• 소음진동
• /
• 제9권2호
• /
• pp.310-316
• /
• 1999

4-Pole parameter method based on an acoustic theory is very popular for the analysis of the acoustic behavior of the car exhaust system. However, this method is applicable only for the simple shape of acoustic elements of the muffler. Numerical methods such as FEM(Finite Element Method) or BEM(Boundary Element Method) can also provide acceptable results for the acoustic analysis of the car exhaust system. Even though these numerical methods have benefits for the analysis of complicated shape of acoustic elements of the muffler, time consuming is another problem during modeling and numerical calculation. Combining benefits of both methods, the new code called the hybrid method for car exhaust system is introduced. And the developed code is utilized for calculation of the transmission loss of a main muffler of an automobile comparing with the experimental results.

• 한국복합재료학회:학술대회논문집
• /
• 한국복합재료학회 2005년도 춘계학술발표대회 논문집
• /
• pp.172-175
• /
• 2005

The numerical simulation is performed for the acoustic emission and the wave propagation due to fiber breakage in single fiber composite plates by the finite element transient analysis. The acoustic emission and the following wave motions from a fiber breakage under a static loading is simulated to investigate the applicability of the explicit finite element method and the equivalent volume force model as a simulation tool of wave propagation and a modeling technique of an acoustic emission. For such a simple case of the damage event under static loading, various parameters affecting the wave motion are investigated for reliable simulations of the impact damage event. The high velocity and the small wave length of the acoustic emission require a refined analysis with dense distribution of the finite element and a small time step. In order to fulfill the requirement for capturing the exact wave propagation and to cover the 3-D simulation, we utilize the parallel FE transient analysis code and the parallel computing technology.

• 한국소음진동공학회논문집
• /
• 제15권10호
• /
• pp.1211-1216
• /
• 2005

Underwater acoustic transducers are widely used for SONAR application, whose important design parameters are shapes. materials, dimensions and supporting structures. Practical design method of transducers consists of manufacturing, experiments and modifications so that it requires much time and expenses. In this study, an analytical method was developed for the Tonpilz type transducers using the commercial finite element analysis code ATILA which can solve the electro-mechanical coupling problems. A finite element model was established including the transducer elements such as ceramic stack, head mass, tail mass, tensile bolt, and molding layers. The proposed model was verified and modified by comparing the in-air and in-water test results of prototypes. The developed analysis method will be effectively used for the sensitivity analysis of design parameters in transducer design process.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2014년도 추계학술대회 논문집
• /
• pp.336-340
• /
• 2014

The noise and vibration have been evaluated by using the finite element model in the vehicle developing stage. The sound pressure of the vehicle compartment is predicted by the acoustic cavity model coupled with the body structure. In general, the structural model has been focused to study in the improvement of the noise. It is not easy to treat the structural model, instead the acoustic cavity model is relatively simple and aids in root cause analysis of vibro-acoustic issues. Therefore, the acoustic transfer function of the cavity is more efficient for finding out the main contribution parts of the vehicle booming noise. And examples about the run-up booming noise demonstrate the validity of the AFT analysis for improving the vibro-acoustic sensitivity.

• International Journal of Aeronautical and Space Sciences
• /
• 제13권2호
• /
• pp.127-153
• /
• 2012

This paper presents an advanced computational method for the prediction of the responses in the frequency domain of general linear dissipative structural-acoustic and fluid-structure systems, in the low-and medium-frequency domains and this includes uncertainty quantification. The system under consideration is constituted of a deformable dissipative structure that is coupled with an internal dissipative acoustic fluid. This includes wall acoustic impedances and it is surrounded by an infinite acoustic fluid. The system is submitted to given internal and external acoustic sources and to the prescribed mechanical forces. An efficient reduced-order computational model is constructed by using a finite element discretization for the structure and an internal acoustic fluid. The external acoustic fluid is treated by using an appropriate boundary element method in the frequency domain. All the required modeling aspects for the analysis of the medium-frequency domain have been introduced namely, a viscoelastic behavior for the structure, an appropriate dissipative model for the internal acoustic fluid that includes wall acoustic impedance and a model of uncertainty in particular for the modeling errors. This advanced computational formulation, corresponding to new extensions and complements with respect to the state-of-the-art are well adapted for the development of a new generation of software, in particular for parallel computers.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
• /
• pp.1346-1353
• /
• 2009

In this study, a numerical study was carried out to simulate the expansion of ground borehole by pulse discharge technology using finite element analysis. Considering the mortar in the borehole as an acoustic medium and the surrounding soil as an elasto-plastic material, the strong shock wave developed by the pulse discharge was modeled using the underwater explosion model. The ground expansion was simulated based on a coupled acoustic-structural analysis with varying properties of mortar and soil, and the behavior between acoustic-structural interface.

• 한국소음진동공학회논문집
• /
• 제13권11호
• /
• pp.882-889
• /
• 2003

This paper presents the method for structure borne noise analysis of a flexible body in multibody system. The proposed method is the superposition method using the flexible multibody dynamic analysis and the finite element one. This method is executed in 3 steps. In the 1st step, time dependent quantities such as dynamic loads, modal coordinates and gross body motion of the flexible body are calculated through a flexible multibody dynamic analysis. And frequency response functions of those time dependent quantities are computed through Fourier transforms. In the 2nd step, acoustic pressure coefficients are obtained through structure-acoustic coupling analyses by the finite element method. In the final step, frequency responses of acoustic pressure at the acoustic nodes are recovered through linear superposition of frequency response functions with acoustic pressure coefficients. The accuracy of the proposed method is verified in the numerical example of a simple car model.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 1996년도 추계학술대회 논문집
• /
• pp.867-871
• /
• 1996

Recently many studies have been carried out to predict the characteristics of vehicle noise and to reduce the noise for enhancing the ride quality. In this study, the structural-acoustic coupling theory and the acoustic finite element theory were reviewed, and the structural acoustic coupling analysis was applied to an automobile. Because of nonuniformed lateral shape of a compartment cavity, the acoustic modes were calculated with 3-D finite element modeling. The structural modes were measured with the modal testing. Using the structural-acoustic cooling analysis, the modes which strongly coupled to the interior noise were identified and the boundary regions which could reduce noise level efficiently by structural modification were predicted.

• 한국음향학회지
• /
• 제13권2호
• /
• pp.68-75
• /
• 1994

본 논문은 두 편으로 연결된 논문의 둘째편으로 광대역 배열변환기의 설계방법과 설계된 변환기의 음향특성을 제시한다. 아울러 유한요소법과 하이브리드형 무한요소법의 결합기법에 의한 설계된 변환기의 음향특성 결과가 등가회로 해석 기법에 의한 결과보다 양호함을 확인하였다. 따라서 제시된 변환기 해석기법이 광대역 배열 변환기의 설계 및 음향특성 해석에 응용될 수 있을 것으로 판단된다.

• 한국소음진동공학회논문집
• /
• 제19권9호
• /
• pp.922-927
• /
• 2009

The transducers used in active sonar on surface ships are packed in a specific geometry in the array drum in order to meet the requirements such as the source level, directional beam pattern, etc. This paper describes the acoustic characteristics of the cylindrical array which is based on a 64 vertical staves arrangement, each stave composed 5 independent transducers. Firstly, the single transducer on the rigid baffle in the water is analyzed with the Finite Element Method. From the result of the FE analysis nodal velocities on the radiation surface is calculated and used with the boundary conditions of the transducers mounted on the array drum. Then the acoustic pressure is calculated in the field points using the Boundary Element Method and the other acoustic informations, the source level, beam pattern, near field and far-field distance, were acquired.