• 한국소음진동공학회논문집
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• 제22권11호
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• pp.1071-1077
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• 2012

Low frequency noises(up to about 200 Hz) such as booming are mainly caused by particular modes, and in general the solutions may be found based on mode controls where conventional methods such as FEM can be used. However, at higher frequencies between 0.3~1 kHz, as the number of modes rapidly increases, radiation characteristics from structures, performances of damping sheets and sound packages may be more crucial rather than particular modes, and consequently the conventional FEM may be less practical in dealing with this kinds of structure-borne problems. In this context, so-called 'mid-frequency simulation model' based on FE-SEA hybrid method is studied and validated to reduce noise in this frequency region. Energy transmission loss(i.e. air borne noise) is also studied. A dash panel component is chosen for this study, which is an important path that transmits both structure-borne and air borne energies into the cavity. Design modifications including structural modifications, attachment of damping sheets and application of different sound packages are taken into account and the corresponding noise characteristics are experimentally identified. It is found that the dash member behaves as a noise path. The damping sheet and sound packages have similar influences on both sound radiation and transmission loss. The comparison between experiments and simulations shows that this model could be used to predict the tendency of noise improvement.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 춘계학술대회 논문집
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• pp.544-545
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• 2010

• 대한기계학회논문집A
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• 제33권7호
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• pp.700-705
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• 2009

In order to enhance the dynamic stiffness of automotive panel, effect of bead and curved surface was investigated. Modal test was performed for principle specimens which have various kinds of beads, holes and curved surfaces. Test was also performed for conventional dash panel assembly and rear floor panel assembly and curved shaped ones. Results showed that curved shape increased the natural frequency of automotive panel more effectively than the bead. Finite element analysis was also performed and yielded good match with the test results.

• 한국화재조사학회논문지
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• 제11권1호
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• pp.83-88
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• 2008

차량화재의 발화지점은 크게 엔진룸과 승객실로 볼 수 있다. 엔진룸에서 발생된 차량화재의 경우 방화벽이 엔진룸과 승객실 사이에 설치되어 있으므로 승객실로 전이는 약 10~15분 정도로 지연되는 것이 일반적이다. 엔진룸은 그 차량의 구동 방식에 따라 종치형과 횡치형으로 배열되는데 이들 엔진 배열에 따라 화염이 전이되는 과정이 각각 다르게 나타나고 좌우 대시 패널에 나타난 소손정도 또한 다르게 나타난다. 따라서 엔진룸에서 발생된 차량 화재 감식시 좌우 대시패널의 소손정도를 먼저 파악하는 것이 발화지점을 빠르게 찾는 방법인 것으로 사료된다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.51-55
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• 2007

In this paper Statistical Energy Analysis has been considered to predict high frequency air borne interior noise. Dash panel Insulation is major part to reduce engine excitation noise. Transmission loss and absorption coefficient are considered to predict dash insulation performance. Transmission lose is derived from coupling loss factor and absorption coefficient is derived from internal damping loss factor. Material Biot properties were used to calculate each loss factors. Insulation geometry thickness distribution was hard to measure, so FeGate software was used to calculate thickness map from CAD drawing. Each predicted transmission losses between conventional insulation and light weight insulation were compared with SEA. Transmission loss measurement was performed to validate each prediction result, and it showed good correlation between prediction and measurement. Finally interior noise prediction was performed and result showed light weight insulation system can reduce 40% weight to keep similar performance with conventional insulation system, even though light weigh insulation system has lower sound transmission loss and higher absorption coefficient than conventional system.

• Earthquakes and Structures
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• 제16권1호
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• pp.55-67
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• 2019

The finite solutions of deflection and the corresponding in-plane stress values of the graded sandwich shallow shell structure are computed in this research article via a higher-order polynomial shear deformation kinematics. The shell structural equilibrium equation is derived using the variational principle in association with a nine noded isoprametric element (nine degrees of freedom per node). The deflection values are computed via an own customized MATLAB code including the current formulation. The stability of the current finite element solutions including their accuracies have been demonstrated by solving different kind of numerical examples. Additionally, a few numerical experimentations have been conducted to show the influence of different design input parameters (geometrical and material) on the flexural strength of the graded sandwich shell panel including the geometrical configurations.

• Structural Engineering and Mechanics
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• 제68권6호
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• pp.721-733
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• 2018

The modal frequency responses of functionally graded (FG) sandwich doubly curved shell panels are investigated using a higher-order finite element formulation. The system of equations of the panel structure derived using Hamilton's principle for the evaluation of natural frequencies. The present shell panel model is discretised using the isoparametric Lagrangian element (nine nodes and nine degrees of freedom per node). An in-house MATLAB code is prepared using higher-order kinematics in association with the finite element scheme for the calculation of modal values. The stability of the opted numerical vibration frequency solutions for the various shell geometries i.e., single and doubly curved FG sandwich structure are proven via the convergence test. Further, close conformance of the finite element frequency solutions for the FG sandwich structures is found when compared with the published theoretical predictions (numerical, analytical and 3D elasticity solutions). Subsequently, appropriate numerical examples are solved pertaining to various design factors (curvature ratio, core-face thickness ratio, aspect ratio, support conditions, power-law index and sandwich symmetry type) those have the significant influence on the free vibration modal data of the FG sandwich curved structure.

• 한국소음진동공학회논문집
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• 제18권11호
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• pp.1199-1205
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• 2008

The vehicle design engineers have studied the method of applying damping materials to the vehicle bodies by computer simulations and experimental methods in order to improve the vibration and noise characteristics of the vehicles. The unconstrained layer damping, being concerned with this study, has two layers(base layer and damping layer) and proyides vibration control of the base layer through extensional damping. Generally this kind of surface damping method is effectively used in reducing structural vibration at frequencies beyond 150Hz. The most important thing is how to apply damping treatment with respect to location and size of the damping material. To solve these problems, the current experimental methods have technical limits which are cumbersome, time consuming, and expensive. This Paper proposes a method based on finite element method and it employes averaged ESE(element strain energy) percent of total of dash panel assembly for 1/1 octave band frequency range by MSC/NASTRAN. The regions of high ESE percent of total are selected as proposed location of damping treatment. The effect of damping treatment is analyzed by comparing the frequency response function of the SPCC bare Panel and the damping treated panels.

• 동력기계공학회지
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• 제14권2호
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• pp.55-59
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• 2010

In the study, it is considered sporty car as 1400cc entry cars using sound generator. These cars are required special sound quality, also sporty sound quality. The operational principle of this sound generator system is that on the operation of the engine intake valves caused pulsating is to shake the membrane of the sound generator on the inside of the driver front dash panel through the intake manifold, which will deliver the required sound quality and tone. For the component constructed sound generator, main design parameters are selected and optimized using the daguchi's method. The results are as follows; The C2 sound level must be minimized and C4 level must be maximized. And also overall level keeps linear characteristics.

• 한국생산제조학회지
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• 제23권6호
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• pp.602-608
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• 2014

Mixed-model production lines are often used in manufacturing systems. In production lines, different product types are simultaneously manufactured by processing small batches. This paper describes a new welding assembly technology involving the development of experimental models for a mixed-model production line in an automobile company. Due to the extensive number of models, the design of a welding assembly system is complicated. Performance evaluation is an important phase in the design of welding assembly lines in a mixed-model production environment. In this study, a new welding assembly technology for a mixed-model production method was used to weld the package tray and dash panel of a vehicle.