Knowledge about the dynamic behaviour is a basic condition for a secure operation of modern machine tools. Hence numerical methods predicting the dynamic properties are gaining in importance. Usually for complex and coupled structures, the results of dynamic property calculation are yet insufficient. Therefore Finite Element model updating is a tool to improve the hypothetical factor of the analysis. Within the present thesis Finite Element modelling is performed using the example of the “Scherenkinematik”, a machine tool based on hybrid-kinematics. Initially the results of an Experimental Modal Analysis are evaluated by identifying Modal parameters and deriving possible structural modifications. In the second part of the thesis, the machines Finite Element model is created using the FEA-Software ANSYS. Afterwards the Finite Element model updating is performed by coupling ANSYS and the CAE-Software FEMtools. Therefore two approaches are formulated and tracked. It turns out, that there is no improvement of the analytical and experimental models correlation, neighter with nor without a steady reduction of the search domain needed for mode coupling. It is reasoned, that the characteristics and the results of an Finite Element updating process are affected by the quality of the model at start time and the approach as well as the technique chosen for model updating and parameter modification. Therefore the CAE-Software FEMtools is suitable to only a limited extent for Finite Element updating of strongly coupled mechanical structures as a result of the sensitivity analysis used for parameter modification.

L'enrichissement des modèles numériques de l'être humain est un enjeu majeur dans la recherche en biomécanique des chocs. Dans le cas des os longs, les propriétés mécaniques sont le plus souvent déterminées à partir de caractéristiques macroscopiques sans prendre en compte l'influence de l'architecture du tissu. Ce manque de considération explique les limites de la biofidélité des modèles proposés actuellement. Fort de ce constat, une approche multi-échelle semble être pertinente pour une amélioration des prédictions obtenues. Cette thèse s'intéresse plus particulièrement au comportement de l'humérus humain dans le cadre de sollicitations dynamiques et propose le développement d'une loi micromécanique pour le décrire. Cette loi est un couplage entre le schéma d'homogénéisation linéaire de Mori-Tanaka pour l'estimation des propriétés mécaniques apparentes de l'humérus avec un raisonnement thermodynamique décrivant la progression de l'endommagement au sein de l'os cortical à l'aide d'une loi de croissance des porosités. La validité de ce modèle a été faite à travers l'estimation de l'effort ultime lors d'essais de type impacts. Pour ce faire, cette étude repose sur les résultats de campagnes expérimentales explorant à différentes échelles les propriétés mécaniques de 13 humérus prélevés de 10 sujets humains post-mortem. Ainsi des essais d'impact ont été réalisés sur pièces anatomiques, les propriétés élastiques mésoscopiques et l'influence de l'endommagement sur ces dernières ont été caractérisées à travers des tests de traction/compression ou de flexion sur éprouvettes et les propriétés microscopiques de la matrice osseuse ont été mesurées par nanoindentation. / The relevant of the human numerical models is a major issue in biomechanical researches. The long bones' mechanical properties are often identified from macro-scale characteristics without taking account of bone structure. This lack of consideration explains the limit of the proposed models biofidelity. A multi-scale approach seems to be relevant for the prediction's improvement, in light of this. This thesis studied the human humerus behavior during dynamical solicitations and propose a micromechanical law to describe it. This law is coupling the linear homogenization scheme of Mori-Tanaka to evaluate the apparent mechanical properties of humerus with a thermo dynamical reasoning to describe the cortical bone damaging by porosities growing. The model validity has been established by the estimation of the maximal load during a impact test. This study is based on the results from multi-scale experimental campaigns exploring the mechanicals properties of 13 humerus from 10 post-mortem human cadavers. So impacts tests have been realized on anatomical specimens, the mesoscopic elastic properties and the damaging influence on them have been characterized by traction, compression or flexion tests and the microscopic properties of bone matrix have been measured by nanoindentation.

The growing shares of renewable energy sources in the market and solar thermal power applications have set higher requirements on steam turbine operation.These requirements are related to flexibility during transients. A key aspect sought of such flexibility is the capability for fast starts. Due to the varying temperature gradients during start-up, the speed at which the turbine can start is constrained by thermal stresses and differential expansion. These phenomena either consume component lifetime or may result in machine failure if not carefully controlled. In order to accomplish faster starts while ensuring that lifing requirements are preserved, it is important to analyze the thermal behavior of the machine. For this, a transient thermal model was developed with a focus on adaptability to different turbine sizes and geometries. The model allows for simple and fast prediction of thermo-mechanical properties within the turbine metal, more importantly, of the temperature distribution and the associated thermal expansion. The next step of this work was to validate the assumptions and simplifications of the model. This was done through the study and comparison of two turbines against measured operational data from their respective power plants. Furthermore,validation studies also included comparisons concerning the geometric detail level of the model. Overall, comparison results showed a large degree of agreement with respect to the measured data and between the geometric detail levels. The validated model was then implemented in studies related to reducing start-up times and peak differential expansion. For this, the potential effects of turbine temperature maintaining modifications were investigated and quantified.The modifications studied included: increasing gland steam pressure, increasing back pressure and increasing barring speed. Results yielded significant improvements starting from 9.5% in the start-up times and 7% in the differential expansion. / <p>QC 20141128</p>

The economic and technologic development experienced by the society in the last decades has caused the demand of a new type of faster and more comfortable transport. This type of demand has been covered by the air transport, the road transport and the railway transport. This situation where the society demands an improvement in her quality of life is the best situation for the birth of the high speed trains. Different studies carried out in the transport field have demonstrated that for distances between four hundred and one thousand of kilometres, the high speed trains provide a lower travelling times than the rest of the transports. These types of high speed trains have increased the axle loads and the average speeds, thus generally a dynamic analysis is required by the ERRI in all the railway bridges when the train speed is higher than 200 Km/h. Besides, when the train speed is going to be higher than 200 Km/h, the vibrations induced in the bridge can reduce the service life of the vehicles and structure, and generally, this fact leads to become the dynamic effect in the principal factor to take into account in order to design the structure. Therefore, an important knowledge in railway bridges dynamic is required to not to oversize the structures with the consequent economic cost. The purpose of this thesis is to study the possibility of accurately predicting the dynamic response of an existing railway bridge, subjected to the high speed train Gröna Tåget, implementing a simplified 2D finite element model with the aid of the program Abaqus. The bridge chosen is the Lögdeälv Bridge, a two spans composite bridge, located along the Bothnia Line (the new Swedish high-speed line), between the localities of Nordmaling and Rundvik. The measured eigenfrequencies due to bending modes of vibration are used for updating the model and then, these frequencies and the accelerations measured are used to compare and validate the different 2D updated models. The parameters used to update the models are; the damping coefficient of the structure, the mass and the stiffness of the bridge, and the supports stiffness. Finally it is concluded that the best model is achieved when the rotational support stiffness is modified in the two extremes supporters of the bridge.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / In this research, an improved first order formulation is presented to study the critical buckling load in functionally graded beams. The formulation has five independent variables in comparison with the Timoshenko theory that has three. The Trefftz criterion is utilized with incremental and fundamental states to define the stability analysis. Virtual work statements are derived for the finite element model where the field variables are interpolated by Lagrange polynomials. The numerical results are compared and verified with other formulations found in literature. Parametric studies are also carried out for buckling behavior due to different slenderness ratios, power-law indices and boundary conditions. Applications of the model to functionally graded materials show the validity of the present approach.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / In this work, a finite element model based on an improved first-order formulation (IFSDT) is developed to analyze buckling phenomenon in laminated composite beams. The formulation has five independent variables and takes into account thickness stretching. Threedimensional constitutive equations are employed to define the material properties. The Trefftz criterion is used for the stability analysis. The finite element model is derived from the principle of virtual work with high-order Lagrange polynomials to interpolate the field variables and to prevent shear locking. Numerical results are compared and validated with those available in literature. Furthermore, a parametric study is presented.

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Developing a more scientific way to determine the load threshold for capillary wall failure would be a big step forward in characterizing whether bruising is result from an abuse or an accident. In this thesis, the upper portion of the human arm was modeled and analyzed under dynamic loading conditions. Since the diameter of the arm is much larger than that of the capillary, a four-level hierarchical sub-modeling method was used to mathematically link the transient response of the global arm model to the response of a small volume in the muscle tissue containing one capillary. Soft tissue in the arm was modeled in two distinct ways. In one method each component of soft tissue was modeled used isotropic linear elastic properties to find the loading threshold that produces a hoop stress in the capillary wall equal to the capillary failure stress. In the other approach, nonlinear, hyper-elastic properties for skin, adipose, muscle tissue and capillary wall were employed to make the tissue behavior more realistic to that of a human arm. Material-appropriate constitutive functions were chosen for each layer. A mathematical technique implement in MATLAB was used to estimate and subtract rigid body motion from the total displacement to avoid excessive displacements of sub-models and focus more on the deformation-only displacement. It was found that modeling the skin, adipose, muscle and capillary as hyper-elastic resulted in significantly smaller deformations but larger loads that resulted in capillary failure.

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