• Title, Summary, Keyword: Modal test

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Modal Test of Missile Structure with Live Warhead and Propellant (활성탄 전기체 동특성 시험기법 연구)

  • Kang, Hwi-Won;Jeon, Byoung-Hee;Yang, Myung-Seog
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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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.

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Modal Test of the 2nd Stage of Small Launch Vehicle (소형 위성 발사체 2단부 모드 시험)

  • Seo, Sang-Hyun;Jeong, Ho-Kyeong;Youn, Se-Hyun;Park, Soon-Hong;Jang, Young-Soon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.258-261
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    • 2006
  • The structure of small launch vehicle can be divided into engine section and payload section. This paper introduces modal test of the payload section of small launch vehicle which is composed to satellite, PLA (Payload Adapter), VEB (Vehicle Equipment Bay), KMS (Kick Motor Support) and KM (Kick Motor). From this test, dynamic properties of the 2nd stage structure of small launch vehicle can be obtained. In this test, to simulate free-free boundary condition, test object was hung by 4 bungee cords and excited by using impact hammer Modal test data are analyzed by using TDAS(Test Data Analysis Software). As the result, modal parameters and mode shapes below 100Hz of the 2nd stage of small launch vehicle were identified.

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Modeling of Beam Structures from Modal Parameters (모달 파라미터를 이용한 보 구조물의 모델링)

  • Hwang, Woo-Seok
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.519-522
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    • 2006
  • Accurate modeling of a dynamic system from experimental data is the bases for the model updating or heath monitoring of the system. Modal analysis or modal test is a routine process to get the modal parameters of a dynamic system. The modal parameters include the natural frequencies, damping ratios and mode shapes. This paper presents a new method that can derive the equations of motion for a dynamic system from the modal parameters obtained by the modal analysis or modal test. The present method based on the relation between the eigenvalues and eigenvectors of the state space equation derives the mass, damping and stiffness matrices of the system. The modeling of a cantilevered beam from modal parameters is an example to prove the efficiency and accuracy of the present method. Using the lateral displacements only, not the rotations, gives limited information for the system. The numerical verification up to now gives reasonable results and the verification with the test data is scheduled.

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Modal Test and Finite Element Model Update of Aircraft with High Aspect Ratio Wings (고세장비 항공기의 모드 시험 및 동특성 유한요소모델 개선)

  • Kim, Sang-Yong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.5
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    • pp.480-488
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    • 2012
  • The aircrafts with high aspect ratio wings made by a composite material have been developed, which enable high energy efficiency and long-term flight by reducing air resistance and structural weight. However, they have difficulties in securing the aeroelastic stability such as the flutter because of their long and flexible wings. The flutter is unstable self-excited-vibration caused by interaction between the structural dynamics and the aerodynamics. It should be verified analytically prior to first flight test that the flutter does not happen in the range of flight mission. Normally, the finite element model is used for the flutter analysis. So it is important to construct the finite element model representing dynamic characteristics similar to those of a real aircraft. Accordingly, in this research, to acquire dynamic characteristics experimentally the modal test of the aircraft with high aspect ratio composite wings was conducted. And then the modal parameters from the finite element analysis(FEA) were compared with those from the modal test. To make analysis results closer to test results, the finite element model was updated by means of the sensitivity analysis on variables and the optimization. Finally, it was proved that the updated finite element model is reliable as compared with the results of the modal test.

Study on Modal Test Method for Vibration Characteristics of the Cylindrical Structure Filled with Liquid (액체가 채워진 원통형 구조물의 진동 특성 규명을 위한 모달 시험 방법 연구)

  • Kim, Gen-Sang;Kim, Mun-Guk;Kim, In-Gul;Park, Jae-Sang;Park, Soon-Hong
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.46 no.8
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    • pp.621-630
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    • 2018
  • In the case of launch vehicles using liquid fuel, natural frequency changes due to fuel consumption after launch, and a modal test is essential to investigate its effect. However, when relying on modal test to characterize the free vibration characteristics, the testing time is excessively increased and accuracy is reduced. Therefore, this paper suggests a modal test method with finite element analysis to overcome these drawbacks. A cylindrical structure filled with liquid are considered as a study model, and modal tests and finite element analyses are performed. The modal tests are conducted by an impulsive method using an impact hammer and accelerometers. Through the comparison of the modal test and the finite element analysis results, the validity of the proposed modal test method is verified. In addition, the free vibration characteristics and the tendency for the cylindrical structure according to the liquid filled ratio were investigated.

Constructing Equations of Motion for a Dynamic System from Modal Parameters (모달 파라미터를 이용한 동적 시스템의 운동 방정식 구성)

  • Hwang, Woo-Seok
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.35 no.1
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    • pp.40-45
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    • 2007
  • Modal analysis or modal test is a routine process to get the modal parameters of a dynamic system. The modal parameters include the natural frequencies, damping ratios and mode shapes. This paper presents a method that can derive the equations of motion for a dynamic system from the modal parameters obtained by the modal analysis or modal test. The present method based on the relation between the eigenvalues and eigenvectors of the state space equation derives the mass, damping and stiffness matrices of the system. The numerical verifications for the simple mass-spring-damper system and the cantilevered beam prove the efficiency and accuracy of the present method.

Modal Test of the 2nd stage structure of KSLV-I (KSLV-I 2단부 구조체 모드 시험)

  • Seo, Sang-Hyeon;Jeong, Ho-Kyeong;Youn, Se-Hyun;Park, Soon-Hong;Jang, Young-Soon
    • Aerospace Engineering and Technology
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    • v.6 no.1
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    • pp.114-119
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    • 2007
  • This paper introduces modal test of the 2nd stage structure of KSLV-I which is composed to satellite, PLA(Payload Adapter), EB(Equipment Bay), KMS(Kick Motor Support) and KM(Kick Motor) without PLF(Payload Fairing). In this test, to simulate free-free boundary condition, test object was hung by 4 bungee cords and excited by using impact hammer. From this test, dynamic properties of the 2nd stage structure of KSLV-I can be obtained. Modal test data are analyzed by using TDAS(Test Data Analysis Software). As the result, modal parameters and mode shapes below 100Hz of the 2nd stage of KSLV-I were identified.

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Model Updating of an Electric Cabinet using Shaking Table Test

  • Cui, Jintao;Cho, Sung-Gook;Kim, Doo-Kie;Koo, Ki-Young;Cho, Yang-Hee
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.59-62
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    • 2008
  • This paper presents the procedure and the results of modal identification testing of a seismic monitoring system central processing unit cabinet for a nuclear power plant. This paper also provides a model updating for making effective analytical modeling of cabinet-type electrical equipment by comparing the test results with the analysis results. From the test results and their interpretation, modal properties (modal frequency, mode shape, and modal damping) of the specimen were satisfactorily identified. However, the analysis results may need to study further to find the effective and presentative model for the cabinet-type electrical equipment. This paper just presents the first stage of the research project "Development of dynamic behavior analysis technique of dynamic structure system" which is trying to build the lumped mass beam stick model even their results do not agree well with the test results.

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Experimental Modal Test on a Scale Model of Floating Structure

  • Park, Soo-Yong;Song, Hwa-Cheol;Park, Dong-Cheon
    • Journal of Navigation and Port Research
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    • v.36 no.2
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    • pp.89-95
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    • 2012
  • Identification of the modal properties of a structural system has received much attention over the years because of its importance in structural model updating, structural health monitoring and structural control. This paper presents experimental modal test results such as natural frequencies and mode shapes of a scale model of floating structure. A modal testing is performed on the structure and modal parameters for the structure are extracted from the measured data. The results are compared to a finite element model and the correlation between the measured and analytical modal parameters is investigated.

Cross modal Transfer in Infancy : Transfer from Touch to Vision (유아의 감각양식간 전이 - 촉각에서 시각으로의 전이 -)

  • Hong, Hee Young
    • Korean Journal of Child Studies
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    • v.7 no.1
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    • pp.67-84
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    • 1986
  • The purpose of the present research was to investigate cross-modal transfer, especially tactual-to-visual transfer in infancy and to study the relation between failure of cross-modal transfer performance and length of familiarization period. The subjects of this study were 60 infants, 10 boys and 10 girls at each level: six, nine, and twelve months of age. All were normal, healthy, full-term babies. The mothers' educational achievement was controlled at more than 12 years of schooling. There were two separate experimental conditions, one 30-sec and one 60-sec familiarization period. Each experimental condition consisted of a tactual familiarization and a visual recognition memory test. Each child was presented with these 2 sets of cross-modal stimuli in one of the 2 experimental conditions. Infants' visual responses in the visual recognition memory test were videotaped for 20 seconds. Visual fixation time to novel and familiar stimuli was observed throughout the test. The data was analyzed with t-test, percentage of total fixation time to novel stimuli, and ANOVA. The results showed that: 1) Significant differences were found in the cross-modal transfer performance from touch to vision between the 3 age groups. This is, 6 and 9 month old infants didn't show cross-modal transfer in the 30-sec condition, but 12 month old infants did show cross-modal transfer in the 30-second. 2) In all 3 age groups, no significant differences were found in cross-modal transfer performance between the two conditions.

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