• Title/Summary/Keyword: speckle interferometry

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Measurement of Tensile Properties Dependent on the Small-Scaled Specimen Dimension for Evaluation of In-Service Materials Properties (사용재 물성 평가를 위한 미소 시험편 크기에 따른 인장 특성 평가)

  • Huh, Yong-Hak;Kim, Dong-Iei;Kim, Dong-Jin;Lee, Hae-Moo;Park, Jong-Seo
    • Journal of the Korean Society of Safety
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    • v.23 no.5
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    • pp.30-34
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    • 2008
  • To evaluate the mechanical properties of in-service materials, tensile properties measurement using small-scaled specimen has been carried out. Tensile testing specimens with various dimensions, including standard and sub-size specimen specified in ASTM and ISO and small-scaled specimen, were prepared. Tensile strain in small-scaled specimen was measured using micro-ESPI system set up in this study. This system was used in the specimen with the parallel length of 2 mm and in subsequently measuring the strain under tensile loading. From each type of tensile specimen, stress-strain curves were determined. The dimension effect of the tensile properties was investigated comparing the tensile results obtained from standard specimens and small-scaled specimens. It was shown that the tensile strength for the small-scaled specimen is lower by 15% than those for the standard specimen.

Study of Development of Image Processing Algorithm for Measurement of Out of Plane Deformation Using the Shearography (전단간섭계를 이용한 내부 결함의 면외 변위 측정을 위한 화상처리 알고리즘 개선에 관한 연구)

  • Choi, In Young;Kang, Young June;Hong, Kyung Min;Kim, Sung Jong;Park, Jong Hyun
    • Journal of the Korean Society for Precision Engineering
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    • v.30 no.1
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    • pp.59-66
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    • 2013
  • The measuring of internal defects of objects using the shearography has many advantages. It is a non-contact and non-destructive method and It has a real time measurement speed and no constraints of object shape. Compared to ESPI(Electronic Speckle Pattern Interferometry), Shearography has a very low error rate by vibration and air turbulence. So shearography provides possibilities of industrial application. In this paper, Image processing algorithm that is measurement of out-of-plane deformation using the shearography is proposed by developed using the LabVIEW 2010 and measurement result of out-of-plane ESPI and Shearography are compared quantitatively.

A Study on Reliability Verification of Resonance Frequency Detection of Vibration Object using Time-average ESPI (시간 평균 ESPI를 이용한 진동 물체의 공진 주파수 검출 신뢰도 검증에 대한 연구)

  • Hong Kyung-Min;Ryu Weon-Jae;Kang Young-Jung;Lee Dong-Hwan
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.10a
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    • pp.930-933
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    • 2005
  • Non-destructive inspection techniques using laser have been breading their application areas as well as growing their measurement skills together with the rapid development of circumferential technology like fiber optics. computer and image processing The ESPI technique is already on the stage of on-line testing with commercial products in developed country nations. Especially, this technique is expected to be applied to the nuclear industry, automobile and aerospace because it is proper for the vibration measurement and it can be applied to objects of a high temperature. This paper describes the use of the ESPI system for measuring vibration patterns on the reflecting objects. Using this system, high-quality Jo fringes for identifying mode shapes are displayed. A bias vibration is introduced into the reference beam to shift the Jo fringes so that fringe shift algorithms can be used to determine vibration amplitude. Using this method. amplitude fields for vibrating objects were obtained directly from the time-average interferometer recorded by the ESPI 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 Dong-Iel;Kee Chang-Doo;Huh Yong-Hak
    • Journal of the Korean Society for Precision Engineering
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    • v.23 no.8 s.185
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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.

A Study on Measurement of In-Plane Displacement using ESPI in Mechanical Structure under torsional load (비틀림하중을 받는 기계구조물의 ESPI를 이용한 면내변위 측정에 관한 연구)

  • Jang, Seok-Won;Lee, Hak-Ju;Choe, Eun-O;Jeong, Chan-Hui
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.4
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    • pp.693-700
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    • 2002
  • Recently, the mechanical structures applied to many industrial products, especially in electronic products, appear to be miniaturized and complicated. This trend makes it difficult to analyze the stress distribution of those mechanical structures and generates new challenges for precise measurement of strain. In order to solve this measurement problem many optical measurement techniques have been suggested. Among those, the ESPI(Electronic Speckle Pattern Interferometry) has been considered as one of the most useful tools. But the shortage of recognition and difficulties of measurement have limited its industrial applications in spite of its excellent capabilities. Therefore in this study, not only the verification of the FEA result but the enhancement of industrial application of ESPI was tried by measuring the in-plane displacement of mechanical structure with ESPI, which is difficult to be measured with strain gauge.

A Study on the Thermal Coefficient Measurements of Special Steel by ESPI at High Temperature (고온에서 ESPI에 의한 특수강의 열팽창계수 측정에 관한 연구)

  • Kim, K.S.;Yang, S.P.;Kim, H.S.
    • Journal of the Korean Society for Nondestructive Testing
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    • v.13 no.2
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    • pp.20-30
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    • 1993
  • Electric Speckle Pattern Interferometry (ESPI) using a CW-laser, a video system and an image processor was applied to the thermal coefficient measurements on free thermal expansions at high temperatures : ESPI provides the distribution of in-plane displacement resolved in a preselected direction. ESPI retains the merits of little or no surface preparation, no contact with the surface and the real-time presentation of interference fringes. Appling ESPI at high temperatures, several problem which caused the reduction of fringe visibility were encountered. The problem on the turbulence in the hot air surrounding high temperature objects will be solved by using a vacuum chamber. The background radiations from the objects were suppressed considerably by an interference filter. The problem on the oxidation of the object surface could't be solved. The interference fringe, whose spacings were calculated by FFT to avoid human error, were observable up to $800^{\circ}C$. The results measured by ESPI were nearly equal to the data which have already been published, up to about $800^{\circ}C$.

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Performance Comparison between Optical Fiber Type ESPI and Bulk Type ESPI for the Internal Defect in Pressure Vessel (광섬유형과 벌크형 ESPI를 이용한 압력용기 내부 결함 측정에 관한 비교 연구)

  • Kim, Seong-Jong;Kang, Young-June;Hong, Kyung-Min;Lee, Jae-Hoon;Choi, Nak-Jung
    • Journal of the Korean Society for Nondestructive Testing
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    • v.32 no.2
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    • pp.177-184
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    • 2012
  • An optical defect detection method using ESPI(electronic speckle pattern interferometry) is proposed. ESPI is widely used as a non-contact measurement system which show deformation and phase map in real time. ESPI can be divided as the in-plane, out-of-plane and shearography by operation principle and target object and also divided with bulk type and optic fiber type by the optic configurations. This paper is focused on optic fiber type out-of-plane ESPI, which has the following advantages: (1) low cost; (2) reduction of the unreliable factors generated by separated optic components; (3) simplification of the optic configuration; (4) great reduction of volume; (5) flexibility, to be easily designed into different structures to adapt to inaccessible environments such as pipeline cavity and so on.

Thermal Deformation Measurement Spherical Glasses Lens Using ESPI (ESPI를 이용한 안경용 렌즈의 열변형 측정)

  • Kim, Koung-Suk;Jang, Ho-Sub;Kim, Hyun-Min;Yang, Seung-Pill
    • Journal of the Korean Society for Nondestructive Testing
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    • v.28 no.2
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    • pp.137-143
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    • 2008
  • The spherical glasses lenses are typically classified into two groups such as (+) diopter lens and (-) diopter lens by the refractive power index. The thermal deformation of a lens is occurred by external heat source and is changed respected to the diopter of a lens. In this paper, the thermal deformation of spherical glasses lenses were quantitatively measured by using ESPI (electronic speckle pattern interferometry) which has an advantage that the non-contact, non-destructive and precise deformation measurement is available due to the coherency characteristic. The temperature changes were measured by IR camera. It makes experiments over 14 types of the plastic glasses lenses. From the results, it was confirmed that the larger diopter lens showed the less thermal deformation in case of the (+) diopter lens. On the other hand, the thermal deformation of the (-) diopter lens was measured with uniform pattern when the same temperature changes were applied. Also, it was found that the thermnal deformation of the (+) diopter lens is less than that of the (-) diopter lens. Therefore, it is expected that when the thermal deformation is occurred to the various types of the lens, the variation of the focal length caused by the thermal distortion of a lens would be measured quantitatively.

Quantitative Comparison of Out-of-Plane Deformation Measured by Dual-Function Interferometer System (이중기능 간섭계에 의해 측정된 면외변형의 정략적 비교)

  • Kim, Kyoung-Suk;Chang, Ho-Seob;Lee, Seung-Seok;Jung, Hyun-Chul;Kwag, Jae-Ho
    • Journal of the Korean Society for Nondestructive Testing
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    • v.28 no.1
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    • pp.33-39
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    • 2008
  • Dual-function interferometer is an interferometer that has all features of ESPI (electronic speckle pattern interferometry) and shearography in one interferometer setup. The deformatiou of an object is directly obtained by ESPI while the slope of the deformation of an object is obtained by shearography. If the result of shearography is divided by shearing amount and integrated by numerical analyzing, then finally the reconstructed deformation of an object that is the same as the results directly obtained by ESPI can be measured by shearography. In this study, rubber and alruminum plates are used as specimen and its out-of-plane deformation is measured by ESPI and shearography setup of the dual-function interferometer. Each of the results obtained by ESPI and shearography is compared by using numerical integration to the result of shearography. From this study, it is confirmed that the reconstructed deformation results obtained by numerical integration good agree with the results obtained by ESPI.

Effect of Local Strain on Low Cycle Fatigue using ESPI System (ESPI System을 이용하여 측정한 국부 변형률이 저사이클 피로수명에 미치는 영향에 관한 연구)

  • Kim, Kyung-Su;Kim, Ki-Sung;Kwon, Jung-Min;Park, Seong-Mo;Kim, Beom-Il
    • Journal of the Society of Naval Architects of Korea
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    • v.43 no.2 s.146
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    • pp.213-219
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    • 2006
  • Low cycle fatigue cracks are mainly detected at discontinuous welded locations with high stresses under repeated cyclic static loads due to cargo leading and unloading. Theoretical and analytical methods have been used for evaluation of local stress and strain which have an effect on a prediction of fatigue life, but those have difficulties of considering stress concentration at notched location and complicated material behavior of welded joint or heat affected zone. Electronic speckle pattern interferometry(ESPI) system is nondestructive and non-contact measurement system which can get the relatively accurate full field strain at critical positions such as welded zone and structural discontinuous location. In this study, local strain was measured on welded cruciform joint by ESPI system and then low cycle fatigue test was performed. Effect of local strain on low cycle fatigue life was examined by measured values using ESPI system. Moreover, experimental fatigue life was compared with established S-N curves using theoretical local strain and stress calculated by Neuber's rule.