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Pure equilibrium tetrahedral finite elements for global error estimation by dual analysis ; Debongnie, Jean-François ; Beckers, Pierre in International Journal for Numerical Methods in Engineering (2010) This study presents a general porocedure of creating pure equilibrium tetrahedral finite elements. These elements are of the Fraeijs de Veubeke type. The spurious kinematical modes which inevitably appear ... [more ▼] This study presents a general porocedure of creating pure equilibrium tetrahedral finite elements. These elements are of the Fraeijs de Veubeke type. The spurious kinematical modes which inevitably appear in this approach are eliminated by converting each tetrahedron in a super-element consisting of four tetrahedral primitive elements. A mathematical discussion on the number of spurious kinematical modes is presented. The development of first and second degree elements is presented in detail, and their efficiency in the frame of global errror estimation by dual analysis is emphasized by two numerical applications. The main attribute of the error estimation by dual analysis is that it provides an upper bound of the discretization error. [less ▲] Detailed reference viewed: 78 (7 ULg)Una proyección sintética para el diseño arquitectónico con la luz del sol ; Masset, Luc ; Beckers, Pierre Conference (2007, October) Detailed reference viewed: 122 (17 ULg)PARTICIPATION OF ULG STUDENTS TO THE SSETI MICROSATELLITE PROGRAMME USING SAMCEF ; ; et al Conference (2007) The objective of this presentation is to discuss the participation of students at the University of Liège to the educational spacecraft project SSETI-ESEO proposed by the European Space Agency. SSETI ... [more ▼] The objective of this presentation is to discuss the participation of students at the University of Liège to the educational spacecraft project SSETI-ESEO proposed by the European Space Agency. SSETI students are now mainly involved in the ESEO satellite for which the University of Liège is in charge of the MECH work package. The students have to propose a design for the structure of the solar panels (including the geometry and materials) and their deployment and pointing mechanisms (including electrical circuits, motors, hinges and actuators). Through detailed finite element computations in the SAMCEF software, they have to verify the structural integrity of the panels during the launch phase and to guarantee a safe deployment once on-orbit. Another task is to ensure an appropriate orientation of the solar panels to collect the maximum power from the sun. An industrial partner specialized in the development of computer-aided engineering solutions, SAMTECH, and a research center, Liège Space Center (CSL), also bring their expertise to the project. [less ▲] Detailed reference viewed: 99 (10 ULg)Eléments finis tétraédriques pour l'analyse duale ; Beckers, Pierre ; Debongnie, Jean-François in Revue Européenne des Éléments Finis (2004), 13(5/6/7), 547-558 The error estimation by pure dual analysis requires two finite element computations. It is based on the results of displacement and equilibrium approaches of a given problem. It allows to compute the ... [more ▼] The error estimation by pure dual analysis requires two finite element computations. It is based on the results of displacement and equilibrium approaches of a given problem. It allows to compute the cumulated global discretization error of the two models by a simple comparison of the total energies computed using both methods. This paper presents the development of a new family of equilibrium type tetrahedral finite elements leading to statically admissible solutions of 3D finite element problems. Two examples of dual analysis using these elements are also presented. [less ▲] Detailed reference viewed: 80 (12 ULg)Face milling and turning simulation with the finite element method Masset, Luc ; Debongnie, Jean-François ; Beckers, Pierre in Habraken, Anne (Ed.) Proceedings of the 4th International ESAFORM Conference on Material Forming (2001, April) The paper describes a new simulation tool that gives the machined surface error in face milling and turning. The form error component due to the workpiece flexibility is computed using Samcef finite ... [more ▼] The paper describes a new simulation tool that gives the machined surface error in face milling and turning. The form error component due to the workpiece flexibility is computed using Samcef finite element code. The finite element analyses are very efficient on industrial applications thanks to the superelement method. Results are obtained in a short time which makes possible a wide range of simulations such as finding the best tool trajectory, testing several tools and cutting conditions and choosing the most suited fixture design. [less ▲] Detailed reference viewed: 162 (6 ULg)Consistency of stress smooting by convolution Debongnie, Jean-François ; Beckers, Pierre Conference (2001, March) A convolution process is presented in order to smoothen finite element stresses. A comprehensive analysis leads to the fact that a pertinent choice of the convolution kernel has to be done, as consistency ... [more ▼] A convolution process is presented in order to smoothen finite element stresses. A comprehensive analysis leads to the fact that a pertinent choice of the convolution kernel has to be done, as consistency conditions have to be satisfied. Such kernels are then presented. [less ▲] Detailed reference viewed: 32 (8 ULg)On a general decomposition of the error of an approximate stress field in elasticity Debongnie, Jean-François ; Beckers, Pierre in Computer Assisted Mechanics and Engineering Sciences [=CAMES] (2001), 8 The errors of finite element approximations are analysed in a general frame, which is completely independent from the way through which the approximate solution was obtained. It is found that the error ... [more ▼] The errors of finite element approximations are analysed in a general frame, which is completely independent from the way through which the approximate solution was obtained. It is found that the error always admits decomposition in two terms, namely the equilibrium error and the compatibility error, which are orthogonal. Each of these admits upper and lower bound that can be computed in a post-processing scheme [less ▲] Detailed reference viewed: 36 (7 ULg)Revisiting early works of the aerospace laboratory of Liège. Dual analysis, 60's and 70's Debongnie, Jean-François ; Beckers, Pierre in Nguyen-Dang, Hung; Ronday, François; Nguyen, Van Diep (Eds.) Proceeding of the International colloquium in mechanics of solids, fluids, structures and interactions (2000, August) The goal of this presentation is to describe the main scientific contribution of the Aerospace Laboratory of the Liège University (LTAS) during the sixties and seventies. This period was very important ... [more ▼] The goal of this presentation is to describe the main scientific contribution of the Aerospace Laboratory of the Liège University (LTAS) during the sixties and seventies. This period was very important for the development of the finite element techniques and the major part of the concepts and the algorithms were defined at that time. The contribution of the LTAS was especially original because it was the only team in the world who was proposing the dual method and included it in a Finite Element code for all the applications : bar, membrane and plates, using for both types of models the same displacement solution algorithm. After the presentation of this method a short description is made about recent improvements proposed by the authors. [less ▲] Detailed reference viewed: 46 (4 ULg)Recent advances in the dual analysis theory Debongnie, Jean-François ; Beckers, Pierre Conference (1999, June) The dual analysis concept, which is one of the oldest methods of measuring the discretization error of finite element models, suffered by its lack of generality in its original version. In fact, severe ... [more ▼] The dual analysis concept, which is one of the oldest methods of measuring the discretization error of finite element models, suffered by its lack of generality in its original version. In fact, severe restrictions were imposed to the boundary conditions, excluding any mixed problem. These restrictions, related to an analysis where stiffness plays a central role, can be avoided by using the proper reference energy, which is the total complementary energy. This leads to convergence curves which are always on the same side of the exact value and whose distance measures the quality of the analyses. [less ▲] Detailed reference viewed: 27 (3 ULg)Modélisation du bridage Beckers, Pierre ; Debongnie, Jean-François ; et al Report (1996) This report is devoted to the modelling of the clamping devices in the projected machining simulation tool Detailed reference viewed: 58 (4 ULg)catalogue des cas-tests Beckers, Pierre ; Debongnie, Jean-François ; et al Report (1996) This report describes the benchmarks which have been done with the machining simulation prototype. Detailed reference viewed: 35 (3 ULg)Comparaisons calculs-essais pour le palier de suspension J64 Beckers, Pierre ; Debongnie, Jean-François ; Masset, Luc Report (1996) This report is devoted to the J64 suspension bearing benchmark. Unfortunately, the actual machining led to considerable vibrations, rendering any comparison impossible. Detailed reference viewed: 25 (3 ULg)Comparaisons calculs-essais pour le carter d'alimentation d'huile TA96 Beckers, Pierre ; Debongnie, Jean-François ; Masset, Luc Report (1996) On this application, the computed results were in the opposite direction as compared to the physical tests. A sound analysis led to the result that a parasitic deformation was due to clamping deformations ... [more ▼] On this application, the computed results were in the opposite direction as compared to the physical tests. A sound analysis led to the result that a parasitic deformation was due to clamping deformations. In fact, the three supports of the work were found to be unsufficiently coplanar. [less ▲] Detailed reference viewed: 31 (4 ULg)Comparaisons calculs-essais pour l'éprouvette cylindrique Beckers, Pierre ; Debongnie, Jean-François ; Masset, Luc Report (1996) In this first application of the machining simulation tool prototype, great difficulties were encountered in the interpretaion of the physical test. In fact, parasitic deformations occured, with a three ... [more ▼] In this first application of the machining simulation tool prototype, great difficulties were encountered in the interpretaion of the physical test. In fact, parasitic deformations occured, with a three-lobed form. This implied the necessity of filtering the experimental data and a physical interpretation of the undue deformation. A theoretical study is performed, leading to the result that this phenomenon is due to the combined effect of the clearance of the clamping jaws and the pre-stress of the dead center. [less ▲] Detailed reference viewed: 34 (3 ULg)Répartition des forces d'usinage Beckers, Pierre ; Debongnie, Jean-François ; Masset, Luc Report (1996) In the frame of the feasability study of a machining simulation tool, this report starts from the fact that the concentrated loads which were formerly used are somewhat defective from several points of ... [more ▼] In the frame of the feasability study of a machining simulation tool, this report starts from the fact that the concentrated loads which were formerly used are somewhat defective from several points of view. A procedure to compute distributed loads is described. [less ▲] Detailed reference viewed: 94 (8 ULg)Dual analysis with general boundary conditions Debongnie, Jean-François ; ; Beckers, Pierre in Computer Methods in Applied Mechanics & Engineering (1995), 122(1-2), 183-192 The dual analysis concept was introduced by Fraeijs de Veubeke [1] as a consequence of upper and lower bounds of the energy. As such bounds exist only in those cases where one type of condition is ... [more ▼] The dual analysis concept was introduced by Fraeijs de Veubeke [1] as a consequence of upper and lower bounds of the energy. As such bounds exist only in those cases where one type of condition is homogeneous, it is commonly admitted that a dual error measure does not exist with general boundary conditions. This paper presents a re-examination of the dual error measure by a way which avoids any use of upper and lower bounds of the energy. It is found that such an error measure holds whatever the boundary conditions be. Furthermore, it is not necessary to obtain the approximate solutions by a Rayleigh-Ritz process, so that the second analysis, which seemed necessary in the original dual analysis concept, may be replaced by any admissible approximation. This implies the possibility of a dual error measure at a simple post-processor level. [less ▲] Detailed reference viewed: 35 (8 ULg)Procedures de limitation des cas de charge Beckers, Pierre ; Debongnie, Jean-François ; et al Report (1995) In the frame of the feasability study of a machining simulation tool, this report is devoted to special procedures allowing a reduction of the computed load cases in order to reduce the computational time. Detailed reference viewed: 51 (5 ULg)Description d'une méthode de reconstitution de la surface usinée Beckers, Pierre ; Debongnie, Jean-François ; et al Report (1995) In the frame of the feasability study of a machining simulation tool, this report is devoted to the obtention of the machined surface from a series of finite element computations Detailed reference viewed: 67 (4 ULg)Recommandations relatives aux maillages Beckers, Pierre ; Debongnie, Jean-François ; et al Report (1995) In the frame of the feasability study of a machining simulation tool, this report is devoted to the obtention of a suitable finite element mesh of the work. Detailed reference viewed: 61 (5 ULg)Procédures d'identification des paramètres de charge Beckers, Pierre ; Debongnie, Jean-François ; et al Report (1995) In the frame of the feasability study of a machining simulation, this report describes how to compute the nodal components of the cutting forces on the finite element mesh. Detailed reference viewed: 43 (4 ULg) |
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