• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계 학술대회논문집(수송기계편)
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• pp.57-60
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• 2005

Modal parameters of a structure are the important factor to control the missile maneuver. In general, a dummy structure is used for the modal test of missile structure instead of the real warhead and propellant because there may be the danger of a explosion by the electric shock of test equipment, such as the exciter and the power amplifier. However, the modal testing of a real missile structure is required to acquire the modal parameters and to analyze the missile performance accurately. The new test system and technique are developed to get rid of the danger and secure the safety during the testing. This test system is made of with the computer network system and controlled remote from test site. Using His new test system, the modal test of real missile structure is performed successfully and its validity is proven.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.72-77
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• 2011

In this study, the natural frequencies and mode shape of an external mounting pod were verified using the modal analysis and modal testing technique for a pod mounted on an aircraft. The procedure associated with the FEM building of an external mounted pod to predict the dynamic behavior of aircraft structures is described. The simplified FEM reflecting the results of the modal testing of a pod is built through the optimization, applied to the structural dynamic model of an Aircraft, used to verified the stability of vibration and flutter of an aircraft.

• 비파괴검사학회지
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• 제21권4호
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• pp.371-382
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• 2001

The recognition of such natural wave guides as plates, rods, hollow cylinders, multi-layer structures or simply an interface between two materials combined with an increased understanding of the physics and wave mechanics of guided wave propagation has led to a significant increase in the number of guided wave inspection applications being developed each year. Of primary attention Is the ability to inspect partially hidden structures, hard to access areas, and teated or insulated structures. An introduction to some physical consideration of guided waves followed by some sample problem descriptions in pipe, ice detection, fouling detection in the foods industry, aircraft, tar coated structures and acoustic microscopy is presented in this paper. A sample problem in Boundary Element Modeling is also presented to illustrate the move in guided wave analysis beyond detection and location analysis to quantification.

• 산업기술연구
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• 제27권A호
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• pp.47-53
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• 2007

A theoretical model based on Rayleigh-Ritz method is proposed to predict the resonance frequency of a W/T(Wind Turbine) tower structure supported by guy cables. In order to verify the validity of the theoretical model, a reduced W/T tower system is manufactured and tested. Frequency response and mode data are determined by modal testing and finite element analysis is performed to calculate the natural frequency of the tower model. Numerical and experimental results are compared with those by the theoretical analysis. Parametric study by the theoretical model shows how the cable tension and cable elasticity influence the resonance frequency of the W/T tower structure. Finally, vibration response under various rotating speed is investigated to examine the possibility of severe resonance.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.1097-1102
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• 2005

Non-Destructive Testing (NDT) is test method which finds the mechanical or natural or artificial defects of the interior or exterior of those without destructing materials and welded products. NDT is a means to assess the perfection of a component or system perfection. NOT images defects using scattered light, sound, electric current, magnetic fields and X-ray. Each NDT method has merits and demerits in the detecting ability of defects according to evaluated subjects. Defects can affect the serviceability of the material or structure, so NDT is important in guaranteeing safe operation as well as in quality control. In this review, we considered the methods of NDT applied to current railway vehicle manufacturing.

• Elastomers and Composites
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• 제18권3호
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• pp.87-98
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• 1983

Fundamental properties and surface treatment effects of domestic kaolin calcined at higher temperature were studied to develop reinforcing fillers for rubbers. The results obtained are as follows: (i) X-ray diffraction and scanning electron microscopy studies revealed kaolinite as a major constituent of the raw kaolin used in this study. (ii) Physical properties of natural rubber vulcanizates compounded with the calcined kaolin fillers treated with poly(maleic anhydride) and sodium polyphosphate are favorably improved. Particularly, the kaolin filler treated with sodium polyphosphate(designated as PT series) shows excellent physical properties compared with hydrated silica.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 추계학술대회논문집
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• pp.581-586
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• 2000

Explosively activated pyro-technic device is used to release exhausted rocket booster or payloads at prescribed times in the rocket's flight. It creates pyro-shock environment that rocket or payload components must survive. With the shock spectra acquired from flight data, laboratory test should be performed before flight to check whether all of component can sustain the shock environment. The pyro-shock environment simulation was created by the resonance fixture response to a projectile impact. Desired shock spectra is realized by adjusting the natural frequency of resonance plate and the velocity of impact hammer. This paper describes the development process of Pyro-shock testing machine, which is designed and tested by Korean engineers, to verify components of Korean Sounding Rocket(KSR-3) and the other Korean space vehicle. Both analytical and experimental techniques are introduced in this paper.

• Computers and Concrete
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• 제18권2호
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• pp.155-163
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• 2016

This paper, proposes 20 models for predicting compressive strength of recycled aggregate concrete (RAC) containing silica fume by using gene expression programming (GEP). To construct the models, experimental data of 228 specimens produced from 61 different mixtures were collected from the literature. 80% of data sets were used in the training phase and the remained 20% in testing phase. Input variables were arranged in a format of seven input parameters including age of the specimen, cement content, water content, natural aggregates content, recycled aggregates content, silica fume content and amount of superplasticizer. The training and testing showed the models have good conformity with experimental results for predicting the compressive strength of recycled aggregate concrete containing silica fume.

• 한국전산구조공학회논문집
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• 제31권1호
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• pp.17-21
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• 2018

오늘날까지 적층 마이크로 외팔보의 고유진동수에 대하여 연구가 진행되었다. 마이크로 보는 실리콘 재질로 만들어 지지만, 그것의 상하 표면은 얇은 금 박막층(~30nm)이 증착되어 있다. 초음파 검사를 위해 초음파 테스트 플랫폼을 사용했으며, 시간영역 신호는 광학적으로 측정되었다. 고유진동수는 파형을 고속 Fourier 변환을 통해 정량화하였으며, 결과적으로 고전적인 보 이론과 일치하는 결과를 보여 주었다. 본 연구는 마이크로/나노스케일 재료와 마이크로 구조에 대한 동적평가기법을 제공할 것으로 기대된다.

• 한국소음진동공학회논문집
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• 제21권2호
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• pp.169-177
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• 2011

In this paper, the natural frequency of a cracked cantilever L-beams with a coupled bending and torsional vibrations is investigate by theory and experiment. In addition, a method for detection of crack in a cantilever L-beams is presented based on natural frequency measurements. The governing differential equations of a cracked L-beam are derived via Hamilton's principle. The two coupled governing differential equations are reduced to one sixth order ordinary differential equation in terms of the flexural displacement. Futher, the dynamic transfer matrix method is used for calculation of a exact natural frequencies of L-beams. The crack is assumed to be in the first mode of fracture and to be always opened during vibrations. In this study, the differences between the actual and predicted positions and sizes of crack are less than about 10 % and 39.5 % respectively.