• Title, Summary, Keyword: strain measurement

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A Study on the Measurement Methods of Plastic Strain Ratio in Automotive sheet steel (자동차용 강판의 소성변형비 측정 방법 연구)

  • 김인수;김인수
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.85-92
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    • 1996
  • The Measurement method of the plastic strain ratio is various in Automotive sheet steel. In this paper, the measurement of the plastic strain are used two different methods, ASTM E 517 method and the automatic strain measurement tensile specimen during the tensile test, and compared the plastic strain ratios from the two methods. The experimental results showed that the measured plastic strain ratios from the automatic strain measurement method are coincide with that from the ASTM E 517 standard measurement in various specimens. Therefore, automatic strain measurement method by two extensometers shows good accuracy. Also, the strain dependance of plastic strain ratios could be recorded by the computer continuously and anisotropy of the strength coefficient, K, and strain hardening exponent, n ,could be compared with each direction automatically through the use of automatic strain measurement system.

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Study on the Compensation of Strain Measurement Error in Sheet Metals (박판 변형률 측정 오차의 보정에 관한 연구)

  • 차지혜;금영탁
    • Transactions of Materials Processing
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    • v.13 no.7
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    • pp.594-599
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    • 2004
  • In the sheet metal forming operations, the strain measurement of sheet panel is an essential work which provides the formability information needed in die design, process design, and product inspection. To measure efficiently complex geometry strains, the 3-dimensional automative strain measurement system, which theoretically has a high accuracy but practically has about 3~5% strain error, is often used. For eliminating the strain error resulted in measuring the strains of formed panels using an automated strain measurement system, the position error calibration method is suggested, which computes accurate strains using the grids with accurate nodal coordinates. The accurate nodal coordinates are calculated by adding the nodal coordinates measured by the measurement system and the position error found using the multiple regression method as a function of the main error parameters obtained from the analysis of strain error in a standard cube. For the verification, the strain distributions of square and dome cups obtained from the position error calibration method are compared with those provided by the finite element analysis and ASAME.

A Study on the Measurement of Surface Strain Using the Image Processing Technique (화상처리법을 이용한 곡면변형률 측정에 관한 연구)

  • 김영수;김형종
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.213-216
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    • 1997
  • The measurement of 3D surface strain using the image processing method is another approach for strain measurement. The advantage of this method is that strains at several points included in a captured image can be obtained automatically from only one process. In this study, the whole process of automated surface strain measurement is presented. The strain distribution on a LDH specimen is illustrated as a result of the trial to develope an automated strain measurement system.

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Improvement of Sensitivity to In-plane Strain/Deformation Measurement by Micro-ESPI Technique (마이크로 ESPI 기법에 의한 면내 변형 측정 민감도 향상)

  • Kim D.I.;Huh Y.H.;Kee C.D.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.1442-1445
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    • 2005
  • Several test methods, including micro strain/deformation measurement techniques, have been studied to more reliably measure the micro properties in micro/nano materials. Therefore, in this study, the continuous measurement of in-plane tensile strain in micro-sized specimens of thin film materials was introduced using the micro-ESPI technique. TiN and Au thin films 1 and $0.47\;\mu{m}$ thick, respectively, were deposited on the silicon wafer and fabricated into the micro-sized tensile specimens using the electromachining process. The micro-tensile loading system and micro-ESPI system were developed to measure the tensile strain during micro-tensile test. The micro-tensile stress-strain for these materials was determined using the algorithm for continuous strain measurement. Furthermore, algorithm for enhancing the sensitivity to measurement of in-plane tensile strain was suggested. According to the algorithm for enhancement of sensitivity, micro-tensile strain data between interfringe were calculated. It is shown that the algorithm for enhancement of the sensitivity suggested in this study makes the sensitivity to the in-plane tensile strain increase.

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A Study on the Evaluation of the Automatic Measurement Method of Plastic Strain Ratio by Two Extensometers (신장계에 의한 소성변형비 자동측정법의 평가에 관한 연구)

  • 김인수
    • Transactions of Materials Processing
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    • v.12 no.5
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    • pp.504-512
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    • 2003
  • The plastic strain ratios(R-values) of low carbon steel sheets were determined by the automatic strain measurement method using two extensometers, the indirect photo method for the same tensile specimen during tensile test and the indirect method for the specimen after tensile test. The experimental results showed that the measured plastic strain ratios from the automatic strain measurement method using two extensometers coincided with those from the indirect photo method and the indirect method for all tensile specimens. In addition, the strain dependence of plastic strain ratios could be continuously recorded and the anisotropy of the strength coefficient, K, and strain hardening exponent, n, could be automatically calculated in three directions by computer through the use of two extensometers. The experimental results showed that the strain dependence of R-value was related to the anisotropy of strain hardening exponent in low carbon steel sheets.

Improvement of the Accuracy and Conveniency in Automated Strain Measurement through High-Resolution Image Processing (고해상도 화상처리를 통한 자동 변형률 측정의 정확도와 편의성 개선)

  • Kim, H.J.;Choi, S.C.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.34-39
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    • 2006
  • An automated surface-strain measurement system, named ASIAS, was developed by using the image processing and stereo vision techniques in the previous studies by the corresponding author and his coworkers. This system has been upgraded mainly to improve the accuracy through image enhancement, sub-pixel measurement, surface smoothing, etc., since the first version was released. The present study has still more improved the convenience of users as well as the accuracy of measurement by processing high resolution images 8 mega pixels or more which can be easily obtained from a portable digital steal camera. It is proved that high resolution image processing greatly decreases the measurement error and gives strain data without considerable deterioration of accuracy even when the deformed grids to be measured and the master grids for camera calibration are captured together in the same image, making the whole process of strain measurement much simpler.

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A Study on the High-Temperature Strain Measurement of Perfectly Flat CRT (완전평면 브라운관의 고온 변형률 측정에 관한 연구)

  • Kang, Dae-Jin;Kim, Kug-Weon;Han, Eung-Kyo
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.8
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    • pp.23-27
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    • 1999
  • The measurement of thr high-temperature strains is one of the challenging subjects in mechanical engineering. For the precise measurement, proper high-temperature strain gauge, cement and skilled technique are needed. In this paper, a high-temperature strain measurement is performed for the perfectly flat CRT. As this CRT is structurally very weak, cracking of the panel frequently occurs during the heat cycle in the furnace. From the measured strain variations of the panel with tension shadow mask, the crack behavior can be explained.

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Evaluation of Fracture Toughness of Al alloys for Propulsive Engine using Strain Measurement (변형률 측정을 이용한 추진기관용 Al 합금의 파괴인성 평가)

  • 김재훈;김덕회;임동규;박성욱;문순일
    • Journal of the Korean Society of Safety
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    • v.17 no.3
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    • pp.13-21
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    • 2002
  • The tincture toughness is evaluated by using U(compact tension) and 3PB(three point bending) specimens of AI alloys far propulsive engine. To evaluate the static fracture toughness, strain gage method is used. The static fracture toughness obtained from the strain measurement is compared with the results by ASTM standard and FEM analysis. For the reliable evaluation of fracture toughness, strain gages are attached at various positions.

Study on the Error Compensation in Strain Measurement of Sheet Metal Forming (박판성형 변형률 측정 오차보정에 관한 연구)

  • 한병엽;차지혜;금영탁
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • pp.270-273
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    • 2003
  • The strain measurement of the panel in the sheet metal forming is essential work which provides experimental data needed to die design, process design, and product inspection. To measure efficiently the complex geometry strain, the 3-dimensional automative strain measurement system, which has high accuracy in theory, but has some 3∼5% errors in practice, is often used. The object of this study is to develop the error compensation technology to eliminate the strain, errors resulted when formed panels are measured using an automated strain measurement system. To achieve the study object, the position error calibration method correcting coordinates of the grid node recognized by a camera using error functions is suggested. Then the position errors were found by calculating the difference in the position of the cube node between real coordinates and measured coordinates in toms of node coordinates and the error calibration equations were derived by regressing the position errors. In order to show the validation of the suggested position error calibration method, finite element analysis and current calibration method was performed for the initial-blankformed.

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Improvement of Sensitivity to In-plane Strain/Deformation Measurement by Micro-ESPI Technique (마이크로 ESPI 기법에 의한 면내 변형 측정 민감도 향상)

  • Kim Dong-Iel;Kee Chang-Doo;Huh Yong-Hak
    • Journal of the Korean Society for Precision Engineering
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    • v.23 no.8
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    • pp.54-63
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    • 2006
  • Enhancement methods of sensitivity to in-plane strain measurement by micro-ESPI(Electronic Speckle Pattern Interferometry) technique were proposed using TiN and Au thin films. Micro-tensile strain over the micro-tensile specimens, prepared in micro-scale by those films, was measured by micro-tensile loading system and micro-ESPI system developed in this study. The subsequent measurement of in-plane tensile strain in the micro-sized specimens was introduced using the micro-ESPI technique, and the micro-tensile stress-strain curves for these films were determined. To enhance the sensitivity to measurement of in-plane tensile strain, algorithms of the phase estimation by using curve fitting of inter-fringe and the discrete Fourier Transform with object-induced dynamic phase shifting were developed. Using these two algorithms, the micro-tensile strain-stress curves were generated. It is shown that the algorithms for enhancement of the sensitivity suggested in this study make the sensitivity to measurement of the in-plane tensile strain increase.