This paper focuses on identifying parameters for optimized distributions of local internal resonators to enhance the vibro-acoustic performance of anti-tetra-chiral auxetic sandwich panels. The ...sandwich panel and its auxetic core are simulated using a full-scale finite element approach. An equivalent homogenized model is then employed to reduce the computational time of the optimization problem. The homogenized model is based on theoretical formulations and verified with the full-scale model. Clusters of resonators are added to the structure to act as local resonators. These resonators are parallel with the through-the-thickness direction of the panel and provide an Absorbing Tuned Auxiliary System (ATAS) to mitigate flexural vibrations over a frequency range. The mechanical parameters of the resonators and the geometrical topology are the design variables. The frequency-dependent radiated mean sound level (RMSL) and the maximum peak value of the Radiated Sound Power Level (RSPL) are two different objective functions for the optimization. The effects of the loading pattern, topology configuration and objective functions on the optimization results are investigated. The use of localized resonators in the anti-tetra chiral sandwich structures can enhance remarkably the sound attenuation of the panels, particularly in the case of local loading conditions. We observe 3.7 and 2.6 dB RMSL attenuations for the local and full coverage sound pressure loadings. In a similar fashion, 15.9 and 11.5 dB attenuation at RSPL peak are also observed in the auxetic panels for the two sound pressure loading conditions.
This paper presents a study of multi-objective structural-acoustic optimization of elastic beams made of functionally graded materials. The goal of this research is to discover the potentials to ...design multi-objective optimal volume fraction for better acoustic performance. The transfer matrix method is applied to obtain the structural-acoustic response of functionally graded beams. The hybrid of particle swarm optimization and cell mapping method is used to search for the Pareto optimal solutions. Two well-known distribution laws of material distribution are considered and compared with the spline interpolation of material distribution when spatially sampled material properties are used as design variables. Several cases are studied to demonstrate the multi-objective optimal design of functionally graded beams.
•A new criterion was proposed to divide the frequency range of cabin noise prediction within full frequency. The full frequency cabin noise prediction was achieved by the finite element method (FEM), ...the finite element and statistical energy analysis hybrid method (FE-SEA) and the statistical energy analysis (SEA) respectively. The results are compared with the measured values, which shows that the prediction values of cabin noise are in good agreement with the measured values.•The combination of genetic algorithm (GA) and sequential quadratic programming (SQP) can not only get better noise reduction scheme but also reduce the optimization time.
A new criterion was proposed to divide the frequency range of cabin noise prediction within full frequency. The vibro-acoustic models of oil tanker for cabin noise prediction in low frequency, middle frequency and high frequency were established. The full frequency cabin noise prediction was achieved by using the Finite Element Method (FEM), the Finite Element and Statistical Energy Analysis hybrid method (FE-SEA) and the statistical energy analysis (SEA) respectively. The results were compared with the measured values, which shows that the error between the simulation value and the measured value is within 4 dB(A). The prediction results of cabin noise are accurate and reliable. The acoustical optimization design of sound absorbing material was realized by using different optimization algorithms. The optimization results show that the combination of genetic algorithm (GA) and sequential quadratic programming (SQP) can be used to get better sound package and also to reduce the optimization time.
Fibrillation is identified as the most energy intensive process step in pulp and paper manufacturing and improved energy efficiency is the motivation for development of alternative technologies. The ...aim of this study is to explore the potential of a new refining concept based on cavitation, focusing on the optimization of acoustic cavitation efficiency of the proposed flow-through sonicator concept. The simulations utilize the linearized wave equation in the frequency domain with an addition of nonlinear attenuation introduced by cavitation bubbles. Verification is made by pressure measurements, calorimetry, and foil tests. The fibrillation capability was validated on chemi-thermo mechanical pulp fibers at low consistencies. Fiber properties was characterized by ultrasonic spectroscopy, fiber analysis and SEM. The objective is to optimize the energy transfer efficiency from electrical input power to acoustic cavitation intensity for efficient fibrillation of cellulose fibers. Results showed changes in fiber dimensions and fiber morphology, however, improvements in tensile strength index, measured and predicted by ultrasonic spectroscopy, was limited to 20 % at an energy level of 804 kWh/bdt. To enhance energy efficiency and paper strength properties, it is suggested to add a hydrodynamic cavitation device prior to the sonicator to initiate cavitation bubbles and to increase turbulence intensity.
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•Developed scalable flow through cylindric sonicator using multiphysical simulations.•The sonicator efficiency is enhanced by coupled structural and acoustic resonances.•The focus is on energy-efficiency and control of mechanical pulping by sonication.•Results show that sonication improve fiber morphology and paper strength properties.•Improved efficiency requires a hydrodynamic cavitation device prior the sonicator.
•Tuned Mass Dampers are used to control random interior sound.•A stochastic acoustic optimization strategy is proposed.•Multi-objective optimization is used along with multiple TMDs.•The optimization ...strategy is able to handle multimodal control of interior sound.
The present work deals with the passive control of interior sound pressure induced by randomly vibrating structure coupled to an enclosure filled with air. The control in the low frequency range is achieved using a Tuned Mass Damper (TMD) device. In order to guarantee an optimal performance of the TMD device, a stochastic acoustic optimization strategy is proposed. In the later, the objective function is the root mean square acoustic pressure measured at a given location inside the cavity. Assuming linear behavior of the vibro-acoustic system, the modal interaction approach is used and the objective function is evaluated by means of spectral analysis. The effectiveness of the proposed strategy is investigated and compared with others from the open literature.
The capability of the proposed optimization strategy to deal with multimodal control of interior sound has also been addressed. To this end, multiple TMDs have been used. The optimal TMD parameters have been obtained using a multi-objective optimization approach and the results that have been gathered show significant attenuations in all target resonant modes.
This paper presents an optimization study of sandwich plates with corrugated cores for minimizing the transmitted sound power, considering the manufacturability of the structure and constraints on ...the structural weight and fundamental frequency. A two-dimensional plate model is developed based on the spectral element method (SEM) for the calculation of the frequency-domain vibration response of the whole sandwich structure subject to airborne excitation, and the Rayleigh integral formula is used to calculate the transmitted sound power via its structure-born path. A genetic algorithm-based multi-parameter optimization method is employed to search for the optimal structural parameters with the objective to minimize the sound power transmitted. It is indicated that the optimization results depend highly on the properties of resonant modes in the targeted frequency band. Because of the local modes of the sandwich structure in the high frequency band, the transmitted sound power can be significantly reduced with neither increasing the structural weight nor deteriorating the bending stiffness.
With the extension of the applications of sandwich panels with corrugated core, sound insulation performance has been a great concern for acoustic comfort design in many industrial fields. This paper ...presents a numerical and experimental study on the vibro-acoustic optimization of a finite size sandwich panel with corrugated core for maximizing the sound transmission loss. The numerical model is established by using the wave-based method, which shows a great improvement in the computational efficiency comparing to the finite element method. Constrained by the fundamental frequency and total mass, the optimization is performed by using a genetic algorithm in three different frequency bands. According to the optimization results, the frequency averaged sound transmission of the optimized models in the low, middle, and high-frequency ranges has increased, respectively, by 7.6 dB, 7.9 dB, and 11.7 dB compared to the baseline model. Benefiting from the vast number of the evolution samples, the correlation between the structural design parameters and the sound transmission characteristics is analyzed by introducing the coefficient of determination, which gives the variation of the importance of each design parameter in different frequency ranges. Finally, for validation purposes, a sound insulation test is conducted to validate the optimization results in the high-frequency range, which proves the feasibility of the optimization method in the practical engineering design of the sandwich panel.
An efficient approach for acoustic topology optimization to minimize the radiated sound power from a vibrating structure is described. The topology optimization is implemented by modifying the local ...stiffness at discrete locations on the surface of the structure. The radiated sound power level from the structure is directly chosen as the objective function to be minimized. A sensitivity analysis is then implemented to further optimize the layout of the locations of the modified local stiffness. To speed up the computational process, the radiated sound power is computed based on mapped acoustic radiation modes. To demonstrate the acoustic topology optimization using mapped acoustic radiation modes, the radiated sound power of a compressor housing is examined. Based on results from the numerical model, the local stiffness of a compressor housing was experimentally modified. Good agreement in sound power reduction obtained both numerically and experimentally was observed for the overall trend for the sound power levels as a function of one-third octave frequency bands.
•Sound power is directly used as the objective function in the topology optimization.•Computational efficiency of sound power prediction is significantly increased.•This optimization technique can be applied to complex structures of any profile.•Overall sound reduction is obtained by both FEM analysis and experimental results.
This paper establishes a many-objective MATLAB with a COMSOL joint parallel simulation optimization method in order to solve the current situation of low efficiency, single objective, and poor effect ...in acoustic optimization design research for a sound-absorbing structure. Our proposed method combines the means for population partitioning, monitoring, and adaptive normalization, within the framework of the NSGA-III algorithm, which takes the hyperplane deployment scheme into account in its entirety. Compared to the traditional genetic algorithm toolbox of the joint COMSOL optimization scheme, it is shown that the joint parallel simulation optimization method that is constructed in this paper achieves a higher optimization efficiency and a better experimental performance, thereby aiding in the identification of the optimal solution to multiple objectives. The optimization efficiency can increase linearly as the number of available cores on the computer increases. This method is then used to construct a parallel, low-frequency, broadband, highly-sound-absorbing structure. Without any constraints on the optimization objective, the diversity of the optimization results is evident within the parameter optimization range of this paper. The optimization results are stable and substantial, with constrained optimization objectives that have some reference value. In addition, the proposed method can solve acoustic vibration optimization problems and can be applied to other finite element optimization problems.
Present work purpose is to optimize the acoustic attenuation properties of a composite sandwich panel used for a high-speed train structure, choosing the best panel configuration which allows to ...improve the performances. Firstly, Nilsson's analytical formulation for Transmission Loss (TL) evaluation has been implemented and experimentally validated on a typical material used for high-speed railway applications, highlighting the opportunity to use a different material to satisfy the new required design specifications. Different materials and stratifications have been then considered and TL parameter of each configuration have been calculated using Nilsson's formulation, characterizing acoustic behavior in the frequency domain. Once found the composition which ensures the best compromise between high acoustic insulation and low weight, the panel has been physically realized. Finally, an experimental and a numerical modal analysis have been performed on it. Starting from both FE simulation and impact testing outcomes, a correlation study through the computation of the Modal Assurance Criterion (MAC), has been carried out. A good agreement between numerical and experimental analyses has been found, obtaining a reliable FE model for future improvements.
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