• 제목/요약/키워드: dFRFs

검색결과 13건 처리시간 0.027초

Identification of Anisotropic Bearing Non-linearity

  • Han, Dong-Ju
    • International Journal of Aeronautical and Space Sciences
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    • 제5권2호
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    • pp.35-42
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    • 2004
  • Among other critical conditions in rotor svstems the large non-linearvibration excited by bearing non-linearity causes the rotor failure. For reducing thiscatastrophic failure and predictive analysis of this phenomena the identificationanalysis of bearing non-linearity in an anisotropic rotor system using the higherorder dFRFs are developed and are shown to be theoretically feasible as innon-rotating structures. For the identification of the anisotropic rotor withanisotropic bearing non-linearity expressed by the displacement in polynomial form,the higher order dFRFs based upon the Volterra series are investigated and depicttheir features by using the simple forms of the normal and reverse dFRFs. Theyproduce additional sub-harmonic resonant peaks, which indicate the existence ofhigher order non-linearties, and show the energy transfer such that the modes fornormal and reuerse dFRFs are exchanged, which are the fundamental differencesfrom what we can expect in linear ones.

방향성 주파수 응답함수에서 입력 잡음의 영향 (The Effect of Input Noise for Directional Frequency Response Functions)

  • 강성우;서윤호;이종원
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2008년도 춘계학술대회논문집
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    • pp.735-741
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    • 2008
  • Identification of asymmetry and anisotropy of rotor system is important for diagnosis of rotating machinery. Directional frequency response functions (dFRFs) are known to be a powerful tool in effectively detecting the presence of asymmetry or anisotropy. In this paper, an input noise effect of dFRFs for rotors is estimated, when both asymmetry and anisotropy are present. The normalized random errors of the dFRFs are calculated to verify the validity of the method, which is demonstrated by numerical simulation with a simple rotor model.

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개폐균열이 존재하는 비대칭 회전부 및 비등방 고정부를 갖는 회전체의 모드해석 (Modal Analysis of Rotor System with Anisotropic Stator and Asymmetric Rotor in the Presence of Breathing Crack)

  • 한동주
    • 대한기계학회논문집A
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    • 제30권4호
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    • pp.442-450
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    • 2006
  • This paper describes the new modal analysis method to detect the presence of the breathing crack in a general rotor system with disk asymmetry and stator anisotropy. It is proposed that the modal analysis using directional frequency response functions (dFRFs), which, accounting for the directivity in modes, clears the heavily over-lapping of other harmonics occurring from non-isotropic properties in addition to those due to crack, can provide an effective method to detect the modes by a crack. The simulations from the simple general rotor model show that the r-dFRFs (reverse dFRFs) for asymmetry confirms a good indicator of the presence of the breathing crack and the instability is primarily influenced by the shaft asymmetry than the breathing crack.

비대칭성과 비등방성이 공존하는 회전체에서의 방향성 주파수 응답 함수 추정 (Estimation of Directional Frequency Response Functions for Asymmetric Rotor with Anisotropic Stators)

  • 서윤호;강성우;서정환;이종원
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2004년도 춘계학술대회논문집
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    • pp.681-686
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    • 2004
  • Identification of asymmetry and anisotropy of rotor system is important for diagnosis of rotating machinery. Directional frequency response functions (dFRFs) are known to be powerful tool in effectively detecting the presence of asymmetry or anisotropy. In this paper, an estimation method of dFRFs for rotors is newly developed, when both asymmetry and anisotropy are present. The method transforms the finite degrees-of-freedom time-varying linear differential equation of motion to an infinite degree-of-freedom time-invariant linear one, employing the modulated coordinates. The validity of the method is demonstrated by numerical simulation with a simple rotor model.

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지지부의 운동을 가진 회전원판의 복소모드시험 (Complex Modal Testing for Rotating Disks with Support Motion)

  • 함종석;이종원
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2000년도 춘계학술대회논문집
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    • pp.1513-1520
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    • 2000
  • Complex modal testing method for rotating disks with support motion is introduced which handles the pairs of two point excitation and responses of the disk as complex input and output, respectively. This method utilizes the directivity information and the separation over the rotational speed of forward and backward traveling wave modes or bending coupled modes in the directional frequency response functions(dFRFs). This method synthesizes the normal/reverse dFRFs and complex wave dFRF, which were originally applied to rotating shaft and rotating disk, respectively, and is applied to complex system with dynamically coupled rotating disks and shaft. Experiments with a commercial hard disk drive spindle system demonstrate the validity of this method.

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회전원판의 진행파 모드 절직경 수 규명-방향성 주파수응답함수의 이용 (Identification of Diametrical Node Number of Travelling Wave Modes is Rotating Disk-Use of Directional Frequency Response Function)

  • 김명업;이종원
    • 대한기계학회논문집A
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    • 제20권3호
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    • pp.960-967
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    • 1996
  • Directional frequency response functions(dFRFs) are introduced for isotropic rotating disks, treating pairs of excitations and measurements as the complex input and output, respectively. It is shown that the dFRFs can be effectively used for separation of the forward and backward travelling wave modes and identification of the diametrical node numbers associated with modes of interst. Numerical simuations and experimental works are performed to demonstrate the analytical development and its validity.

방향성 주파수 응답 함수를 이용한 일반 회전체의 비대칭성 규명 (Identification of Asymmetry in General Rotors from Directional Frequency Response Functions)

  • 서윤호;강성우;이종원
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2005년도 춘계학술대회논문집
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    • pp.941-944
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    • 2005
  • Asymmetry of rotor systems is an important factor for identification of dynamic characteristics including the stability and response of rotors and for condition monitoring. In this work, asymmetry of rotors is identified by applying curve-fitting method to the directional frequency response functions (dFRFs), which are known as a powerful tool for detecting the presence and degree of asymmetry. This method minimizes least square error between analytical and measured dFRFs by iteratively updating physical parameters associated with rotor asymmetry. The effectiveness of the identification method is demonstrated by experiments with a laboratory test rotor.

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KF-16D 지상진동시험 (Ground Vibration Test of KF- 16D)

  • 변관화;박찬익;김종헌
    • 한국항공우주학회지
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    • 제33권5호
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    • pp.41-49
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    • 2005
  • 본 논문에서는 KF-16D 항공기의 동특성을 실험적으로 규명하기 위해 수행한 지상진동시험의 시험 방법, 센서 및 장비 설치, 시험 결과 검증 방법 및 시험 결과를 기술하였다. 지상진동시험은 외부 장착물 장착 형상에 따라 7가지 형상으로 분류하여 실시하여 외부장착물 부착 형상에 따른 항공기의 동특성 변화를 정량적으로 산출하였고 비행 중 항공기 진동 모드의 정량적인 변화량을 예측할 수 있게 하였다. 항공기 지지는 항공기 비행 상태의 조건을 구현하기 위하여 착륙장치 타이어의 공기압을 최소로 하였다. 시험은 6개~8개의 가진기를 사용하여 다점 랜덤 가진법으로 항공기를 가진하고 약 200개의 가속도계로부터 항공기의 응답을 측정하였다. 시험결과 관심 있는 낮은 주파수영역에서 선형성을 보여 양질의 주파수 응답함수를 얻었으며, 상반성을 만족함을 알 수 있었다. 측정된 가진력과 응답신호로부터 주파수 응답 함수를 구하였으며, 고유 진동수와 감쇠 계수는 주파수 응답함수로부터 다기준 최소 자승 복소 지수법을 적용하여 산출하였다. 고유진동모드는 최소 자승 주파수 영역법으로 사용하여 구성하였다.

Complex Modal Testing of Asymmetric Rotors Using Magnetic Exciter Equipped with Hall Sensors

  • Lee, Chong-Won;Kim, Si-Kyoung
    • Journal of Mechanical Science and Technology
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    • 제15권7호
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    • pp.866-875
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    • 2001
  • The complex modal testing methods developed for asymmetric rotors are briefly discussed and their performances are experimentally evaluated. For the experiments, a laboratory test rotor is excited by using a newly developed, cost effective magnetic exciter equipped with Hall sensors, which measure the excitation forces. It is concluded that the exciter system is characterized by a wide bandwidth and a high resolution for both the excitation and force measurement, and that the one-exciter/two-sensor technique for complex modal testing of asymmetric rotors is superior to the standard two-exciter/two-sensor technique in terms of practicality and realization.

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