• Title/Summary/Keyword: Displacement estimation

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New J Testing Method Using Load-COD Curve for Circumferential Through-Wall Cracked Pipes under Bending (하중-균열열림변위를 이용한 굽힘하중이 작용하는 원주방향 관통균열 배관의 새로운 J 실험법)

  • Huh Nam-Su;Kim Yun-Jae;Kim Young-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.1 s.244
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    • pp.60-65
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    • 2006
  • The present paper provides experimental J estimation equation for the circumferential through-wall cracked pipe under four-point bending, based on the load-crack opening displacement (COD) record. Based on the limit analysis and the kinematically admissible rigid-body rotation field, the plastic ${\eta}$-factor for the load-COD record is derived and is compared with that for the load-load line displacement record. Comparison with the J results from detailed elastic-plastic finite element (FE) analysis shows that the proposed method based on the load-COD record provides reliable J estimates even for shallow cracks, whereas the conventional approach based on the load-load line displacement record gives erroneous results for shallow cracks. Thus, the proposed J estimation method could be recommended for testing the circumferential through-wall cracked pipe, particularly with shallow cracks.

Estimation of Displacement Responses from the Measured Dynamic Strain Signals Using Mode Decomposition Technique (모드분해기법을 이용한 동적 변형률신호로부터 변위응답추정)

  • Kim, Sung-Wan;Chang, Sung-Jin;Kim, Nam-Sik
    • Proceedings of the KSR Conference
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    • 2008.06a
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    • pp.109-117
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    • 2008
  • In this study, a method predicting the displacement responseof structures from the measured dynamic strain signal is proposed by using a mode decomposition technique. Dynamic loadings including wind and seismic loadings could be exerted to the bridge. In order to examine the bridge stability against these dynamic loadings, the prediction of displacement response is very important to evaluate bridge stability. Because it may be not easy for the displacement response to be acquired directly on site, an indirect method to predict the displacement response is needed. Thus, as an alternative for predicting the displacement response indirectly, the conversion of the measured strain signal into the displacement response is suggested, while the measured strain signal can be obtained using fiber optic Bragg-grating (FBG) sensors. To overcome such a problem, a mode decomposition technique was used in this study. The measured strain signal is decomposed into each modal component by using the empirical mode decomposition(EMD) as one of mode decomposition techniques. Then, the decomposed strain signals on each modal component are transformed into the modal displacement components. And the corresponding mode shapes can be also estimated by using the proper orthogonal decomposition(POD) from the measured strain signal. Thus, total displacement response could be predicted from combining the modal displacement components.

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Issues in structural health monitoring for fixed-type offshore structures under harsh tidal environments

  • Jung, Byung-Jin;Park, Jong-Woong;Sim, Sung-Han;Yi, Jin-Hak
    • Smart Structures and Systems
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    • v.15 no.2
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    • pp.335-353
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    • 2015
  • Previous long-term measurements of the Uldolmok tidal current power plant showed that the structure's natural frequencies fluctuate with a constant cycle-i.e., twice a day with changes in tidal height and tidal current velocity. This study aims to improve structural health monitoring (SHM) techniques for offshore structures under a harsh tidal environment like the Uldolmok Strait. In this study, lab-scale experiments on a simplified offshore structure as a lab-scale test structure were conducted in a circulating water channel to thoroughly investigate the causes of fluctuation of the natural frequencies and to validate the displacement estimation method using multimetric data fusion. To this end, the numerical study was additionally carried out on the simplified offshore structure with damage scenarios, and the corresponding change in the natural frequency was analyzed to support the experimental results. In conclusion, (1) the damage that occurred at the foundation resulted in a more significant change in natural frequencies compared with the effect of added mass; moreover, the structural system became nonlinear when the damage was severe; (2) the proposed damage index was able to indicate an approximate level of damage and the nonlinearity of the lab-scale test structure; (3) displacement estimation using data fusion was valid compared with the reference displacement using the vision-based method.

Improvement of Medical Ultrasound Strain Image Using Lateral Motion Compensation (측방향 움직임 보상을 이용한 초음파 의료용 변형률 영상의 화질개선)

  • Park, Myung-Ki;Kwon, Sung-Jae;Jeong, Mok-Kun
    • The Journal of the Acoustical Society of Korea
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    • v.30 no.5
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    • pp.239-248
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    • 2011
  • In order to improve the quality of strain images in medical ultrasound imaging, displacements need to be accurately estimated. In this paper, in order to apply one-dimensional displacement estimation methods to two-dimensional motion estimation, the axial and lateral displacements are separately estimated. In order to estimate lateral displacements, one-dimensional signals aligned in the lateral direction are converted to analytic signals, which are then crosscorrelated. Strain images are produced by first compensating two-dimensional displacements for lateral motion with lateral motion displacement estimates obtained from the proposed lateral displacement estimation algorithm and then estimating axial displacements. Both phantom and human data experiments show that the proposed method provides better signal-to-noise ratio and contrast-to-noise ratio characteristics than a conventional strain imaging method that utilizes axial displacement estimates only.

A Study on the PES Estimation for Developing High-TPI HDD (HIGH-TPI HDD 구현을 위한 PES ESTIMATION에 관한 연구)

  • Koh, Jeong-Seok;Kang, Seong-Woo;Han, Yun-Sik;Kim, Young-Hoon;Hwang, Tae-Yeon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2002.11b
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    • pp.122-127
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    • 2002
  • A frequency-domain PES estimation and its prediction method are proposed for the tightly-coupled servo/mechanical design of high-TPI HDD system above 100 kTPI. The major two disturbance energies which are related with mechanical vibrations inside of HDD are used to predict the drive-level PES, while considering closed-loop servo dynamics. One is the torque disturbance which mainly comes from aerodynamic excitation of HSA system and the other is the displacement disturbance from disk-spindle dynamics. In order to obtain the accurate error transfer function of closed-loop servo control, the plant model is measured by accurate experiment. The measured PES is compared with predicted one in terms of frequency-domain PES spectrum and its standard variation value. It is proved that the proposed frequency-domain PES estimation/prediction method is capable of predicting drive-level PES of high-TPI hard disk drive.

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A Study on Tool Wear Diagnosis by Measuring Spindle Displacement (주축 변위 측정을 통한 공구 마모 진단에 관한 연구)

  • 김진현;김일해;장동영;한동철
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.1
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    • pp.222-228
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    • 2003
  • A reliable tool wear monitoring technique is the one of important aspects for achieving an integrated and self-adjusting manufacturing system. In this paper, a tool wear estimation approach for turning is proposed. This approach uses the model of cutting force, spindle displacement and their relation. A series of experiments were conducted by designing experimental techniques to determine the relationship between flank wear and cutting force coefficient as well as cutting parameters such as cutting speed, depth of cut and feed. The proposed model performance has shown that the spindle displacement model predicts tool wear with high accuracy and spindle displacement signal is possible to replace cutting force signal.

A Study on Tool Wear Diagnosis by Measuring Spindle Displacement (주축 변위 측정을 통한 공구 마모 진단에 관한 연구)

  • 김진현;김일해;장동영;한동철
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2001.04a
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    • pp.459-464
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    • 2001
  • A reliable tool wear monitoring technique is the one of important aspects for achieving an integrated and self-adjusting manufacturing system. In this paper, a tool wear estimation approach for turning is proposed. This approach uses the model of cutting force, spindle displacement and their relation. A series of experiments were conducted by designing experimental techniques to determine the relationship between flank wear and cutting force coefficient as well as cutting parameters such as cutting speed, depth of cut and feed. The proposed model performance has shown that the spindle displacement model predicts tool wear with high accuracy and spindle displacement signal is possible to replace cutting force signal.

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Laser pose calibration of ViSP for precise 6-DOF structural displacement monitoring

  • Shin, Jae-Uk;Jeon, Haemin;Choi, Suyoung;Kim, Youngjae;Myung, Hyun
    • Smart Structures and Systems
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    • v.18 no.4
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    • pp.801-818
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    • 2016
  • To estimate structural displacement, a visually servoed paired structured light system (ViSP) was proposed in previous studies. The ViSP is composed of two sides facing each other, each with one or two laser pointers, a 2-DOF manipulator, a camera, and a screen. By calculating the positions of the laser beams projected onto the screens and rotation angles of the manipulators, relative 6-DOF displacement between two sides can be estimated. Although the performance of the system has been verified through various simulations and experimental tests, it has a limitation that the accuracy of the displacement measurement depends on the alignment of the laser pointers. In deriving the kinematic equation of the ViSP, the laser pointers were assumed to be installed perfectly normal to the same side screen. In reality, however, this is very difficult to achieve due to installation errors. In other words, the pose of laser pointers should be calibrated carefully before measuring the displacement. To calibrate the initial pose of the laser pointers, a specially designed jig device is made and employed. Experimental tests have been performed to validate the performance of the proposed calibration method and the results show that the estimated displacement with the initial pose calibration increases the accuracy of the 6-DOF displacement estimation.

Estimation of yield strength due to neutron irradiation in a pressure vessel of WWER-1000 reactor based on the correction of the secondary displacement model

  • Elaheh Moslemi-Mehni;Farrokh Khoshahval;Reza Pour-Imani;M.A. Amirkhani-Dehkordi
    • Nuclear Engineering and Technology
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    • v.55 no.9
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    • pp.3229-3240
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    • 2023
  • Due to neutron radiation, atomic displacement has a significant effect on material in nuclear reactors. A range of secondary displacement models, including the Kinchin-Pease (K-P), Lindhard, Norgett-Robinson-Torrens (NRT), and athermal recombination-corrected displacement per atom (arc-dpa) have been suggested to calculate the number of displacement per atom (dpa). As neutron elastic interaction is the main cause of displacement damage, the focus of the current study is to calculate the atomic displacement caused by the neutron elastic interaction in order to estimate the exact amount of yield strength in a WWER-1000 reactor pressure vessel. To achieve this purpose, the reactor core is simulated by MCNPX code. In addition, a program is developed to calculate the elastic radiation damage induced by the incident neutron flux (RADIX) based on different models using Fortran programming language. Also, due to non-elastic interaction, the displacement damage is calculated by the HEATR module of the NJOY code. ASME E-693-01 standard, SPECTER, NJOY codes, and other pervious findings have been used to validate RADIX results. The results showed that the RADIX(arc-dpa)/HEATR outputs have appropriate accuracy. The relative error of the calculated dpa resulting from RADIX(arc-dpa)/HEATR is about 8% and 46% less than NJOY code, respectively in the ¼ and ¾ vessel wall.

Estimation of Dynamic Vertical Displacement using Artificial Neural Network and Axial strain in Girder Bridge (인공신경망과 축방향 변형률을 이용한 거더 교량의 동적 수직 변위 추정)

  • Ok, Su Yeol;Moon, Hyun Su;Chun, Pang-Jo;Lim, Yun Mook
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.34 no.6
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    • pp.1655-1665
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    • 2014
  • Dynamic displacements of structures shows general behavior of structures. Generally, It is used to estimate structure condition and trustworthy physical quantity directly. Especially, measuring vertical displacement which is affected by moving load is very important part to find or identify a problem of bridge in advance. However directly measuring vertical displacement of the bridge is difficult because of test conditions and restriction of measuring equipment. In this study, Artificial Neural Network (ANN) is used to suggest estimation method of bridge displacement to overcome constrain conditions, restriction and so on. Horizontal strain and vertical displacement which are measured by appling random moving load on the bridge are applied for learning and verification of ANN. Measured horizontal strain is used to learn ANN to estimate vertical displacement of the bridge. Numerical analysis is used to acquire learning data for axis strain and vertical displacement for applying ANN. Moving load scenario which is made by vehicle type and vehicle distance time using Pearson Type III distribution is applied to analysis modeling to reflect real traffic situation. Estimated vertical displacement in respect of horizontal strain according to learning result using ANN is compared with vertical displacement of experiment and it presents vertical displacement of experiment well.