Efficient dispersion curve computations for periodic vibro-acoustic structures using the (generalized) Bloch mode synthesis

Periodic structures such as metamaterials and phononic crystals hold potential as promising compact and lightweight solutions for noise and/or vibration attenuation in targeted frequency ranges. The performance of these structures is usually investigated by means of dispersion curves. The input for dispersion curve computations is often a finite element model of the corresponding unit cell. Nowadays, the vibration and noise attenuation of the periodic structures are generally tackled as separate problems and their performance is investigated with either structural or acoustic dispersion curves, respectively. Recently, vibro-acoustic unit cell models have come to the fore which can exhibit simultaneous structural and acoustic stopbands. However, the vibro-acoustic coupling inside the unit cell is usually not taken into account during the dispersion curve computations. To consider this coupling during their performance assessment, the computation of vibro-acoustic dispersion curves is required. Although these dispersion curves provide valuable information, the associated computational cost rapidly increases with unit cell model size. Model order reduction techniques are important enablers to overcome this high cost. In this work, the Bloch mode synthesis (BMS) and generalized BMS (GBMS) unit cell model order reduction techniques are extended to be applicable for 2D and 3D periodic vibro-acoustic systems. Through a verification case, the methodologies are shown to enable a strongly reduced dispersion curve calculation time while maintaining accurate predictions

The constitutional dilemma of European integration

The paper analyzes European integration from a constitutional economics perspective. It is argued that the use of the Prisoners' Dilemma as a description of the advantages of European integration is fallacious. If the situation is a PD, the solution is impossible; if it is not, it is unnecessary

Development of System-level Model Reduction Techniques for Flexible Multibody Simulation (Ontwikkeling van system-niveau modelreductietechnieken voor flexibele meerlichamensystemen)

In recent years, flexible multibody simulation has become an essential tool in the computer aided design of many systems. However, current formalisms require a very large computational load, and these techniques are not feasible for many applications which require models to be run at a high rate. In order to address this limitation, this doctoral research investigates a novel system level reduction technique for flexible multibody models: Global Modal Parameterization (GMP). This approach allows a considerable reduction in the number of degrees-of-freedom and eliminates the constraint equations from the equations of motion, leading to compact ordinary differential models.The research mainly focusses on improvements of the formalism for hard real-time systems and reduction of computational load for complex mechanism. The basic GMP formulation is also extended in order to facilitate the reduction of complicated systems. By combining GMP reduced models of sub-systems these complicated system can be efficiently simulated. Finally, the GMP methodology is also extended to generalized geometric nonlinearities. This allows the treatment of a more general set of mechanisms.The presented methods will contribute to the development of a wide array of model based engineering techniques in optimization, state-estimation and control, which were previously infeasible.status: publishe

KU Leuven in-house multibody research code

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Feasibility Study Optical Force Sensing

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Comparison of lumped and coupled mass matrix for flexible multibody simulation

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