The present thesis shows the analysis, calibration, and application of the stress modified criticai strain criterion to predict ductile failure for an A285 steel. To obtain the mechanical behavior of the material, experimental tests were carried out by implementation of 5 different types of geometries: smooth round bar, notched round bar (R=1 , 2, 3 mm), and, deep and shallow cracked SE(B) specimens. Then, for the calibration process of the mechanical properties finite element models were generated, using 30 solid elements with 8 nodes (C308), matching the geometry and the properties of the tested specimens. To calibrate the elastoplastic behavior was used the experimental and numerical response obtained from the smooth and notched round bar specimens; and, for the damage calibration was used the responses obtained from both deep and shallow crack SE(B) specimens. Once the mechanical properties were calibrated, then there were obtained the SMSC criterion factors represented by the equation ..... and, the damage condition which is represented by the displacement at failure (.......) and exponential factor (....). This calibrated model was able to recover the SE(B) experimental responses that validate the use of the characterized material in a complex structure. Then, the fully characterized material was applied in two pipelines which have externai initial circumferential elliptical crack; being the first one pipe with shallow crack and the second one with deep crack. Finally, both pipes were submitted to tension loads to predict the ductile damage behavior, obtaining the necessary load to the crack start growing, and the evolution of the failure. / A presente dissertação apresenta o processo de análise, calibração e aplicação das propriedades mecânicas, incluindo o comportamento elastoplástico e de dano, para o aço A285, utilizando o critério \"Stress modified criticai strain\" (SMCS). Para obter o comportamento mecânico do material, testes experimentais foram realizados com a implementação de 5 tipos diferentes de geometrias: barra cilíndrica sem entalhe, barra cilíndrica com entalhe (R = 1, 2, 3 mm) e corpos de prova SE(B) com trinca inicial profunda e rasa. Para o processo de calibração das propriedades mecânicas foram gerados modelos de elementos finitos, utilizando elementos sólidos 30 com 8 nós (C3D8), que representam de forma adequada a geometria e as propriedades dos corpos de prova testados. Para calibrar o comportamento elastoplástico e iniciação do dano, utilizou-se a resposta experimental e numérica obtida para as amostras de barra cilíndrica com e sem entalhe; e, para a calibração da evolução do dano, foram utilizadas as respostas obtidas para os espécimes SEB de trincas profundas e rasa. Este modelo calibrado foi capaz de recuperar as respostas experimentais dos corpos de prova SE(B), o que valida o uso do material caracterizado em uma estrutura complexa. Uma vez calibradas as propriedades mecânicas, foram obtidos os fatores do critério SMSC representados pela equação ....... , e, a condição de dano que é representada pelo deslocamento na falha .... e o fator de amolecimento exponencial .... . Depois, o material totalmente caracterizado foi aplicado em dois dutos que possuem trinca elíptica circunferencial inicial externa; sendo o primeiro tubo com trinca superficial e o segundo com trinca profunda. Finalmente, ambos os tubos foram submetidos a cargas de tensão para prever o comportamento do dano dúctil, obtendo a carga necessária para o início do crescimento da trinca e a evolução da falha.

De nos jours, la gestion des flux de matière autour de la zone decontact représente un des principaux verrous scientifiques pourl'amélioration des simulations des procédés d'usinage comme, parexemple, le procédé FSW. Les méthodes basées sur la mécanique desmilieux continus sont couramment utilisées dans ces simulations maiselles rencontrent de nombreuses difficultés dans les zones decontact. Une explication "physique" à ces difficultés estl'utilisation des équations issues de la mécanique des milieuxcontinus pour décrire des phénomènes discontinus. À ce point, laméthode des éléments discrets s'est révélée être une alternative auxapproches continues pour traiter le problème causé par cesdiscontinuités. Cette méthode est en revanche très gourmande en termede temps de calcul.Une solution à long terme passe par un couplage entre méthodescontinues et discrètes qui requiert une zone de recouvrement où lesdeux approches coexistent. Cette zone est classiquement placée dansune région continue et cela oblige à développer la méthode deséléments discrets pour qu'elle puisse opérer dans ce type derégion. Le travail de thèse présente une méthode pour simuler laconduction de la chaleur et le comportement mécanique des milieuxcontinus élasto-plastiques. Cette méthode peut travailler dans la zonecontinue de recouvrement et, en plus, elle peut être facilementcouplée avec les méthodes discontinues classiques.Le couplage entre l'aspect thermique et l'aspect mécanique estégalement étudié et comparé aux résultats expérimentaux issus de labibliographie. / Currently, almost all material manufacturing processes are simulatedusing methods based on continuum approaches. These methods, thoughwidely studied, face difficulties with contact problems that areusually found in processes such as FSW. One "physical" explanationto this issue is given by the fact that these methods use equationsbased on continuum mechanics to describe discontinuous problems. Insome cases, the Discrete Element Method is used to overcome theseproblems. However, it is known to be a very time-consuming method.Thus, a long term solution consists of coupling both continuum anddiscontinuous approaches. This solution requires an overlapping zonewhere the two methods work together. This overlapping zone isclassically placed on a continuous region. Consequently, the DiscreteElement Method must be improved to be reliable in such a region. Thepresent work describes a DEM approach to simulate elasto-plasticmechanical behaviour and heat conduction through a continuousmaterial. This method can be used both to carry out calculations onthe continuous overlapping zone as well as to be coupled withclassical Discrete Element Method in order to deal with discontinuousproblems.Finally, coupling between thermal and mechanical aspects is studiedand compared to experimental results found in the bibliography.

Notre connaissance des effets d'une rayure sur les surfaces polymères reste à approfondir. L'expérimentation donne des observations précieuses des phénomènes qui apparaissent durant la rayure, cependant, l'accès aux champs de contraintes et de déformations dans le matériau n'est pas possible, ce qui est pourtant un élément clé pour la prédiction de l'amorce des fissures.Nous utilisons un essai de rayure sur des matériaux transparents, qui permet la visualisation in situ des endommagements, des dimensions de la zone de contact et du frottement. Les endommagements, en termes de craquelures, fissurations et bandes de cisaillement sont identifiés sur trois polymères massifs (PMMA, CR39 & PC). En parallèle, nous utilisons la modélisation 3D par éléments finis pour étudier la réponse mécanique pendant la rayure de ces trois matériaux polymères, afin d’identifier des critères d'amorçage de fissures. Enfin, des systèmes revêtus sont étudiés et le délaminage et la fissuration du film sont discutés. Ces considérations font entrevoir les perspectives possibles en termes de pistes d'amélioration pour la protection des substrats par dépôt de films minces. / Our knowledge of scratch effects on polymeric surfaces is still limited. The experimental approach gives precious observations of phenomena which occur during scratching, however, it does not allow to get insight the stress distribution within the material, a key feature for crack initiation prediction.A scratch test is used on transparent materials, that allows to visualize in situ damages appearance, the dimension of the contact zone and friction. The damages, in terms of crazing, cracking and shear bands are identified on three bulk polymers (PMMA, CR39 & PC).In parallel, we use 3D finite element modelling to study the mechanical response during a scratch test on these three polymeric materials, in order to identify crack initiation criteria.Finally, coated systems are studied and delamination/cracking of thin films are discussed. These considerations point to possible prospects in terms of improvement paths for the protection of substrates by thin films coating.

Seitdem die Methode der Finiten Elemente dank der rapiden Fortschritte der Hard- und Softwareentwicklung ihr anfängliches Nischendasein aufgeben konnte, ist sie zu einem unverzichtbaren Werkzeug der Produktentwicklung geworden. Anwenderseitig wurde mit dieser Entwicklung jedoch nicht immer Schritt gehalten. Anstelle der wenigen Spezialisten früherer Jahre nutzt inzwischen beinahe jeder, der über die entsprechenden Programme verfügt, die FEM, mit zuweilen zweifelhaften Resultaten – »The stark reality is that probably the majority of users are blissfully unaware that their analyses are invalid.« (Horspool 2010). In diesem Beitrag wird die aktuelle Anwendungssituation untersucht, und es werden Ausbildungskonzepte vorgestellt, die zu besseren und sichereren Analysen führen sollen. In den folgenden drei kleinen Szenarien sind zur Einstimmung typische Fehlschlüsse – ein wenig überzogen – dargestellt.

Ålö is a supplier of products for agricultural tractors. They mainly develop and manufacture front loaders, which traditionally are used to handle hay, but today are employed also in various other application areas. Ålö's products revolve around the front loader, where one of the products is the subframe. The subframes are the mechanical adjustment required for the front loaders to fit different tractors. The design of the subframe can sometimes be difficult to develop since it is limited by the tractor and its attachment points. The Product Integration Department at Ålö wants to investigate a software called Generative Design to facilitate the process of developing new subframes. Three different tractor models with a plate-like geometry are investigated. In addition, a tractor model for which an alternative casting subframe should be developed is investigated. A total of three different methods for the development of subframes are applied. For two of the methods, separate load cases need to be simulated on the two different parts of the subframe. The load cases used for the simulations are obtained by hand calculation. For each method, the time it takes from modelling to optimized design is investigated. In addition, information about other optimization programs is obtained. The result of this project is that the software has too few adjustment possibilities and that the generated design becomes too complex to be successfully used in the development of new subframes with sheet structure. However, an optimized cast design was developed, which provides a weight reduction of 17 kg. The total time of the design process, from the introduction of scanned data to the final subframe concept, is about six hours. Two topology optimization programs are considered better suited for the project and a further study is recommended to explore the software Altaire Inspire. / Ålö är en leverantör av produkter till jordbrukstraktorer. De utvecklar och tillverkar i huvudsak frontlastare som i grunden används för att hantera hö, men som idag har flera olika användningsområden. Ålös produkter kretsar runt frontlastaren där en av produkterna är fundament. Fundamenten är den mekaniska anpassningen som krävs för att frontlastare ska passa till olika traktorer. Designen för fundamenten kan ibland vara svår att ta fram då konstruktionen är begränsad av traktorn och dess infästningspunkter. Avdelningen Produktintegration på Ålö vill undersöka om programmet Generative Design kan underlätta proceduren att ta fram nya fundament. Vid Projektarbetet så utvärderas tre olika traktormodeller där designen ska ha en plåtliknande geometri. Utöver det så undersöks en traktormodell där ett alternativt gjutet fundament ska framtas. Totalt tre olika metoder för framtagning av fundament appliceras. För två av metoderna så krävs det att separata lastfall simuleras på de två olika delarna av fundamentet. Lastfallen som används vid simulering framtas genom handberäkning. En tidsredovisning framtas från modellering till optimerad design och information om andra optimeringsprogram erhålls. Det projektet resulterat i är att Generative Design har för få inställningsmöjligheter och att den genererade designen blir för komplex för att kunna användas vid framtagning av nya fundament som har plåtstruktur. Däremot så har en optimerad gjuten design framtagits vilket ger en viktbesparing på 17 kg jämförd med den nuvarande designen. Tidsredovisningen ger en sammanlagd tid på sex timmar från införandet av inskannad data till konceptfundament. Två topologioptimeringsprogram anses bättre lämpad för projektet och en vidare undersökning rekommenderas inom mjukvaran Altaire Inspire.

Proplate, a world leading company, is expert on volume-based cutting and machining of both ordinary steel as well as stainless steel. One of Proplate’s mayor products is tension bars, which is a component made to balance high forces and give stability to structures such as cranes, buildings, bridges and much more. Proplate builds their tension bars in different high strength steel materials, purchased from SSAB, and sells them worldwide. Proplate would like to market themselves better and wishes to produce a catalogue for the maximum load that can be applied to their tension bars, as competitors Pretec and Macalloy, already have for their tension bars. The purpose of the project has been to investigate the tension bars and the maximum load they can withstand before failure. The tension bars have been modeled in the CAD-program Creo Parametric, and then sent to the finite element method program ABAQUS to analyze their structural strength. Three different types of tension bars, and a fourth tension bar (called the walnut-strap) used as a connecting element between some of the tension bars, were investigated. They were modeled with sprints, to hold several tension bars together, and with a construction called loader, to simplify the model load application step. The three different types of tension bars have been analyzed as individual and also when connected to other tension bars. Some tension bars could be directly connected to each other with sprints, and some used the walnut-strap to connect other tension bars to each other. The project was limited to fatigue analyses, which is an important factor to control. This could instead be a great continuation of the project. The results from the strength analyses show that the stress is higher at the surfaces around the hole at the end of each tension bar, and the maximum load the tension bars can withstand depends on this area. The length, thickness and orientation of the tension bar has been varied, and the maximum load that each model can withstand has been listed. The length and direction of the tension bars did not influence the result for singular tension bars, but the thickness did. Both the length and the thickness of the tension bars did influence the result when multiple tension bars where connected to each other. Tables have been derived which shows the absolute maximum load that the tension bars can withstand. Proplate can use the tables in their catalogue, and they can also put a safety factor on the models to make them safer. Another part of the study was to investigate advantages and disadvantages with if the sprints, the connecting element between the tension bars, were replaced with screws instead. The result describes the yield strength needed for the screws and how the structures would behave compared to the current structure. A larger investigation into the effect of using screws may be one way to continue the work after this project, together with other investigations of, for instance, the use of compression bars. / Proplate är ett världsledande företag, som är experter på volymbaserad skärning och tillverkning i både vanligt stål såväl som rostfritt stål. En av Proplates huvudprodukter är deras dragstag, som är en komponent gjord för att balansera stora krafter och tillbringa stabilitet till strukturer, exempelvis lyftkranar, byggnader, broar med mera. Proplate bygger sina dragstag med hjälp av olika typer av höghållfasta stålsorter, köpta från SSAB, och säljer sedan produkterna över hela världen. Proplate skulle vilja marknadsföra sig bättre och önskar att ta fram en katalog över den maximala kraften som kan appliceras på dragstagen, vilket konkurrenter som Macalloy och Pretec redan har för sina dragstag. Syftet med projektet är att undersöka dragstagen och den maximala kraften som dragstagen klarar av innan de går sönder. Dragstagen har modellerats upp i CAD-programmet Creo Parametric, och sedan skickats till finita-elementmetodsprogrammet ABAQUS för hållfasthetsanalyser. Tre olika typer av dragstag, och en fjärde variant (kallad valnöts-staget) som använts som ett sammankopplande element mellan olika typer av dragstagen, har undersökts. De har modellerats tillsammans med sprintar, för att hålla samman flera dragstag, och en konstruktion vid namn loader, som ska förenkla kraftapplikationssteget i analyserna. De tre olika typerna av dragstag har analyserats individuellt och sammankopplade till andra dragstag samtidigt. Några av dragstagen kunde direkt sammankopplas till andra dragstag med hjälp av sprintar, men andra behövde valnöts-staget för att sammankoppla dragstagen till varandra. Projektet var avgränsat så att utmattningslaster, vilket är en mycket viktig faktor, inte analyserades. Resultatet från hållfasthetsanalyserna visar att spänningarna i ytan kring ett hål i kanterna av dragstagen blir som störst, och den maximala kraften som dragstagen kan klara av är beroende på denna yta. Dragstagens längd, tjocklek och orientering i rummet har varierat, och den maximala kraften som varje modell kan klara av har tabellerats. Dragstagens längd och riktning i rummet påverkade inte resultatet när individuella dragstag analyserades, men dess tjocklek gjorde det. Både längden och tjockleken av dragstagen påverkade resultatet när flera dragstag blivit sammankopplade till varandra. Tabellerna visar den absolut maximala kraften som dragstagen kan klara av. Proplate kan använda dessa tabeller till deras katalog, och de kan också lägga till en säkerhetsfaktor på modellerna för att göra dem säkrare. En annan del av analyserna var att undersöka fördelarna och nackdelarna om sprintarna, som är det sammankopplande elementet mellan de olika dragstagen, blivit utbytta mot skruvar istället. Resultatet beskriver vilken sträckgräns som skulle behövas för skruvarnas material och hur strukturen skulle bete sig i jämförelse till den nuvarande strukturen. En större undersökning angående effekten med skruvar kan vara en bra fortsättning på arbetet efter detta projekt, tillsammans med andra undersökningar som exempelvis angående användning av tryckstag.

The main topic of this Master thesis is proposal of the streamline the production of the machined part of a handguard. The aim of the work is to evaluate the current machining process, to design possible innovation, to select the best way of construction of a design part. The conclusion will be devoted technical and economic evaluation in terms of time, cost and material consumption.

Med den rådande befolkningsökningen tyder prognosen över bostadsförsörjningen att de behövs byggas fler bostäder för att uppfylla bostadsbehovet. Byggnadsbranschen står idag för cirka 20 % utav det totala koldioxidutsläppen i Sverige. Av detta skäl finns det ett behov att utveckla mer miljövänligare och hållbara tekniker för att uppfylla de ställda kraven gällande hållbart byggande. Trä och konstruerade träprodukter anses vara ett miljövänligt material och bör användas som stommaterial i byggnader i större utsträckning än det görs idag.    Detta arbete innefattar att jämföra de strukturella prestanda hos limträbalkar och armerade betongbalkar i flervåningsbyggnad. Som startpunkt modelleras en befintlig byggnad utifrån de dokument som tillhandhålls av ritningar och andra anvisningar för den avsedda referensbyggnaden. Bärverksanalysen utfördes i FEM-design till syfte att kontrollera limträbalkar beteende i nedböjning, spänning, tvärsnittsmått och bärighet. Arbetet genomfördes i två steg, referens byggnadens betongkonstruktion modelleras noggrant i första steget. I det andra steget ersätts armerade betongbalkar av limträbalkar i syfte att jämföra deras strukturella prestanda.     Det erhållna visar att limträets lätta vikt medför en minskning på ca 24 % på byggnadens totalvikt. Styvhetsegenskaper är limträbalkar största nackdel jämfört med armerad betongbalk, eftersom ett utbytte av balkarna med liknande dimension i 8 m spännvidd gav upphov till ca 65 % ökning på deformationer. Vid användning av limträbalkar ska spännvidden på 8 m halveras, samt större limträtvärsnitt och pelare placeras ut för att uppfylla det ställda kraven gällande bruks-och brottgränstillståndet. / With the prevailing population increase, the forecast of housing supply indicates that more housing needs to be built to meet the housing need. The construction industry today accounts for about 20% of the total carbon dioxide emissions in Sweden. For this reason, there is a need to develop more environmentally friendly and sustainable technologies to meet the set requirements regarding sustainable construction. Wood and constructed wood products are considered an environmentally friendly material and should be used as frame materials for buildings to a greater extent than is done today.   This work includes comparing the structural performance of glulam beams and reinforced concrete beams in multi-story building. As a starting point, an existing building is modeled on the basis of the documents provided by drawings and other instructions for the intended reference building. The structural analysis was performed in FEM design for the purpose of checking the behavior of glulam beams in deflection, stress, cross-sectional dimensions and load-bearing capacity. The work was carried out in two stages, the reference building's reinforced concrete structure is carefully modeled in the first stage. In the second stage, reinforced concrete beams are replaced by glulam beams in order to compare their structural performance.   The results show that the light weight of glulam leads to a reduction of about 24% in the total weight of the building. Rigidity properties are the biggest disadvantages of glulam beams compared to reinforced concrete beams, since a replacement of the beams with a similar dimension in 8 m span gave rise to about 65% increase in deformations. When using glulam beams, the span of 8 m must be halved, and larger glulam cross-sections and columns must be placed to meet the set requirements regarding serviceability and ultimate limit states.

Les faisceaux d'aiguilles des assemblages combustibles des réacteurs à neutrons rapides à caloporteur sodium (RNR-Na) se déforment au cours de leur irradiation, ce qui impacte l’écoulement du caloporteur et la distribution de températures dans l’assemblage, dont la connaissance est essentielle pour la démonstration de sûreté. De plus, les mécanismes à l’origine de cette déformation, à savoir le gonflement et le fluage thermique et d’irradiation, dépendent fortement de la température de la gaine du combustible, d'où l'existence d'un couplage entre les évolutions thermo-hydraulique et thermomécanique des assemblages. Par le passé, ce couplage a été négligé dans les simulations numériques, et une approche plus conservative a été privilégiée : les simulations thermo-hydrauliques étaient réalisées sans tenir compte de la déformation géométrique, et les distributions de températures résultantes étaient utilisées comme des données d'entrée pour les simulations thermomécaniques. L'objectif de cette thèse est de définir une méthodologie pour l'évaluation du comportement des assemblages combustibles de type RNR-Na sous irradiation en prenant en compte le couplage entre leurs évolutions thermo-hydraulique et thermomécanique.A cet effet, un nouveau couplage numérique a été développé entre le code industriel de dynamique des fluides numérique (CFD) STAR-CCM+ et DOMAJEUR2, code basé sur la méthode aux éléments finis, développé par le CEA et dédié à la modélisation du comportement thermomécanique des assemblages combustibles RNR-Na sous irradiation. Ce couplage a été réalisé par l'échange de la déformation de la gaine, calculée par DOMAJEUR2, et de son champ de températures, obtenu avec le modèle CFD qui prend en compte de manière explicite la déformation géométrique des aiguilles combustibles. De plus, les conditions aux limites thermo-hydrauliques utilisées dans les simulations CFD, comme le débit massique de sodium dans le faisceau, sont ajustées pour tenir compte de cette déformation.Cette méthodologie a été appliquée à des faisceaux respectivement de 7 et 19 aiguilles combustibles munies de fils espaceurs, avec des caractéristiques géométriques et des conditions aux limites représentatives des RNR-Na de quatrième génération, ont été analysés. Dans le cas des faisceaux combustibles fortement irradiés, les simulations couplées conduisent à une réduction significative de la déformation diamétrale des aiguilles combustibles, par rapport aux simulations non couplées, causée par la prise en compte de l'augmentation de la température de la gaine induite par la déformation. En raison de la déformation plus faible, la contrainte maximale de la gaine a été réduite. De plus, des simulations ont été menées afin de vérifier que, en situation de fonctionnement normal, la dépendance de la neutronique à l’évolution de la thermo-hydraulique et de la thermomécanique est faible. Enfin, une contribution à la validation de cette méthodologie de simulation couplée a été réalisée avec un benchmark numérique basé sur un outil de simulation couplé existant et en simulant l'irradiation d'un assemblage combustible expérimental. Contrairement à l'approche innovante développée dans le cadre de ce travail de thèse, l'outil de simulation existant utilise un modèle thermo-hydraulique simplifié et ne tient pas compte de l'impact de la déformation sur le débit massique du caloporteur, qui, selon les résultats de l'évaluation, a une importance majeure. La simulation de l'irradiation expérimentale a conduit à une déformation maximale de la gaine et un gradient de déformations en accord avec les grandeurs mesurées, bien que des limitations liées aux lois empiriques de gonflement utilisées dans DOMAJEUR2 pour le calcul du gonflement aient été identifiées. La reformulation de ces lois à l'aide de la méthodologie de simulation couplée développée constitue une perspective à ce travail de thèse. / The fuel pin bundles of Sodium-cooled Fast Reactors (SFR) undergo significant geometrical changes during their irradiation, which affect the coolant flow and temperature distributions in the fuel assemblies, the knowledge of which is essential for safety assessments. Moreover, as the mechanisms responsible for the deformation of the fuel bundles, namely the swelling and creep, strongly depend on the fuel cladding temperature, a coupling between the thermal-hydraulic and thermomechanical evolutions of the fuel assemblies exists. In the past, this coupling has been neglected, and a more conservative approach has been preferred. In this conservative approach, the thermal-hydraulic simulations are conducted without considering the geometrical deformation, and the resulting temperature distributions are used as input for the thermomechanical simulations. The objective of this thesis is to define a new methodology for the evaluation of the behavior of SFR fuel bundles under irradiation that considers the coupling between their thermal-hydraulic and thermomechanical evolutions.To this end, a new numerical coupling has been developed between the industrial Computational Fluid Dynamics (CFD) code STAR-CCM+ and DOMAJEUR2, a finite element code dedicated to the modeling of the thermomechanical behavior of SFR fuel assemblies under irradiation. The coupling has been implemented via the exchange of the cladding deformation, calculated by DOMAJEUR2, and its associated temperature field, obtained with a CFD model implemented in STAR-CCM+ that explicitly considers the geometrical deformation of the fuel pins. In addition, the thermal-hydraulic boundary conditions used in the CFD simulations, such as the sodium mass flow rate through the bundle, are also automatically adjusted to account for the deformation.Study cases consisting of bundles of 7 and 19 wire-wrapped fuel pins, with geometrical characteristics and boundary conditions representative of fourth generation SFRs, were analyzed in order to gain insight on the effects of the coupling. For highly irradiated fuel bundles, the coupled simulations were shown to lead to a significant reduction of the diametral strain of the fuel pins, with respect to non-coupled simulations, caused by the deformation-induced cladding temperature increase. Consequence of the lower deformation, the cladding maximal stress was also significantly reduced. Additionally, neutronic simulations were conducted in order to verify that, in nominal operational conditions, its coupling with thermal-hydraulics and thermomechanics is of minor importance. Finally, a contribution to the validation of the developed coupled simulation methodology was realized by performing a numerical benchmark against a preexisting coupled simulation tool, and by simulating the irradiation of an experimental fuel assembly. Unlike the novel approach developed in this work, the preexisting simulation tool employs a simplified thermal-hydraulic model and does not consider the impact of the deformation on the coolant mass flow rate, which was found to be of major importance. The simulation of the experimental irradiation yielded a maximal cladding deformation and deformation gradient that are in good agreement with the measured values, although limitations related to the empirical swelling laws employed in DOMAJEUR2 to compute the swelling were identified. The reformulation of these laws using the developed coupled simulation methodology constitutes a perspective of this work.

In this thesis, we study a numerical tool named multi-mesh method within the framework of the adaptive finite element method. The aim of this method is to minimize the size of the linear system to get the optimal performance of simulations. Multi-mesh methods are typically used in multi-physics problems, where more than one component is involved in the system. During the discretization of the weak formulation of partial differential equations, a finite-dimensional space associated with an independently refined mesh is assigned to each component respectively. The usage of independently refined meshes leads less degrees of freedom from a global point of view. To our best knowledge, the first multi-mesh method was presented at the beginning of the 21st Century. Similar techniques were announced by different mathematics researchers afterwards. But, due to some common restrictions, this method is not widely used in the field of numerical simulations. On one hand, only the case of two-mesh is taken into scientists\' consideration. But more than two components are common in multi-physics problems. Each is, in principle, allowed to be defined on an independent mesh. Besides that, the multi-mesh methods presented so far omit the possibility that coefficient function spaces live on the different meshes from the trial and test function spaces. As a ubiquitous numerical tool, the multi-mesh method should comprise the above circumstances. On the other hand, users are accustomed to improving the performance by taking the advantage of parallel resources rather than running simulations with the multi-mesh approach on one single processor, so it would be a pity if such an efficient method was only available in sequential. The multi-mesh method is actually used within local assembling process, which should not be conflict with parallelization. In this thesis, we present a general multi-mesh method without the limitation of the number of meshes used in the system, and it can be applied to parallel environments as well. Chapter 1 introduces the background knowledge of the adaptive finite element method and the pioneering work, on which this thesis is based. Then, the main idea of the multi-mesh method is formally derived and the detailed implementation is discussed in Chapter 2 and 3. In Chapter 4, applications, e.g. the multi-phase flow problem and the dendritic growth, are shown to prove that our method is superior in contrast to the standard single-mesh finite element method in terms of performance, while accuracy is not reduced.