Browsing Complete repository Arts & humanities   Archaeology   Art & art history   Classical & oriental studies   History   Languages & linguistics   Literature   Performing arts   Philosophy & ethics   Religion & theology   Multidisciplinary, general & others Business & economic sciences   Accounting & auditing   Production, distribution & supply chain management   Finance   General management & organizational theory   Human resources management   Management information systems   Marketing   Strategy & innovation   Quantitative methods in economics & management   General economics & history of economic thought   International economics   Macroeconomics & monetary economics   Microeconomics   Economic systems & public economics   Social economics   Special economic topics (health, labor, transportation…)   Multidisciplinary, general & others Engineering, computing & technology   Aerospace & aeronautics engineering   Architecture   Chemical engineering   Civil engineering   Computer science   Electrical & electronics engineering   Energy   Geological, petroleum & mining engineering   Materials science & engineering   Mechanical engineering   Multidisciplinary, general & others Human health sciences   Alternative medicine   Anesthesia & intensive care   Cardiovascular & respiratory systems   Dentistry & oral medicine   Dermatology   Endocrinology, metabolism & nutrition   Forensic medicine   Gastroenterology & hepatology   General & internal medicine   Geriatrics   Hematology   Immunology & infectious disease   Laboratory medicine & medical technology   Neurology   Oncology   Ophthalmology   Orthopedics, rehabilitation & sports medicine   Otolaryngology   Pediatrics   Pharmacy, pharmacology & toxicology   Psychiatry   Public health, health care sciences & services   Radiology, nuclear medicine & imaging   Reproductive medicine (gynecology, andrology, obstetrics)   Rheumatology   Surgery   Urology & nephrology   Multidisciplinary, general & others Law, criminology & political science   Civil law   Criminal law & procedure   Criminology   Economic & commercial law   European & international law   Judicial law   Metalaw, Roman law, history of law & comparative law   Political science, public administration & international relations   Public law   Social law   Tax law   Multidisciplinary, general & others Life sciences   Agriculture & agronomy   Anatomy (cytology, histology, embryology...) & physiology   Animal production & animal husbandry   Aquatic sciences & oceanology   Biochemistry, biophysics & molecular biology   Biotechnology   Entomology & pest control   Environmental sciences & ecology   Food science   Genetics & genetic processes   Microbiology   Phytobiology (plant sciences, forestry, mycology...)   Veterinary medicine & animal health   Zoology   Multidisciplinary, general & others Physical, chemical, mathematical & earth Sciences   Chemistry   Earth sciences & physical geography   Mathematics   Physics   Space science, astronomy & astrophysics   Multidisciplinary, general & others Social & behavioral sciences, psychology   Animal psychology, ethology & psychobiology   Anthropology   Communication & mass media   Education & instruction   Human geography & demography   Library & information sciences   Neurosciences & behavior   Regional & inter-regional studies   Social work & social policy   Sociology & social sciences   Social, industrial & organizational psychology   Theoretical & cognitive psychology   Treatment & clinical psychology   Multidisciplinary, general & others      by title 0-9 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z or enter first few letters:    OK Showing results 149201 to 149220 of 159833     7456 7457 7458 7459 7460 7461 7462 7463 7464 7465 7466     Topology optimization of airbus engine pylonsGrihon, Stephane; Fleury, Claude ; Remouchamps, AlainConference given outside the academic context (2005)Detailed reference viewed: 91 (0 ULiège) Topology optimization of compliant mechanisms: Application to vehicle suspensions.Tromme, Emmanuel ; Lemaire, Etienne ; Duysinx, Pierre Conference (2011, November 14)An efficient method to design a compliant vehicle suspension with only topology optimization.Detailed reference viewed: 101 (20 ULiège) Topology Optimization of Continuum Structures with Local Stress ConstraintsDuysinx, Pierre ; Bendsoe, Martin Philipin International Journal for Numerical Methods in Engineering (1998), 43We introduce an extension of current technologies for topology optimization of continuum structures which allows for treating local stress criteria. We rst consider relevant stress criteria for porous ... [more ▼]We introduce an extension of current technologies for topology optimization of continuum structures which allows for treating local stress criteria. We rst consider relevant stress criteria for porous composite materials, initially by studying the stress states of the so-called rank 2 layered materials. Then, on the basis of the theoretical study of the rank 2 microstructures, we propose an empirical model which extends the power penalized sti ness model (also called SIMP for Solid Isotropic Microstructure with Penalization for intermediate densities). In a second part, solution aspects of topology problems are considered. To deal with the so-called 'singularity' phenomenon of stress constraints in topology design, an -constraint relaxation of the stress constraints is used. We describe the mathematical programming approach that is used to solve the numerical optimization problems, and show results for a number of example applications. [less ▲]Detailed reference viewed: 114 (7 ULiège) Topology Optimization of Continuum Structures with Stress ConstraintsDuysinx, Pierre ; Bendsoe, Martin Philipin Gutkowski, W.; Mroz, Z. (Eds.) Proceedings of the Second World Congress of Structural and Multidisciplinary Optimization (WCSMO2) (1997, May)We introduce an extension of topology optimization of continuum structures to deal with local stress criteria. We first consider relevant stress criteria for porous composite materials, initially by ... [more ▼]We introduce an extension of topology optimization of continuum structures to deal with local stress criteria. We first consider relevant stress criteria for porous composite materials, initially by studying the stress states of the so-called rank 2 layered materials. Then, an empirical model is proposed for the power law materials (also called SIMP materials). In a second part, solution aspects of topology problems are considered. To deal with the so-called 'singularity' phenomenon of stress constraints in topology design, an $\epsilon$ constraint relaxation of the stress constraints is used. We describe the mathematical programming approach that is used to solve the numerical optimization problems. The proposed strategy is applied to illustrative applications. [less ▲]Detailed reference viewed: 131 (9 ULiège) Topology optimization of electromechanical microsystems against pull-in voltageLemaire, Etienne ; Duysinx, Pierre ; Rochus, Véronique et al (2006)The present work is dedicated to the application of topology optimization in the multiphysic field of MEMS. Precisely, it describes how it is possible to maximize pull-in voltage of an electromechanical ... [more ▼]The present work is dedicated to the application of topology optimization in the multiphysic field of MEMS. Precisely, it describes how it is possible to maximize pull-in voltage of an electromechanical microsystem for which the optimization domain is insulated from the electric field. The electromechanical coupling is modeled by the use of a monolithic analysis. The optimization task is completed with the help of a sequential convex linear approximation schemes (CONLIN). [less ▲]Detailed reference viewed: 38 (10 ULiège) Topology optimization of electrostatic MEMS including stability constraintsLemaire, Etienne Doctoral thesis (2013)Among actuation techniques available for MEMS devices, electrostatic actuation is often used as it provides a short response time and is relatively easy to implement. However, these actuators possess a ... [more ▼]Among actuation techniques available for MEMS devices, electrostatic actuation is often used as it provides a short response time and is relatively easy to implement. However, these actuators possess a limit voltage called pull-in voltage beyond which they are unstable. The pull-in effect, can eventually damage the device since it can be impossible to separate the electrodes afterward. Consequently, pull-in phenomenon should be taken into account during the design process of electromechanical microdevices to ensure that it is avoided within utilization range. In this thesis, a topology optimization procedure which allows controlling pull-in phenomenon during the design process is developed. A first approach is based on a simplified optimization problem where the optimization domain is separated from the electrical domain by a perfectly conducting material layer making the optimization domain purely mechanical. This assumption reduces the difficulty of the optimization problem as the location of the electrostatic forces is then independent from the design. However, it allows us to develop and validate a design function based on pull-in voltage in the framework of a topology optimization problem. Nevertheless, in some applications, the developed pull-in voltage optimization procedure suffers from design oscillations that prevent from reaching solution. In order to solve this issue, we propose to investigate an alternative approach consisting in formulating a linear eigenproblem approximation for the nonlinear stability problem. The first eigenmode of the proposed stability eigenproblem corresponds to the actual pull-in mode while higher order modes allow estimating upcoming instability modes. By including several instability modes into a multiobjective formulation, it is possible to circumvent the oscillations encountered with pull-in voltage design function. Next, the possibility to generalize the pull-in optimization problem by removing the separation between optimization and electrostatic domains is studied. Unlike the original method, the dielectric permittivity has then to depend on the pseudo-density like the Young Modulus to represent the different electrostatic behavior of void and solid. Additionally, in order to render perfect conducting behavior for the structural part of the optimization domain, a fictitious permittivity is also introduced into the material model. Difficulties caused by non-physical local instability modes could be solved by using a force filtering technique which removes electrostatic forces originating from numerical inaccuracies of the modeling method. Thanks to these improvements, the optimization problem based on the pull-in design function can be generalized. As a result, the optimizer is able to adapt the electrostatic force distribution applied on the structure which leads to a higher efficiency of the optimal device. In order to illustrate the interest of the pull-in voltage design function, the pull-in voltage optimization problem is merged with the electrostatic actuator optimization problem. In this new optimization problem, the pull-in voltage does not appear anymore in the objective function but in a constraint which prevents the pull-in voltage to decrease below a given minimal value. Firstly, the new optimization problem is compared to the basic electrostatic actuator design procedure on basis of a numerical application. The pull-in voltage constraint proved to be very useful since it prevents the pull-in voltage of the mechanism to decrease below the driving voltage during the optimization process. Finally, the effect of geometric nonlinearity modeling is also tested on numerical applications of our optimization procedure. [less ▲]Detailed reference viewed: 226 (38 ULiège) Topology optimization of electrostatic micro-actuators including electromechanical stability constraintLemaire, Etienne ; Van Miegroet, Laurent ; Rochus, Véronique et alConference (2011, November 16)Detailed reference viewed: 50 (8 ULiège) Topology optimization of mechanical and aerospace components subject to fatigue stress constraintsDuysinx, Pierre ; Collet, Maxime ; Bauduin, Simon et alConference (2015, June 08)While topology optimization has been based mostly on compliance type formulations, industrial applications call for more elaborated formulations including several restrictions on the local displacements ... [more ▼]While topology optimization has been based mostly on compliance type formulations, industrial applications call for more elaborated formulations including several restrictions on the local displacements and the stress constraints in some critical zones. Topology optimization with stress constraints was initially considered in Duysinx & Bendsoe (1998). Later the stress constraint formulation was further extended to consider non equal stress constraints limits Bruggi & Duysinx (2012) and to improve the solution efficiency using different strategies such as global stress constraint formulations (Duysinx & Sigmund, 1998, Le et al. 2010). In the present work, the authors are investigating the formulations of stress constraint topology optimization to support the redesign of structural components that have to be fabricated using additive manufacturing. In this perspective, design problem requirements include tackling fatigue constraints during stress constrained topology optimization. The work investigates different formulations of fatigue resistance which could be appropriate in a topology approach. At first the classical approach of mechanical engineering based on SN curves and Goodman or Soderberg lines. The treatment of these fatigue restrictions can take advantage of former work developed for unequal stress constraints by considering mean and alternating components of the stress state. In a second step our research is now focussing on more complex situations (3D stress states) which require resorting to more advanced criteria. Dang Van fatigue theory (Dang Van, Griveau, Message, 1989) has been selected but calls for a more elaborated procedure that is currently validated. Topology optimized structural layouts predicted using classical stress criteria, Goodman and Dang Van theories are compared. [less ▲]Detailed reference viewed: 194 (20 ULiège) Topology optimization of mechanical components fabricated by additive manufacturing for a Shell Eco Marathon vehicleAlarcon Soto, Pablo ; Collet, Maxime ; Bauduin, Simon et alConference (2017, June 07)Since 2004, a team of students and researchers of University of Liege takes part to the Shell Eco Marathon race with a lightweight electric vehicle. The goal of this pedagogical project is to design ... [more ▼]Since 2004, a team of students and researchers of University of Liege takes part to the Shell Eco Marathon race with a lightweight electric vehicle. The goal of this pedagogical project is to design, fabricate and operate a vehicle exhibiting the least energy consumption. A key factor to reduce the energy consumption is to minimize the vehicle mass. Besides the body structure made of CRFP, engineers have also to focus on the weight reduction of any mechanical parts of the powertrain, transmission and of rolling gear. The combination of topology optimization with additive manufacturing techniques allows to propose innovative designs exhibiting a high performance to weight ratio. Topology optimized designs are often characterized by a high geometrical complexity that is not possible to manufacture without 3D printing. This work presents the CAE design methodology that was developed to combine topology and shape optimization with 3d printing manufacturing. Novel developments both in shape and topology optimization have also been realized for the specific character of these components. The design methodology is illustrated with several applications of components of our new Eco Marathon prototype. They include a support for electric traction motors and different torque arms of the steering mechanism to be implemented in the new 2017 vehicle. The presentation is going to show the different design steps from the specifications and the formulation of the design problem to the 3D-printing of the parts: the topology optimization, interpretation and CAD reconstruction, shape optimization and detailed finite element verification of the solution. The optimization is performed thanks to the commercial software NX-TOPOL and the final CAD design is reconstructed in the CATIA environment software after a smoothing procedure in the NX-CAD environment. We show that the final design can be 3D-printed and a comparison with a design produced using traditional design approach is provided. [less ▲]Detailed reference viewed: 48 (9 ULiège) Topology optimization of membranes made of orthotropic materialRion, Vincent; Bruyneel, Michaël in Moes, Nicolas; Desaxcé, Gery (Eds.) Collection of Papers from Prof. Nguyen Dang Hung’s Former Students (2006)Detailed reference viewed: 24 (0 ULiège) Topology optimization of microbeams including layer deposition manufacturing constraintsLemaire, Etienne ; Rochus, Véronique; Fleury, Claude et alConference (2007, May)As many manufacturing techniques, microfabrication methods possess limitations. Consequently, manufacturing constraints have to be considered during microsystems design process. Therefore, the direct use ... [more ▼]As many manufacturing techniques, microfabrication methods possess limitations. Consequently, manufacturing constraints have to be considered during microsystems design process. Therefore, the direct use of automatic design tools like topology optimization is not possible. For instance, optimal topologies generally contain closed cavities that cannot be produced using the usual microfabrication techniques like layer deposition. The present paper intends to add a layer deposition constraint to the optimization problem using recent developments of CONLIN software. However, with this new optimization procedure we could observe that classical sensitivities filtering makes optimization problem rather unstable while filtering the density field itself keeps good convergence properties. [less ▲]Detailed reference viewed: 57 (6 ULiège) Topology Optimization of Structural Components Included in Flexible Multibody SystemsBruls, Olivier ; Lemaire, Etienne ; Eberhard, Peter et alin Proceedings of the 7th World Congress on Structural and Multidisciplinary Optimization (2007, May)This work addresses the topology optimization of structural components embedded in multibody systems with large amplitude motions. Generally, topology optimization techniques consider that the structural ... [more ▼]This work addresses the topology optimization of structural components embedded in multibody systems with large amplitude motions. Generally, topology optimization techniques consider that the structural component is isolated from the rest of the mechanism and use simplified quasi-sta tic load cases to mimic the complex loadings in service. In contrast, this paper proposes an optimization procedure based on the dynamic simulation of the full multibody system with large amplitude motions and elastic deflections. We show that the simulation model, which involves a nonlinear finite element formulation, a time integration scheme and a sensitivity analysis, can be efficiently exploited in an optimization loop. The method is applied to truss structural components. Each truss is represented by a structural universe of beams with a topology design variable attached to each one. A SIMP model (or a variant of the power law) is used to penalize intermediate densities. The optimization formulation is stated as the minimization of the mean compliance over a time period or as the minimization of the mean tip deflection during a given trajectory, subject to a volume constraint. In order to illustrate the benefits of the integrated design approach, the case of a two degrees-of-freedom robot arm is developed. [less ▲]Detailed reference viewed: 79 (12 ULiège) Topology Optimization of Structural Components: A Multibody Dynamics-Oriented ApproachBruls, Olivier ; Lemaire, Etienne ; Duysinx, Pierre et alin Proceedings of the Multibody Dynamics ECCOMAS Conference (2009)This work addresses the topology optimization of structural components embedded in multibody systems with large amplitude motions. Generally, topology optimization techniques consider that the structural ... [more ▼]This work addresses the topology optimization of structural components embedded in multibody systems with large amplitude motions. Generally, topology optimization techniques consider that the structural component is isolated from the rest of the mechanism and use simplified quasi-static load cases to mimic the complex loadings in service. In contrast, this paper proposes an optimization procedure based on the dynamic simulation of the full multibody system with large amplitude motions and elastic deflections. We show that the simulation model, which involves a nonlinear finite element formulation, a time integration scheme and a sensitivity analysis, can be efficiently exploited in an optimization loop. The method is applied to truss structural components. Each truss is represented by a separate structural universe of beams with a topology design variable attached to each one. A SIMP model (or a variant of the power law) is used to penalize intermediate densities. The optimization formulation is stated as the minimization of the mean compliance over a time period or as the minimization of the mean tip deflection during a given trajectory, subject to a volume constraint. In order to illustrate the benefits of the integrated design approach, the case of a two degrees-of-freedom robot arm is developed. [less ▲]Detailed reference viewed: 123 (13 ULiège) Topology Optimization with Different Stress Limit in Tension and CompressionDuysinx, Pierre in Bloebaum, C. (Ed.) Proceedings of the 3rd World Congress of Structural and Multidisciplinary Optimization WCSMO3 (1999, May)This report presents new progresses in topology optimization of continuum structures with stress constraints. One principal contribution consists in the consideration of equivalent stress criteria which ... [more ▼]This report presents new progresses in topology optimization of continuum structures with stress constraints. One principal contribution consists in the consideration of equivalent stress criteria which can generalization of von Mises criterion and which are able to take into account non equal stress limits in tension and compression. A literature review led us to consider Raghava and Ishai criteria, which include a contribution of hydrostatic pressure. With the help of these criteria topology optimization can predict more realistic designs in which structural members are able to withstand better tension loads than compression loads, or vice-versa, as it is sometimes encountered in civil engineering or in composite material design. The implementation and sensitivity analysis aspects of Raghava and Ishai criteria in the Finite Element context are presented. We also present recent advanced developments to the solution of topology problems with stress constraints like the stress constraint relaxation technique and the numerical optimization procedure based on convex approximations and dual optimizers. Finally numerical applications will show the original character of the stress based topology designs ad versus compliance designs when there are unequal stress limits or when there are more than one load case. [less ▲]Detailed reference viewed: 331 (6 ULiège) Topology optimization with self-weight loading: (un-expected) problems and solutionsBruyneel, Michaël ; Duysinx, Pierre in Bendsoe, M. P.; Olhoff, Niels; Rassmussen, John (Eds.) Proceedings of the 2nd Max Planck Workshop on Engineering Design Optimization (2001, October)Detailed reference viewed: 62 (1 ULiège) La toponymie comme archéologie linguistique. Regard sur Les noms de lieux antiques et tardo-antiques d'Augustonemetum / Clermont-Ferrand d'Emmanuel Grélois et Jean-Pierre ChambonBoutier, Marie-Guy in Bulletin de la Commission Royale de Toponymie et de Dialectologie = Handelingen van de Koninklijke Commissie voor Toponymie en Dialectologie (2011), 83Detailed reference viewed: 165 (8 ULiège) Toponymie et anthroponymie dans l'Atlas linguistique de la WallonieBaiwir, Esther in Germain, Jean; Tamine, Michel (Eds.) Mode(s) en onomastique. Onomastique belgoromane (2015)Detailed reference viewed: 93 (10 ULiège) La toponymie et le statut de l’enquêteur de terrain, entre linguiste et ethnologueDelorme, Jérémie Conference (2009, October 13)Detailed reference viewed: 15 (1 ULiège) Toponymie majeure de la Wallonie : bref état des lieuxBoutier, Marie-Guy in Bulletin de la Commission Royale de Toponymie et de Dialectologie = Handelingen van de Koninklijke Commissie voor Toponymie en Dialectologie (2007), 79Detailed reference viewed: 111 (11 ULiège) La toponymie orale du Grand-Bornand. Principes de méthode pour la collecte, la mise en ordre et l'analyse des noms de lieux traditionnelsDelorme, Jérémie Conference given outside the academic context (2006)Detailed reference viewed: 29 (3 ULiège)