Water Ingress Nondestructive Evaluation of Aviation Composites Panels using Active Thermography: Qualitative and Quantitative Aspects

Yoonjae Chung(정윤재),Seungju Lee(이승주),Chunyoung Kim(김준영),Wontae Kim(김원태) 한국비파괴검사학회 2022 한국비파괴검사학회 춘계학술대회 초록집 Vol.2022 No.5

능동 적외선 열화상 기법에 의한 SM45C 이면결함 검출 열영상에 관한 연구

정윤재(Yoonjae Chung),Shrestha Ranjit,김원태(Wontae Kim) 한국비파괴검사학회 2015 한국비파괴검사학회지 Vol.35 No.3

능동적 열화상 기법은 넓은 면적을 동시에 검사할 수 있으며, 결함부와 건전부 사이의 위상차로부터 결함의 유무를 판단할 수 있다. 지금까지 다양한 재료와 시험편을 가지고 결함 검출 기법에 대한 발전이 이루어졌다. 본 논문에서는 위상잠금 열화상 기법을 적용하여 각각 다른 결함의 크기와 깊이의 인공결함을 갖는 SM45C 시험편을 가지고 제안된 기법을 검증하였으며, 결론으로서 결함의 크기, 깊이에 따른 위상 이미지와 진폭 이미지 검사 결과를 비교하여 결함 검출능을 평가할 수 있었다. Active thermography techniques have the capability of inspecting a broad range simultaneously. By evaluating the phase difference between the defected area and the healthy area, the technique indicates the qualitative location and size of the defect. Previously, the development of the defect detection method used a variety of materials and the test specimen was done. In this study, the proposed technique of lock-in is verified with artificial specimens that have different size and depth of subsurface defects. Finally, the defect detection capability was evaluated using comparisons of the phase image and the amplitude image according to the size and depth of defects.

PCA 이미지 융합을 통한 복합재료 수분 함침에 대한 위상잠금 열화상 이미지의 SNR 향상

정윤재(Yoonjae Chung),이승주(Seungju Lee),김원태(Wontae Kim) 한국비파괴검사학회 2021 한국비파괴검사학회지 Vol.41 No.5

항공우주를 포함한 다양한 산업에서 허니콤 샌드위치 구조의 사용이 증가함에 따라 효과적이고 효율적인 비파괴검사 기법을 개발할 필요성이 대두되고 있다. 최근 능동적외선 열화상은 비접촉, 비파괴 방식으로서 넓은 검사면적을 빠르게 정량적인 검사가 가능하여 복합재료의 비파괴검사 및 평가를 위한 유망한 기술로 큰 주목을 받고 있다. 본 연구에서는 허니콤 샌드위치 구조의 수분 함침 검출에 대한 위상잠금 열화상의 실험적 연구를 수행했으며, 주성분분석(PCA) 이미지 융합을 통하여 진폭 및 위상 이미지를 융합하고 신호대잡음비(SNR)을 향상시켰다. The growing use of honeycomb sandwich structures in various industries, including aerospace, raises the necessity to develop effective and efficient non-destructive testing techniques. Recently, active thermography, which is a non-contact, non-destructive method that enables quantitative inspection of a large inspection area in a short time, is attracting significant attention as a promising technology for non-destructive inspection and evaluation of composite materials. In this study, an experimental investigation of lock-in thermography was conducted for the detection of water ingress of honeycomb sandwich structures. In addition, the signal-to-noise ratio (SNR) was enhanced by fusing the amplitude and the phase images using principal component analysis (PCA) fusion.

위상잠금 열화상을 이용한 알루미늄 구조 이면결함에 대한 검출능 연구

정윤재(Yoonjae Chung),김원태(Wontae Kim) 한국비파괴검사학회 2017 한국비파괴검사학회지 Vol.37 No.4

본 고에서는 결함 매개변수의 정량적인 결정을 가능하게 하는 위상잠금 열화상 기법을 적용하여 알루미늄 결함시편에서 가진 주파수 영향에 따른 결함 검출능에 대하여 연구를 수행하였다. 가진 주파수는 0.01 Hz ~ 0.1 Hz가 적용되었으며, 열화상 데이터는 4점법 데이터 프로세싱을 통하여 위상과 진폭을 분석하였다. 또한, 위상차 분석을 통하여 가진 주파수에 따른 결함 크기 및 깊이가 결함 검출에 미치는 영향을 분석하였다. 본 연구결과로부터 알루미늄과 같은 높은 열전도도를 갖는 재료 결함검사에 있어 위상잠금 열화상을 이용하여 결함 검출능에 대한 유용한 정보를 얻을 수 있었다. This study explored the effects of excitation frequency on defect detectability, which allows a quantitative determination of defect parameters by using lock-in thermography(LIT). The excitation frequency applied ranged from 0.1 Hz to 0.01 Hz. Thermal image data were analyzed by phase and amplitude through four-point data processing, and the effect of defect diameter and depth on defect detection were analyzed through phase difference analysis. As results, valuable detectability by LIT on defect inspection of aluminum material was obtained.

능동 적외선열화상 기법을 이용한 이면결함 검출에서의 측정 불확도

정윤재(Yoonjae Chung),김원태(Wontae Kim),최원재(Wonjae Choi) 한국비파괴검사학회 2015 한국비파괴검사학회지 Vol.35 No.5

능동적 열화상 기법은 재료의 수동적 열적결함에 있어 기존의 적외선 열화상 기법에 비해 우수한 결함 검출능력을 보이는 것으로 알려져 있다. 적외선 비파괴 검사는 지금까지 다양한 검출 기법에 대한 발전이 이루어졌으나 신뢰성에는 다소 의문이 있다. 따라서 본 논문에서는 위상잠금 열화상기법을 적용하여 각각 다른 결함의 크기와 깊이의 인공결함을 갖는 SM45C 시험편을 가지고 제안된 기법을 검증하고, 불확도를 평가하여 위상잠금 열화상 기법을 이용한 결함의 크기측정에 대한 신뢰성을 검토하였다. Active infrared thermography methods have been known to possess good fault detection capabilities for the detection of defects in materials compared to the conventional passive thermal infrared imaging techniques. However, the reliability of the technique has been under scrutiny. This paper proposes the lock-in thermography technique for the detection and estimation of artificial subsurface defect size and depth with uncertainty measurement.

이면 결함 평가를 위한 적외선 열화상 실험 및 시뮬레이션의 불확도 연구

정윤재(Yoonjae Chung),김원태(Wontae Kim) 한국비파괴검사학회 2018 한국비파괴검사학회지 Vol.38 No.3

본 논문에서는 위상잠금 열화상과 시뮬레이션에서의 결함 검출과 크기 측정에 대한 연구와 불확도 요인을 분석하였다. SM45C의 결함 검출 연구를 수행하기 위하여 위상 잠금 열화상 기법을 적용하였다. 또한, 상용소프트웨어 ANSYS15.0을 활용하여 유한요소해석 모델 개발 및 불확도 연구를 수행했다. 결과로서 가진 주파수에 따른 결함 크기 측정 불확도 상관관계를 분석하였다. 마지막으로 위상 잠금 열화상과 유한요소모델의 불확도 평가 결과를 제시하였다. In this study, the factors leading to uncertainty in defect size detection and measurement in lock-in thermography and simulation were investigated. The lock-in thermography technique was applied to measure the size of subsurface defects in SM45C specimens. In addition, the development of a finite element analysis model using ANSYS 15.0 software and an uncertainty study were carried out. As a result, the uncertainty of the defect size measurement, according to the excitation frequency, was analyzed. The uncertainty evaluation results of the lock-in thermography and the finite element model are presented herein.

다중 위상잠금 주파수 알고리즘을 활용한 폴리프로필렌/유리섬유 복합재 이면결함 정량적 평가

정윤재(Yoonjae Chung),이승주(Seungju Lee),김준영(Chunyoung Kim),김원태(Wontae Kim) 한국비파괴검사학회 2023 한국비파괴검사학회 춘계학술대회 초록집 Vol.2023 No.5

백서 하지 골격근의 허혈-재관류 손상에 의한 부종 및 eicosanoids의 변동에 미치는 indomethacin의 효과

김진,정윤재,손병규 大韓成形外科學會誌 2000 Archives of Plastic Surgery Vol.27 No.1

Ischemia and reperfusion of skeletal muscle occurs in acute vascular occlusion and revascularization, in elective vascular surgery, in upper and lower extremity surgery by means of a tourniquet, and in free transplantation of muscle containing cutaneous flaps. During revascularization of skeletal muscle after ischemia, lipid mediators, mainly eicosanoids are released that may have a role in the pathogenesis of reperfusion injury. The exact role of eicosanoids in the imposed ischemia-reperfusion induced functional deficits in skeletal muscle is still unknown, we compared tissue edema and the changes of eicosanoids and the effects of cyclooxygenase inhibitor indomethacin in the rat right hindlimb by application of tourniquet ischemia-reperfusionn injury. After 4-hours of ischemia, reperfusion was established 4 hours by releasing tourniquet. Experimental groups comparised ischemia-reperfused animals pretreated with indomethacin 20 mg/kg. The control animals received normal saline, 4 hours of ischemia without reperfusion. To assess tissue edema, wet/dry weight ratios were determined and the concentrations of prostaglandins and thromboxane were measured by the high performance liquid chromatography with UV detector at 195 nm. Ischemia itself did not result in muscle edema and did not increase the release of cyclooxygenase metabolites, but muscle edema(52%, p<0.01), and the relase of 6-keto-PGF₁α(151%, p<0.01), thromboxane B₂(98%, p<0.05), and PGE₂(127%, p<0.01) were significantly increased by reperfusion. Indomethacin treatment ameliorated limb edema(35%, p<0.05 versus ischemis-reperfusion control) and decreased 6-keto-PGF₁α(65%, p<0.05) releases. These results support view that cyclooxygenase products may play significant roles in the formation of ischemic muscle edema and suggest that nonsteroidal antiinflammatory agents and eicosanoids antagonists might be beneficial to the management of acute limb ischemia-reperfusion injury.

Wavelet transform applied to lock-in thermographic data for detection of inclusions in composite structures: Simulation and experimental studies

Shrestha, Ranjit,Chung, Yoonjae,Kim, Wontae Elsevier 2019 Infrared physics & technology Vol.96 No.-

<P><B>Abstract</B></P> <P>In this work, we focused on lock-in infrared thermography as a non-destructive testing method for detection of inclusions in glass fiber reinforced plastic composite structures. The sample consisted of artificial inserts made of copper sheets to simulate inclusions of different shapes and sizes at varying depth levels. In an experimental study, the sample was excited at several modulation frequencies by a sinusoidal heat flux, and a thermal infrared camera was utilised for monitoring of surface temperature of a thermal wave that propagated into the sample. In simulation, ThermoCalc™-3D software based on finite difference method was used for the replication of the physical phenomena that were present in the experiment. The effect of the applied heat flux and time for different sizes and depths of inclusions was analysed to investigate the thermal response. Wavelet transform was applied to compute phase angle data from the temperature-time history of each pixel for the assessment of the inclusions. The investigation into the effects of wavelet parameters; scale and shift, modulation frequencies, inclusion sizes, and depths on the phase contrast was conducted and discussed. The simulation results were found to have a good correlation with the experimental results, thus demonstrating potential in detecting inclusions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> GFRP composite with artificial inclusion was tested by LIT. </LI> <LI> Wavelet transform was used to compute the phase angle images from the thermal data. </LI> <LI> An investigation was performed for the selection of wavelet parameters; scale and shift. </LI> <LI> The effects of inclusion size and depth on phase contrast were analysed. </LI> <LI> Experimental verification of simulated LIT was done to assess inclusions. </LI> </UL> </P>

Thermal Behavior Variations in Coating Thickness Using Pulse Phase Thermography

Ranjit, Shrestha,Chung, Yoonjae,Kim, Wontae The Korean Society for Nondestructive Testing 2016 한국비파괴검사학회지 Vol.36 No.4

This paper presents a study on the use of pulsed phase thermography in the measurement of thermal barrier coating thickness with a numerical simulation. A multilayer heat transfer model was ussed to analyze the surface temperature response acquired from one-sided pulsed thermal imaging. The test sample comprised four layers: the metal substrate, bond coat, thermally grown oxide and the top coat. The finite element software, ANSYS, was used to model and predict the temperature distribution in the test sample under an imposed heat flux on the exterior of the TBC. The phase image was computed with the use of the software MATLAB and Thermofit Pro using a Fourier transform. The relationship between the coating thickness and the corresponding phase angle was then established with the coating thickness being expressed as a function of the phase angle. The method is successfully applied to measure the coating thickness that varied from 0.25 mm to 1.5 mm.