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Théorie des poutres faiblement vrillées Debongnie, Jean-François Report (1978) A weakly pre-twisted beam theory is presented by an original way which renders the mathematical developments fairly simple. The proposed approach has the interesting property that in the finite element ... [more ▼] A weakly pre-twisted beam theory is presented by an original way which renders the mathematical developments fairly simple. The proposed approach has the interesting property that in the finite element frame, the error of the theory converges to zero when the mesh is refined. [less ▲] Detailed reference viewed: 77 (2 ULg)Eléments de tores isoparamétriques développés en séries de Fourier Debongnie, Jean-François Report (1978) This paper is an exposure of the theoretical backgrounds of two isoparametric tor finite elements with a Fourier decomposition. In a second part, a user's manual is given. Finally, practical examples are ... [more ▼] This paper is an exposure of the theoretical backgrounds of two isoparametric tor finite elements with a Fourier decomposition. In a second part, a user's manual is given. Finally, practical examples are given. [less ▲] Detailed reference viewed: 29 (1 ULg)Modélisation de problèmes hydroélastiques par éléments finis. Application aux lanceurs aérospatiaux Debongnie, Jean-François Doctoral thesis (1978) This thesis is devoted to the finite element analysis of hydro-elastic vibrations arising in launchers. It sets a general formulation generalizing Tong's one by a logical step in a lagrangian point of ... [more ▼] This thesis is devoted to the finite element analysis of hydro-elastic vibrations arising in launchers. It sets a general formulation generalizing Tong's one by a logical step in a lagrangian point of view. A specialized solution algorithm is presented. As launchers are axisymmetric structures, a general theory of axisymmetric structures with cosinusoidal modes is presented, including shells, volumes, and incompressible structures. The problem of setting the ccorrest limiting conditions on the axis is treated. Special pressure terms are also treated. [less ▲] Detailed reference viewed: 60 (6 ULg)Analyse des contraintes thermiques dans les plaques tubulaires de réchauffeurs haute pression par la méthode des éléments finis ; Debongnie, Jean-François in Revue M (1978), 24(2), 1-8 The authors investigate the intricate problem of thermal stresses in the tubesheets of high pressure heaters, with emphasis to transient conditions. First, the finite elements method is used with ... [more ▼] The authors investigate the intricate problem of thermal stresses in the tubesheets of high pressure heaters, with emphasis to transient conditions. First, the finite elements method is used with tridimensional models made of isoparametric elements with 20 nodes. The results are compared with measures provided by tests on a HP heater in operation. Then, analysis with axisymmetric elements is investigated and its limitation is defined. A simple analytical method is developed on this basis, which permits a valuable approach for preliminary design. [less ▲] Detailed reference viewed: 85 (3 ULg)Sur la formulation de Herrmann pour l'étude des solides incompressibles Debongnie, Jean-François in Journal de Mécanique (1978), 17(4), 531-558 An exposition of Herrmann's formulation is givent first, and its extension to the anisotropic case is presented following a new way. Using this method, the matrix of material coefficients can be computed ... [more ▼] An exposition of Herrmann's formulation is givent first, and its extension to the anisotropic case is presented following a new way. Using this method, the matrix of material coefficients can be computed in a fully automated manner. The existence of the solution is discussed next. Four criteria are obtained. Three of these are necessary and sufficient, and the fourth, only necessary but of fairly simple use. Some applications are presented to illustrate the theoretical results. [less ▲] Detailed reference viewed: 55 (3 ULg)Manuel théorique et pratique du programme d'analyse de Fourier Debongnie, Jean-François Report (1978) This manual describes the theoretical foundations and the practical use of a pre-processor leading to data for SAMCEF in the case of axisymmetrical structures with a Fourier development Detailed reference viewed: 58 (4 ULg)Introduction du calcul des vitesses critiques dans DYNAM Debongnie, Jean-François ; Géradin, Michel Report (1977) The computation of critical speeds has been introduced in the DYNAM software, in all axisymmetrical elements. This report describes the adopted formulation and presents some application cases. Detailed reference viewed: 44 (3 ULg)A new look at Herrmann's formulation of incompressibility Debongnie, Jean-François in Wellford, L.; Carter, Jr. (Eds.) Proceedings of the symposium on applications of computer methods in engineering (vol.2) (1977, August) An exposition of Herrmann's formulation is given first, and its extension to the anisotropic case is presented following a new way. Using this method, the matrix of material coefficients can be calculated ... [more ▼] An exposition of Herrmann's formulation is given first, and its extension to the anisotropic case is presented following a new way. Using this method, the matrix of material coefficients can be calculated in a fully automated manner. The existence of the solution is briefly discussed next. A necessary and sufficient condition is obtained which turns to be of unpratical use. Fortunately, this condition is in most practical cases equivalent to another one, which is of fairly simple use. These concepts are illustrated by an example. [less ▲] Detailed reference viewed: 160 (4 ULg)L'intégration dans les éléments finis Debongnie, Jean-François Report (1976) This paper presents some quadrature methods which may be successfully applied to finite elements. Detailed reference viewed: 57 (2 ULg)Formulation de l'étude linéarisée des structures précontraintes Debongnie, Jean-François Report (1976) Pre-stress may have a consderable effect on the behaviour of thin walled structures. The general case is non linear. However, there is a class of situations where the study remains linear, as for example ... [more ▼] Pre-stress may have a consderable effect on the behaviour of thin walled structures. The general case is non linear. However, there is a class of situations where the study remains linear, as for example, a plate with a membranar pre-stress. The present paper focuses on the basic hypotheses of such a linearized analysis an on its exact formulation. [less ▲] Detailed reference viewed: 25 (1 ULg)On the approximation of incompressible solids in the displacement method Debongnie, Jean-François Report (1976) A mathematical analysis of the numerical approximation to incompressibility with nearly incompressible displacement finite elements is presented. It explains why, as observed by many authors, convergence ... [more ▼] A mathematical analysis of the numerical approximation to incompressibility with nearly incompressible displacement finite elements is presented. It explains why, as observed by many authors, convergence to the incompressible solution is not necessarily obtained when Poisson's ration is increased up to 0.5. It also allows predicting under which conditions convergence of the nearly incompressible approach is guaranteed. [less ▲] Detailed reference viewed: 21 (1 ULg)Exercices de théorie des structures Debongnie, Jean-François Learning material (1976) Recueil d'exercices donnés aux étudiants suivant le cours de Théorie des Structures du prof. Sander Detailed reference viewed: 935 (8 ULg)Introduction des effets de précontraintes dans l'élément fini de coque de type 18 de SAMCEF Debongnie, Jean-François Report (1976) The eigenfrequencies of a shell containing a liquid are modified by the static pressure of the fluid. This implies the computation of the static stress, its transmission to the dynamic analysis where the ... [more ▼] The eigenfrequencies of a shell containing a liquid are modified by the static pressure of the fluid. This implies the computation of the static stress, its transmission to the dynamic analysis where the pre-stress has to be included in the analysis. A lot of tests have been performed in order to verify the correctness of the approach. [less ▲] Detailed reference viewed: 79 (2 ULg)Analyse dynamique des structures pouvant être incompressibles et application à un élément fini de tore triangulaire Debongnie, Jean-François Report (1975) This report is the continuation of a former report about incompressible structures in statics. Its essential purpose is to derive the mass matrix of the triangular tor element based on Herrmann's ... [more ▼] This report is the continuation of a former report about incompressible structures in statics. Its essential purpose is to derive the mass matrix of the triangular tor element based on Herrmann's formulation. A special focus is brought on the problem of teh condensation of the pressure d.o.f.'s. Examples are presented, in order to assess the correct working of the program. In one of these, details are given on the approprate way of condensing the pressures in the incompressible case. Finally, chapter 4 is devoted to the problem of the convergence of pure displacement models to the correct solution when Poisson's ratio converges to 0.5. [less ▲] Detailed reference viewed: 89 (2 ULg)Préservation des modes rigides et conditions sur les déplacements au voisinage de l'axe dans les coques tron-coniques de révolution Debongnie, Jean-François Report (1975) The classical approach of the shell theory proceeds as follows. After an exact development of the strain expressions, one neglects any term containing the factor h/R. But this method destruct the exact ... [more ▼] The classical approach of the shell theory proceeds as follows. After an exact development of the strain expressions, one neglects any term containing the factor h/R. But this method destruct the exact representation of rigid body modes. An alternative to this procedure is presented here, where special care is given to the preservation of the rigid body modes. The second part of this report is focused on the necessary conditions on the displacements on the axis. This study is based on the fact that the strains have to remain finite values. [less ▲] Detailed reference viewed: 100 (1 ULg)Etude des structures élastiques anisotropes pouvant être incompressibles et application à un élément fini de tore triangulaire Debongnie, Jean-François Report (1975) This paper presents the extension of herrmann's formulation to all cases, isotropic or not, where the local flexibility matrix presents at most one singularity, that is an isotropic pressure. Starting ... [more ▼] This paper presents the extension of herrmann's formulation to all cases, isotropic or not, where the local flexibility matrix presents at most one singularity, that is an isotropic pressure. Starting from Reissner's principle, a matrix is introduced, which behaves as the inverse of the flexibility matrix for any deviatoric stress. This matrix may be obtained in a full-automatic scheme. Then, a triangular tor element is developped from this formulation. Finally, tests are presented. [less ▲] Detailed reference viewed: 33 (2 ULg)Application de la méthode des éléments finis à l'étude du comportement dynamique d'un fluide incompressible et non visqueux contenu dans une structure élastique de révolution Debongnie, Jean-François ; Report (1974) This report is devoted to the bases of the formulation which is implemented in SAMCEF in order to treat fluid-structure interactions in launcher tanks. Detailed reference viewed: 35 (3 ULg)Elément de coque à géométrie de révolution Debongnie, Jean-François Report (1974) The first par of this report is focused on the formulation of the conical shell element in SAMCEF. In chapter 2, benchmark applications of this element in statics are discussed. Chapter 3 is devoted to ... [more ▼] The first par of this report is focused on the formulation of the conical shell element in SAMCEF. In chapter 2, benchmark applications of this element in statics are discussed. Chapter 3 is devoted to numerical tests in modal analysis. [less ▲] Detailed reference viewed: 69 (2 ULg)Vibrations asymétriques d'une coque de révolution autour d'un état d'équilibre thermo-élastique Debongnie, Jean-François ; ; et al Report (1974) This paper describes a theory of shells of revolution. Staring with geometrical considerations, the expression of the strains is deduced. A particular form of the displacement field is then chosen, from ... [more ▼] This paper describes a theory of shells of revolution. Staring with geometrical considerations, the expression of the strains is deduced. A particular form of the displacement field is then chosen, from which follow the shell strains and changes of curvature. The equilibrium equations are then deduced from a variational point of view. Constitutive equations are then stated and simplified owing to the powers of the parameter h/R. The problem of vibrations round an equilibrium state is then formulated, including the so-called stability terms.Inertia terms are then developed. IN order to treat asymmetrical vibrations, a Fourier development of the displacements is introduced, which allows a clear separation of the eigenmodes. [less ▲] Detailed reference viewed: 57 (3 ULg)Analyse dynamique des systèmes hydroélastiques de révolution par la méthode des éléments finis. Application à l'étude du phénomène "POGO" dans les lanceurs à ergols liquides. Debongnie, Jean-François ; in Collection des publications de la Faculté des Sciences Appliquées, Université de Liège (1974), 50 The small oscillations of elastic containers partially filled with liquids are studied. After a brief review of the previously published work on this subject, a new variational formulation of the problem ... [more ▼] The small oscillations of elastic containers partially filled with liquids are studied. After a brief review of the previously published work on this subject, a new variational formulation of the problem is presented. The application uses the finite element method and a new algorithm of solution is proposed. The accuracy of the method is illustrated by several examples including a two tanks launcher structure. [less ▲] Detailed reference viewed: 46 (8 ULg) |
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