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Comparison of sound power level of the panel with two adjacently located domes and the panel with two diagonally located domes.
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This paper investigates the structural–acoustic characteristics of the automotive-type panels with dome-shaped indentations. These indentations are used to increase the stiffness of the panel whilst keeping its bulk weight constant. To investigate the effect of domes upon sound radiation, four panels with different arrangements of domes are investi...
Similar publications
This paper investigates the structural-acoustic characteristics of the automotive-type panels with dome-shaped indentations. These indentations are used to increase the stiffness of the panel whilst keeping its bulk weight constant. To investigate the effect of domes upon sound radiation, four panels with different arrangements of domes are investi...
Citations
... Ancak, 150 Hz ve altındaki öz frekans değerlerindeki değişim, ihmal edilebilir ölçüde önemsizdir. Yüzey betim en iyilemesi de etkin bir çözüm yöntemidir [15]. Yapının kararlaştırılan kısımlarının revize edilerek kompozit malzemeler ile ikmal edilmesi de makbul bir çözüm yöntemidir [16]. ...
Low frequency booming problem, which is frequently observed in automobiles, negatively affects the acoustic performance and reduces the total comfort. In the current study, vibration and acoustic characteristics of a sedan are examined. In this work, where it is aimed to improve the acoustic comfort of a vehicle, an approach that uses both experimental and computational methods together is adopted. The study is confined to the 33-193 Hz bandwidth, where low frequency booming problems are observed. A finite element model of the vehicle is constructed and structural and acoustical modes are computed. The structural modes of the vehicle are calculated experimentally, as well, and the computational model is updated using experimental results. The effective forces that act on the structure are identified experimentally using transfer path analysis. The low frequency booming problems, which could not have been predicted at the design stage, are diagnosed by assessing both the results of experimental data and computational analysis. In accordance with the outcomes, modification studies are performed on the experimentally verified finite element model using tuned mass dampers.
... They are one of the main sources of noise due to their relatively poor hindering the propagation of elastic waves if there is an excitation. Improving the vibrational response of thin-walled structures can be achieved via indenting some portions (Kumar et al. 2013). Such a strategy is needed when holes on the plate are not wanted and there is a limited design space along its normal direction and the cost is also important. ...
... Li et al. (2016) approached the same problem with bi-directional evolutionary structural optimization (BESO) method. Kumar et al. (2013) optimized the location of several dome-shaped indentations to improve structuralacoustic performance of thin-walled panels. ...
The vibrational response of thin plates is improved by a new approach of indenting some portions along the normal direction so that the interval between two successive eigenfrequencies is enlarged while keeping their mass the same. Binary-coded genetic algorithm (GA) is used as the search algorithm. A stochastically-applied deterministic filter is developed like another genetic operator for GA to accelerate the convergence speed. The corresponding eigenfrequencies and their mode shapes are found by using finite element analysis. The results indicate significant improvement for the band-gap over no indentation designs and show the effectiveness of the new operator of GA.
... To guarantee the calculation precision of finite element method for acoustic analysis, at least six elements are contained in an acoustic wavelength. The wave equation of sound is = ⁄ , where , and are the wavelength of acoustic, acoustic velocity and frequency, respectively [32]. The finite element method has a higher accuracy of acoustic analysis in low frequency range, so the upper limit of calculating frequency is set to 200 Hz [23]. ...
It is very important to predict the acoustic radiation of vehicle body for the control of interior noise. Firstly, the kinetic equations of coupled acoustic-structural finite element method are explained and the numerical analytical methods of noise transfer function and acoustic panel participation are further obtained. Then the coupled acoustic-structural finite element model of body in white and passenger compartment cavity of a minicar is established and verified by modal test. The passive side of engine mounting points are chosen as the excitation points, and driver’s right ear is the output point of sound pressure response. The noise transfer function is calculated and the critical frequency of vehicle interior noise is obtained. The acoustic panel participation analysis of vehicle roof and floor are conducted, and the key acoustic panels are identified. In order to reduce the noise of critical frequency, the measures, pasting damping material and welding beam, are adopted. The results indicate that, compared with the results of structure improvement of modal method, the vehicle interior noise is controlled more effectively by using the acoustic panel participation analytical method.
... As part of the validation process of the numerical experiment, the first step adopted in this study was to perform experimental modal analysis of the cavity, in which one expects a correlation regarding the global modes, and to determine how the damping behaviour of these cavities would vary in frequency when comparing various types of vehicles (Cameron et al., 2010;Kumar et al., 2013). ...
This work focuses on finding a numerical solution for vehicle acoustic studies and improving the usefulness of the numerical experimental parameters for the development stage of a new automotive project. Specifically, this research addresses the importance of modal cavity damping for vehicle exerts during numerical studies. It then seeks to suggest standardized parameter values of modal cavity damping in vehicular acoustic studies.
The standardized value of modal cavity damping is of great importance for the study of vehicular acoustics in the automotive industry because it would allow the industry to begin studies of the acoustic performance of a new vehicle early in the conception phase with a reliable estimation that would be close to the final value measured in the design phase. It is common for the automotive industry to achieve good levels of numerical-experimental correlation in acoustic studies after the prototyping phase because this phase can be studied with feedback from the simulation and experimental modal parameters.
Thus, this research suggests values for modal cavity damping, which are divided into two parts due to their behaviour:
The sequence of this study shows how we arrived at these values.
... The finite element method (FEM) was used for the structural analysis and a full calculation was made of the sound power. More recently, this approach has been applied to minimise the sound radiation from rectangular panels with dome-shaped indentations [9]. ...
... The optimisation algorithm is based upon a genetic algorithm described in Refs. [9,12]. Each iteration of the optimisation algorithm generates design variables related to the modification of the panel. ...
In this paper, an optimisation method is presented that turns the structural modes of an automotive-type panel into weak acoustic radiators. The advantage of the proposed method is that the optimum design does not depend upon a specific excitation mechanism. Hence, the optimised panel can be used in the early stages of vehicle product design when specific knowledge about the excitation forces is not available. In the proposed method the boundary conditions of the panel are specified such that the panel can be considered in isolation from the rest of the structure. The optimisation of the structural modes of the panel is then achieved by placing a number of constraint masses and stiffeners of optimum size and weight at optimum locations on the plate. Firstly, a theoretical model of a simply-supported plate is developed that takes into account the constraints at arbitrary positions and orientations. Then a genetic algorithm is used to minimise the sound power radiated by different modes on the plate by finding the optimum design for the constraints. Secondly, the use of added masses and stiffeners is then applied to a floor panel of a simplified model of a vehicle body structure in order to reduce the radiated sound. Predicted and experimental results of the radiated sound power from a reference flat panel and from various optimised panel designs are presented to illustrate the effectiveness of the optimised designs in reducing radiated sound from the structure. A combination of masses and stiffeners is shown to be an effective way of constructing weakly radiating structural modes on the panel.
This paper is aimed to analyze and control the structure-borne noise of a trimmed body (TB) under excitation by three engine mounts using panel acoustic participation (PAP) method. For each TB panel, the acoustic frequency response function is applied to obtain critical frequencies of interest under each excitation. The PAP analysis is then carried out at all critical frequencies. Panels of acoustic significance are identified by the correlation coefficient matrix (CCM) method for all excitations. The acoustic contributions from those panels may be positive or negative. It is found the control of the total interior noise level can be achieved by suppressing the vibration of positive contribution panels or by increasing the vibration of negative contribution panels. It is verified by installing dynamic vibration absorbers at selected positions on the positive contribution panel to reduce the vibration to control noise level and on the negative contribution panel to reduce the vibration to increase noise level. The PAP method is also compared with the other methods such as the operational deflection shape (ODS) analysis and the structural vibration modal analysis. It is concluded that the PAP method is more effective to control the structure-borne noise.
This paper is aimed to investigate the structural-borne acoustics analysis and multi-objective optimization of an enclosed box structure by using the panel acoustic participation (PAP) and response surface methodology (RSM). The acoustic frequency response function is applied to achieve the critical frequency of interest under each excitation. The PAP analysis is then carried out at all critical frequencies and the remarkable acoustic panels are identified. The correlation coefficient matrix method is proposed for reselecting and grouping the positions of acoustic panels identified to paste damping layer to control noise. With the help of faced central composite design, an efficient set of sample points are generated and then the second-order polynomial functions of sound pressure response at each critical frequency are computed and verified by the adjusted coefficient of multiple determination. The functional relationships between sound pressure responses and the thicknesses of damping layers are investigated, and multi-objective optimization of the thicknesses of damping layers is developed. The results indicate that, by using the PAP and RSM, the structural-borne acoustics at critical frequencies are calculated conveniently and controlled effectively. The optimization process of the explicit optimization model proposed in this paper is simple and the computational time is saved.
In this paper, the structural acoustics analysis and optimization of an enclosed box-damped structure are investigated by using the response surface methodology (RSM). Acoustic frequency response function analysis, i.e. a unit harmonic force imposing on structure and calculating the sound pressure in cavity, is applied to achieve the critical frequency. The acoustic sensitivity analysis of sound pressure level with respect to the thicknesses of damping layer panels are employed to identify the significant variables. With the help of faced central composite design, an efficient set of sample points are generated, and then the second order polynomial function of the sound pressure response at critical frequency is computed and verified by the adjusted coefficient of multiple determination. After the response surface function is verified, the effect of the thicknesses of damping layer panels on sound pressure is analyzed quantitatively, and the thicknesses of damping layer panels are further optimized to minimize the sound pressure response of the target node. The results indicate that, by using the RSM, the computational time for structural acoustic is saved and the optimization process is simple. The sound pressure of the target node is controlled effectively with less damping material used.
