• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.5
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• pp.41-49
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• 2005

This paper discusses the test procedure, instrumentation, verification methodology and the results of the ground vibration test(GVT) performed on the KF-16D aircraft to estimate experimentally dynamic characteristics of the aircraft. The modal tests for 7 external store configurations were conducted to estimate effects of external stores on the aircraft vibration modes. To emulate free-free boundary conditions the test aircraft was mounted on its landing gear structure with deflated tires during the GVT. The airframe modal tests were done by burst random excitations with 6 to 8 shakers and about 200 accelerometers. Frequency response functions(FRFs) were measured for each test, and the FRFs were reduced and analyzed to identify the dynamic parameters interested. The analyses were carried out in two steps. To extract modal parameters such as, frequencies and damping ratios, the poly-reference least square complex exponential method was used in the time domain. The mode shape coefficients were estimated with the least squares frequency domain method to identify the vibration modes.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.77-77
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• 2009

ELV(; End of Life Vehicles)를 비롯한 최근 환경 동향은 자동차 전장 모듈에 대하여 다양한 무연 솔더 적용을 요구하고 있다. 특히 자동차 엔진룸과 트랜스미션은 가동 중 고온 및 진동의 지속적인 영향을 받기 때문에 이와 유사한 환경에서의 신뢰성 연구가 필요한 시점이다. 이에 본 연구에서는 Sn3.5Ag, Sn0.7Cu, Sn5.0Sb 솔더 조성에 대하여 복합환경 조건하에서 접합부 신뢰성을 평가하였다. 복합환경을 구현하기 위하여 $-40{\sim}150^{\circ}C$ 범위의 온도 사이클과 랜덤 진동을 동시에 인가하였으며, 진동 가속도 3G, 진동주파수는 10~1000Hz 로 설정하여 자동차 환경을 충족하였다. 복합시험의 1 cycle 은 20 시간이며, 총 120 시간의 시험 동안 진동의 영향 및 진동과 고온이 동시에 작용하였을 경우의 영향에 대해 비교하였다. 테스트 모듈 제작을 위해 450 um 의 솔더볼이 적용되었으며, 각 조성의 솔더볼을 이용하여 BGA test chip 제작하였고, 제작된 BGA test chip 은 다시 daisy chain PCB 위에 실장 및 리플로우 공정을 통해 접합되었다. 테스트 동안 In-situ 로 저항의 변화를 관찰하여 파단의 유무를 판단하였고 전자주사현미경을 통해 파괴 기전을 평가하였다. 복합시험 시간에 따른 전단강도를 측정하였으며, 각 조성에 대하여 상이한 전단강도 변화를 관찰하였다. 계면 IMC 형상은 전단강도 변화에 영향을 주었으며, 특히 높은 온도가 IMC 성장을 촉진시켜 전단강도 감소에 영향을 주었다. 본 복합환경 시험 조건에서는 Sn0.7Cu 가 가장 안정적이었으며, 파단면을 관찰한 결과 연성파괴 모드가 관찰되었다.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.6
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• pp.533-541
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• 2020

This study using ABAQUS investigates the nonlinear vibration responses when thermal and random acoustic loads are applied simultaneously to the stiffened composite panels. The nonlinear vibration analyses are performed with changing the number of stiffeners, and layup condition of the skin panel. The panel and stiffeners both are modeled using shell elements. Thermal load (ΔT) is assumed to have the temperature gradient through the thickness direction of the stiffened composite panel. The random acoustic load is represented as stationary white-Gaussian random pressure with zero mean and uniform magnitude over the panels. The thermal postbuckling analysis is conducted using RIKS method, and the nonlinear dynamic analysis is performed using Hilber-HughesTaylor time integration method. When ΔT = 25.18 ℃ and SPL = 105 dB are applied to the stiffened composite panel, the effect of the number of stiffener is investigated, and the snap-through responses are observed for composite panels without stiffeners and with 1 and 3 stiffeners. For investigation of the effect of layup condition of the skin panel, when ΔT = 38.53 ℃ and SPL = 110 dB are applied to the stiffened composite panel, the snap-through responses are shown when the fiber angle of the skin panel is 0°, 30°, and 60°.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.768-771
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• 2003

The impulse between launch vehicle and atmosphere can generate a lot of noise and vibration during the process of launching a satellite. Structurally, electronic equipment (KOMPSAT 2, RDU : Remote Drive Unit) of a satellite consists of aluminum case containing PCB (Printed circuit boards). Each PCB has resistors and IC (Integrated circuits). Noise and vibration of wide frequency band are transferred to the inside of fairing, subsequently creating vibration of the electronic equipment of the satellite. In this situation. random vibration can cause malfunctioning of the electronic equipment of the device. Furthermore, when tile frequency of random vibration meets with natural frequency of PCB. fatigue fracture nay occur in the part of solder joint. The launching environment, thus. needs to be carefully considered when designing the electronic equipment of a satellite. In general. the safety of the electronic equipment is supposed to be related to the natural frequency, shapes of mode and dynamic deflection of PCB in the electronic equipment. Structural vibration analysis of PCB and its electronic components can be performed using either FEM(Finite Element Method) or vibration test. In this study. the natural frequency and dynamic deflection of PCB are measured by FEM, aud the safety of the electronic components of PCB is being evaluated according to the results. This study presents a unique method for finite element modeling and analysis of PCB and its electronic components. The results of FEA are verified by vibration test. The method proposed herein may be applicable to various designs from the electronic equipments of a satellite to home electronics.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.561-566
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• 2013

This study aims to develop the control system of vehicle height and apply this developed system to common passenger car. The vibration characteristics to affect ride comfort are examined through driving tests. The hydraulic control system of vehicle height is designed by Macpherson type used most commonly at current passenger car. Tests in this study are operated by the vehicle installed with genuine suspension system of Macpherson type, tuning suspension system and hydraulic control system of vehicle height. As vibration characteristics transmitted to vehicle become random types values of PSD(Power Spectrum Density) are compared.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.742-750
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• 1986

The lateral vibrating motion of a railway vehicle over a certain critical speed is a well known problem in the field of train dynamics. It is known that the train equations of motion are strongly coupled and highly nonlinear with the motion and causing that it is very difficult to solve the equations simultaneously. In this paper, a 8 degree of feedom model of a railway vehicle was suggested to solve the rail vehicle lateral motion. In stead of solving the nonlinear equation simultaneously, statistical linearization technique was adopted to solve those equations. The analysis results from the statistical linearization method were directly compared with those from direct nonlinear equations and found that the linearization technique can be very effective and economical for railroad vehicle analysis. By the way, it was found that the analysis results can analytically explain the intermittent hunting phenomena which has been frequently observed in experiments.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.2
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• pp.157-164
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• 2016

The paper studies a comparison analysis of semi-active control strategies for a Macpherson strut type suspension system consisting of MR(magneto-rheological) damper. As a first step, in order to formulate governing, a dynamic full model of a Macpherson strut is developed considering the kinematics. The nonlinear equation of motion of the strut is then linearized around the equilibrium point. A new adaptive moving sliding model controller is developed for fast response of the system. A newly proposed adaptive moving sliding mode control strategy is then compared with conventional sliding mode controller and skyhook controller. The comparison is made for two different types of road inputs; bump and random road profiles showing superior vibration control performance in time and frequency domains.

• Journal of Broadcast Engineering
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• v.15 no.6
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• pp.715-722
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• 2010

As one of applications in augmented realities, this paper presents a bubble popping system utilizing a haptic vibro-tactile mouse. In this system, virtual bubbles randomly float in the 3D space. By using the vibro-tactile mouse grabbed by a user, the bubbles are popped when they are touched by the mouse in the 3D space. Then a bubble popping effect with addition mouse vibration is delivered to the user's hand through the mouse. The proposed system is developed on ARToolkit environment. Therefore, basic components such as a camera and a marker pattern are required. The systems is composed of a vibro-haptic mouse, a webcam, a marker pattern, a graphic bubble object, and graphic mouse. Mouse vibration as well as bubble fade-out effect is delivered. Therefore, the combination of visual and tactile bubble popping effects outperforms the usage of a single effect in the experience of augmented reality.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.6
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• pp.586-594
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• 2009

This paper is the study on random, sinusoidal and shock vibration responses for the STSAT-3(science and technology satellite-3) proto-model which is the first small size all-composite satellite in Korea. The structure system of the STSAT-3 forms box type structure by joining several hybrid sandwich panels comprised of honeycomb core and carbon fiber reinforced laminated composite skins on both side. Mode shape, stress, displacement and acceleration responses are obtained on both the frequency domain and time domain by means of a commercial FEA software MSC/NASTRAN. From these analysis results, failure, safety factor and design validity are assessed. These results can be successfully applicable as reference data when a new satellite is developed as well as giving out an excellent criteria in satellite vibration treatment design.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.1
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• pp.7-13
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• 2011

Accurate response analysis of long span bridges subjected to seismic excitation is important for earthquake hazard mitigation. In this paper, the performance of a typical four span continuous reinforced concrete bridge model subjected to asynchronous multiple seismic excitations at the supports is investigated in both the time and frequency domains and the results are compared with that from a relevant uniform support excitations. In the time domain analysis, a linear modal superposition approach is used to compute the peak response values. In the frequency domain analysis, linear random vibration theory is used to determine the root mean square response values where the cross correlation effects between the modal and the support excitations on the seismic response of the bridge model are included. From the two sets of results, a practical range of peak factors which are defined to be the ratio of peak and the root mean square responses are suggested for displacements and forces in members. With reliable practical values of peak factors, the frequency domain analysis is preferred for the performance based design of bridges because of the computational advantage and the generality of the results as the time domain analysis only yields results for the specific excitation input.