In design of bridges and for estimation of dynamic properties and load carrying capacity Finite Element Method (FEM) is often used as a tool. The physical quantities used in the Finite Element (FE) model are often connected to varying degrees of uncertainty. To deal with these uncertainties conservative parameter estimates and safety factors are used. By calibrating the bridge FE model to better fit with the response of the real structure, less conservative parameter values can be chosen. This method of comparing measured and response with estimates from a FE model and calibrating the model parameters is called Finite Element Model Updating (FEMU). In the present thesis different aspects of FEMU are investigated. The first part comprises a literature review covering all aspects of FEMU with special focus on the choice of updating parameters, objective functions for iterative updating procedures and the automatic pairing of modes. This part is concluded with a flowchart suggesting a systematic approach to a FEMU project. In the second part of the text two bridge case studies are presented. In the first case study a railway bridge in the north of Sweden is studied. A detailed FE bridge model from a previous project is used as a simulation model for extraction of modal data by eigenvalue analysis. Then simplified models are created and attempts to update these models are performed. The updating parameters are chosen based on a simple sensitivity analysis. Tests are performed to investigate the influence of chosen updating parameters and objective function on the computational cost and the quality of the updated model. Case study number two is more comprehensive and focuses on the sensitivity analysis for the choice of updating parameters and on the choice of objective function. A road bridge in the Stockholm area is used and as for case study one a detailed model from a previous project is used as simulation model. Also a new criteria for the automatic pairing of modes is presented and tested. In the end an attempt to verify two of the updated models is performed. / <p>QC 20150825</p>

The work reported in this thesis presents a general overview of the dynamic response of short-span railway bridges considering soil-structure interaction. The study aims to identify the effect of the surrounding and underlying soil on the global stiffness and damping of the structural system. This may lead to better assumptions and more efficient numerical models for design.A simple discrete model for calculating the dynamic characteristics of the fundamental bending mode of single span beam bridges on viscoelastic supports was proposed. This model was used to study the effect of the dynamic stiffness of the foundation on the modal parameters (e.g. natural frequency and damping ratio) of railway beam bridges. It was shown that the variation in the underlying soil profiles leads to a different dynamic response of the system. This effect depends on the ratio between the flexural stiffness of the bridge and the dynamic stiffness of the foundation-soil system but also on the ratio between the resonant frequency of the soil layer and the fundamental frequency of the bridge. The effect of the surrounding soil conditions on the vertical dynamic response of portal frame bridges was also investigated both numerically and experimentally. To this end, different numerical models (i.e. full FE models and coupled FE-BE models) have been developed. Controlled vibration tests have been performed on two full-scale portal frame bridges to determine the modal properties of the bridge-soil system and calibrate the numerical models. Both experimental and numerical results identified the substantial contribution of the surrounding soil on the global damping of short-span portal frame bridges. A simplified model for the surrounding soil was also proposed in order to define a less complicated model appropriate for practical design purposes. / <p>QC 20180315</p>

Le contexte de ce travail concerne le process d'Infusion de Résine Liquide (LRI) développé dans le cadre du projet « FUSelage COMPosite » par DAHER SOCATA. Ce process de fabrication permet de réaliser des pièces de formes complexes et des panneaux entiers de fuselage en composites, ce qui réduit considérablement les étapes d'assemblages et donc les temps de production. Les travaux de thèse portent sur l'identification expérimentale du comportement d'un fuselage composite. Ce travail se divise en deux parties qui sont la qualification du contrôle non destructif (CND) par rapport à une taille de défaut critique et l'identification du comportement d'une structure composite orthotrope en présence de ce défaut. Le premier volet consiste à évaluer les techniques de CND basées sur des mesures de champs (acoustiques, thermiques et densimétriques), capables de détecter des défauts internes de types délaminage et porosité au sein de structures composites monolithiques et sandwichs, et fournissant une visualisation des résultats par une cartographie de défauts 2D ou 3D. Le choix de ces méthodes a été motivé par la volonté de DAHER SOCATA d'acquérir de nouvelles compétences en matière de CND. Le deuxième volet consiste à évaluer les paramètres élastiques d'une structure composite orthotrope (structure comprenant une zone saine et une zone localement dégradée) via une procédure d'identification, à partir de mesures de champs, globale et locale par recalage de modèles éléments finis. Cette procédure se décompose en quatre parties avec tout d'abord l'identification des propriétés de la structure saine, ensuite la localisation de la zone dégradée, l'intégration de celle-ci dans le modèle éléments finis, et l'identification des propriétés de cette dernière. / The context of this work concerns the process of Liquid Resin Infusion (LRI) developed under the project "composite fuselage" by DAHER SOCATA. This manufacturing process can produce parts with complex shapes and entire panels of composite fuselage, reducing assembly steps and therefore the production time. The thesis work focused on the experimental identification of the behavior of a composite fuselage. This work is divided into two parts which are the qualification of non destructive testing (NDT) compared to a critical defect size and the identification of the behavior of an orthotropic composite structure with defect. The first part is to evaluate the NDT techniques based on full field measurements (acoustic, thermal and densimetric), capable of detecting internal defects as porosities and delaminations in monolithic and sandwich composite structures, and providing a results visualization by a 2D or 3D defects map. The choice of these methods was motivated by DAHER SOCATA which wants to learn new NDT skills. The second part is to evaluate the elastic parameters of an orthotropic composite structure (structure composed by a virgin zone and a damaged zone) through an identification process from field measurements, by global and local step. This procedure is divided into four parts with two identification steps and a image processing step.

Die vorliegende Arbeit liefert eine ausführliche systematische Untersuchung der Gestellschwingungen von Rollen- und Bogen-Offsetdruckmaschinen. Sie dient dazu, die modalen Eigenschaften (Eigenfrequenzen, Eigenformen) zu identifizieren und die erzwungenen Schwingungen zu simulieren. An drei Rollen-Offsetdruckmaschinen wurden experimentelle und theoretische Modalanalysen durchgeführt. Es wurden die Einflüsse des Baugrundes, der Aufstellung und der Schraubenverbindung auf die modalen Eigenschaften analysiert. Weiterhin wurde die Standsicherheit bei seismischer Erregung überprüft. Für alle vier untersuchten Offsetdruckmaschinen wurden FE-Modelle unter Berücksichtigung ihrer Besonderheiten gebildet und mittels der Messergebnisse abgesichert. Bei Bogen-Offsetdruckmaschinen wurden erzwungene Schwingungen bei vier verschiedenen Erregungen und bei ungleichmäßiger Aufstellung simuliert. Aus den vorliegenden Resultaten können Schlussfolgerungen für die Weiterentwicklung von Druckmaschinen gezogen werden. / This work provides a detailed systematical research about the frame vibrations of web-offset-printing machines and sheetfed-offset-printing machines. It serves to identify the modal properties (natural frequencies and mode shapes) and to simulate the forced vibrations. The experimental and theoretical modal analysis have been realised at three web-offset-printing machines. The influences of the base, installation and screw connection on the modal properties have been analysed, furthermore the stand security under seismic excitation has been verified. The FE-models of all four investigated offset-printing machines have been built under consideration of their characteristics and have been updated with measurement results. Forced vibrations of sheetfed-offset-printing machines have been simulated on four different excitations and for uneven installation. The results of this work can be used for the further development of printing-machines.

Reservoir economic performance is based upon future cash flows which can be generated from a reservoir. Future cash flows are a function of hydrocarbon volumetric flow rates which a reservoir can produce, and the market conditions. Both of these functions of future cash flows are associated with uncertainties. There is uncertainty associated in estimates of future hydrocarbon flow rates due to uncertainty in geological model, limited availability and type of data, and the complexities involved in the reservoir modeling process. The second source of uncertainty associated with future cash flows come from changing oil prices, rate of return etc., which are all functions of market dynamics. Robust integration of these two sources of uncertainty, i.e. future hydrocarbon flow rates and market dynamics, in a model to predict cash flows from a reservoir is an essential part of risk assessment, but a difficult task. Current practices to assess a reservoir’s economic performance by using Deterministic Cash Flow (DCF) methods have been unsuccessful in their predictions because of lack in parametric capability to robustly and completely incorporate these both types of uncertainties. This thesis presents a procedure which accounts for uncertainty in hydrocarbon production forecasts due to incomplete geologic information, and a novel real options methodology to assess the project economics for upstream petroleum industry. The modeling approach entails determining future hydrocarbon production rates due to incomplete geologic information with and without secondary information. The price of hydrocarbons is modeled separately, and the costs to produce them are determined based on market dynamics. A real options methodology is used to assess the effective cash flows from the reservoir, and hence, to determine the project economics. This methodology associates realistic probabilities, which are quantified using the method’s parameters, with benefits and costs. The results from this methodology are compared against the results from DCF methodology to examine if the real options methodology can identify some hidden potential of a reservoir’s performance which DCF might not be able to uncover. This methodology is then applied to various case studies and strategies for planning and decision making. / text

Thesis deals with determination of layerwise mechanical properties of composite ceramics by indirect method, namely Youngs modulus. Based on literature review, it was found that a method to determine elastic properties of one or more components of multi layered composites based on experimental modal analysis and finite element modal analysis, or analytical approach exists. Method based on FE modal analysis was applied to ceramic laminate, where it was attempt to determine youngs modulus of one component. Beyond that, it was attempt to determine Youngs moduli of both components using first two bending resonant frequencies. Results were unsatisfying. Sensitivity analysis showed that layers with unknown Youngs modulus were overly sensitive to small changes in input parameters due to their small relative thickness with respect to thickness of laminate and due to location in laminate. Based on this conclusion, recommendations were made with respect to suitable geometry of test specimens.

In the global framework of improving vibro-acoustic numerical prediction quality together with the need to decrease the number of prototyping stages, this manuscript focuses on achieving greater accuracy for acoustic numerical simulations by making use of a parametric updating technique, which enables tuning the model parameters inside physically meaningful boundaries. The improved model is used for the next prototyping stages, allowing more accurate results within reduced simulation times. The updating technique is based on recent works dealing with the constitutive relation error method (CRE) applied to acoustics. The updating process focuses on improving the acoustic damping matrix related to the absorbing properties of the materials covering the borders of the acoustic domain. / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished

Cette thèse vise à étudier le comportement mécanique de l’acier de cuve 16MND5 (ou A508cl3 pour la norme anglaise) à l’échelle de la microstructure en croisant des approches expérimentale et numérique. Plusieurs contributions au développement de l’essai de traction in-situ à l’intérieur de MEB ont été apportées. En premier, les biais de mesure de différentes modalités (BSE, EBSD et SE) d’acquisition d’images sous MEB ont été caractérisés et corrigés. Les images MEB de différentes modalités ont été corrélées de façon précise afin de décrire la topographie de l’éprouvette. Les images d’orientation cristallographique (EBSD) ont été corrélées afin de révéler la rotation cristalline et les champs de déplacement de surface au long de la traction. La déformation élastique de l’éprouvette a été mesurée par corrélation intégrée des images de diffraction électronique à haute-résolution. Les microstructures fines de l’éprouvette à trois dimensions après déformation ont été mesurées par FIB-EBSD. L’essai a également été simulé par calcul de plasticité cristalline sur un maillage 3D, basé sur les microstructures mesurées dans la configuration déformée. Un algorithme a été proposé pour estimer la configuration initiale de l’éprouvette et identifier les paramètres de loi de plasticité en procédant par itérations. Un cas test synthétique 2D a été employé pour valider la faisabilité de l’algorithme. Deux lois de plasticité cristalline ont été testées sur le maillage 3D: dynamique des dislocations des cristaux cubiques centrés, et une version modifiée de la loi Méric-Cailletaud. Pour cette dernière loi, deux jeux de paramètres ont été identifiés pour les ferrites et bainites par recalage des éléments finis. / The PhD project is devoted to the study of the mechanical response of the reactor pressure vessel steel A508cl3 (or 16MND5 in French nomenclature) at the microscopic scale by experimental analyses and numerical simulations. Different aspects of in-situ tests inside an SEM chamber have been considered. First, the characterization and corrections of bias and uncertainties of different SEM imaging modalities (SE, BSE, and EBSD) have been performed. Precise registrations of SEM images in different modalities have been developed in order to give a comprehensive description of the sample surface topographies. Crystallographic orientation maps (from EBSD analyses) are registered to measure the crystal rotation and displacement fields along the tensile test. The elastic deformations of the surface are assessed by integrated correlation of high-resolution electron diffraction images. The 3D microstructure of the analyzed sample is revealed a posteriori by combining FIB milling andEBSD images.The experimental test is also simulated by crystal plasticity calculations on a 3D mesh created according to the 3D microstructure observed in the deformed configuration. An algorithm has been proposed to estimate its initial configuration and to identify the plastic parameters iteratively. A synthetic 2D model has been used to prove its feasibility. Two crystal plasticity laws have been validated on the 3D mesh, namely dislocation dynamics for body-centered cubic crystals and a modified version of Méric-Cailletaud model. In thepresent work finite element model updating was used to provide two sets of parameters (for ferrite and bainite) for the latter law.

No description available.

Die vorliegende Arbeit liefert eine ausführliche systematische Untersuchung der Gestellschwingungen von Rollen- und Bogen-Offsetdruckmaschinen. Sie dient dazu, die modalen Eigenschaften (Eigenfrequenzen, Eigenformen) zu identifizieren und die erzwungenen Schwingungen zu simulieren. An drei Rollen-Offsetdruckmaschinen wurden experimentelle und theoretische Modalanalysen durchgeführt. Es wurden die Einflüsse des Baugrundes, der Aufstellung und der Schraubenverbindung auf die modalen Eigenschaften analysiert. Weiterhin wurde die Standsicherheit bei seismischer Erregung überprüft. Für alle vier untersuchten Offsetdruckmaschinen wurden FE-Modelle unter Berücksichtigung ihrer Besonderheiten gebildet und mittels der Messergebnisse abgesichert. Bei Bogen-Offsetdruckmaschinen wurden erzwungene Schwingungen bei vier verschiedenen Erregungen und bei ungleichmäßiger Aufstellung simuliert. Aus den vorliegenden Resultaten können Schlussfolgerungen für die Weiterentwicklung von Druckmaschinen gezogen werden. / This work provides a detailed systematical research about the frame vibrations of web-offset-printing machines and sheetfed-offset-printing machines. It serves to identify the modal properties (natural frequencies and mode shapes) and to simulate the forced vibrations. The experimental and theoretical modal analysis have been realised at three web-offset-printing machines. The influences of the base, installation and screw connection on the modal properties have been analysed, furthermore the stand security under seismic excitation has been verified. The FE-models of all four investigated offset-printing machines have been built under consideration of their characteristics and have been updated with measurement results. Forced vibrations of sheetfed-offset-printing machines have been simulated on four different excitations and for uneven installation. The results of this work can be used for the further development of printing-machines.