Title Participants Abstract
"The impact of damping on the sound transmission loss of locally resonant metamaterial plates" "Lucas Van Belle, Claus Claeys, Elke Deckers, Wim Desmet" "Vibro-acoustic locally resonant metamaterials with structural stop band behaviour can lead to a strongly increased sound transmission loss in a targeted frequency range. This work assesses the impact of damping in the constituents of metamaterial plates on their acoustic insulation performance by means of infinite periodic and finite structure modelling. Besides applying the hybrid Wave Based - Finite Element unit cell method for infinite plates and the Finite Element Method for finite plates, qualitative dispersion curve based predictions are extended to quantitative sound transmission loss approximations by introducing a dispersion curve based equivalent plate method. Both an idealised and a realisable locally resonant metamaterial plate are analysed. Damping in the resonators in particular is found to have an important impact in and around the stop band, reducing the sound transmission loss peak, but improving the subsequent dip and reducing resonant transmission in a broadening frequency range around the stop band. The damping influenced sound transmission loss predictions for the realisable locally resonant metamaterial plate are experimentally validated by means of insertion loss measurements. It is shown that, by including damping in the infinite periodic structure modelling, acoustic insulation performance predictions with improved accuracy are obtained."
"Explicit and efficient topology optimization of frequency-dependent damping patches using moving morphable components and reduced-order models" "Xiang Xie, Hui Zheng, Wim Desmet, Stijn Jonckheere" "Viscoelastic materials have been widely applied as the lightweight structures are growingly used in many industrial sectors in order to improve the cost-efficiency of products. The present work is devoted to minimize the kinetic energy of thin-shell structures subjected to harmonic excitations within a certain frequency range by seeking the optimal layouts of frequency-dependent viscoelastic damping patches under a prescribed area constraint. An explicit topology optimization approach based on the moving morphable components (MMC) is applied, where the number of design variables is substantially reduced compared to the traditional density-based implicit framework. This is achieved by introducing a set of geometry parameters (i.e. design variables) to explicitly describe the boundary of structural components which are viscoelastic patches in this paper. Meanwhile, the unnecessary degrees of freedom (DOFs) related to void regions from the finite element (FE) model are removed at every step of numerical optimization thanks to the explicit boundary evolution. The adjoint method is adopted to derive the sensitivity of the objective function with respect to a design variable. Furthermore, an adaptive model order reduction (MOR) technique for the frequency-dependent system is provided to simplify the computational complexity of the dynamical equation and the adjoint equation as well. With the MMC to reduce the number of design variables in the topology formulation and the MOR to reduce the number of DOFs in the FE model, the optimization simulation can be largely sped up. Numerical examples are presented to demonstrate that the combination of the MMC- and MOR-technique is able to distribute constrained-layer damping patches reasonably and very efficiently."
"Application of a-priori hyper-reduction to the nonlinear dynamic finite element simulation of a rolling car tire" "Daniel De Gregoriis, Frank Naets, Peter Kindt, Wim Desmet" "The a-priori Multi-Expansion Modal (MEM) hyper-reduction method for nonlinear structural dynamics finite element problems is described, extended and applied to the dynamic nonlinear finite element simulation of a car tire rolling over a rough road surface, including geometrical, material, follower force and contact nonlinearities. Rather than using time-domain training simulation data, a-priori calculated static nonlinear contact configurations and eigenmodes are used as a reduction basis and to perform the hyper-reduction element sampling. The hyper-reduction element sampling is performed by solving an L1 optimization problem subject to a set of equality constraints. This yields a reduced set of elements with an a-priori known cardinality, which depends on the amount of constraints taken into consideration and the reduction basis dimension. It is shown that care has to be taken during the hyper-reduction process when considering distributed contact constraints, as is the case for e.g. a tire rolling over a rough road surface. Large speedup factors can be obtained while still retaining a relatively high accuracy, making application of the MEM method suitable to for instance industrial design optimization cases."
"Flexible multi-level fast multipole BEM with direct solver for industrial acoustic problems" "Yue Li, Onur Atak, Wim Desmet"
"Loose bolt detection in a complex assembly using a vibro-acoustic sensor array" "Philip Becht, Elke Deckers, Claus Claeys, Bert Pluymers, Wim Desmet"
"Loose bolt detection in a complex assembly using a vibro-acoustic sensor array" "Philip Becht, Elke Deckers, Claus Claeys, Bert Pluymers, Wim Desmet" "© 2019 Elsevier Ltd A non-destructive testing strategy is proposed that combines microphone measurements and structural measurements in one array. The aim is to lower the total inspection time by reducing the number of structural sensors. This is possible by making use of the easier and faster installation of microphones as compared to structural sensors. Structural sensors are needed to limit the influence of background noise. The proposed algorithm is based on the theory of the Time-Reversal MUltiple SIgnal Classification (TR-MUSIC) algorithm. In addition to the novelty of using a vibro-acoustic array, this publication presents a strategy on how to select only the most ‘valuable’ regions of the frequency spectrum for the TR-MUSIC algorithm and an option to use the algorithm with a number of excitations below the theoretically necessary minimum. The proposed procedure is applied in an experiment that targets the localisation of loose or removed bolts in an assembly of aluminium beams and a honeycomb panel, mounted with rivets, bolts and double-sided tape. Although none of the bolts is in the line of sight of the sensor array, all introduced defects can be found in this experiment. This includes the localisation of multiple defects as well. By adding artificial measurement noise to the microphone measurements, it is demonstrated that a combined vibro-acoustic array can cope with a high ambient noise level, while the process fails if a comparable measurement error is also applied to the structural sensors."
"Design and experimental validation of a metamaterial solution for improved noise and vibration behavior of pipes" "Alireza Nateghi, Luca Sangiuliano, Claus Claeys, Elke Deckers, Bert Pluymers, Wim Desmet" "This paper investigates a metamaterial solution for efficient vibration attenuation and acoustic radiation reduction of an aluminum pipe. To this end, using unit cell predictions, locally resonant structures are designed to have a pronounced flexural resonance frequency at the vicinity of a dominant vibration mode of the pipe. A direct approach of the Bloch-Floquet theorem is adopted to provide the dispersion relation representing wave motion in an infinite metamaterial pipe. Using these wave dispersion relations, the frequency range of the stopband zone created by the metamaterial solution is predicted. The dynamic behavior of the finite counterpart is predicted using the Finite Element Method (FEM). The resonant structures are produced from polymethyl methacrylate (PMMA) panels and are added to the host structure. In order to properly characterize both the vibrational behavior of the metamaterial pipe and the acoustic radiation from its wall, impact tests using roving hammer technique is performed on the pipe and both accelerations and acoustic pressures are measured at different locations. The experimental results show a pronounced stopband zone created by the addition of a few rows of resonant structures. Moreover, comparisons between the measurements and numerical predictions show a good agreement."
"Prediction of dynamic hub forces as a source of structure-borne tire/coarse road noise using a high-fidelity simulation approach" "Daniel De Gregoriis, Frank Naets, Peter Kindt, Wim Desmet"
"Robust virtual sensing of the exterior noise radiation from a complex structure in different acoustic environments" "Sjoerd van Ophem, Elke Deckers, Wim Desmet" "By using a numerical model of a vibro-acoustic system in combination with a small set of measurements in a Kalman filter, it is possible to estimate the sound pressure at locations where no microphones are present. This can be achieved with increased accuracy as compared to using only the numerical model due to the inclusion of the expected process and measurement noise. This procedure is also known as virtual sensing. In this paper, a model-based virtual sensor is built for a complex, deep drawn structure that radiates sound into the free field. A finite element model is used that is extended with infinite elements to approximate the Sommerfeld radiation condition. Since the original model is too large to be used in a Kalman filter, it is reduced by a stable Krylov based model order reduction technique. The performance of this virtual sensor is tested in a semi-anechoic chamber, and additionally in several acoustical environments that do not conform to the Sommerfeld condition in order to validate whether the Kalman filter can handle the additional uncertainties. The obtained results show that the filter performs well, which means that the required modeling effort can be reduced significantly by assuming free-field conditions."
"Model order reduction with Krylov subspaces of exterior acoustic BEM systems" "Dionysios Panagiotopoulos, Elke Deckers, Wim Desmet"