• Title/Summary/Keyword: 레이저 전단 간섭계

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The Evaluation of Thin Pressure Vessel′s Internal Defects by Laser Shearography (레이저 전단 간섭계를 이용한 압력용기의 내부 결함 평가)

  • 장경영;장석원;현민관
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.929-933
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    • 2003
  • Internal defects of thin pressure vessel used in the power plants or the chemical plants may be created and grow due to corrosion or creep fatigue to reduce the strength and cause critical failure during operation. Therefore it is very important to detect this defect at the early stage. For this purpose, non-destructive, non-contact and highly sensitive method should be considered for on-line application. In this paper, a laser shearographic interferometer is applied to inspect circular defects and notch defects existed inside of thin pressure vessel under the presence of pressure up to 3 times of atmospheric pressure. The influences of the defect shape and size as well as the internal pressure to the characteristic pattern in the shearography fringe are investigated, and the quantitative evaluation of the defect size is tried. Also the experimental results are compared with the destructive test results to show the applicability of this method to the quantitative evaluation of internal defects in the thin pressure vessel.

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Detection of Real Defects in Composite Structures by Laser Measuring System (레이저 계측시스템에 의한 복합재료 구조물의 실제결함 검출)

  • 정성균;김태형;김경석;강영준
    • Composites Research
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    • v.15 no.5
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    • pp.19-26
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    • 2002
  • Real defects in composite structures were detected by using laser measuring system. Four types of real defects, that is, impact-induced delamination in a composite laminate, debond in a honeycomb structure, free-edge delamination in a composite laminate and debond in an adhesive joint, were made by applying several types of loads to the specimens. Laser measuring system such as ESPI and shearography technique were used to detect those defects. Thermal loading method, which can easily induce the surface deformation of specimen, was used to detect the defects. Experimental results show that the defects in composite structures could be easily detected by ESPI and shearography technique. Moreover, it shows that ESPI and shearography technique could be usefully applied to the detection of defects in various kinds of composite structures.

Deformation Analysis of Wall Thinning Pipe by Using Laser Measurement (레이저 계측을 이용한 곡관 감육부의 변형 해석)

  • Kim K.S.;Jung H.C.;Jung S.W.;Kwag J.H.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2006.05a
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    • pp.27-28
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    • 2006
  • This study performs to investigate deformation of wall thinning pipe and to find out the position of the internal thinning defect by shearography. Shearography is one of optical methods those have applied to nondestructive testing (NDT) and the strain/stress analysis. This technique has the merit of the directly measuring the first derivative of displacement, sensitivity of which can be adjusted by the handling of optical component in interferometer. In this paper, we tested carbon steel pipe locally wall thinned and loaded internal pressure and developed the nondestructive out-of-plane deformation analysis technique fur internal thinning defect of elbow by shearography. From the results, it was confirmed that this technique is proper to the practical application on the pipe line system with internal defect.

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Skin friction measurements using He-Ne laser (He-Ne 레이저를 이용한 표면전단응력 측정에 관한 연구)

  • Choi, Seung-Ho;Lee, Yeol
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.7
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    • pp.939-947
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    • 1997
  • An experimental study of the skin friction measurement in a turbulent boundary-layer has been carried out. The skin friction measurements are made using the laser interferometer skin friction (LISF) meter, which optically detects the rate of thinning of an oil applied to the test surface. This technique produces reliable skin friction data over a wide range of flow situations up to 3-dimensional complicated flows with separation, where traditional skin friction measurement techniques are not applicable. The present measured data in a turbulent boundary-layer on a flat plate using the LISF technique shows a good comparison with the result from the previous velocity profile techniques, which proves the validity of the present technique. An extensive error analysis is carried out for the present technique yielding an uncertainty of about .+-.8%, which makes them suitable for CFD code validation purposes. Finally the measurements of the skin friction in a separated region after a surface-mounted obstacle are also presented.