• 제목/요약/키워드: Modal Structure

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대형구조물의 모우드 해석방법 (A Modal Analysis Technique for Large Structural Systems)

  • 이인원;이종원;정길호
    • 대한토목학회논문집
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    • 제13권5호
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    • pp.77-83
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    • 1993
  • 자유도가 큰 구조물의 고유진동수와 모드를 구하기 위한 방법으로 Lanczos 방법과 분할 구조 해석법을 조합한 수치 해석법을 개발했다. 이 방법은 분할하지 않은 전체 구조물의 강성 행렬이나 질량 행렬을 구할 필요가 없고, 오직 분할 구조물의 강성 행렬과 질량 행렬만을 필요로 한다. 구조물을 유한 요소 해석법과 같은 수치 해석법을 사용할 때의 일반적인 가정, 즉 선형 탄성 구조물이라는 가정외에 어떤 다른 가정도 하지 않기 때문에 분할 구조로 나눈 경우와 나누지 않은 경우에 계산된 고유진동수와 모드가 동일하다. 또한, 행렬 연산시 분할 구조물의 강성 행렬과 질량 행렬만을 사용하기 때문에, 소형의 컴퓨터에서도 자유도가 큰 구조물을 해석해 낼 수 있다. 이것은 분할 구조물 각각을 여러명의 사람이 독립적으로 설계, 또는 해석한 결과를 조합하여 전체 구조물을 해석할 수 있음을 뜻한다. 이 방법의 수치 해석의 예로서, 헬리콥터 꼬리의 트러스 구조물을 사용하여 처음 10개의 고유진동수와 모드를 계산해 보였다.

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주행 중 실내소음과 Wheel의 Lateral Dynamic Stiffness와의 상관관계에 대한 시험적 연구 (The Experimental Study on the Correlation of the Interior Noise of a Driving Vehicle with Lateral Dynamic Stiffness of the Wheel)

  • 김병진;사정환;박진성;박현우;조성근;정헌술
    • 대한기계학회논문집 C: 기술과 교육
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    • 제2권1호
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    • pp.9-13
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    • 2014
  • 현재 소비자들이 자동차를 선택하는 여러 이유 중에서, NVH 성능이 아주 중요한 역할을 하고 있다. 근래 하이브리드 및 전기자동차들은 전통적인 차량의 주요 소음원 이었던 엔진의 소음이 거의 발생되지 않아 자동차 실내의 소음에 대한 관심은 더욱 커지고 있다. 해외 참고문헌에 의하면 자동차 휠의 높은 Lateral Dynamic Stiffness(LDS)가 운전 중 발생되는 Structure Bone Noise(SBN)를 저감시키는 것으로 기술되어 있다. 하지만 유효한 기준 및 시험적 결과가 미비하여, 본 연구에서는 LDS가 서로 다른 휠에 동일 타이어를 부착하여 실내소음을 시험 측정하였다. 그 결과 휠의 LDS에 따라 실내소음이 변화되는 것을 확인하였다. 이는 휠의 최적설계로 실내소음의 저감이 가능할수 있다.

유연한 지지 구조와 유체 동압 베어링으로 지지되는 HDD의 회전 유연 디스크-스핀들 시스템에 대한 유한 요소 고유 진동 해석 (Finite Element Modal Analysis of a Spinning Flexible Disk-spindle System Supported by Hydro Dynamic Bearings and Flexible Supporting Structures in a HDD)

  • 한재혁;장건희
    • 한국소음진동공학회논문집
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    • 제15권3호
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    • pp.251-258
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    • 2005
  • The free vibration of a spinning flexible disk-spindle system supported by hydro dynamic bearings (HDB) in an HDD is analyzed by FEM. The spinning flexible disk is described using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. It is discretized by annular sector element. The rotating spindle which includes the clamp, hub, permanent magnet and yoke, is modeled by Timoshenko beam including the gyroscopic effect. The flexible supporting structure with a complex shape which includes stator core, housing, base plate, sleeve and thrust pad is modeled by using a 4-node tetrahedron element with rotational degrees of freedom to satisfy the geometric compatibility. The dynamic coefficients of HDB are calculated from the HDB analysis program, which solves the perturbed Reynolds equation using FEM. Introducing the virtual nodes and the rigid link constraints defined in the center of HDB, beam elements of the shaft are connected to the solid elements of the sleeve and thrust pad through the spring and damper element. The global matrix equation obtained by assembling the finite element equations of each substructure is transformed to the state-space matrix-vector equation, and the associated eigen value problem is solved by using the restarted Arnoldi iteration method. The validity of this research is verified by comparing the numerical results of the natural frequencies with the experimental ones. Also the effect of supporting structures to the natural modes of the total HDD system is rigorously analyzed.

Damage assessment of shear connectors with vibration measurements and power spectral density transmissibility

  • Li, Jun;Hao, Hong;Xia, Yong;Zhu, Hong-Ping
    • Structural Engineering and Mechanics
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    • 제54권2호
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    • pp.257-289
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    • 2015
  • Shear connectors are generally used to link the slab and girders together in slab-on-girder bridge structures. Damage of shear connectors in such structures will result in shear slippage between the slab and girders, which significantly reduces the load-carrying capacity of the bridge. Because shear connectors are buried inside the structure, routine visual inspection is not able to detect conditions of shear connectors. A few methods have been proposed in the literature to detect the condition of shear connectors based on vibration measurements. This paper proposes a different dynamic condition assessment approach to identify the damage of shear connectors in slab-on-girder bridge structures based on power spectral density transmissibility (PSDT). PSDT formulates the relationship between the auto-spectral densities of two responses in the frequency domain. It can be used to identify shear connector conditions with or without reference data of the undamaged structure (or the baseline). Measured impact force and acceleration responses from hammer tests are analyzed to obtain the frequency response functions at sensor locations by experimental modal analysis. PSDT from the slab response to the girder response is derived with the obtained frequency response functions. PSDT vectors in the undamaged and damaged states can be compared to identify the damage of shear connectors. When the baseline is not available, as in most practical cases, PSDT vectors from the measured response at a reference sensor to those of the slab and girder in the damaged state can be used to detect the damage of shear connectors. Numerical and experimental studies on a concrete slab supported by two steel girders are conducted to investigate the accuracy and efficiency of the proposed approach. Identification results demonstrate that damages of shear connectors are identified accurately and efficiently with and without the baseline. The proposed method is also used to evaluate the conditions of shear connectors in a real composite bridge with in-field testing data.

유체속에 잠긴 동축원통 구조물의 진동특성 및 지진응답에 대한 유체부가질량 영향 (Effect of Fluid Added Mass on Vibration Characteristics and Seismic Responses of Immersed Concentric Cylinders)

  • 구경회;이재한
    • 한국지진공학회논문집
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    • 제5권5호
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    • pp.25-33
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    • 2001
  • 현재 국내에서 개발중인 액체금속로 원자로구조물의 내진설계 및 지진해석을 위하여 원자로내부에 존재하는 유체-구조물 상호작용을 고려한 단순지진해석 모델링 개발이 필수적이다. 이를 위하여 본 논문에서는 유체속에 잠긴 동축원통 구조물의 유체부가질량에 대한 이론적 배경을 검토하였으며 기존의 유체부가질량법을 고려하여 시간이력 지진응답해석을 수행할 수 있는 Runge-Kutta 수치해석 알고리즘을 사용한 해석코드를 개발하였다. 개발된 지진해석코드를 사용하여 유체속에 잠긴 두개의 동축원통 구조물의 진동특성과 지진응답에 대한 유체부가질량의 영향을 살펴보았다. 적용예로서 두개의 동축원통에 대한 단순지진해석모델을 가정하고 유체부가질량을 고려한 진동특성해석과 지진응답해석을 수행한 결과 유체가 채워진 동축원통 구조물은 유체와의 상호작용으로 인하여 구조물의 진동특성과 지진응답특성이 크게 영향을 받으며 지진응답해석시 연계항을 포함한 유체부가질량의 영향을 신중하게 고려할 필요가 있는 것으로 나타났다.

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지진하중을 받는 비선헝 추계적 시스템의 불규칙진동해석 (Random Vibration Analysis of Nonlinear Stochastic System under Earthquake Using Statistical Method)

  • Moon, Byung-Young;Kang, Gyung-Ju;Kang, Beom-Soo
    • 한국지진공학회논문집
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    • 제5권6호
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    • pp.55-64
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    • 2001
  • 본 논문에서는 비선형 추계적 구조시스템의 지진에 대한 동적응답 해석방법을 제안하였다. 부분구조합성법에 기초한 섭동법을 응용하여 지진외력에 의한 불규칙진동의 시간응답과 주파수응답 해석과정을 정식화하였다. 이 방법에서는 대형 .동적 시스템의 지배방정식인 비선형 미분방정식을 몇 개의 비선형 모달방정식으로 근사 변환한다. 각 분계는 비선형 복원력항을 모드좌표로 근사변환함으로써 선형화하여 합성되어진다. 모드좌표에서 섭동법을 이용하여 비선형 운동방정식의 불규칙 진동에 대한 해를 구함으로 해석과정이 축소되어진다. 제안된 방법의 적합성과 유효성을 평가하기 위하여 비선형성을 가진 기계구조 시스템을 해석하였다. 이 해석결과는 불규칙 진동 응답을 해석하는데 유효한 접근방법으로 판단되며 내진 설계에 기여할 것으로 예상된다.

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Optimum design and vibration control of a space structure with the hybrid semi-active control devices

  • Zhan, Meng;Wang, Sheliang;Yang, Tao;Liu, Yang;Yu, Binshan
    • Smart Structures and Systems
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    • 제19권4호
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    • pp.341-350
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    • 2017
  • Based on the super elastic properties of the shape memory alloy (SMA) and the inverse piezoelectric effect of piezoelectric (PZT) ceramics, a kind of hybrid semi-active control device was designed and made, its mechanical properties test was done under different frequency and different voltage. The local search ability of genetic algorithm is poor, which would fall into the defect of prematurity easily. A kind of adaptive immune memory cloning algorithm(AIMCA) was proposed based on the simulation of clone selection and immune memory process. It can adjust the mutation probability and clone scale adaptively through the way of introducing memory cell and antibody incentive degrees. And performance indicator based on the modal controllable degree was taken as antigen-antibody affinity function, the optimization analysis of damper layout in a space truss structure was done. The structural seismic response was analyzed by applying the neural network prediction model and T-S fuzzy logic. Results show that SMA and PZT friction composite damper has a good energy dissipation capacity and stable performance, the bigger voltage, the better energy dissipation ability. Compared with genetic algorithm, the adaptive immune memory clone algorithm overcomes the problem of prematurity effectively. Besides, it has stronger global searching ability, better population diversity and faster convergence speed, makes the damper has a better arrangement position in structural dampers optimization leading to the better damping effect.

에어컨의 구조 소음 저감을 위한 실내기 모터 브라켓의 설계 (The Design of the Motor Bracket for Reduction of Structure- Borne Noise in Package Air-Conditioner)

  • 심현진;이성진;강태호;이정윤;오재응
    • 대한기계학회논문집A
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    • 제30권2호
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    • pp.202-209
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    • 2006
  • As the economic power is improved and the customer's demand is hard to please, the noise and vibration is the most important yardstick that can determine the quality of the product. Especially, as the airconditioner's demand increase suddenly, the product of quality and the noise is becoming a decisive factor of determining whether purchase the product or not. Therefore, every manufactory is investing a lot of money and research to cut down the unpleasantness induced from noise and vibration. And they are emphasizing their product's difference by advertising a silence very actively. With these reason, the demand of a silent indoor air-conditioner is the essential research filed when the product is develop(:d. In this study, the noise and vibration is visualized in the space and frequency domain by using experimental methods such as operational deflection shape (ODS), modal testing and sound intensity. Also the location of noise source and its characteristic is analyzed in an acoustical point of view to reduce the structure borne noise that come from the fan motor, and the pertinent control method is suggested. Furthermore, the most suitable shape of the motor bracket is suggested by applying FEM and DOE (Design of experiments) in the noise and vibration point a view.

Performance evaluation method of homogeneous stereo camera system for full-field structural deformation estimation

  • Yun, Jong-Min;Kim, Ho-Young;Han, Jae-Hung;Kim, Hong-Il;Kwon, Hyuk-Jun
    • International Journal of Aeronautical and Space Sciences
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    • 제16권3호
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    • pp.380-393
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    • 2015
  • This study presents how we can evaluate stereo camera systems for the structural deformation monitoring. A stereo camera system, consisting of a set of stereo cameras and reflective markers attached on the structure, is introduced for the measurement and the stereo pattern recognition (SPR) method is utilized for the full-field structural deformation estimation. Performance of this measurement system depends on many parameters including types and specifications of the cameras, locations and orientations of them, and sizes and positions of markers; it is difficult to experimentally identify the effects of each parameter on the measurement performance. In this study, a simulation framework for evaluating performance of the stereo camera systems with various parameters has been developed. The maximum normalized root-mean-square (RMS) error is defined as a representative index of stereo camera system performance. A plate structure is chosen for an introductory example. Its several modal harmonic vibrations are generated and estimated in the simulation framework. Two cases of simulations are conducted to see the effects of camera locations and the resolutions of the cameras. An experimental validation is carried out for a few selected cases from the simulations. Using the simultaneous laser displacement sensor (LDS) measurements as the reference, the measurement errors are obtained and compared with the simulations.

유연한 지지 구조와 유체 동압 베어링으로 지지되는 HDD의 회전 유연 디스크-스핀들 시스템에 대한 유한 요소 고유 진동 해석 (Finite Element Modal Analysis of a Spinning Flexible Disk-Spindle System Supported by Hydro Dynamic Bearings and Flexible Supporting Structures In a HDD)

  • 한재혁;장건희
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2003년도 추계학술대회논문집
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    • pp.572-578
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    • 2003
  • The free vibration of a spinning flexible disk-spindle system supported by hydro dynamic bearings in a HDD is analyzed by FEM. The spinning flexible disk is described using Kirchhoff plate theory and von Karman non-linear strain, and its rigid body motion is also considered. It is discretized by annular sector element. The rotating spindle which includes the clamp, hub, permanent magnet and yoke, is modeled by Timoshenko beam including the gyroscopic effect. The flexible supporting structure with a complex shape which includes stator core, housing, base plate, sleeve and thrust pad is modeled by using a 4-node tetrahedron element with rotational degrees of freedom to satisfy the geometric compatibility. The dynamic coefficients of HDB are calculated from the HDB analysis program, which solves the perturbed Raynolds equation using FEM. Introducing the virtual nodes and the rigid link constraints defined in the center of HDB, beam elements of the shaft are connected to the solid elements of the sleeve and thrust pad through the spring and damper element. The global matrix equation obtained by assembling the finite element equations of each substructure is transformed to the state-space matrix-vector equation, and the associated eigenvalue problem is solved by using the restarted Arnoldi iteration method. The validity of this research is verified by comparing the numerical results of the natural frequencies with the experimental ones. Also the effect of supporting structures to the natural modes of the total HDD system is rigorously analyzed.

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