• 한국정밀공학회지
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• 제21권10호
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• pp.154-161
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• 2004

An experimental method for measuring side-necking deformation near a crack-tip is described. It is based on Stereoscopic Digital Speckle Photography and Digital Image Correlation, and it is simple and robust to mechanical vibration inherent to a hydraulic material test system. The validity and accuracy are evaluated through a calibration fur rigid body translation. A case study has been performed for a CT specimen made of a ductile steel and the three dimensional profiles of the side-necked region are presented as the load increases. Also, the details of the procedure and the surface treatment are discussed.

• 한국가시화정보학회:학술대회논문집
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• 한국가시화정보학회 2004년도 Proceedings of 2004 Korea-Japan Joint Seminar on Particle Image Velocimetry
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• pp.47-55
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• 2004

Several interpolations for image deformation in PIV were evaluated. The tested interpolation methods are linear, quadratic, truncated sinc, windowed sinc, cubic, Lagrange, Gaussian $2^{nd}\;and\;6^{th}$ interpolators. Bias errors and random errors were evaluated in the range of $0\~3.0$ pixel uniform displacement using synthetic images. We also measured the time cost of each interpolator with respect to kernel size. The cubic interpolator with $6\times6$ kernel showed the best results in terms of the performance and time cost.

• 대한전자공학회논문지SP
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• 제47권1호
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• pp.91-96
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• 2010

본 논문에서는 핵연료봉의 변형에 대한 고정도 검사방법을 제안한다. 핵 연료봉과 이를 관측하는 영상 센서의 광축을 수직으로 구성한다. 영상 센서의 광축을 기준으로 45도 또는 그보다 높은 각도로 레이저 라인빔을 연료봉 표면에 조사하면 연료봉의 수평 방향 변위가 영상 센서에서는 수직 방향 변위로 관측된다. 핵 연료봉 표면에 일정 각도로 입사된 레이저 라인빔이 영상 센서면에서는 일정 두께를 갖는 포물선 형태로 관측되게 된다. 센서 화면에 나타나는 일정 두께의 포물선을 영상처리하여 타원으로 모델링하고 타원의 장축과 단축의 기울기를 구한다. 포물선의 변곡점과 모델링한 타원의 장축과 단축이 교차하는 지점을 특징점으로 추출한다. 이와 같은 영상처리 알고리즘을 이용하여 핵 연료봉의 수평방향 변위에 따른 특징점 좌표의 수직방향 편차를 계산한다. 크러드가 형성된 핵연료봉 시편에 대해 고해상도 영상센서를 사용하여 실험한 결과 중성자 조사후 핵연료봉의 변형 검사기준인 $150{\mu}m$ 보다 3배 이상 개선된 $50{\mu}m$ 이하의 검사 정밀도를 달성하였다.

• 대한기계학회논문집B
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• 제28권3호
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• pp.271-280
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• 2004

Assessment of image registration for Pressure Sensitive Paint (PSP) was performed. A 16 bit camera and LED lamp were used with Uni-FIB paint (ISSI). Because of model displacement and deformation at 'wind-on' condition, a large error of the intensity ratio was induced between 'wind-on' and' wind-off images. To correct the error, many kinds of image registrations were tested. At first, control points were marked on the model surface to find the coefficients of polynomial transform functions between the 'wind-off' 'wind-on' images. The 2nd-order polynomial function was sufficient for representing the model displacement and deformation. An automatic detection scheme was introduced to find the exact coordinates of the control points. The present automatic detection algorithm showed more accurate and user-friendly than the manual detection algorithm. Since the coordinates of transformed pixel were not integer, five interpolation methods were applied to get the exact pixel intensity after transforming the 'wind-on' image. Among these methods, the cubic convolution interpolation scheme gave the best result.

• 대한기계학회논문집
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• 제18권6호
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• pp.1365-1373
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• 1994

Elasto-dynamic deformation of flexible linkage mechanism was analyzed using the finite element method. A computer program was constructed and applied to analyze a specific crank-level 4-bar mechanism, in which the elasto-dynamic deformation of the mechanism system was obtained using mode superposition method in the case of constant input speed and the effect of geometric stiffness on the mechanism is included. Experimental verification of numerical results was conducted by measuring the elasto-dynamic deformation of mid-points of coupler and lever for the 4-bar lingkage mechanism using high speed camera and image data processing systeem. For the elasto-dynamic deformation at the lever mid-point, the numerical results including geometric stiffness almost agree with the experimental ones. However, the numerical results excluding geometric stiffness good agree with the experimental ones at the couper mid-point.

• 한국가시화정보학회지
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• 제19권3호
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• pp.77-83
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• 2021

Solid oxide fuel cell (SOFC) operates at high temperatures in range of 600-800℃. Since layers of SOFC are composed of different substances, different thermal expansion in SOFC can result in defects under high temperature conditions. For understanding relation between temperature field and the thermal deformation in SOFC, temperature and strain field were simultaneously estimated using thermographic phosphors by optical measurement. Temperature fields were obtained by the life-time method, and the temperature differences of one specimen was checked with thermocouple. The thermal deformation was estimated by digital image correlation (DIC) method with extracted phosphorescence images. To investigate the deformation accuracy of DIC measurement, thermographic phosphors were coated with and without grid pattern on aluminum surface. Simultaneous measurement of temperature fields and thermal deformation were carried out for YSZ. This study will be helpful to multi-sensing of temperature field and thermal deformation on SOFC cells.

• 대한기계학회논문집A
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• 제41권8호
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• pp.745-750
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• 2017

본 연구에서는 두께 $12{\mu}m$의 구리박막에 대한 인장시험을 수행하였으며, 변위 측정은 디지털이미지를 기반으로 한 디지털이미지상관법을 이용하였다. 일반적인 디지털이미지상관법에서 시험편 표면의 큰변형으로 인해 변형률계산에 큰 오차가 발생하는 문제점을 개선하여, 시험편 전영역에 걸쳐 정밀하게 변형률을 계산할 수 있었으며 직접 시험편의 표면에서 변형률을 정확하게 측정할 수 있었다. 계산된 시험편 표면의 변형률 분포는 일반적인 벌크소재의 시험편에서와는 달리 전체적으로 균일하지가 않고 그 변화폭이 매우 크며, 항복응력이하의 탄성범위에 있는 경우에도 변형률분포는 균일하지 않다. 이것은 구리박막의 전해증착 제조공정에서 발생한 시험편의 거칠기가 비교적 큰 영향을 준 것으로 판단된다.

• 한국산학기술학회논문지
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• 제20권10호
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• pp.203-208
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• 2019

디지털 워터마킹은 디지털 컨텐츠에 대한 불법적인 복제를 방지하기 위한 저작권 보호 용도로 개발 되었으나, 최근에는 의료 영상과 같은 디지털 컨텐츠에 대하여 무결성을 검증하고 불법적인 조작이나 변형 위치를 감지하기 위한 기술로도 활용하고 있다. 디지털 컨텐츠에 대한 불법적인 복제를 방지하기 위한 저작권 보호 기술에서는 디지털 컨텐츠에 삽입된 워터마크가 왜곡이나 필터링과 같은 다양한 공격에 대하여 강인해야 하는 특성이 있어야 한다. 그러나 디지털 컨텐츠에 대한 조작이나 변형을 감지하기 위한 기술에서는 컨텐츠에 대한 사소한 변형에 대해서도 삽입된 워터마크가 쉽게 제거되어야 하는 특성이 있어야 컨텐츠에 대한 변형 여부를 확인할 수 있다. 따라서 본 논문에서는 디지털 영상에 대한 변형이나 조작 여부를 쉽게 확인하기 위한 워터마킹 기술을 제안한다. 제안 방법에서는 영상에 대한 변형 유, 무를 확인하기 위해 전체 영상을 $16{\times}16$ 블록 단위로 변형 여부를 검사하고 변형이 발생 된 블록에 대해서는 $4{\times}4$ 블록 단위로 검사를 수행하여 변형이 발생 된 위치를 확인한다.

• 산업기술연구
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• 제17권
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• pp.21-29
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• 1997

In this paper, an adaptive image binarization scheme is proposed for automated surface strain measurement. At first, we reviewed an image based 3D deformation factor measurement briefly. Then, a new adaptive thresholding method is proposed for the extraction of lattice pattern from a deformed plate image using its local mean and variance. Some experimental results are presented to verify the effectiveness of our approaches.

• 한국압력기기공학회 논문집
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• 제14권1호
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• pp.8-14
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• 2018

Printed circuit heat exchangers (PCHEs) are widely used with an increasing demand for industrial applications. PCHEs are capable of operating at high temperatures and pressure. We consider a PCHE as a candidate intermediate heat exchanger type for a high temperature gas-cooled reactor (HTGR). For conventional application using stainless steels, design and manufacturing of PCHEs are well established. For applications to HTGR, knowledge of longitudinal conduction and deformation of channel is required to estimate design margin. This paper analyzes the effects of longitudinal conduction and deformation of channel on thermal performance using a code internally developed for design and analysis of PCHEs. The code has a capability of two dimensional simulations. Longitudinal conduction is estimated using the code. In HTGR operating condition, about ten percent of design margin is required to compensate thermal performance. The cross-sectional images of PCHE channels are obtained using an optical microscope. The images are processed with computer image process technique. We quantify the deformation of channel with dimensional parameters. It is found that the deformation has negative effect on structural integrity. The deformation enhances thermal performance when the shape of channel is straight in laminar flow regime. It reduces thermal performance in cases of a zigzag channel and turbulent flow regime.