• Title, Summary, Keyword: 모드시험

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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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외부하중을 고려한 추진기관 연소관의 구조 해석

  • 구송회;이방업;조원만;이환규
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • pp.159-167
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    • 1995
  • 본 연구는 유도탄 비행시험시에 연소관의 스커트와 날개 장착용 브라켓에 작용하는 공력하중과 연소관에 내압이 동시에 작용하는 추진기관에 대하여 구조 해석하였다. 추진기관의 스커트부 및 브라켓부의 공력하중은 3차원적으로 작용하기 때문에 대칭성을 이용한 $180^{\circ}C$3차원 구조 해석을 수행하여 비행시험, 수압시험, 지상시험 모드에 대하여 응력 수준을 비교하였다. 해석 결과 3가지 모드의 최대 등가응력은 거의 같으며, 비행시험시 공력하중이 앞마개부에 미치는 영향은 최대 등 가응력의 6%이내로 상당히 작았다. 수압시험 모드와 지상시험 모드의 실험치와 해석치를 비교한 결과 정확한 해석을 위해서는 점화기를 모델링과 점화기와 연소관, 브라켓과 연소관에 접촉요소의 적용, 3차원 비선형 해석등 보다 상세한 해석이 필요함을 알 수 있었다.

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Seismic Response Prediction of a Structure Using Experimental Modal Parameters from Impact Tests (충격시험에 의한 실험모드특성을 이용한 구조물의 지진응답 예측)

  • Cho, Sung-Gook;Joe, Yang-Hee;So, Gi-Hwan
    • Journal of the Earthquake Engineering Society of Korea
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    • v.14 no.2
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    • pp.75-84
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    • 2010
  • An in-cabinet response spectrum should be generated to perform the seismic qualification of devices and instruments mounted inside safety-related electrical equipment installed in nuclear power plants. The response spectrum is available by obtaining accurate seismic responses at the device mounting location of the cabinet. The dynamic behavior of most of electrical equipment may not be easily analyzed due to their complex mass and stiffness distributions. Considering these facts, this study proposes a procedure to estimate the seismic responses of a structure by a combination of a test and subsequent analysis. This technique firstly constructs the modal equations of the structure by using the experiment modal parameters obtained from the impact test. Then the seismic responses of the structure may be calculated by a mode superposition method. A simple steel frame structure was fabricated as a specimen for the validation of the proposed method. The seismic responses of the specimen were estimated by using the proposed technique and compared with the measurements obtained from the shaking table tests. The study results show that it is possible to accurately estimate the seismic response of the structure by using the experimental modal parameters obtained from the impact test.

Analysis of Experimental Modal Properties of an Electric Cabinet via a Forced Vibration Test Using a Shaker (가진기를 이용한 강제진동시험에 의한 전기 캐비닛의 실험적 모드특성 분석)

  • Cho, Sung-Gook;So, Gi-Hwan
    • Journal of the Earthquake Engineering Society of Korea
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    • v.15 no.6
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    • pp.11-18
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    • 2011
  • Accurate modal identification analysis is required to reasonably perform a seismic qualification of safety-related electric equipment installed in nuclear power plants (NPPs). This study evaluates a variation of the modal properties of an electric equipment cabinet structure in NPPs according to the excitation levels. For the study, an actual electric equipment cabinet was selected as a specimen and was dynamically tested by using a portable exciter in accordance with the level of input vibration energy. Tests were classified into two sets: with-door cases, and without-door cases. Frequency response functions were computed from the signals of the acceleration responses and input motions measured from the vibration tests. A polynomial curve fitting algorithm was used to extract the modal properties from the frequency response functions. This study reviews the variation of the modal properties according to the variation of the excitation levels. The results of the study show that the modal frequencies and the modal dampings of the object specimen varies nonlinearly according to the excitation level of the test motion. Attaching the door increases the modal damping of the cabinet.

Impact Test for Measurement of the Carbody Bending Modes of Railway Vehicle (철도차량 차체 굽힘모드 측정을 위한 충격시험)

  • Shin, Bum-Sik;Choi, Yeon-Sun
    • Journal of the Korean Society for Railway
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    • v.15 no.5
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    • pp.423-428
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    • 2012
  • As the speed of high speed train increases, the prediction of ride comfort becomes important. The exciting frequencies due to rail irregularity in high-speed train closes to the second and third natural frequencies of the carbody. The dynamic characteristics of railway vehicles should be checked by modal analysis numerically and experimentally. In this study the bending test for railway vehicle is reviewed and the impact test is suggested to find the natural frequencies and the mode shapes of the carbody. The validity of the impact test is checked with the test for a sample plate which reflects the aspect ratio of the original carbody. The bending test by the impact and the displacement methods of JIS E7105 for a prototype carbody were done in the field and compared. The results show that the impact test can find more accurate natural frequencies and the mode shapes of the carbody than those of the displacement method.

Determination of Mode I Fracture Toughness of Rocks Using Wedge Splitting Test (쐐기 분열 시험을 이용한 암석의 모드 I 파괴인성 측정)

  • Ko, Tae Young;Kim, Taek Kon;Lee, Dae Hyuk
    • Tunnel and Underground Space
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    • v.29 no.6
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    • pp.523-531
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    • 2019
  • In the applications of rock mechanics or rock engineering including drill and blast, drilling and mechanical excavation, the fracture toughness is an important factor. Several methods have been proposed to measure the fracture toughness of rocks. In this study, wedge splitting test specimen which is prepared with ease and tested under compression loading was used to obtain mode I fracture toughness of rocks. The equation of stress intensity factor through numerical analysis is proposed from the stress state of crack tip considering both vertical and horizontal loads due to the vertical load acting on the wedge. The validity of the wedge splitting test method was confirmed by comparing the mode I fracture toughness values obtained by the GD and SENB test specimens.

Study on Application of Noise Path Analysis for Improving Interior Noise at the Idle of a Passenger Vehicle (차량의 아이들시 실내소음 개선을 위한 소음경로 해석이론의 적용에 관한 연구)

  • Lee, Yang-Sub;Song, Yoon-Chul
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.8
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    • pp.155-161
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    • 1999
  • 아이들 상태에서 차실 내에 불쾌감을 주는 매우 높은 크기의 소음이 발생하였다. 본 논문에서는 아이들 시 문제소음의 원인을 분석하고 저감하는데 필요한 관련이론의 적용과 이에 수반되는 데이터측정, 데이터처리 및 데이터 해석과정을 자세하게 기술하였다. 소음진동 측정 및 분석 결과 문제의 소음은 엔진의 회전 2.5차 성분을 가지고 구조기인소음이었다. 아이들 시 문제의 실내소음에 영향을 미치는 구조전달경로들의 기여도를 분석하기 위해 소음경로해석시험 및 모드시험을 실시하였다. 시험분석 결과에 따라 기여도가 놓은 배 기계 및 트랜스미션계의 진동 전달특성을 개선하므로써 만족할 수준의 소음 저감효과를 얻었다.

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Analysis of Flight Test Result for Control Performance of Smart UAV (스마트무인기의 비행제어 성능관련 비행시험 결과분석)

  • Kang, Young-Shin;Park, Bun-Jin;Cho, Am;Yoo, Chang-Sun;Koo, Sam-Ok
    • Aerospace Engineering and Technology
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    • v.12 no.1
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    • pp.22-31
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    • 2013
  • Flight tests on flight control performance of helicopter, conversion and airplane mode for the Smart UAV were completed. Automatic take-off and landing, automatic return home as well as automatic approach to hover were performed in helicopter mode. Climb/descent, left/right turn using speed and altitude hold mode were performed in each $10^{\circ}$ tilt angle in conversion mode. The rotor speed in airplane mode was reduced to 82% from 98% RPM in order to increase rotor efficiency with reducing Mach number at tip of rotors. It reached to the designed maximum speed, $V_{TAS}$=440 km/h at 3 km altitude. This paper presents the flight test result on full envelopment of Smart UAV. Detailed test plan and test data on control performance were also presented to prove that all data meets the flying qualities requirement.

Fracture Toughness of Concrete Brazilian Disk according to Maximum Size of Coarse Aggregate (굵은골재의 최대치수에 따른 콘크리트 브라질리언 디스크의 파괴인성)

  • Lee, Seung-Hoon;Kim, Hee-Sung;Jang, Hee-Suk;Jin, Chi-Sub
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.10 no.3
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    • pp.185-196
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    • 2006
  • Fracture toughness is a material property for crack initiation and propagation in fracture mechanics. For mode I fracture toughness measurement in concrete, RILEM committees 89-FMT proposed three-point bend tests based on the two-parameter fracture model. But, there is no proposed test method as a standard for mixed mode test for now. And RILEM three-point bend test procedure is complicate. Therefore, in this study, brazilian disks of various size were designed as the concrete with a similar specified concrete strength and maximum size of coarse aggregate($G_{max}$) were respectively 20mm and 40mm. And mode I fracture toughness of brazilian disks was compared with that of RILEM three-point bend test. As a result, it was suggested appropriate size(thickness, diameter) and notch length ratio of brazilan disk on the $G_{max}$. And it was verified that stress intensity factors for mixed mode can be easily calculated with the disk specimen. Stress intensity factors of a concrete brazilian disk were evaluated with finite element analysis and five terms approximation for comparison.