The Experts below are selected from a list of 133851 Experts worldwide ranked by ideXlab platform
Noboru Kikuchi - One of the best experts on this subject based on the ideXlab platform.
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structural topology and shape optimization for a frequency response problem
Computational Mechanics, 1993Co-Authors: Noboru Kikuchi, Ichiro HagiwaraAbstract:A topology and shape optimization technique using the homogenization method was developed for stiffness of a linearly Elastic Structure by Bendsoe and Kikuchi (1988), Suzuki and Kikuchi (1990, 1991), and others. This method has also been extended to deal with an optimal reinforcement problem for a free vibration Structure by Diaz and Kikuchi (1992). In this paper, we consider a frequency response optimization problem for both the optimal layout and the reinforcement of an Elastic Structure. First, the structural optimization problem is transformed to an Optimal Material Distribution problem (OMD) introducing microscale voids, and then the homogenization method is employed to determine and equivalent “averaged” structural analysis model. A new optimization algorithm, which is derived from a Sequential Approximate Optimization approach (SAO) with the dual method, is presented to solve the present optimization problem. This optimization algorithm is different from the CONLIN (Fleury 1986) and MMA (Svanderg 1987), and it is based on a simpler idea that employs a shifted Lagrangian function to make a convex approximation. The new algorithm is called “Modified Optimality Criteria method (MOC)” because it can be reduced to the traditional OC method by using a zero value for the shift parameter. Two sensitivity analysis methods, the Direct Frequency Response method (DFR) and the Modal Frequency Response method (MFR), are employed to calculate the sensitivities of the object functions. Finally, three examples are given to show the feasibility of the present approach.
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Topology and Generalized Layout Optimization of Elastic Structures
Topology Design of Structures, 1993Co-Authors: Martin P. Bendsøe, Alejandro R. Diaz, Noboru KikuchiAbstract:An overview of the method of homogenization to find the optimum layout of a linearly Elastic Structure is presented. The work discussed here presents a formulation to address the simultaneous optimization of the topology, shape and size of the Structure. The discussion includes optimization of plane, plate and three dimensional shell Structures.
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Structural Optimization of Linearly Elastic Structures Using the Homogenization Method
Shape and Layout Optimization of Structural Systems and Optimality Criteria Methods, 1992Co-Authors: Noboru Kikuchi, Katsuyuki SuzukiAbstract:There are three major structural optimization problems of a linearly Elastic Structure; namely, 1) sizing, 2) shape, and 3) layout(topology) optimization problems. The characteristics of these problems can be summarized as follows:
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a homogenization method for shape and topology optimization
Computer Methods in Applied Mechanics and Engineering, 1991Co-Authors: Katsuyuki Suzuki, Noboru KikuchiAbstract:Abstract Shape and topology optimization of a linearly Elastic Structure is discussed using a modification of the homogenization method introduced by Bendsoe and Kikuchi together with various examples which may justify validity and strength of the present approach for plane Structures.
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Structural Optimization of a Linearly Elastic Structure using the Homogenization Method
Composite Media and Homogenization Theory, 1991Co-Authors: Noboru Kikuchi, Katsuyuki SuzukiAbstract:We shall describe a brief review of the structural optimization of a linearly Elastic Structure, and we shall present a new method to solve the sizing, shape, and layout (topology) problems based on the theory of homogenization. Many numerical examples of the optimal design are also presented as well as a mathematical formulation of a relaxed design problem.
Yiannis Andreopoulos - One of the best experts on this subject based on the ideXlab platform.
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Response of an Elastic Structure Subject to Air Shock Considering Fluid-Structure Interaction
Journal of Aerospace Engineering, 2010Co-Authors: Weimin Nian, Kolluru V. L. Subramaniam, Yiannis AndreopoulosAbstract:Shock-wave interaction with an Elastic Structure is investigated using a coupled numerical analysis approach, which considers solid-fluid interaction within an arbitrary Lagrangian-Eulerian framework. The analysis is performed considering a compressive shock wave, where the shock front is followed by constant pressure. An analysis procedure, which considers the change in the fluid domain due to the deformation of the solid and changes in the overpressure due to the movement of the Elastic Structure, is developed. Approximate numerical procedures for solving the Riemann problem associated with the shock are implemented within the Godunov finite volume scheme for the fluid domain. The influences of parameters such as structural stiffness and mass of the system on the displacement, velocity, and energy of the Elastic Structure following the shock-wave incidence are investigated. Immediately after the contact of the shock wave with the solid surface the pressure at the face of the Elastic solid rises to a value which is equal to that obtained off of a fixed rigid wall. Subsequently, the motion of the piston produces changes in the applied pressure. The overpressure applied to the Elastic system does not have a fixed profile but it depends on its Elastic stiffness and Structure mass. It is shown that there is a continuous exchange of energy between the air and the moving Elastic Structure, which produces a damped motion of the solid. The effect of damping is considerable for the cases of low Elastic stiffness and low structural mass, where the resulting motion of the solid is nonoscillatory. The conventional analysis procedure, which ignores the energy exchange between the air and the moving solid, predicts an undamped oscillatory response of the Structure for all cases considered. It is shown that neglecting the interaction between the air and solid can produce significant error in the total energy of the Structure and the dynamic load factor when the resulting motion is nonoscillatory.
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Blast response simulation of an Elastic Structure: Evaluation of the fluid–Structure interaction effect
International Journal of Impact Engineering, 2009Co-Authors: Kolluru V. L. Subramaniam, Weimin Nian, Yiannis AndreopoulosAbstract:Blast pressure wave interaction with an Elastic Structure is investigated using a numerical analysis approach, which considers fluid-Structure interaction (FSI) within an Arbitrary Lagrange Euler (ALE) framework. Approximate numerical procedures for solving the Riemann problem associated with the shock are implemented within the Godunov finite volume scheme for the fluid domain. The structural displacement predicted by ignoring FSI is larger than the corresponding displacement considering FSI. The influence of the structural and blast pressure wave parameters on the importance of FSI is studied using an analysis of variables. Two non-dimensional parameters corresponding to the ratios of blast duration to the time period of the Structure and the velocity of the Structure to the particle velocity of the incident blast pressure wave are identified. It is shown that for a given blast pressure wave, the error in the maximum displacement predicted by ignoring FSI effect during structural motion is directly proportional to the ratio of the Structure velocity to the particle velocity of the incident blast pressure wave. There is a continuous exchange of energy between the Structure and air during the structural motion, which is significant when the structural velocity is significant compared to the particle velocity of incident blast pressure wave. FSI effect become insignificant when the ratio of velocities starts approaching zero.
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blast response simulation of an Elastic Structure evaluation of the fluid Structure interaction effect
International Journal of Impact Engineering, 2009Co-Authors: Kolluru V. L. Subramaniam, Weimin Nian, Yiannis AndreopoulosAbstract:Blast pressure wave interaction with an Elastic Structure is investigated using a numerical analysis approach, which considers fluid-Structure interaction (FSI) within an Arbitrary Lagrange Euler (ALE) framework. Approximate numerical procedures for solving the Riemann problem associated with the shock are implemented within the Godunov finite volume scheme for the fluid domain. The structural displacement predicted by ignoring FSI is larger than the corresponding displacement considering FSI. The influence of the structural and blast pressure wave parameters on the importance of FSI is studied using an analysis of variables. Two non-dimensional parameters corresponding to the ratios of blast duration to the time period of the Structure and the velocity of the Structure to the particle velocity of the incident blast pressure wave are identified. It is shown that for a given blast pressure wave, the error in the maximum displacement predicted by ignoring FSI effect during structural motion is directly proportional to the ratio of the Structure velocity to the particle velocity of the incident blast pressure wave. There is a continuous exchange of energy between the Structure and air during the structural motion, which is significant when the structural velocity is significant compared to the particle velocity of incident blast pressure wave. FSI effect become insignificant when the ratio of velocities starts approaching zero.
J Ducarne - One of the best experts on this subject based on the ideXlab platform.
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vibrations of an Elastic Structure with shunted piezoelectric patches efficient finite element formulation and electromechanical coupling coefficients
International Journal for Numerical Methods in Engineering, 2009Co-Authors: Olivier Thomas, J DucarneAbstract:This article is devoted to the numerical simulation of the vibrations of an Elastic mechanical Structure equipped with several piezoelectric patches, with applications for the control, sensing and reduction of vibrations. At first, a finite element formulation of the coupled electromechanical problem is introduced, whose originality is that provided a set of non-restrictive assumptions, the system's electrical state is fully described by very few global discrete unknowns: only a couple of variables per piezoelectric patches, namely (1) the electric charge contained in the electrodes and (2) the voltage between the electrodes. The main advantages are (1) since the electrical state is fully discretized at the weak formulation step, any standard (Elastic only) finite element formulation can be easily modified to include the piezoelectric patches (2) realistic electrical boundary conditions such that equipotentiality on the electrodes and prescribed global charges naturally appear (3) the global charge/voltage variables are intrinsically adapted to include any external electrical circuit into the electromechanical problem and to simulate shunted piezoelectric patches. The second part of the article is devoted to the introduction of a reduced-order model (ROM) of the problem, by means of a modal expansion. This leads to show that the classical efficient electromechanical coupling factors (EEMCF) naturally appear as the main parameters that master the electromechanical coupling in the ROM. Finally, all the above results are applied in the case of a cantilever beam whose vibrations are reduced by means of a resonant shunt. A finite element formulation of this problem is described. It enables to compute the system EEMCF as well as its frequency response, which are compared with experimental results, showing an excellent agreement. Copyright © 2009 John Wiley & Sons, Ltd.
Muriel Boulakia - One of the best experts on this subject based on the ideXlab platform.
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Well-posedness for the coupling between a viscous incompressible fluid and an Elastic Structure
Nonlinearity, 2019Co-Authors: Muriel Boulakia, Sergio Guerrero, Takeo TakahashiAbstract:In this paper, we consider a system modeling the interaction between a viscous incompressible fluid and an Elastic Structure. The fluid motion is represented by the classical Navier-Stokes equations while the Elastic displacement is described by the linearized Elasticity equation. The Elastic Structure is immersed in the fluid and the whole system is confined into a general bounded smooth domain of R3. Our main result is the local in time existence and uniqueness of a strong solution of the corresponding system.
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On the interaction problem between a compressible fluid and a Saint-Venant Kirchhoff Elastic Structure
Advances in Differential Equations, 2017Co-Authors: Muriel Boulakia, Sergio GuerreroAbstract:In this paper, we consider an Elastic Structure immersed in a compressible viscous fluid. The motion of the fluid is described by the compressible Navier-Stokes equations whereas the motion of the Structure is given by the nonlinear Saint-Venant Kirchhoff model. For this model, we prove the existence and uniqueness of regular solutions defined locally in time. To do so, we first rewrite the nonlinearity in the Elasticity equation in an adequate way. Then, we introduce a linearized problem and prove that this problem admits a unique regular solution. To obtain time regularity on the solution, we use energy estimates on the unknowns and their successive derivatives in time and to obtain spatial regularity, we use elliptic estimates. At last, to come back to the nonlinear problem, we use a fixed point theorem.
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Existence of strong solutions for the motion of an Elastic Structure in an incompressible viscous fluid
Interfaces and Free Boundaries, 2012Co-Authors: Muriel Boulakia, Erica Schwindt, Takeo TakahashiAbstract:In this paper we study a three-dimensional fluid-Structure interaction problem. The motion of the fluid is modeled by the Navier-Stokes equations and we consider for the Elastic Structure a finite dimensional approximation of the equation of linear Elasticity. The time variation of the fluid domain is not known a priori, so we deal with a free boundary value problem. Our main result yields the local in time existence and uniqueness of strong solutions for this system.
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Regular solutions of a problem coupling a compressible fluid and an Elastic Structure
2009Co-Authors: Muriel Boulakia, Sergio GuerreroAbstract:We are interested by the three-dimensional coupling between a compressible viscous fluid and an Elastic Structure immersed inside the fluid. They are contained in a fixed bounded set. The fluid motion is modelled by the compressible Navier-Stokes equations and the Structure motion is described by the linearized Elasticity equation. We establish the local in time existence and the uniqueness of regular solutions for this model. We emphasize that the equations do not contain extra regularizing term. The result is proved by first introducing a problem linearized and by proving that it admits a unique regular solution. The regularity is obtained thanks to successive estimates on the unknowns and their derivatives in time and thanks to elliptic estimates. At last, a fixed point theorem allows to prove the existence and uniqueness of regular solution of the nonlinear problem.
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Existence of Weak Solutions for the Three-Dimensional Motion of an Elastic Structure in an Incompressible Fluid
Journal of Mathematical Fluid Mechanics, 2006Co-Authors: Muriel BoulakiaAbstract:We study here the three-dimensional motion of an Elastic Structure immersed in an incompressible viscous fluid. The Structure and the fluid are contained in a fixed bounded connected set Ω. We show the existence of a weak solution for regularized Elastic deformations as long as Elastic deformations are not too important (in order to avoid interpenetration and preserve orientation on the Structure) and no collisions between the Structure and the boundary occur. As the Structure moves freely in the fluid, it seems natural (and it corresponds to many physical applications) to consider that its rigid motion (translation and rotation) may be large.
Roger Ohayon - One of the best experts on this subject based on the ideXlab platform.
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Novel formulation for the effects of sloshing with capillarity on Elastic Structures in linear dynamics
International Journal for Numerical Methods in Engineering, 2020Co-Authors: Roger Ohayon, Quentin Akkaoui, Christian Soize, Evangéline Capiez‐lernoutAbstract:This paper is devoted to the linear dynamics of liquid-Structure interactions for an Elastic Structure filled with compressible liquid (acoustic liquid), with sloshing and with capillarity effects on the free surface in presence of a gravity field. The objective is to detail the formulation and to quantify the role played by the Elasticity in the neighborhood of the triple contact line between the free surface of the compressible liquid and the Elastic Structure in presence of sloshing and capillarity effects. Most of the works consider that the Structure is totally not deformable (rigid tank). Nevertheless, for taking into account the Elasticity of the tank, some works have introduced an approximation, which consists in considering a locally undeformable Structure in the neighborhood of the triple contact line. The theory presented requires the use of quadratic finite elements for discretizing a new introduced boundary condition. An application has specifically been constructed and presented for quantifying the role played by the Elasticity of the Structure in the neighborhood of the triple contact line.
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Computational modeling of a coupled fluid-Structure system with sloshing and capillarity
2017Co-Authors: Quentin Akkaoui, Evangéline Capiez-Lernout, Christian Soize, Roger OhayonAbstract:This paper is devoted to a numerical approach in vibroacoustics of a linear Elastic Structure coupled with a compressible liquid with sloshing and capillarity effects. This work is based on a new formulation for the boundary condition on the contact angle. A reduced-order model is constructed using a projection basis made up of Elastic modes, acoustic modes, and sloshing-capillarity modes. Then a numerical study of a coupled fluid-Structure system discretized with finite element modeling is presented.
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Structural-Acoustic Vibration Reduction Using Switched Shunt Piezoelectric Patches: A Finite Element Analysis
Journal of Vibration and Acoustics, 2010Co-Authors: Walid Larbi, Jean-françois Deü, Monica Ciminello, Roger OhayonAbstract:Inthis paper, we present a finite element formulation for vibrationreduction in structural-acoustic systems using passive or semipassive shunt techniques.The coupled system consists of an Elastic Structure (with surface-mountedpiezoelectric patches) filled with an inviscid linear acoustic fluid. Anappropriate finite element formulation is derived. Numerical results for anElastic plate coupled to a parallelipedic air-filled interior acoustic cavityare presented, showing the performances of both the inductive shuntand the synchronized switch shunt techniques.
