• Journal of the Society of Naval Architects of Korea
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• v.49 no.5
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• pp.384-390
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• 2012

Power Flow Analysis (PFA) is introduced for solving the noise and vibration analysis of structures in medium-to-high frequency ranges. The vibration analysis software, $PFADS_{C{+}{+}}$ R4 based on Power Flow Finite Element Method (PFFEM) and the noise prediction software, $NASPFA_{C{+}{+}}$ R1 based on Power Flow Boundary Element Method (PFBEM) are developed. In this paper, the coupling equation which represents relation between structural energy and acoustic energy is developed for vibro-acoustic coupling analysis. And vibro-acoustic coupling analysis software based on PFA and coupling equation is developed. Developed software is composed of translator, cavity-finder, solver and post-processor over all. Translator can translate FE model into PFADS FE model and cavity-finder can automatically make NASPFA BE model from PFADS FE model for noise analysis. The solver module calculates the structural energy density, intensity of structures, the fictitious source on the boundary and the acoustic energy density at the field in acoustic cavities. Some applications of vibro-acoustic coupling analysis software to various structures and cruise ship are shown with reliable results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.27 no.1
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• pp.36-42
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• 2017

Helical gear excitation is transmitted to a gearbox through the shafts and bearings and the vibration of the gearbox radiates the noise in the air. Therefore gearbox modeling is essential to evaluate the gear noise. This work deals with vibration and acoustic analysis of a cylindrical shell-type gearbox with/without holes excited by helical gears and focuses on the development of the simple gearbox model. To do so, helical gears and bearing forces are calculated. Gearbox with/without holes is modeled by the aluminum end plates and PMMA cylindrical shell body. The vibration mode and the forced harmonic response were calculated by the commercial FE software and the end plate of the gearbox is more contributed to vibration than the body. Acoustic analysis was also conducted by the commercial acoustic software and a cylindrical shell type gearbox with/without holes has the similar vibro-acoustic characteristics.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.12-22
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• 2007

This paper presents to predict the powertrain structure-borne noise which is primary resource of interior noise. As the first step, it is built up a hybrid powertrain model which is based on the real powertrain which is verified with static and dynamic properties. The methods for verifying are modal analysis and running vibration testing which are experimentally implemented. Based on the Hybrid powertrain component model, an initial predictive assembly model is simulated. As the second step, the characteristic transfer functions are measured that are dynamic stiffness of rubber mounts and vibro-acoustic transfer function based on the acoustic reciprocity. Several techniques utilizing special experimental devices have been proposed for this research. Finally, the structure-borne noise by powertrain will be predict and verify with dynamic simulation and experiment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.110-113
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• 2005

Theoretical models to study the vibro-acoustic performance of a sandwich panel are proposed. The wave propagation characteristics are analyzed, and dispersion relation is derived. The vibration Is analyzed using the Mindlin plate theory. The vibration of the compliantly supported Mindlin plate is investigated using the Rayleigh-Ritz method. The Timoshenko beam functions are used as trial functions. The model is applied to numerically investigate the influence of the plate mechanical properties. The vibro-acoustic properties are mostly determined by bending deformation at low frequencies. At higher frequencies, the shear deformation has a strong influence. The proposed numerical model is used to estimate the optimal panel properties that result in minimum sound radiation. With increasing dynamic stiffnesses the vibration response decreases but the radiating wavenumber components increase.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.862-866
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• 2002

High intensity vibro-acoustic testing is the appropriate method for flight qualification testing of space flight vehicle which must ensure the acoustic environment of launch. To qualify vibro-acoustic environment during its flight, High Intensity Acoustic Test was performed for KOMPSAT-2(Korea Multi-Purpose SATellite) STM(Structural Thermal Model). This paper presents the detailed description on the high intensity acoustic test for KOMPSAT-2. Additionally the test results was compared with the analysis ones, which were estimated with 3-D SEA(Statistical Energy Analysis) model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.96-102
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• 2001

High intensity vibro-acoustic testing is the appropriate method for flight qualification testing of space flight vehicle which must ensure the acoustic environment of launch. Growing demand for satellites and launch vehicles in korea has resulted in a recent increase in the demand for high intensity vibro-acoustic test facility. The test facility is designed to provide an acoustic environment of 152 ㏈( re 20 ${\mu}$Pa) overall sound pressure level over the band width of 30 Hz to 10,000 Hz in the reverberant chamber. The reverberant chamber has a volume of 1,000 ㎥ with interior dimensions of 8.7m${\times}$l0m${\times}$12m, which can accommodate not only satellites but also launch vehicle payload fairing. Korea Aerospace Research Institute and Korean industries have been carrying out the development of the reverberant chamber and auxiliary devices, such as automatic control system, monitoring/safety device, and jet nozzle, etc. This paper presents the detailed description of High Intensity Acoustic Chamber of KARI, which will be the first and unique testing facility in Korea.

• Journal of KSNVE
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• v.10 no.5
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• pp.806-810
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• 2000

This paper presents a practical method for reduction of interior noise and improvement of sound quality in compartment of passenger car. The tested vehicle has a booming noise problem at rear passenger seats. In order to identify the transfer path of interior noise, the running modal analysis, the vibro-acoustic frequency transfer response and the noise path analysis are systematically employed. Using these various methods, it has been founded that the rear part of the roof of the test car was a noise source for the booming noise. Through the modification of the roof, the booming noise has been reduced and sound quality inside car also has been improved.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.291-291
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• 2013

The interior vehicle noise due to the exterior aerodynamic field is an important topic in the acoustic design of a car. The air flow detached from the A-pillar and impacting the side windows are of particular interest as they are located close to the driver / passenger and provides a lower insulation index than the trimmed car body parts. HMC is interested in the numerical prediction of this aerodynamic noise generated by the car windows with the final objective of improving the products design and reducing this noise. The methodology proposed in this paper relies on two steps: the first step involves the computation of the exterior flow and turbulence induced non-linear acoustic field using the CAA(Computational aeroacoustics) solver CAA++. The second step consists in the computation of the vibro-acoustic transmission through the side window using the finite element vibro-acoustic solver Actran. The internal air cavity including trim component are included in the simulation. In order to validate the numerical process, an experimental set-up has been created based on a generic car shape. The car body includes the windshield and two side windows. The body is made of aluminum and trimmed with porous layers. First, this paper describes the method including the CAA and the vibro-acoustic models, from the boundary conditions to the different components involved, like the windows, the trims and the car cavity is detailed. In a second step, the experimental set-up is described. In the last part, the vibration of the windshield and windows, the total wind noise level results and the relative contributions of the different windows are then presented and compared to measurements. The influence of the flow yaw angle (different wind orientation) is also assessed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.562-562
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• 2014

Assessment of aerodynamic noise is becoming increasingly important for automotive manufacturers. Flow passing a vehicle may indeed lead to high interior noise level and affect cabin comfort. Interior noise results from various mechanisms including aerodynamic fluctuations of the disturbed flow around the side mirror or pillar, hydrodynamic and acoustic loading of the car panels and windows, vibration of these panels and acoustic radiation inside the vehicle. Objective of the present study is to capture these important mechanisms in a simulation model and demonstrate the ability of the combined simulation tools Fluent / Virtual.Lab to provide accurate aerodynamic and interior noise prediction results. Previous study focused on the noise generated by the turbulence around the A-pillar structure of the HSM (Hyundai simplified model). The present study also includes the effect of the side-mirror and rain-gutter structures. Complete modeling process is presented including details on the unsteady CFD simulation and the vibro-acoustic model with absorption materials. Guidelines and best practices for building the simulation model are also discussed.

• Steel and Composite Structures
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• v.44 no.6
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• pp.829-843
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• 2022

This manuscript work presents a comprehensive continuum model capable to investigate the effect of porosity on vibro-acoustic behaviour of functionally graded (FG) beams resting on an elastic foundation subjected to thermal and mechanical loadings. Effects of uniform temperature rise and edge compressive load on the sound radiation characteristics are studied in a comparative manner. The numerical analysis is carried out by combining finite element method with Rayleigh's integral. Detailed parametric studies are accomplished, and influences of power law index, porosity volume, porosity distribution and boundary conditions on the vibro-acoustic response characteristics are analyzed. It is found that the vibro-acoustic response under mechanical edge compression is entirely different compared to from that under the thermal load. Furthermore, nature of grading of porosity affects the sound radiation behaviour for both the loads. The proposed model can be used to obtain the suppression performance of vibration and noise FG porous beams under thermal and mechanical loads.