• Title/Summary/Keyword: modal strain

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Prediction of Strain Responses from Displacement Response Measurements (변위응답의 측정으로부터 변형률응답의 예측)

  • 이건명;신봉인;이한희
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2001.11b
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    • pp.1384-1387
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    • 2001
  • Presented is a method to predict strain responses from displacement measurements on a mechanical structure. The method consists of forming a transformation matrix, which is calculated from displacement and strain modal matrices. The modal matrices can be obtained by either finite element analysis or modal testing. One disadvantage of the method is that it requires displacements on all measuring points be measured simultaneously. The strain prediction method is applied to a simple simulated system.

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Characteristics and Applications of a Strain Modal Testing Method (변형률 모드시험방법의 특성 및 응용)

  • 차주환;하태희;이건명
    • Journal of KSNVE
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    • v.8 no.3
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    • pp.420-427
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    • 1998
  • A strain modal testing method has been applied to a cantilever beam to investigate the characteristics of the method. By applying the method to an analytical and an experimental system, it was shown that accurate modal parameters can be estimated from strain frequency response functions using a current modal parameter extraction algorithm. The modal parameters estimated by the method are more accurate than those by the conventional method which uses accelerometers when the tested system is of light weight. The method can be used to predict strain responses and excitation forces for given excitation forces and responses, respectively. Cracks on a structure can be detected by measuring strian FRFs and comparing them with the original ones.

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A Study on the Characteristics and Applications of a Strain Modal Testing Method (변형률 모드시험방법의 특성 및 응용)

  • 차주환;하태희;이건명
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1997.10a
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    • pp.216-221
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    • 1997
  • A strain modal testing method has been applied to a cantilever beam to investigate the characteristics of the method. By applying the method to an analytical and an experimental system, it was shown that accurate modal parameters can be estimated from the FRFs using a current modal parameter extraction algorithm. The modal parameters estimated by the method are more accurate than those by the conventional method which uses accelerometers when the tested system is of light weight. The strain response for a given excitation force and the force which causes the response can be predicted using the measured strain FRFS.

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Improved Genetic Algorithm-Based Damage Detection Technique Using Modal Strain Energy (모드변형에너지를 이용한 향상된 유전알고리즘 기반 손상검색기법)

  • Park Jae-Hyung;Lee Jung-Mi;Kim Jeong-Tae;Ryu Yeon-Sun
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2006.04a
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    • pp.459-466
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    • 2006
  • The objective of this study is to improve the accuracy of damage detection using natural frequency and modal strain energy. The following approaches are used to achieve the goal. First, modal strain energy is introduced and newly GA-based damage detection technique using natural frequency and modal strain energy is proposed. Next, to verify efficiency of the proposed technique, damage scenarios for free-free beams are designed and the vibration modal tests as damage cases are conducted. Finally, feasibility of proposed technique is verified in comparison with a GA-based damage detection technique using natural frequency and mode shape.

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Damage detection in jacket type offshore platforms using modal strain energy

  • Asgarian, B.;Amiri, M.;Ghafooripour, A.
    • Structural Engineering and Mechanics
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    • v.33 no.3
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    • pp.325-337
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    • 2009
  • Structural damage detection, damage localization and severity estimation of jacket platforms, based on calculating modal strain energy is presented in this paper. In the structure, damage often causes a loss of stiffness in some elements, so modal parameters; mode shapes and natural frequencies, in the damaged structure are different from the undamaged state. Geometrical location of damage is detected by computing modal strain energy change ratio (MSECR) for each structural element, which elements with higher MSECR are suspected to be damaged. For each suspected damaged element, by computing cross-modal strain energy (CMSE), damage severity as the stiffness reduction factor -that represented the ratios between the element stiffness changes to the undamaged element stiffness- is estimated. Numerical studies are demonstrated for a three dimensional, single bay, four stories frame of the existing jacket platform, based on the synthetic data that generated from finite element model. It is observed that this method can be used for damage detection of this kind of structures.

Damage Detection of a Steel Member Using Modal Testing (강부재의 손상발견을 위한 모달실험 기법)

  • Jang, Jeong Hwan;Lee, Jung Whee;Kim, Sung Kon;Chang, Sung Pil
    • Journal of Korean Society of Steel Construction
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    • v.9 no.4 s.33
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    • pp.467-477
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    • 1997
  • A series of experimental tests have been performed on a tube beam in which artificial damage is applied in order to address damage detectability using modal analysis. Modal parameters considered are frequency, displacement mode shape and strain mode shape CoMAC(Coordinate Modal Assurance Criterion) and Modal Vector Error have been adopted for presenting the change of displacement mode shape and strain mode shape. It is revealed strain mode shape is the most sensitive to damage.

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Modal Analysis Employing In-plane Strain of Cantilever Plates Undergoing Translational Acceleration (병진 가속을 받는 외팔 평판의 면내 변형율을 이용한 진동 해석)

  • Lim, Hong-Seok;Yoo, Hong-Hee
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.667-672
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    • 2004
  • A modeling method for the modal analysis of cantilever plates undergoing in-plane translational acceleration is presented in this paper. Cartesian deformation variables are employed to derive the equations of motion and the resulting equations are transformed into dimensionless forms. To obtain the modal equation from the equations of motion, the in-plane equilibrium strain measures are substituted into the strain energy expression based on Von Karman strain measures. The effects of two dimensionless parameters (related to acceleration and aspect ratio) on the modal characteristics of accelerated plates are investigated through numerical studies.

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Modal Analysis Employing In-plane Strain of Cantilever Plates Undergoing Translational Acceleration (병진 가속을 받는 외팔 평판의 면내 변형률을 이용한 진동 해석)

  • Yoo Hong Hee;Lim Hong Seok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.6 s.237
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    • pp.889-894
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    • 2005
  • A modeling method for the modal analysis of cantilever plates undergoing in-plane translational acceleration is presented in this paper. Cartesian deformation variables are employed to derive the equations of motion and the resulting equations are transformed into dimensionless forms. To obtain the modal equation from the equations of motion, the in-plane equilibrium strain measures are substituted into the strain energy expression based on Von Karman strain measures. The effects of two dimensionless parameters (related to acceleration and aspect ratio) on the modal characteristics of accelerated plates are investigated through numerical studies.

Experimental Study on Characteristics of Strain Modal Testing and its Application (변형률 모드시험법 특성의 실험적 고찰 및 응용)

  • Ju, Young-Sam;Lee, Hyung-Seok;Lee, Gun-Myung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.519-524
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    • 2000
  • The types of responses which are generally measured in the modal testing are displacement, velocity or acceleration. In strain modal testing, however, strain responses subject to excitation forces are measured. In this paper, the characteristics of strain modal testing are investigated experimentally. Investigated are the effects of frequency range, excitation force level, and excitation signal on the quality of measured strain frequency response functions. It has been shown that a strain FRF at a point can be predicted from displacement FRFs and strain FRFs at other points.

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Modal Strain Energy-based Damage Detection in Beam Structures using Three Different Sensor Types (보구조물의 모드변형에너지기반 손상 검색: 3가지 타입 센서의 비교)

  • Ho, Duc-Duy;Hong, Dong-Soo;Kim, Jeong-Tae
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2011.04a
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    • pp.680-683
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    • 2011
  • This study deals with damage detection in beam structure by using modal strain energy-based technique with three different sensor types: accelerometer, lead zirconate titanate (PZT) piezoelectric sensor and electrical strain gage. First, the use of direct piezoelectric effect of PZT sensor for dynamic strain response are presented. Next, a modal strain energy-based damage detection method is outlined. For validation, forced vibration tests are carried out on lab-scale aluminum cantilever beam. The dynamic responses are measured for several damage scenarios. Based on damage localization results, the performance of three different sensor types is evaluated.

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