Finite Element Simulation of Smart Lightweight Structures for Active Vibration and Interior Acoustic Control

The paper presents a numerical approach to active vibration and noise control of smart lightweight structures. The structure is provided with thin piezoelectric wafers as actuators and sensors to control vibrations of the structure. Fully coupled electromechanical field equations were taken into account where model based controllers are applied for design purposes. The objective of vibration control of elastic structures is to reduce interior noise levels. Hence, the mechanical field is also coupled with the acoustic field, and consequently a fully coupled electro-mechanical-acoustical problem needs to be solved. The numerical solution is based on the finite element method, introducing a velocity potential for the acoustic fluid to receive overall symmetric system matrices of the semi-discrete form of the equation of motion. It is shown that the vibro-acoustic coupling can be neglected for controller design purposes, and consequently the modal truncation technique considering only the uncoupled structural modes, can be adapted to vibro-acoustic systems. The behaviour of a smart plate structure coupled with an acoustic cavity is studied as a reference example

Adaptive Local-Global Analysis by pNh Transition Elements

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Local Buckling of Composite Laminated Cylindrical Shells with Oblique Edges under External Pressure: Asymptotic and Finite Element Simulations

The problem of local buckling ofa thin composite laminated cylindrical shell under external pressure is studied. Each layer of the shell is assumed to be isotropic. The special case of the shell being non-circular and/or having no plane edges is considered here. Presupposing that buckling takes place in the neighborhood of some so-called “weakest” generator, the asymptotic Tovstik’s method is appliedfinding the critical pressure and the elgenmodes. As an example, buckling of a three-layered circular thin cylinder with a sloped edge is investigated. Besides the asymptotic approach the finite element simulation is applied to facilitate the estimation of the range to which the results obtained can be applied

Numerische und experimentelle Untersuchung des Bewegungsverhaltens flexibler, innendruckgesteuerter Endoskope

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Wave Propagation Analysis using High-Order Finite Element Methods: Spurious Oscillations excited by Internal Element Eigenfrequencies

From a computational point of view, the numerical analysis of ultrasonic guided waves is still a very demanding task. Because of the high-frequency regime both a fine spatial and temporal discretization is required. To minimize the numerical costs, efficient and robust algorithms ought to be developed. One promising idea is therefore to focus on high-order finite element methods (ho-FEM).The current article investigates the behavior of the p-version of the finite element method (p-FEM) and the spectral element method (SEM) with respect to the existence of spurious oscillations in the solution. Convergence studies have shown that it is possible to observe non-physical oscillations under certain conditions. These parasitic vibrations, however, significantly deteriorate the accuracy of the simulation. For this reason, we analyse this phenomenon in detail and propose solutions to avoid its occurrence.Without loss of generality, we employ a two-dimensional plane strain model to derive a guideline as to how to avoid these spurious oscillations, placing a special emphasis on the relation between the element size, the polynomial degree of the high-order shape functions and the excitation frequency.Our results show that accurate simulations are possible if the model is generated according to the proposed methodology. Moreover, the implementation of the guideline into an existing finite element software is straightforward; these properties turn the method into a useful tool for practical wave propagation analyses

CAD-FEM-Kopplung auf der Grundlage etablierter Datenschnittstellen

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About the Vibration Modes of Square Plate-like Structures

In the experimental vibration analysis of an oil pan, two eigenmodes are observed that did not appear to be those of a standard rectangular plate vibration. As a result, a numerical, analytical and experimental investigation is launched to discover where these modes are originating from. In this paper, the finite element method is applied to determine the vibration behavior numerically, and experimental results are obtained with the help of a laser doppler vibrometer in order to determine the origin of these two eigenmodes

Dynamic-explicit finite element simulation of complex problems in civil engineering by parallel computing

The paper deals with the simulation of the non-linear and time dependent behaviour of complex structures in engineering. Such simulations have to provide high accuracy in the prediction of deformations and stability, by taking into account the long term influences of the non-linear behaviour of the material as well as the large deformation and contact conditions. The limiting factors of the computer simulation are the computer run time and the memory requirement during solving large scale problems. To overcome these problems we use a dynamic-explicit time integration procedure for the solution of the semi-discrete equations of motion, which is very suited for parallel processing. In the paper at first we give a brief review of the theoretical background of the mechanical modelling and the dynamic-explicit technique for the solution of the semi-discrete equations of motion. Then the concept of parallel processing will be discussed . A test example concludes the paper

Modellfehlerschätzung für Balkenprobleme - ein Vergleich mit 3D Finite-Elemente-Lösungen

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