A Mecânica do Dano Contínuo (MDC) teve importante desenvolvimento desde os trabalhos iniciais de Kachanov e Rabotnov sendo uma ferramenta prática para considerar processos de danificação em materiais e estruturas em nível de contínuo macroscópico. Neste trabalho, apresenta-se uma aplicação da teoria do dano anisotrópico baseada em teorias desenvolvidas a partir dos trabalhos de Murakami. Nas formulações apresentadas, o tensor de dano de quarta ordem M (que relaciona tensões aplicadas e tensões efetivas) é determinado com base no tensor Ω (densidade de área tridimensional devida ao dano) que, por sua vez, pode ser determinado com base em dados experimentais. São propostas três formulações teóricas que são transformadas em formulações incrementais e incorporadas em um programa computacional de elementos finitos (para placas e cascas laminadas em material compósito) que considera efeitos geométricos não-lineares. A primeira e segunda formulação são casos particulares da terceira formulação que é um modelo termodinâmico tridimensional. As forças termodinâmicas associadas à evolução do tensor de dano são deduzidas a partir da expressão da dissipação intrínseca. Um critério fenomenológico para o dano é proposto. Em consistência com a positividade da dissipação intrínseca é adotada uma regra de normalidade para a evolução da força termodinâmica. Também é proposta, baseada em dados experimentais, uma lei para o encruamento associada ao processo de dano. Os modelos são validados comparando resultados numéricos a soluções analíticas ou a resultados experimentais. A formulação viscoelástica é definida do dano elástico e por componentes viscoelásticas representadas no formato de variáveis de estado e, posteriormente, validadas através de resultados experimentais. / The Continuum Damage Mechanics (CDM) had important development since the initial works of Kachanov and Rabotnov and constitutes now a practical tool to account for macroscopic damage in materials and structures. In this work, an application of an anisotropic damage theory based in Murakami theory is presented. In the formulations presented here, the fourth order damage tensor M (that relates Cauchy stress and effective stress) is determined on the basis of the tensor Ω (damaged three-dimensional area density) that, can be determined through experimental data. The three theoretical formulations presented here are transformed into incremental formulations and implemented in a finite element program (for plates and shell structures in composite material) taking account of geometrically non-linear effects. The first and second formulations are particular cases of the third formularization that is a tridimensional model for continuous damage formulated. The thermodynamic force associated with the evolution of the damage tensor is deduced from the expression of the intrinsic dissipation. A phenomenological criterion for damage yielding is proposed. In consistence with the positivity of the intrinsic dissipation, a normality rule is adopted for the evolution of the thermodynamic force. In addition, a hardening law associated with the damage process is identified from available experiment results. The models are validated by comparison with closed-form solutions or with experiment results. The viscoelastic formulation is defined through damage elastic and viscous components and set in a state variables format and then validated by comparison with experimental creep tests.

Friction Spot Welding (FSpW) é um processo de solda ponto por fricção, que opera na fase sólida do material e permite unir duas ou mais chapas de metal sobrepostas. Além de ser bastante usado para soldar materiais leves, ele também é aplicável a qualquer material que apresente boa plasticidade. Neste trabalho são analisados dois materiais: AA Alclad 2024-T351 e AA 2024-T351, diferindo entre si no uso, ou não, da camada de proteção contra a corrosão (Alclad). As uniões são feitas sob os mesmos parâmetros do processo, previamente estudados para o material com Alclad. Dois parâmetros são utilizados: um dito ótimo, capaz de produzir soldas com bom desempenho mecânico e reprodutibilidade e um segundo, dito insuficiente, por produzir soldas de baixo desempenho mecânico e baixa reprodutibilidade. Pretende-se, com este trabalho, avaliar os efeitos que a camada Alclad pode acarretar nas juntas soldadas, em seu desempenho mecânico, no modo de fratura, na microestrutura e na geometria da junta. Os resultados apresentam uma grande influência do Alclad, tendo em vista que durante o processo o recobrimento migra das superfícies das chapas para o centro da solda. Assim, uma interface deste material, que possui baixa resistência mecânica, é criada, influenciando negativamente o desempenho da junta e alterando o modo de fratura. O principal escopo desta dissertação é realizar uma análise da fratura do ensaio de cisalhamento, com o uso do método de elementos finitos. Portanto, fazse necessário estudar e desenvolver um modelo numérico capaz de representar a nucleação, coalescimento, formação de uma ou mais trincas e a consequente propagação até a fratura do corpo. Para a realização da análise utilizou-se o modelo numérico de fratura Johnson-Cook (JC), o qual expressa a tensão equivalente como uma função da deformação plástica, da taxa de deformação e da temperatura. Realizou-se, ainda, um estudo acerca das teorias do Continuum Damage Mechanics (CDM), bem como se fez necessário obter novos parâmetros para o modelo, que descrevessem o fenômeno e o material. Nesse sentido, serão realizadas duas análises, sendo que a primeira considera o efeito da camada de Alclad e, a segunda, considera uma solda livre de defeitos. Espera-se identificar os locais em que trinca é nucleada e analisar a resposta da junta, passo a passo, durante a propagação da trinca, até a fratura completa do corpo. E, por fim, avaliar a interferência no modelo numérico da presença da camada contra a corrosão Alclad. / Friction Spot Welding (FSpW) is a friction spot weld process, it operates in the solid-state of the material and allows joining two or more sheets in overlap configuration. It is used to join light weight materials, also is suitable to any material that shows good ductility. In this work two different materials are analyzed AA Alclad 2024-T351 e AA 2024-T351, between them the use, or not, of the corrosion protection layer Alclad. The welds are made under the same process parameters previously studied to the material with Alclad. Two parameters are utilized: the first one is the optimum parameter capable to produce welds with good mechanical performance and reproducibility, and another one inadequate because it produces joins with poor mechanical response and reproducibility. It is intended with this work, to evaluate the effects that the Alclad layer can cause in the welds, in its mechanical performance, fracture mode, microstructure and geometry of the join. The results showed a considerable influence of the Alclad, considering that during the process, it migrates from the sheet surface to the center of the weld. Thus, an interface of this material, that has a very low hardness, is created, influencing negatively the performance of the weld and changing the fracture mode. The aim of this dissertation is to perform an analysis of the fracture from the lap shear test, using the finite element method. Therefore, becomes necessary study and develop a numerical model capable to represent the nucleation, coalescence, formation of one or more cracks and, the consequent propagation until the fracture of the body. To perform the analysis it was used the numerical model of fracture called Johnson-Cook (JC), which expresses the equivalent stress as a function of the plastic deformation, the strain rate and the temperature. It was also made a study about the Continuum Damage Mechanics (CDM) theories, and it was necessary to obtain new parameters for the model, that describe the phenomenon and the material. In this sense, it will be performed two analyses, and the first considers the Alclad layer and, the second, considers a weld without defects. It is expected to identify the places where the crack nucleated, and analyze the behavior of the weld, step by step, during the crack propagation, until the complete fracture of the component. And, finally, evaluate the interference in the numerical model of the presence of the protection corrosion layer Alclad.

Made available in DSpace on 2016-12-08T17:19:38Z (GMT). No. of bitstreams: 1 capa-introducao.pdf: 136742 bytes, checksum: f3fec628299a200f8267c463e8e1e3d9 (MD5) Previous issue date: 2011-07-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The development of new materials, in addition to the increasing industrial demand for more efficient numerical tools capable of predicting defects in metal forming processes, has stimulated research on new material models. In this context, the Continuum Damage Mechanics has proved to be able of successfully predicting ductile failure onset in metal forming operations. The main objective of this work is the study of a thermo-elastic-plastic formulation and thermo-mechanical coupling schemes aiming at prediction of mechanical degradation of ductile materials. The material internal degradation is described using a modified version of Lemaitre s (1985) damage model, in which the void opening and void closure effects associated to tensile and compressive stress states are accounted for. The mechanical and thermal problems are formulated using the Finite Element Method. Coupling of thermal effects is defined by a sensitivity factor included in the yield function and by a component describing the energy generated due to dissipation of plastic work. Two coupling procedures are addressed in this work: staggered scheme and iterative scheme. Accuracy of the iterative coupling scheme is assessed by the analysis of the load increment size. In this case, the results show that the iterative procedure is more accurate than the staggered scheme. The study of the coupled thermal and mechanical effects is discussed by the analysis of the influence of the temperature and the heat transfer coefficient based upon the simulation of tensile tests of U-notched specimens. The results show that the internal degradation of the material is strongly affected by its temperature and heat transfer coefficient, i.e., higher temperatures increase the material capacity to deform with smaller rates of material degradation. / O surgimento de novos materiais, aliado ao aumento da demanda industrial por ferramentas numéricas capazes de prever o aparecimento de defeitos em processos de conformação mecânica, tem estimulado o desenvolvimento de novos modelos materiais. A Mecânica do Dano Contínuo, em cujo contexto este trabalho está inserido, provou ser uma abordagem capaz de prever o início da fratura dúctil em operações de conformação mecânica. O principal objetivo deste trabalho é o estudo da formulação termo-elastoplástica de problemas com acoplamento termomecânico visando a sua aplicação na predição da degradação mecânica de materiais dúcteis. A descrição da degradação interna do material é feita através da modificação do modelo de dano de Lemaitre (1985) para incluir efeitos de abertura e fechamento de vazios relacionados a estados de tensão trativos e compressivos. Os problemas térmico e mecânico são formulados utilizando o método de Elementos Finitos. O acoplamento dos efeitos térmicos é definido através da inclusão de um fator de sensibilidade na função de escoamento e da geração de calor por dissipação plástica. Dois métodos de acoplamento foram abordados: método particionado e método iterativo. A avalição da precisão do método de solução iterativo do problema acoplado é feita através da análise de influência do incremento de carga. Neste caso, os resultados obtidos mostraram que o método iterativo é mais preciso que o método particionado. O estudo dos efeitos térmico e mecânico acloplados é feito através da análise da influência da temperatura e do coeficiente de troca de calor na simulação de um ensaio de tração usando um corpo de prova cilíndrico. Os resultados mostram que a degradação interna do material é fortemente influenciada pela temperatura do material e pelo coeficiente de troca de calor, ou seja, quanto maior a temperatura, maior é a capacidade do material de se deformar plasticamente com uma redução da taxa de degradação. interna do material.

Friction Spot Welding (FSpW) é um processo de solda ponto por fricção, que opera na fase sólida do material e permite unir duas ou mais chapas de metal sobrepostas. Além de ser bastante usado para soldar materiais leves, ele também é aplicável a qualquer material que apresente boa plasticidade. Neste trabalho são analisados dois materiais: AA Alclad 2024-T351 e AA 2024-T351, diferindo entre si no uso, ou não, da camada de proteção contra a corrosão (Alclad). As uniões são feitas sob os mesmos parâmetros do processo, previamente estudados para o material com Alclad. Dois parâmetros são utilizados: um dito ótimo, capaz de produzir soldas com bom desempenho mecânico e reprodutibilidade e um segundo, dito insuficiente, por produzir soldas de baixo desempenho mecânico e baixa reprodutibilidade. Pretende-se, com este trabalho, avaliar os efeitos que a camada Alclad pode acarretar nas juntas soldadas, em seu desempenho mecânico, no modo de fratura, na microestrutura e na geometria da junta. Os resultados apresentam uma grande influência do Alclad, tendo em vista que durante o processo o recobrimento migra das superfícies das chapas para o centro da solda. Assim, uma interface deste material, que possui baixa resistência mecânica, é criada, influenciando negativamente o desempenho da junta e alterando o modo de fratura. O principal escopo desta dissertação é realizar uma análise da fratura do ensaio de cisalhamento, com o uso do método de elementos finitos. Portanto, fazse necessário estudar e desenvolver um modelo numérico capaz de representar a nucleação, coalescimento, formação de uma ou mais trincas e a consequente propagação até a fratura do corpo. Para a realização da análise utilizou-se o modelo numérico de fratura Johnson-Cook (JC), o qual expressa a tensão equivalente como uma função da deformação plástica, da taxa de deformação e da temperatura. Realizou-se, ainda, um estudo acerca das teorias do Continuum Damage Mechanics (CDM), bem como se fez necessário obter novos parâmetros para o modelo, que descrevessem o fenômeno e o material. Nesse sentido, serão realizadas duas análises, sendo que a primeira considera o efeito da camada de Alclad e, a segunda, considera uma solda livre de defeitos. Espera-se identificar os locais em que trinca é nucleada e analisar a resposta da junta, passo a passo, durante a propagação da trinca, até a fratura completa do corpo. E, por fim, avaliar a interferência no modelo numérico da presença da camada contra a corrosão Alclad. / Friction Spot Welding (FSpW) is a friction spot weld process, it operates in the solid-state of the material and allows joining two or more sheets in overlap configuration. It is used to join light weight materials, also is suitable to any material that shows good ductility. In this work two different materials are analyzed AA Alclad 2024-T351 e AA 2024-T351, between them the use, or not, of the corrosion protection layer Alclad. The welds are made under the same process parameters previously studied to the material with Alclad. Two parameters are utilized: the first one is the optimum parameter capable to produce welds with good mechanical performance and reproducibility, and another one inadequate because it produces joins with poor mechanical response and reproducibility. It is intended with this work, to evaluate the effects that the Alclad layer can cause in the welds, in its mechanical performance, fracture mode, microstructure and geometry of the join. The results showed a considerable influence of the Alclad, considering that during the process, it migrates from the sheet surface to the center of the weld. Thus, an interface of this material, that has a very low hardness, is created, influencing negatively the performance of the weld and changing the fracture mode. The aim of this dissertation is to perform an analysis of the fracture from the lap shear test, using the finite element method. Therefore, becomes necessary study and develop a numerical model capable to represent the nucleation, coalescence, formation of one or more cracks and, the consequent propagation until the fracture of the body. To perform the analysis it was used the numerical model of fracture called Johnson-Cook (JC), which expresses the equivalent stress as a function of the plastic deformation, the strain rate and the temperature. It was also made a study about the Continuum Damage Mechanics (CDM) theories, and it was necessary to obtain new parameters for the model, that describe the phenomenon and the material. In this sense, it will be performed two analyses, and the first considers the Alclad layer and, the second, considers a weld without defects. It is expected to identify the places where the crack nucleated, and analyze the behavior of the weld, step by step, during the crack propagation, until the complete fracture of the component. And, finally, evaluate the interference in the numerical model of the presence of the protection corrosion layer Alclad.

Dans un contexte d’évaluation de la criticité des chargements, les travaux de thèse ont les objectifs suivants : prendre en compte les phénomènes sous-jacents à le rupture ductile : les phénomènes de dissipation volumique (plasticité et endommagement) et surfaciques (fissuration). On s'intéresse également à régulariser la solution vis-à-vis du maillage, à prédire le phénomène de transition de mode de rupture plan vers un mode de propagation oblique observé pour certains essais. La méthode utilisée est basée sur la méthode des discontinuités fortes. Un des enjeux majeurs de ces travaux est d’étendre son champ d'application au cadre de la modélisation de la rupture ductile, notamment en présence de plasticité et d'endommagement dans le volume. Une première partie des travaux est consacré à l'établissement d'un modèle en hypothèse de petites déformations, avec un modèle matériau de plasticité et d'endommagement couplé de Lemaitre pour le volume et un modèle cohésif endommageable pour le comportement surfacique. Les deux modes de rupture I et II ont été considérés dans les essais numériques. Des résultats montrant les capacités de régularisation de la méthode employée ont été présentés pour divers essais. Une seconde partie des travaux a été consacré à la formulation d'un modèle en hypothèse de grandes transformations, avec également des résultats probants en termes de régularisation de la dépendance à la taille de maille. Les deux éléments présentés ont été implémentés en formulation implicite et explicite, dans FEAP (Finite Element Analysis Program), logiciel académique développé à UC Berkeley par Taylor, et plus récemment dans le logiciel de calcul Eléments Finis Abaqus. / In the context of loadings criticality analysis, the thesis work have the following objectives : to take into account the underlying phenomena to ductile fracture : the volumetrie (plasticity and damage) and surfacic (fracture) dissipativ mechanisms. We also aim at regularizing the solution with regards to meshing, predicting the transition from a straigh crack propagation to a slant fracture mode observed for certain tests. The chosen method relies on the stron discontinuity method. One of the major challenges of this work is to extend its framework to the ductile fractur modeling framework, by accounting for plasticity and damage in the bulk. The first part of this work is dedicated to th establ'ishment of a model in small strain hypothesis, with a material model that takes into account coupied plasticity an damage in the QUik and a damageable model for the cohesive surfacic behavior. Both modes 1 and Il have been taken int) account in thnumerical examples. Results attesting the regularizing capabilities of the method are presented fo different tests. The second part of this work is dedicated to the formulation of a finite strain mode!, and results showin the good regularizing capabilities of the method are also shown. Both elements have been implemented in FEAP (Finit Element Analysis Program), an academie software developed at UC Berkeley by Taylor, and more recently in the finit element software Abaqus.

L'analyse sismique des structures de génie civil est une problématique majeure pour la sécurité des personnes et la pérennité des ouvrages. L'étude expérimentale permet de comprendre le comportement réel de la structure mais occasionne des problèmes de coût important et d'effet d'échelle souvent inévitable dû aux dimensions des structures. D'un autre côté, l'étude numérique propose une bonne approximation du comportement global mais la représentation précise des phénomènes locaux (fissuration, perte de matière, flambement, grands déplacements) dans les zones fortement endommagées est délicate et souvent insuffisante. Ce travail de thèse propose l'élaboration d'une technique de sous-structuration hybride pour coupler un modèle numérique à une plateforme expérimentale. Ainsi, la partie faiblement endommagée de la structure est modélisée numériquement tandis que la partie fortement endommagée est testée expérimentalement. Cette méthode permet de coupler le réalisme de l'expérimental avec le faible coût numérique sans toutefois perdre en précision. Après avoir élaboré une méthode de couplage hybride peu intrusive pour le code de calcul (Cast3m), un modèle d'endommagement anisotrope adapté aux chargement sismique (effet unilatéral, déformations permanentes) est développé dans le cadre de la thermodynamique des milieux continus. Afin de valider la méthode hybride, une étude expérimentale est menée sur une structure type en béton armé. La fissuration de la partie expérimentale est étudiée grâce à la corrélation d'images. Ce travail expose donc une alternative intéressante aux analyses classiques des structures importantes soumises à des sollicitations complexes. / The seismic analysis of civil engineering structures is a major problem for the safety of the persons and the sustainability of the structures. The experimental study allows to understand the real behavior of the structure but causes problems of important cost and often inevitable scale effect owed in dimension of the structures. On the other hand, the numerical study proposes a good estimate of the global behavior but the accurate modelling of the local phenomena (cracking, losses of material, buckling, large displacements) in the strongly damaged zones is delicate and often insufficient. This work of this thesis proposes the elaboration of a hybrid technique of sub-structuring to couple a numerical model with an experimental platform. So, the weakly damaged part of the structure is numerically modelled whereas the strongly damaged part is experimentally tested. This method allows to couple the precision and the realism of the experimental with the numerical moderate cost without losing however in precision. Having elaborated a few intrusive hybrid method of coupling for the code of calculation (Cast3m), a anisotropic damage model adapted for seismic load (unilateral effect, permanent strains) is developed within the framework of the thermodynamics of the continuous media. To validate the hybrid method, an experimental study is led on a typical reinforced concrete structure. The cracking of the experimental part is studied thanks to images correlation. This work thus exposes an interesting alternative to the classic analyses of the important structures subjected to complex loading.

Orientador: Marco Lúcio Bittencourt / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-22T09:29:00Z (GMT). No. of bitstreams: 1 Suzuki_JorgeLuis_M.pdf: 2667128 bytes, checksum: 86588ab0b8799da0e2c3f0242102caea (MD5) Previous issue date: 2013 / Resumo: Este trabalho apresenta uma implementação em ambiente C++ da teoria do Dano em Meio Contínuo para hiperelasticidade sob regime compressível e quasi-incompressível. Para o caso quasi-incompressível, uma formulação mista (u=p) é tratada com um procedimento de projeção local da pressão hidrostática. O dano é um escalar que dependente da máxima deformação atingida. Para a validação dos métodos implementados, são realizados estudos de convergência através da imposição de soluções analíticas, variando a ordem de interpolação e o número de elementos. Também é analisado o comportamento da tensão através de ciclos de carregamento, para a observação da perda de rigidez progressiva sob os efeitos de dano. A formulação implementada contorna o problema de travamento de malha, sendo que de maneira geral, solução é melhor aproximada com o aumento do grau polinomial combinado com o aumento do número de elementos / Abstract: The objective of this work is the application of the high-order hpFEM to the analysis of hyperelastic materials coupled to isotropic damage. A mixed (u=p) formulation with a pressure projection procedure is used in conjunction with the hpFEM to overcome the volumetric locking. The isotropic damage model introduces a scalar variable that evolves coupled with the maximum attained strain. It is based on the equivalent stress concept, by applying a reduction factor over the stress tensor. A cyclic loading test was performed to reproduce the Mullins effect. Convergence analyses were made for a compressible and a quasi-incompressible material imposing analytical solutions. Both materials presented a spectral convergence rate for the p refinement using smooth solutions. In the case of quasi-incompressibility, the material showed locking-free characteristics, but the approximation errors were higher compared to the compressible case / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

Indiana University-Purdue University Indianapolis (IUPUI) / Additively manufactured (AM) metals have been increasingly fabricated for structural applications. However, a major hurdle preventing their extensive application is lack of understanding of their mechanical properties. To address this issue, the objective of this research is to develop a computational model to simulate the creep behavior of nickel alloy 718 manufactured using the laser powder bed fusion (L-PBF) additive manufacturing process. A finite element (FE) model with a subroutine is created for simulating the creep mechanism for 3D printed nickel alloy 718 components. A continuum damage mechanics (CDM) approach is employed by implementing a user defined subroutine formulated to accurately capture the creep mechanisms. Using a calibration code, the material constants are determined. The secondary creep and damage constants are derived using the parameter fitting on the experimental data found in literature. The developed FE model is capable to predict the creep deformation, damage evolution, and creep-rupture life. Creep damage and rupture is simulated as defined by the CDM theory. The predicted results from the CDM model compare well with experimental data, which are collected from literature for L-PBF manufactured nickel alloy 718 of creep deformation and creep rupture, at different levels of temperature and stress. Using the multi-regime Liu-Murakami (L-M) and Kachanov-Rabotnov (K-R) isotropic creep damage formulation, creep deformation and rupture tests of both the secondary and tertiary creep behaviors are modeled. A single element FE model is used to validate the model constants. The model shows good agreement with the traditionally wrought manufactured 316 stainless steel and nickel alloy 718 experimental data collected from the literature. Moreover, a full-scale axisymmetric FE model is used to simulate the creep test and the capacity of the model to predict necking, creep damage, and creep-rupture life for L-PBF manufactured nickel alloy 718. The model predictions are then compared to the experimental creep data, with satisfactory agreement. In summary, the model developed in this work can reliably predict the creep behavior for 3D printed metals under uniaxial tensile and high temperature conditions.

Woodbe Engineering AB is a freshly started company that has developed a new type of joint for cross-laminated timber (CLT). The joint does not include any metallic fasteners, which improves sustainability, the ergonomics for the workers and time efficiency. The joint is designed to connect floor and wall elements in multi-storey buildings, by milling a dovetail in the floor element, and a fitting track in the wall element using a CNC machine. Before the product can be used on the market, it needs to be verified. This verification can either be done using physical tests, calculations, or a combination of both. The company has performed experimental small-scale tests, where the load-bearing capacity was tested. Later this year, large scale tests are to be performed. The purpose of this work is to develop a simulation model that can predict the results of the physical test. A simulation model that yields accurate results can be a good substitution for physical testing, due to a lower cost, better time efficiency, and parameters that can easily be changed. CLT is made up of several layers of wooden plates with different directions. The wood itself is quite complex to model. It has different properties in different directions, both ductile and brittle fracture modes and a large scatter of material properties. To capture this behaviour, a material model which incorporates orthotropic elasticity with linear fracture mechanics has been used. The behaviour of the material model has been evaluated with tests in both tension and compression in different directions. The accuracy of the material model was investigated by a simulation of the small-scale tests where the load-bearing capacity and the mode of fracture was investigated. A simulation of the large-scale experiment has also been conducted, where predictions of the load-bearing capacity and the first mode of failure was investigated. Also, a calculation script has been developed, which calculates the shear stress in the dovetail.  The results of the simulations clearly show the capability of the material model. Load-displacement graphs show ductile and brittle behaviour in compression and tension respectively. The strength is the highest along the fibres of the wood, with a fast decrease as the angle is increased. The simulation of the small-scale tests showed the initiation of rolling shear damage in the bottom transverse layer of the dovetail at a load level of 87 kN. The load continued to rise until a maximum load of 112 kN, while the damaged region grew upwards into the next layer. As compared to the physical tests, the mean maximum capacity of the joint was 125 kN, where rolling shear cracks could be found in the upper transverse layer in all tested specimens. Some of the tested specimens showed damage initiation at a load level of 84 kN. For the larger experiment, the same mode of damage was initiated at a load level of 161 kN which continued to rise until a maximum load level of 165 kN. The calculated values of the shear stress showed a critical shear force of 26 kN per dovetail. This value is 60 and 63 % of the simulated critical shear forces. The results of the simulation are in good agreement with the reference experiment in terms of damage initiation and maximum load. However, a large scatter of material properties, approximations of material orientations and interactions between individual layers results in a low level of predictability in terms of damage evolution and ductility in the material. / Woodbe Engineering AB är ett nystartat företag som har utvecklat en ny typ av knutpunkt för korslimmat trä (KLT). Förbandet innefattar inga metalliska förbindare, vilket förbättrar hållbarheten, ergonomin för arbetarna och tidseffektiviteten. Förbandet är konstruerat för att binda samman golv- och väggelement i flervåningsbyggnader, genom att fräsa tappar i golvelementen och motsvarande spår i väggelementen med hjälp av en CNC-maskin. Innan produkten kan användas på marknaden, behöver den verifieras. Verifikationen kan antingen ske genom fysiska tester eller beräkningar, alternativt en kombination av båda. Företaget har gjort experimentella tester i mindre skala där bärförmågan provades. Senare i år ska prover i större skala utföras. Syftet med arbetet är att utveckla en simuleringsmodell som kan förutspå resultaten hos de fysiska proverna. En simuleringsmodell som ger tillförlitliga resultat kan vara ett bra substitut till fysiska prover genom en lägre kostnad, de är mer tidseffektiva och parametrar kan enkelt ändras. KLT är uppbyggt av flera lager av träskivor med olika riktningar. Träet själv är relativt komplext att modellera. Det har olika egenskaper i olika riktningar, samtidiga duktila och spröda brottmoder och har en stor spridning av materialegenskaper. För att fånga upp dessa egenskaper, har en materialmodell som innefattar ortotrop elasticitet och linjär brottmekanik använts. Beteendet hos materialmodellen har utvärderats med tester i både drag och tryck i olika riktningar. Noggrannheten hos materialmodellen har undersökts genom en simulering av redan testade småskaleprover, där bärförmågan och brottmoden undersöktes. En simulering av fullskaleproverna har också gjorts, där en förutsägelse av bärförmågan och den första brottmoden har gjorts. Dessutom har ett beräkningsskript tagits fram som beräknar skjuvspänningen i tappen. Resultaten av simuleringarna visar tydligt förmågan hos materialmodellen. Kraft-förskjutningskurvor visar duktila och spröda beteenden i tryck respektive drag. Hållfastheten är högst i fiberriktningen, med en snabb minskning när vinkeln till fibrerna ökar. Simuleringen av småskaleproverna visade initiering av rullskjuvningsbrott i det undre tvärgående lagret i tappen vid en last av 87 kN. Lasten ökade till den maximala lasten 112 kN, medan det skadade området växte uppåt in i nästa lager. I jämförelse med de fysiska testerna var den maximala medellasten 125 kN, och rullskjuvningssprickor i det övre tvärgående lagret kunde hittas i alla provexemplar. Några av de provade exemplaren visade brottinitiering vid en last av 84 kN. Simuleringen av den större uppställningen visade samma typ av brottinitiering vid en last av 161 kN som ökade till en maximal last av 165 kN. Beräknade värden av skjuvspänning i tappen visade en kritisk skjuvkraft av 26 kN per tapp. Detta värde är 60 och 63 % av de simulerade kritiska skjuvkrafterna. Resultatet av simuleringen stämmer bra överens med referensexperimentet gällande brottinitiering och maxkapacitet. Dock, på grund av en stor spridning av materialegenskaper, approximationer gällande materialriktningar och samverkan mellan individuella lager, är nivån av förutsägbarhet låg gällande brottillväxt och duktilitet i materialet.

Ultra-high temperature ceramics (UHTCs) are a class of materials that maintain their structural integrity at high temperatures, e.g. 2000 °C. They have been limited in their aerospace applications because of their relatively high density and the difficulty involved in forming them into complex shapes, like leading edges and inlets. Recent advanced processing techniques have made significant headway in addressing these challenges, where the introduction of multiscale porosity has resulted in lightweight UHTCs dubbed multiscale porous UHTCs. The effect of multiscale porosity on material properties must be characterized to enable design, but doing so experimentally can be costly, especially when attempting to replicate hypersonic flight conditions for relevant testing of selected candidate samples. As such, this dissertation seeks to computationally characterize the thermomechanical properties of multiscale porous UHTCs, specifically titanium diboride, and validate those results against experimental results so as to build confidence in the model. An implicit quasi-static variant of the Material Point Method (MPM) is developed, whose capabilities include intrinsic treatment of large deformations and contact which are needed to capture the complex material behavior of the as-simulated porous UHTC microstructures. It is found that the MPM can successfully obtain the elastic thermomechanical properties of multiscale porous UHTCs over a wide range of temperatures. Furthermore, characterizations of post-elastic behavior are found to be qualitatively consistent with data obtained from uniaxial compression experiments and Brazilian disk experiments. / Doctor of Philosophy / This dissertation explores a class of materials called ultra-high temperature ceramics (UHTCs). These materials can sustain very high temperatures without degrading, and thus have the potential to be used on hypersonic aircraft which routinely experience high temperatures during flight. In lieu of performing experiments on physical UHTC specimens, one can perform a series of computer simulations to figure out how UHTCs behave under various conditions. This is done here, with a particular focus what happens when pores are introduced into UHTCs, thus rendering them more like a sponge than a solid block of material. Doing computer simulations instead of physical experiments is attractive because of the flexibility one has in a computational environment, as well as the significantly decreased cost associated with running a simulation vs. setting up and performing an experiment. This is especially true when considering challenging operating environments like those experienced by high-speed aircraft. The ultimate goal with this research is to develop a computational tool than can be used to design the ideal distribution of pores in UHTCs so that they can best perform their intended functions.