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A ‘nodeless’ dual superelement formulation for structural and multibody dynamics application to reduction of contact problems Géradin, Michel ; in International Journal for Numerical Methods in Engineering (2015) Detailed reference viewed: 32 (5 ULg)Electrostatic Simulation using XFEM for Conductor and Dielectric Interfaces Rochus, Véronique ; ; Van Miegroet, Laurent et al in International Journal for Numerical Methods in Engineering (2011), 85(10), 12071226 ManyMicro-Electro-Mechanical Systems (e.g. RF-switches, micro-resonators and micro-rotors) involve mechanical structures moving in an electrostatic field. For this type of problems, it is required to ... [more ▼] ManyMicro-Electro-Mechanical Systems (e.g. RF-switches, micro-resonators and micro-rotors) involve mechanical structures moving in an electrostatic field. For this type of problems, it is required to evaluate accurately the electrostatic forces acting on the devices. Extended Finite Element (X-FEM) approaches can easily handle moving boundaries and interfaces in the electrostatic domain and seem therefore very suitable to model Micro-Electro-Mechanical Systems. In this study we investigate different X-FEM techniques to solve the electrostatic problem when the electrostatic domain is bounded by a conducting material. Preliminary studies in one-dimension have shown that one can obtain good results in the computation of electrostatic potential using X-FEM. In this paper the extension of these preliminary studies to 2D problem is presented. In particular a new type of enrichment functions is proposed in order to treat accurately Dirichlet boundary conditions on the interface. [less ▲] Detailed reference viewed: 142 (25 ULg)Electromechanical FEM models and electrostatic forces near sharp corners ; ; et al E-print/Working paper (2009) Accounting for multiphysical coupling in models of Micro Electro Mechanical Systems (MEMS) is essential for accurate simulations. One essential multiphysical effect in MEMS is the electromechanical ... [more ▼] Accounting for multiphysical coupling in models of Micro Electro Mechanical Systems (MEMS) is essential for accurate simulations. One essential multiphysical effect in MEMS is the electromechanical coupling since electrostatic forces are often used for actuation or sensing in those devices. Often MEMS are designed such that their shape exhibits many corners. In this paper two different numerical approaches are used to model this coupling using the Finite Element Method: the electrostatic forces are either derived from the variational approach or a local approach based on the Maxwell stress tensor such as implemented in commercial Finite Element codes. The evaluation of electrostatic forces near corners is investigated in detail and in this paper the two approaches are compared around corners. Although the issue of numerical models around singularities is not new, the question addressed here is related to the computation of electric forces in the vicinity of corners. Since those forces are quadratic functions of the electric field, namely the gradient of the electric potential, here the primal unknown, computing those forces accurately is a challenge in itself. Elements which use special shape functions are used to discretize the field near this corner singularity as well. In the work presented here, it is shown that a significant discrepancy appears in the electrostatic force computed around a corner depending on the discretization approach considered, and we conclude that the variational approach or equivalently the full Maxwell tensor should be used to properly evaluate electrostatic forces around corners. [less ▲] Detailed reference viewed: 97 (6 ULg)Comparing Simulations and Measurements of Prestressed MEMS ; Rochus, Véronique ; in ECCOMAS (2008) Detailed reference viewed: 15 (0 ULg)Modelling the electromechanical coupling of RF switch using Extended Finite Element Rochus, Véronique ; Van Miegroet, Laurent ; Duysinx, Pierre et al (2008) Detailed reference viewed: 57 (13 ULg)MEMS Modelling using Non-Conforming Elements Rochus, Véronique ; ; Golinval, Jean-Claude (2008) Detailed reference viewed: 10 (1 ULg)Modelling strategies for microstructures moving in an electric field Rochus, Véronique ; ; in International Conference on Computational Methods for Coupled Problems in Science and Engineering (2007) Detailed reference viewed: 14 (2 ULg)Finite Element Discretizations to Evaluate Electrostatic Forces Around Corners ; ; Rochus, Véronique (2007) Detailed reference viewed: 12 (1 ULg)Dielectrophoresis Simulation for MEMS Applications: Comparison of the different numerical approaches Rochus, Véronique ; in 9th US Natinal Congress on Computational Mechanics (2007) Detailed reference viewed: 42 (2 ULg)Extended Finite Element for Electromechanical Coupling Rochus, Véronique ; in Proceedings of Thermal, Mechanical and Multiphysics Simulation and Experiments in Micro-Electronics and Micro-systems EuroSime (2007) Detailed reference viewed: 12 (1 ULg)Rounding the Corner in an Electromechanical FEM Model ; ; Rochus, Véronique in International Conference on Computational Methods for Coupled Problems in Science and Engineering (2007) Detailed reference viewed: 12 (0 ULg)Correlation of Experimental and Numerical Results on Electrostatically Actuated Micro-Beams Rochus, Véronique ; ; Golinval, Jean-Claude in Technical Proceedings of the 2006 NSTI Nanotechnology Conference and Trade Show (2006), 3 The aim of this paper is to validate numerical simula- tions of electromechanical coupling in micro-structures using some experimental results. The micro-structures studied here consist in a micro-bridge ... [more ▼] The aim of this paper is to validate numerical simula- tions of electromechanical coupling in micro-structures using some experimental results. The micro-structures studied here consist in a micro-bridge and two cantilever micro-beams. Multi-physics models of micro-electro- mechanical systems (MEMS) based on the ¯nite ele- ment method (FEM) are used to model the strongly coupled electro-mechanical interactions and to perform static analyses taking into account large displacements. In all the cases treated here the numerical results are in very good agreement with the experimental results. [less ▲] Detailed reference viewed: 16 (2 ULg)Simulation of Strong Coupling and Dynamic Pull-in Rochus, Véronique ; ; Golinval, Jean-Claude Scientific conference (2005) Detailed reference viewed: 8 (0 ULg)Finite Element Modeling of Electro-Mechanical Coupling in Capacitive Micro-Systems Rochus, Véronique ; ; Golinval, Jean-Claude Conference given outside the academic context (2005) In this paper advanced multi-physics simulations of micro-electro-mechanical systems (MEMS) are used to investigate their dynamic behaviour. The strong coupled electro-mechanical Finite Element (FE ... [more ▼] In this paper advanced multi-physics simulations of micro-electro-mechanical systems (MEMS) are used to investigate their dynamic behaviour. The strong coupled electro-mechanical Finite Element (FE) formulation is used to model the electro-mechanical interactions and to perform modal and transient analysis taking into account large deformation e®ects. The application examples simulate two micro-resonators consisting in a clamped-clamped beam suspended over a substrate (the lower electrode). When a voltage is applied between the beam and the substrate, electrostatic forces appear which force the beam to bend. When the applied voltage is increased up to the pull-in limit, the electrostatic force becomes dominant and the plates stick together. The pull-in voltage is an essential design parameters in capacitive micro-systems. Here we also de¯ne a new design parameter describing the limit dynamic behaviour, namely the dynamic pull-in voltage. [less ▲] Detailed reference viewed: 52 (3 ULg)Dynamical behaviour of electro-mechanical coupled problem Rochus, Véronique ; ; Golinval, Jean-Claude Conference (2004) MEMS are very small devices in which electric as well as mechanical dynamics phenomena appear. Because of the microscopic scale, some strong coupling effects between the different physical fields appear ... [more ▼] MEMS are very small devices in which electric as well as mechanical dynamics phenomena appear. Because of the microscopic scale, some strong coupling effects between the different physical fields appear, and some forces, which are negligible at macroscopic scales, have to be taken into account. In order to make a good design of these micro-systems, it is important to analyse the coupling between the electrical and mechanical fields. This paper concerns the modelling of the strong electromechanical coupling appearing in micro-electro-mechanical systems (MEMS). The finite element method (FEM) is used to perform dynamical analysis taking into account large mesh displacements. Analysing the vibration of microsystems is a fundamental issues in the design of a broad range of sensors and actuators. The state of the art currently consists in using staggered procedures to compute quasi-static configurations based on the iteration between a structural model loaded by electrostatic forces and an electrostatic model defined on a domain following the deformation of the structure. Staggered iteration then leads to a static equilibrium position. Performing a perturbation analysis around the static equilibrium yields the electromechanical linearized stiffness needed for computing the eigenfrequencies. Obviously, performing the perturbation analysis to evaluate the tangent stiffness for every degree of freedom leads to very high computing costs and therefore onlythe tangent stiffness associated with presumed modes (typically some purely structural modes) are computed. Such a procedure can lead to important inaccuracies for designs where the electrostatic coupling is not quasi-uniform. In our work, we have developed a fully coupled electro-mechanical formulation that allows to find static equilibrium positions in a non-staggered way and which provides fully consistent tangent stiffness matrices for vibration analysis. The efficiency of the approach will be illustrated on modes of micro-electromechanical devices. The results obtained indicate that using this approach pull-in can be computed very accurately and at low computational cost. Also the coupled electromechanical modes obtained in the vicinity of equilibrium positions can be significantly different from the approximations obtained using a structural reduction at forehand. Numerical results are checked against analytical results where appropriate. The formulation developed for the strongly coupled electromechanical problem allows consistent vibration analysis of the system and yields more accurate vibration eigenmodes and frequencies than the classical staggered approaches. A second interest of the coupled tangent matrix is the computation of the dynamical behaviour of the coupled problem when we apply suddenly a voltage to the electrodes. Even under the pull-in voltage, the overshoot of the dynamical response may reduce the distance between the plate so that the electric force becomes dominant and the plates stick together. This phenomenon is called the dynamical pull-in. We will also treat it in this research. [less ▲] Detailed reference viewed: 42 (4 ULg) |
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