• Title/Summary/Keyword: Displacement Sensitivity

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Vision-based remote 6-DOF structural displacement monitoring system using a unique marker

  • Jeon, Haemin;Kim, Youngjae;Lee, Donghwa;Myung, Hyun
    • Smart Structures and Systems
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    • v.13 no.6
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    • pp.927-942
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    • 2014
  • Structural displacement is an important indicator for assessing structural safety. For structural displacement monitoring, vision-based displacement measurement systems have been widely developed; however, most systems estimate only 1 or 2-DOF translational displacement. To monitor the 6-DOF structural displacement with high accuracy, a vision-based displacement measurement system with a uniquely designed marker is proposed in this paper. The system is composed of a uniquely designed marker and a camera with a zooming capability, and relative translational and rotational displacement between the marker and the camera is estimated by finding a homography transformation. The novel marker is designed to make the system robust to measurement noise based on a sensitivity analysis of the conventional marker and it has been verified through Monte Carlo simulation results. The performance of the displacement estimation has been verified through two kinds of experimental tests; using a shaking table and a motorized stage. The results show that the system estimates the structural 6-DOF displacement, especially the translational displacement in Z-axis, with high accuracy in real time and is robust to measurement noise.

Design Sensitivity Analysis for the Vibration Characteristic of Vehicle Structure (수송체 구조물의 진동특성에 관한 설계민감도 해석)

  • 이재환
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 1992.10a
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    • pp.19-24
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    • 1992
  • Design sensitivity analysis method for the vibration of vehicle structure is developed using adjoint variable method. A variational approach with complex response method is used to derive sensitivity expression. To evaluate sensitivity, FEM analysis of ship deck and vehicle structure are performed using MSC/NASTRAN on the super computer CRAY2S, and sensitivity computation is carried on PC. The accuracy of sensitivity is verified by the results of finite difference method. When compared to structural analysis time on CRAY2S, sensitivity computation is remarkably economical. The sensitivity of vehicle frame can be used to reduce the vibration responses such as displacement and acceleration of vehicle.

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Micro-Machined Capacitive Linear Encoder with a Mechanical Guide (마이크로 머시닝으로 제작한 기계적 가이드를 갖는 정전용량 선형 인코더)

  • Kang, Daesil;Moon, Wonkyu
    • Journal of Sensor Science and Technology
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    • v.21 no.6
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    • pp.440-445
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    • 2012
  • Contact-type Linear Encoder-like Capacitive Displacement Sensor (CLECDiS) is a novel displacement sensor which has wide measurable range with high resolution. The sensor, however, is very sensitive to relative rotational alignment between stator and mover of the sensor as well as its displacement. In addition to, there can be some disturbances in the relative rotational alignment, so some noises occur in the sensor's output signal by the disturbances. This negative effect of the high sensitivity may become larger as increasing sensitivity. Therefore, this negative effect of the high sensitivity has to be compensated and reduced to achieve nanometer resolution of the sensor. In this study, a new type capacitive linear encoder with a mechanical guide is presented to reduce the relative rotational alignment problem. The presented method is not only to reduce the alignment problem, but also to assemble the sensor to the stage conveniently. The method is based on a new type CLECDiS that has mechanical guide autonomously. In the presented sensor, when the device is fabricated by micro-machining, the guide-rail is also fabricated on the surface of the sensor. By the direct fabrication of the guide-rail with high precision micro-machining, errors of the guide-rail can be reduced significantly. In addition, a manual yaw alignment is not required to obtain large magnitude of the output signal after the assembly of the sensor and the stage. The sensor movement is going to follow the guide-rail automatically. The prototype sensor was fabricated using the presented method, and we verify the feasibility experimentally.

Quantitative Determination of Out-of-plane Displacement by Shearography (Shearography의 1차도함수로부터 면외변위의 정량적 추출)

  • Kim, Koung-Suk;Yoon, Hong-Seok;Park, Chan-Ju;Choi, Jung-Suk
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.772-776
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    • 2004
  • The paper describes the quantitative determination of out-of-plane displacement from result of Shearogrpahy, which can measure the first-order partial derivative of out-of-plane displacement directly. However, the differential sensitivity of Shearography is related to the amount of shearing, which is manually adjustable in optical interferometer and affects the quantitative determination. The relationship between those is inspected by comparing ESPI with Shearography. From the result, the amount of shearing plays a modulation factor of out-of-plane displacement and small amount of shearing gives good agreement with out-of-plane displacement.

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Structural damage identification using incomplete static displacement measurement

  • Lu, Z.R.;Zhu, J.J.;Ou, Y.J.
    • Structural Engineering and Mechanics
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    • v.63 no.2
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    • pp.251-257
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    • 2017
  • A local damage identification method using measured structural static displacement is proposed in this study. Based on the residual force vector deduced from the static equilibrium equation, residual strain energy (RSE) is introduced, which can localize the damage in the element level. In the case of all the nodal displacements are used, the RSE can localize the true location of damage, while incomplete displacement measurements are used, some suspicious damaged elements can be found. A model updating method based on static displacement response sensitivity analysis is further utilized for accurate identification of damage location and extent. The proposed method is verified by two numerical examples. The results indicate that the proposed method is efficient for damage identification. The advantage of the proposed method is that only limited static displacement measurements are needed in the identification, thus it is easy for engineering application.

Effect of Constitutive Material Models on Seismic Response of Two-Story Reinforced Concrete Frame

  • Alam, Md. Iftekharul;Kim, Doo-Kie
    • International Journal of Concrete Structures and Materials
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    • v.6 no.2
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    • pp.101-110
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    • 2012
  • This paper focuses on the finite element (FE) response sensitivity and reliability analyses considering smooth constitutive material models. A reinforced concrete frame is modeled for FE sensitivity analysis followed by direct differentiation method under both static and dynamic load cases. Later, the reliability analysis is performed to predict the seismic behavior of the frame. Displacement sensitivity discontinuities are observed along the pseudo-time axis using non-smooth concrete and reinforcing steel model under quasi-static loading. However, the smooth materials show continuity in response sensitivity at elastic to plastic transition points. The normalized sensitivity results are also used to measure the relative importance of the material parameters on the structural responses. In FE reliability analysis, the influence of smoothness behavior of reinforcing steel is carefully noticed. More efficient and reasonable reliability estimation can be achieved by using smooth material model compare with bilinear material constitutive model.

Development of Optical Fiber Coupled Displacement Probe Sensor with a New Compensation Method (보상법을 적용한 광섬유 변위센서의 개발)

  • ;;;P. Sainsot;L. Flamand
    • Journal of the Korean Society for Precision Engineering
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    • v.19 no.12
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    • pp.27-32
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    • 2002
  • The intensity modulated type (reflective method) optical fiber sensor is a well -known method and widely applied to the displacement measurements and other industrial purposes. This type sensor has the advantages of relatively cheap cost, small sensor size and easiness of operation. The sensitivity of the sensor is very dependent of several error terms; the variation in the intensity of the light source and the changes in the surface reflectivity of the object. An optical fiber coupled displacement probe with a new compensation method is presented in this paper. The proposed displacement sensor can measure the displacements of the target surface independent of surface reflectivity error that is caused by the materials and surface processing grade.

Effect of Test Parameter on Ball Shear Properties for BGA and Flip Chip Packages (BGA 및 Flip Chip 패키지의 볼전단 특성에 미치는 시험변수의 영향)

  • Gu, Ja-Myeong;Jeong, Seung-Bu
    • Proceedings of the KWS Conference
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    • 2005.06a
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    • pp.19-21
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    • 2005
  • The ball shea. tests for ball grid array (BGA) and flip chip packages were carried out with different displacement rates to find out the optimum condition of the displacement rate for this test. The BGA packages consisted of two different kinds of solder balls (eutectic Sn-37wt.%Pb and Sn-3.5wt.%Ag) and electroplated Au/Ni/Cu substrate, whereas the flip chip package consisted of electroplated Sn-37Pb solder and Cu UBM. The packages were reflowed up to 10 times, or aged at 443 K up to 21 days. The variation of the displacement rate resulted in the variations of the shear properties such as shear force, displacement rate at break, fracture mode and strain rate sensitivity. The increase in the displacement rate led to the increase of the shear force and brittleness of solder joints.

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VALIDITY OF CLINICAL, TRANSCRANIAL RADIOGRAPHIC AND MAGNETIC RESONANCE IMAGING METHOD IN THE DIAGNOSIS OF INTERNAL DERANGEMENT OF TEMPOROMANDIBULAR JOINT (악관절장애 환자의 임상 및 측사위경두개 촬영에 의한 진단과 자기공명영상에 의한 진단의 비교연구)

  • Choi Jeong Hee;Chung Hyun Dae
    • Journal of Korean Academy of Oral and Maxillofacial Radiology
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    • v.21 no.2
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    • pp.327-336
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    • 1991
  • The purpose of this study was to evaluate the validity among the clinical, transcraial radiographic and MRI diagnosis in internal derangement of the temporomandibular joint. Fourty two temporomandibular joints were assessed in twenty one patients who visited the dental department of Chonnam National University Hospital with the complaint of temporomandibular disorder from Oct. 1990 to Oct. 1991. The results were as follows: 1. In the clinically symptomatic 29 TMJs, 26 (89.7%) joints reveal disc displacement and 3 (10.3%) joints reveal normal disc position on MRI. The sensitivity of clinical diagnosis was 0.77, and the specificity was 0.63. 2. In the normal 22 TMJs on the trans cranial radiographic finding, 16 (72.7%) joints reveal disc displacement, and 6 (27.3%) joints reveal normal disc position on MRI. In the abnormal 20 TMJs on the transcranial radiographic finding, 18 (90%) joints reveal disc displacement, and 2 (10%) joints reveal normal disc position on MRI. The sensitivity of trans cranial radio- graph was 0.53, and the specificity was 0.75.

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Shape Optimum Design of Cantilever with Weight and Journal Bearing Cap (자중을 고려한 외팔보와 저널 베어링 덮개의 형상 최적설계)

  • Lim, O-Kang;Lee, Jin-Suk;Cho, Heon;Lee, Byung-Woo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.12 no.3
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    • pp.427-435
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    • 1999
  • In the field of shape optimum design, much efforts are needed in regridding method and shape design sensitivity analysis. In this paper, Bezier curve is used to make the boundary of a structure and the improved direct differentiation method is used to calculate the shape design sensitivity. To regrid the finite element model, modified displacement field is presented in this paper. The modified displacement field makes more fine grid at large curvature. The purpose of this paper is to obtain the optimum shape of a cantilever with weight and a 3-dimensional journal bearing cap.

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