionsinduce an increase in the size of nanoscale oxides associated with a decrease of their volume fraction
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Beaurin, Gauthier. "SIMULATION ET ÉTUDE EXPÉRIMENTALE DES CONTRAINTES RÉSIDUELLES DANS LES DÉPÔTS DURS NOREM DES MATÉRIELS DE ROBINETTERIE." Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00759226.
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L'intégrité des portées d'étanchéité des robinets des centrales REP nécessite l'emploi de revêtements durs comme par exemple le Norem02, base Fe, déposés par soudage PTA (Plasma Transfered Arc). La prédiction de leur tenue en service nécessite la connaissance de leur état mécanique en fin de fabrication. Pour cela, la simulation numérique du procédé de dépôt doit être effectuée. La microstructure du Norem02 est essentiellement constituée d'une matrice austénitique parsemée d'ilôts de ferrite et de carbures. Son évolution et ses éventuelles transformations allotropiques sont étudiées durant des cycles thermiques représentatifs de ceux subis par le matériau au cours du dépôt, amenant à la conclusion que l'évolution métallurgique de l'alliage n'a que très peu d'influence sur ses propriétés mécaniques. En s'appuyant sur des essais jusqu'à 1000°C de dilatométrie libre, de traction isotherme, ainsi que de traction-compression, l'évolution des caractéristiques thermomécaniques est déterminée en fonction de la température et une loi de comportement élasto-plastique à écrouissage cinématique non linéaire est identifiée. Des mesures expérimentales de températures, déplacements, déformations et contraintes résiduelles lors d'essais de dépôt PTA sur des maquettes représentatives de la géométrie réelle d'un robinet permettent l'identification d'un chargement thermique équivalent. Enfin, des simulations numériques sont conduites en utilisant le code éléments finis développé au sein d'EDF R&D Code_Aster. Elles permettent la validation du caractère prédictif des modèles développés par comparaison entre les résultats mécaniques simulés et expérimentaux. Une excellente corrélation est ainsi observée entre les températures mesurées et simulées tout au long du procédé. De la même façon, à l'issue du refroidissement, les distorsions, déformations et contraintes résiduelles expérimentales et simulées sont en adéquation, validant ainsi la stratégie de modélisation proposée dans ces travaux.
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Guedoiri, Ammar. "Contribution à la modélisation et à la simulation numérique du soudage par friction et malaxage." Phd thesis, Paris, ENSAM, 2012. http://pastel.archives-ouvertes.fr/pastel-00842393.
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Le soudage par friction malaxage " Friction Stir Welding " est un procédé d'assemblage de pièces en phase semi solide. Le cordon de soudure est obtenu grâce à un outil de révolution composé d'un épaulement et d'un pion. Ce procédé utilise le principe de la conversion de l'énergie mécanique en énergie thermique par frottement de l'outil avec les pièces à assembler. Ce travail de thèse est une contribution à la modélisation expérimentale et à la simulation numérique de ce procédé permettant de fournir des modèles pour aider à la compréhension des phénomènes thermiques et mécaniques ainsi que les interactions entre les paramètres de soudage. Les études expérimentales sont principalement orientées vers la caractérisation de l'écoulement de matière à l'aide de marqueurs et vers l'optimisation des paramètres du procédé. L'effet de la géométrie de l'outil (outil à pion cylindrique ou outil avec méplats) sur l'écoulement de la matière au cours du soudage est étudié. Pour représenter la géométrie de l'écoulement et prédire les champs thermiques et mécaniques à l'état stationnaire, des modèles formulés sur la base de la dynamique des fluides sont adoptés dans la présente thèse. Deux modèles thermomécaniques sont développés: (1) un premier modèle numérique construit sous Fluent permet d'étudier le comportement thermomécanique et l'écoulement au cours du soudage FSW. Une loi de comportement dépendante de la température et de la vitesse de déformation est utilisée et une discussion sur les conditions de contact entre l'outil et les plaques à souder est présentée. Les résultats de l'écoulement sont comparés avec ceux obtenus expérimentalement dans le cas de suivi des trajectoires de particules de cuivre. (2) un deuxième modèle original basé sur une procédure itérative est mis en œuvre permettant le soudage de plaque de grandes dimensions. En effet, pour une meilleure prise en compte des conditions aux limites thermiques, un modèle thermomécanique construit autour de l'outil de soudage et couplé avec un modèle thermique pour tout le reste du domaine étudié. Ce modèle permet de prendre en compte le transfert de chaleur dans l'outil et dans la plaque support. Les cycles thermiques et la plage de viscosité pour deux alliages d'aluminium (AA7020-T6 et AA6061-T3) sont analysés et comparés avec succès aux résultats expérimentaux. Les efforts et le couple de soudage calculés numériquement sont validés par rapport à la littérature.
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Seang, Chansopheak. "Evaluation numérique des contraintes résiduelles appliquée à l'acier DP600 soudé par laser de haute puissance Nd : YAG." Phd thesis, INSA de Rennes, 2013. http://tel.archives-ouvertes.fr/tel-00875121.
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Les études sur les procédés de soudage et sur la fiabilité des structures assemblées apparaissent actuellement comme un domaine de recherche actif, ouvert et complexe, car elles nécessitent de combiner de nombreuses connaissances dans différents domaines de la physique, de la mécanique et des procédés. La distribution des contraintes résiduelles joue un rôle important dans la vie des structures en favorisant la rupture par fatigue ou par fissuration. Ainsi, une meilleure compréhension des contraintes résiduelles évite l'utilisation de facteurs de sécurité plus élevés et, par conséquent permet de mieux optimiser le cycle de vie des structures soudées. A travers ce travail de thèse, nous nous sommes intéressés au soudage par laser d'un acier dual phase DP600, soudé en configuration par recouvrement, dont l'application est l'utilisation dans le domaine automobile. Cette thèse présente deux volets : un volet expérimental et un volet numérique.L'étude expérimentale nous a permis d'une part d'appréhender les conséquences métallurgiques et mécaniques du procédé laser sur l'acier DP600 et d'autre part d'utiliser et de valider les résultats numériques des modèles développés. L'étude numérique a eu pour objectif de prédire l'histoire thermique, métallurgique et l'évolution des caractéristiques mécaniques des tôles soudées par faisceau laser. Nous avons développé, sur un code de calcul par élémentsfinis Abaqus, trois modèles numériques. Le modèle thermomécanique, nous a permis de simuler la distribution spatio-temporelle de la température. Dans ce cas, le chargement appliqué est dépendant des paramètres du procédé etdes caractéristiques du faisceau laser et est associé à des conditions aux limites. Pour le modèle mécanique, nous avonsconsidéré un comportement élasto-plastique avec un chargement thermique transitoire, résultat du modèle thermique.Le deuxième modèle thermo-métallurgique nous a permis de simuler les phénomènes d'austénisation pendant la phase de chauffage (modèle de Waeckel) et de prendre en compte les fractions volumiques des phases martensitiques générées par les transformations de phases austénite-martensite lors du refroidissement (modèle de Koistinen-Marburger). Enfin, dans la dernière partie de simulation, nous avons réalisé le couplage thermo-metallo-mécanique. Les résultats obtenus dans la partie précédente, ont été implémentés dans deux modèles mécaniques : le modèle mécanique classique et le modèle mécanique avec prise en compte de la déformation liée aux effets de dilatation métallurgique. Cet effet a été intégré à travers le coefficient de dilatation thermique des phases ferritiques et martensitiques et des fractions volumiques obtenues à partir du modèle thermo-métallurgique. Les résultats ont montré que la répartition des contraintes résiduelles dans la zone de fusion et dans la zone affectée thermiquement sous l'effet de la déformation thermo-métallurgique donne des valeurs supérieures à celles estimées par le modèle élasto-plastique classique.
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Saadlaoui, Yassine. "Simulation numérique des procédés thermomécaniques dans une approche couplant les écoulements du fluide avec les déformations du solide : application au soudage laser et à la fusion d'un lit de poudre." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSES005.
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Dans le cadre de ce travail, des méthodes numériques sont développées afin de simuler le soudage laser et la fusion d’un lit de poudre tout en tenant compte de leur complexité. Ces méthodes se reposent sur une nouvelle stratégie de couplage fluide/solide. Elles permettent de simuler la formation de la zone fondue en tenant compte des écoulements du fluide à travers les deux effets de la tension de surface ("effet de courbure" et "effet Marangoni") et la flottabilité. Une approche ALE est utilisée afin de suivre l’évolution de la surface libre. L’interaction entre les écoulements du fluide dans le bain fondu et les déformations du solide dans le métal de base est assurée en imposant les vitesses du solide au cours du calcul fluide. Plusieurs tests analytiques et numériques sont utilisés afin de valider la formulation du problème fluide et la nouvelle stratégie de couplage fluide/solide. Les résultats montrent l’efficacité et la robustesse des méthodes numériques développées.Comme première application, une simulation thermomécanique du soudage laser est réalisée. Les résultats obtenus montrent une bonne cohérence avec les résultats de la littérature. La deuxième application consiste à simuler la fusion d’un lit de poudre. Elle permet de prendre en compte le retrait de la couche de poudre après fusion et le changement des propriétés thermophysiques en fonction de l’état de matière (poudre ou compact).Si le travail de thèse a consisté principalement à développer des méthodes numériques, il comporte aussi une partie expérimentale. Un montage spécifique a ainsi été réalisé en utilisant différents outils d’instrumentation. Ces outils ont permis dans un premier temps de mieux comprendre les phénomènes physiques mis en jeu par les deux procédés. Dans un deuxième temps, une base de données (morphologie du bain, température et contraintes résiduelles) sur des pièces soudées est constituée. Cette base de données permettra dans un travail ultérieur, de réaliser une démarche de validation globale des méthodes numériques proposéesIn the current study, numerical methods are developed to simulate the laser welding and the melting of a powder bed while taking into account their complexity. These methods are based on a new strategy of fluid/solid coupling. They allow to simulate the formation of the melted zone by taking into account the fluid flows through the two effects of the surface tension ("curvature effect" and "Marangoni effect") and the buoyancy. An ALE approach is used to follow the evolution of the free surface. The interaction between the fluid flows in the molten pool and the deformations in the solid part is ensured by imposing the velocities of the solid nodes during the fluid computation. Several analytical and numerical tests are used to validate the formulation of the fluid problem and the new strategy of fluid/solid coupling. The results confirm the efficiency and the robustness of the numerical methods developed.As first application, a thermal-fluid-mechanical simulation of laser welding is carried out. The results obtained show a good correlation with the literature results. The second application consists of simulating the melting of a powder bed. It allows to take into account the shrinkage of the powder layer after melting, and the change of the thermalphysical properties depending on the material state (powder or compact).Although the study consisted mainly in developing numerical methods, it also includes an experimental part. Specific set-up has been done using different instrumentation tools. These tools allow to better understand the physical phenomena involved during the two processes. In a second step, a database (morphology of molten pool, temperature and residual stresses) on welded parts is constituted. This database will allow in a subsequent work to carry out a global validation process of the proposed numerical methods
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Friedrich, Nils [Verfasser]. "Approach to consider welding residual stresses in fatigue analysis using numerical simulations / Nils Friedrich." Hamburg : Universitätsbibliothek der Technischen Universität Hamburg-Harburg, 2020. http://d-nb.info/1219963631/34.
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Sarre, Benjamin. "Influence du soudage laser Nd˸YAG sur les propriétés métallurgiques et mécaniques de l'alliage de titane TA6V." Thesis, Troyes, 2018. http://www.theses.fr/2018TROY0019.
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Le soudage est une opération consistant à assembler deux ou plusieurs pièces afin d’assurer la continuité d’une structure. Toutefois, l'opération de soudage n'est pas sans conséquence pour le matériau cible. En effet, l'état métallurgique et mécanique de ce dernier est profondément affecté. Cette étude vise à une meilleure compréhension de l'influence du procédé de soudage sur l'état métallurgique et mécanique de l'alliage de titane TA6V. L'état métallurgique de la liaison soudée a été caractérisé. Ces analyses ont mis en évidence un fort gradient de microstructure entre la zone fondue et le métal de base. Ces évolutions engendrent des contraintes résiduelles. Ces dernières ont été évaluées par le biais de la diffraction des rayons X. Une campagne d'essais a été réalisée à l'ESRF (ligne BM02). Les champs de contraintes ont été comparés aux prédictions d'un modèle de comportement mécanique. Les évolutions de microstructure sont également la source d'un gradient de propriétés mécaniques. Le comportement mécanique des liaisons soudées a été étudié. La zone fondue présente des caractéristiques mécaniques supérieures à celles du métal de base. La rupture intervient au sein de ce dernier, malgré la présence de défauts dans la zone fondue. Les résultats ont été comparés au modèle de Gurson-Tvergaard-Needleman. Le modèle permet de restituer de façon très satisfaisante le comportement mécanique des liaisons soudéesWelding operation consists of assembling two or more pieces to ensure the continuity of a structure. The resulting assembly may withstand mechanical loads. However, the welding operation modifies the state of materials. In other words, the metallurgical and mechanical behaviour of the latter is deeply affected. This work aims to better understand the influence of welding on the metallurgical and mechanical behavior of the Ti-6Al-4V titanium alloy. Comprehensive metallurgical analyses of the welded joint are carried out and reveal a sharp and strong microstructure gradient between the fusion zone and the base metal. Several residual stress fields are quantified by X-ray diffraction analyzes. Those residual stress fields are then compared with finite element simulations of the welding of a Ti-6Al-4V titanium alloy. The simulation are based on a weakly coupled model that accounts for temperature, stresses and phase transformations. The failure behaviour of the welded joint is studied. An overmatch was highlighted with mechanical tests. The fracture finally occurs in the base metal despite the presence of defects in the fusion zone. A Gurson-Tvergaard-Needleman approach is carried on. The mechanical parameters are quantified from mechanical tests on homogeneous samples of base metal and of a representative microstructure of the welded joint, which has been obtained from heat treatments. The model are in good agreement with mechanical tests
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Dohnal, Ivo. "Numerická simulace svařování lopatky a rotoru turbíny." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2010. http://www.nusl.cz/ntk/nusl-229216.
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Numeric simulation welding of the turbine vane and rotor - master’s thesis is ordered by the Siemens Industrial Turbomachinery ltd. company. Simulation welding is done in program SYSWELD. Used welding materials are X22CrMoV12-1 (turbine vane), 30CrMoNiV5-11 (rotor), TOPCORE 838 B (additional material). These are temperature-resistant and fire-resistant welding materials. The SYSWELD program works on the principle of finite elements method. By SYSWELD is done the evaluation of temperature and stress fields and material structure after welding. Here is a part , which deals with computations of welding crevices.
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Silva, Miguel Castro. "Numerical simulation of strains and stresses in welding." Master's thesis, 2020. http://hdl.handle.net/10773/31335.
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Welding is one of the best known methods in the industry for joining a wide variety of materials. This process inevitably creates stresses and strains in the components due to the high energy intensity released by the heat source. Nowadays it is almost mandatory to quantify these changes in the parts that go through the welding process. This is the only way to comply with strict quality parameters ensuring that the part fulfils the assigned function. It is very common to use experimental methods to do this analysis. However, the use of computational methods in welding process simulation was being increasing significantly. Numerical simulation, based on the Finite Element Method, appears to make it easier for engineers to predict and analyse complex phenomena.
In this work two numerical simulation models of the welding process by laser were developed on Dual-Phase 600 steel plates. Two types of joints were tested: butt and in T. The deformations and stresses caused were quantified using the Simufact software.A soldadura é dos métodos mais conhecidos na indústria para unir uma grande variedade de materiais. Este processo cria inevitavelmente tensões e deformações nos componentes devido à alta intensidade de energia libertada pela fonte de calor. Nos dias que correm torna-se quase obrigatório quantificar estas alterações nas peças que passam pelo processo de soldadura. Só assim é possível cumprir rigorosos parâmetros de qualidade, garantindo que a peça cumpre a função atribuída. É muito comum recorrer a métodos experimentais para fazer esta análise. No entanto, o uso de métodos computacionais em simulação de processos de soldadura tem crescido significativamente. A simulação numérica, baseada no Método de Elementos Finitos, surge para facilitar aos engenheiros a prevenção e análise de fenómenos complexos. No presente trabalho foram desenvolvidos dois modelos de simulação numérica do processo de soldadura através de laser em chapas de Dual-Phase 600. Foram testados 2 tipos de juntas: topo a topo e em T. As deformações e tensões causadas pelo processo foram quantificadas com recurso ao software Simufact.
Mestrado em Engenharia Mecânica
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Chen, Jin-Syong, and 陳錦雄. "Experimental and Numerical Simulation ofMultilayer Welding on Stern Tube." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/53283900006099999161.
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碩士國立臺灣海洋大學
輪機工程學系
103
Ship propulsion shaft system will vary with the various needs change and causes torsional, compressive and bending stress. Also, the waterway restrictions due to environmental factors, ship has sailing crisis when re- floats as lightheadness causing the stern section fracture. Nowadays the shipyard applies gas metal arc welding method technology, with more eco- nomic effectiveness. The gas metal arc welding method has the advantages of rapid production but the heat leads large welding deformation and stress concentration. As the important part of the ship, the butt welding process must have strict control to guarantee the strength and rigidity. In this thesis, we adopt the finite element analysis to model and predict weld bead temperature, thermal stress and strain and structure deformation. NotonlytheFiniteelementMethodsfindoutthetemperatureproblemsaris- ing from welding, but also avoid welding deformation after welding phe- nomenon. For the construction of various factors on the functioning reg- ularity based on the weld temperature, the stress and strain fields will be fully understand the operation of the welding process and comparison with the experimental model. This model will to maintain accuracy, but also has a great, much computationally efficient, centralized heat welding charac- teristics reflect movement for segmenting process for moving heat source, but the member is actually relatively large structures for the calculation and computationonalargescale,andalsomoredifficulttoachieveconvergence to solve. We use segmented moving heat source model will comparable to the heat source model and thus also the efficiency and accuracy can be achieved consistency. This thesis adopts the inherent-strain method to predict the welding de- formationwithexperimentalmodel. Numericalsimulationofweldinginthe field of general simple welded structure with analytical calculation formula and some experiences formula, welding numerical analogy with a system, flexible features produce the results need to be physical analog modeling verification before a reference to the production line. It will be applied to virtually component production. Keywords: ship propulsion shafting, finite element method, welding deformation, segmented moving heat source model.
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ITOH, Y., and M. HIROHATA. "NUMERICAL SIMULATION OF WELDING DEFORMATION AND RESIDUAL STRESS BY FEM WITH SHELL ELEMENTS." 2013. http://hdl.handle.net/2237/18866.
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"Numerical simulation of welding with application on the dynamic behavior characterization of welded structures." Tese, Biblioteca Digital da Universidade Federal de Uberlândia, 2006. http://www.bdtd.ufu.br//tde_busca/arquivo.php?codArquivo=1050.
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Ho, Hung-Wei, and 何宏瑋. "Numerical Simulation of Rollover Test on Complete Vehicle Considering the Effects of Welding Joints." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/96799827940227069042.
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碩士大葉大學
車輛工程學系碩士班
96
Buses are the high loading capacity transportation on the road. When a major accident happened, the passengers would be serious injury. When a rollover accident of a bus happened, the damage often occurred in the weld zone. For passengers’ safety, the design of superstructure of the bus should consider the weld zone which would affect the strength of a bus rollover accident. From the previous numerical analysis, the weld zone often idealistic assemble at an concurrent way. But those analysis did not account of the effects of welding. This paper adopted nonlinear software LS-DYNA to study the rollover strength of bus. At first, this paper added the failure criteria of both fillet welding and butt welding to the extrusion simulation analysis of a bus frame structure. Then compared the difference with the result of idealistic assemble at concurrent way. The result densely match with the previous experiment which considered welding. The elongation which the weld zone of roof structure failure is only 7.4% different from the previous experiment. The elongation which the weld zone of pillar structure failure is only 3.7% different from the previous experiment. The weld zone of bottom did not failure, so the result of numerical analysis is match with the previous experiment. Secondly, this paper based on the regulation, ECE R66(Economic Commission for Europe), to establish a computer simulation of bus rollover test, and used a certain type of Europe bus to study the effect of both the concur rant and the welding failure. Meanwhile, this paper tested whether the Europe bus is match the ECE R66. The result showed that the finite element model of the ideal concurrent way can absorbed energy due to the stiffer structure. When considering the finite element model of the welding effect, due to the failure criteria, the mechanical behavior is more closer to the actual situation. Also, the result showed that both the concurrent and the welding did not pass the regulation ECE R66. Finally, this paper adopted two common size of pipe, 40mm×80mm×3mm and 60mm×40mm×3mm, to study The different impact on structure strength when using different size of ring cross-section. The result showed that the 40mm×80mm×3mm pipe of bus’s ring could pass regulation ECE R66, and the pipe only increased 7.17% of the overall weight. This paper adopted computer simulation which used on equivalent approval method to do the rollover test on complete vehicle. Due to consider the welding failure, the result of this paper is close to the reality. This paper can provide a reference for the bus manufactory to do future manufacturing and design.
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Silva, Sebastien Guillaume Victor Blanpain da. "Análise térmica e mecânica do processo Friction Stir Welding." Master's thesis, 2019. http://hdl.handle.net/10316/86548.
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Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e TecnologiaA presente dissertação, tem como principal objectivo a análise numérica das condições termomecânicas do processo de soldadura Friction Stir Welding (FSW). Por forma a realizar essa análise, desenvolveram-se dois modelos numéricos, um bidimensional (2D) e outro tridimensional (3D). Aferiu-se a influência do comportamento viscoplástico do material de base nas condições termomecânicas, através da comparação de cinco materiais virtuais distintos, descritos pela lei constitutiva de Norton-Hoff. Avaliou-se também a influência das velocidades de rotação e de avanço da ferramenta nas condições termomecânicas do processo.Os ciclos térmicos, a distribuição da temperatura, o fluxo do material de base e o binário foram analisados na interface entre a ferramenta e o material de base e ao longo da secção transversal do modelo. Deste modo, foi possível relacionar os outputs do processo (temperatura e binário), os parâmetros do processo (velocidades de rotação e avanço da ferramenta) e o comportamento mecânico dos materiais de base.A análise dos resultados permitiu concluir que as condições termomecânicas são fortemente afetadas pelo comportamento mecânico dos materiais de base e pelos parâmetros do processo. De facto, as temperaturas máximas registadas são maioritariamente afetadas pela velocidade de rotação da ferramenta e pelo comportamento mecânico do material de base, enquanto que a velocidade de avanço da ferramenta influencia as taxas de aquecimento e de arrefecimento registadas durante o processo. Verificou-se ainda que as temperaturas máximas mais elevadas resultam em maiores quantidades de fluxo de material devido ao amacimanto do mesmo, e consequentemente, a maiores valores de binário da ferramenta. Também se concluiu que a resistência mecânica dos materiais de base, às temperaturas do processo, tem uma grande influência nas condições termomecânicas do mesmo.
The current dissertation aims the analysis of the thermomechanical conditions during the welding by Friction Stir Welding (FSW) process, using numerical simulation. For this purpose, a two dimensional (2D) and a three dimensional (3D) models were developed. The role of the viscoplastic behaviour of the base material on the thermomechanical conditions was analysed by comparing five distinct virtual materials, described using the Norton-Hoff constitutive law. The influence of tool rotation and welding speeds, on the thermomechanical conditions, were also analysed. Thermal cycles and temperature distribution, on the tool/base material interface and along the model's transverse cross-section, were analysed, as well as the base materials flow and the spindle torque. In this way, it was possible to relate the process outputs (temperature and torque), with the process parameters (tool rotation and welding speeds) and the base materials mechanical behaviour. The results analysis enabled to conclude that the thermomechanical conditions are strongly affected by the base material and the process parameters. In fact, the maximum temperatures registered are mainly governed by the tool rotation speed and the base materials mechanical behaviour, while the welding speed governs the heating and the cooling rates. Higher maximum temperatures lead to higher amounts of material flow due to the material softening, and consequently, to higher spindle torque values. It was also found that the base materials strength, at service temperatures, is the most influencing factor on thermomechanical conditions.
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Loureiro, Tiago José Maia. "Exploring the capabilities of Smoothed Particle Hydrodynamics (SPH) in the simulation of manufacturing processes." Master's thesis, 2019. http://hdl.handle.net/10773/31265.
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Challenging problems of computational mechanics may often be characterized by large deformations that are common in manufacturing processes such as friction stir welding. The finite element method faces difficulties in simulating large deformations, due to severe mesh distortion. Over the last few, years, meshfree methods have been an alternative applied to the studies, pointing a new generation of more effective computational methods for solving more complex problems such as Smoothed Particle Hydrodynamics (SPH). The present work focus on the application of the SPH method on the numerical simulation of the friction welding process, using the Abaqus numerical simulation software. However, Abaqus presents some limitations, since it includes the SPH formulation but with a reduced functionality, not allowing to analyze temperature variations throughout the process. In order to overcome these limitations, several numerical simulations were performed with changes in the material properties according to the analysis temperature, and in the friction coefficient between the work material and the toolProblemas desafiadores da mecânica computacional podem muitas vezes ser caracterizados por grandes deformações em processos de manufactura, tais como a soldadura por fricção, mais conhecido por ”friction stir welding” (FSW). Os métodos mais comuns, como o método de elementos finitos apresentam grande dificuldade na simulação de grandes deformações, devido à severa distorção presente na malha. Nos últimos anos, métodos que não envolvam malha têm sido uma alternativa aplicada a este tipo de problemas, apontando uma nova geração de métodos computacionais mais eficazes para resolver problemas mais complexos, tais como o método ”Smoothed Particle Hydrodynamics” (SPH). O presente trabalho centra-se na aplicação do método SPH na simulação numérica do processo de soldadura por fricção, com resurso ao software de simulação numérica Abaqus. Contudo o Abaqus apresenta algumas limitações, uma vez que inclui a formulação SPH mas com uma funcionalidade reduzida, não permitindo analisar variações de temperaturas ao longo do processo. De maneira a superar estas limitações foram realizadas várias simulações numéricas com alterações das propriedades do material consoante a temperatura de análise, e do coeficiente de atrito entre o material de trabalho e a ferramenta.
Mestrado em Engenharia Mecânica
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Pragosa, Ricardo António Soares. "Simulação Numérica da Soldadura por Impacto de Alumínio-Aço." Master's thesis, 2020. http://hdl.handle.net/10316/92099.
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Dissertação de Mestrado Integrado em Engenharia Mecânica apresentada à Faculdade de Ciências e TecnologiaThe present work aims to study, by numerical simulation, using the commercial hydrodynamic program Ansys Autodyn, the morphology and interfacial phenomena in welding aluminum plates to steel by impact. The effect of the impact velocity and the collision angle on the conditions developed at the plate interface, namely on the formation of the jet, on the formation and morphology of waves, the existence of fusion and the temperature and pressure reached, were considered. The numerical results were compared with experimental results obtained in previous studies. The study focused on the bonding of AA 6061-T6 aluminum to AISI 304 stainless steel and high hardness V250 carbon steel.In the Ansys Autodyn simulation software, the mesh method used to reproduce the formation of jet and wave formation more accurately was the Smoothed Particles Hydrodynamics method. The equation of state chosen for the metal plates was the Mie-Grüneisen shock equation, which was associated with the Steinberg-Guinan behavior model. A total of 50 numerical tests were performed.The Al-SS weldability window revealed that the simulations obtained are generally within the weldability limits, with good welding results and interfaces with well-defined waves. It was found that the ideal pressure to obtain the best results was between 2 GPa and 4 GPa. On the contrary, in the Al-CS weldability window, the results obtained in the simulations were not in line with the weldability limits. The interfaces obtained were, in most cases, flat, due to the high hardness of the steel, being quite difficult to connect the two metals. The pressure close to the interface estimated to provide the best welding results was from 4 GPa to 7 GPa.The numerical and experimental results, when compared, did not show total harmony with regard to the morphology of the interface, mainly due to the difference in hardness of welded metals in both approaches.
O presente trabalho tem como objetivo estudar, por simulação numérica, com recurso ao programa comercial hidrodinâmico Ansys Autodyn, a morfologia e os fenómenos interfaciais em soldadura de chapas de alumínio a aço por impacto. Foi considerado o efeito da velocidade de impacto e do ângulo de colisão nas condições desenvolvidas na interface das placas, nomeadamente na formação do jato, na formação e morfologia de ondas, a existência de fusão e a temperatura e pressão atingidas. Os resultados numéricos foram comparados com resultados experimentais obtidos em trabalhos anteriores. O estudo incidiu na ligação do alumínio AA 6061-T6 ao aço inoxidável AISI 304 e ao aço carbono V250 de elevada dureza.No software de simulação Ansys Autodyn, o método de malha utilizado para reproduzir com maior exatidão a formação de jato e de ondas foi o método Smoothed Particles Hydrodynamics. A equação de estado escolhida para as placas metálicas foi a equação de Shock de Mie-Grüneisen, que foi associada ao modelo de comportamento de Steinberg-Guinan. Foram realizados, no total, cerca de 50 ensaios numéricos.A janela de soldabilidade Al-SS revelou que as simulações obtidas estão, de modo geral, dentro dos limites de soldabilidade, com bons resultados de soldadura e interfaces com ondas bem definidas. Verificou-se que a pressão ideal para obter os melhores resultados situava-se entre os 2 GPa e os 4 GPa. Pelo contrário, na janela de soldabilidade Al-CS, os resultados obtidos nas simulações não estavam em sintonia com os limites de soldabilidade. As interfaces obtidas foram, na maior parte dos casos, planas, devido à elevada dureza do aço, sendo bastante difícil ligar os dois metais. A pressão próxima da interface estimada para proporcionar os melhores resultados de soldadura foi de 4 GPa a 7 GPa.Os resultados numéricos e experimentais, quando comparados, não mostraram total sintonia no que respeita à morfologia da interface, devido essencialmente à diferença de dureza dos metais soldados em ambas as abordagens.
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Tsai, Min-Chun. "Numerical simulations of heat transfer and fluid flow phenomena in gas tungsten arc welding." 1988. http://catalog.hathitrust.org/api/volumes/oclc/20387808.html.
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