• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 학술대회 논문집 정보 및 제어부문
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• pp.273-275
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• 2005

Active thermography is being used since several years for remote non-destructive testing. It provides thermal images for remote detection and imaging of damages. Also, it is based on propagation and reflection of thermal waves which are launched from the surface into the inspected component by absorption of modulated radiation. For energy deposition, it use external heat sources (e.g., halogen lamp or convective heating) or internal heat generation (e.g., microwaves, eddy current, or elastic wave). Among the external heat sources, the ultrasound is generally used for energy deposition because of defect selective heating up. The heat source generating a thermal wave is provided by the defect itself due to the attenuation of amplitude modulated ultrasound. A defect causes locally enhanced losses and consequently selective heating up. Therefore amplitude modulation of the injected ultrasonic wave turns a defect into a thermal wave transmitter whose signal is detected at the surface by thermal infrared camera. This way ultrasound thermography(UT) allows for selective defect detection which enhances the probability of defect detection in the presence of complicated intact structures. In this paper the applicability of UT for fast defect detection is described. Examples are presented showing the detection of defects in PCB material. Measurements were performed on various kinds of typical defects in PCB materials (both Cu metal and non-metal epoxy). The obtained thermal image reveals area of defect in row of thick epoxy material and PCB.

• 대한기계학회논문집A
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• 제37권4호
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• pp.443-446
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• 2013

적외선 열화상 기술은 넓은 면적을 동시에 검사할 수가 있고, 크랙 또는 박리와 같은 결함을 실시간으로 검출할 수 있으며, 일반적으로 적외선 열화상은 열복사로 피사체에서 방사되는 적외선 영역을 열화상 카메라를 통하여 가시적인 화상을 만들어 주는 기술이며 모든 물체의 분자가 열에 의해 교란되어 발생하는데 분자 운동은 물체의 온도가 올라가면 증가하고 온도가 내려가면서 감소한다. 본 연구에서는 초음파 서모그래피 기술과 기법의 적용과 타당성을 확인하여 엔진블록의 자동차산업 전반에 수요가 많은 대상체로 하였고, 결함 부위에 비파괴 신뢰성평가에 대한 실험을 수행하여 기술하였다.

• 비파괴검사학회지
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• 제35권1호
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• pp.25-30
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• 2015

풍력발전기의 핵심 부품인 풍력 블레이드는 예상치 못한 풍 하중과 공력 특성으로 인해 불안전한 상태에 놓여 있다. 그에 따라 필연적으로 발생하는 내부 결함을 검출하기 위해 초음파탐상을 이용한 비파괴검사가 주로 진행되어 왔다. 하지만 블레이드의 소재 특성으로 인해 음향 신호 분석에 따른 문제점이 발생한다. 따라서 본 연구에서는 풍력 블레이드 인공결함시험편을 제작후, 능동적 광 적외선열화상 비파괴검사 방법을 이용하여 결함의 크기를 정량화하기 위한 실험을 진행하였다. 100 kW 급 블레이드 내부의 결함 크기 정량화를 위해 알루미늄 켈리브레이션 테이프를 사용하였으며, 게재물(inclusion), 디본딩(debonding), 주름(wrinkle) 결함을 삽입하였다. 실험 결과 모두에서 뚜렷한 결함 검출이 가능하였으며, 결함 크기 정량화 결과 debonding 인공 결함 (${\phi}50.0mm$)에서 최대 98.0%의 정확성을 보였다.

• Tribology and Lubricants
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• 제30권2호
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• pp.124-129
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• 2014

The piping system accounts for a large portion of the machinery structure of a plant, and is considered as a very important mechanical structure for plant safety. Accordingly, it is used in most energy plants in the nuclear, gas, and heavy chemical industries. In particular, the piping system for a nuclear plant is generally complicated and uses the reactor and its cooling system. The piping equipment is exposed to diverse loads such as weight, temperature, pressure, and seismic load from pipes and fluids, and is used to transfer steam, oil, and gas. In ultrasound infrared thermography, which is an active thermography technology, a 15-100 kHz ultrasound wave is applied to the subject, and the resulting heat from the defective parts is measured using a thermography camera. Because this technique can inspect a large area simultaneously and detect defects such as cracks and delamination in real time, it is used to detect defects in the new and renewable energy, car, and aerospace industries, and recently, in piping defect detection. In this study, ultrasound infrared thermography is used to detect information for the diagnosis of nuclear equipment and structures. Test specimens are prepared with piping materials for nuclear plants, and the optimally designed ultrasound horn and ultrasound vibration system is used to determine damages on nuclear plant piping and detect defects. Additionally, the detected images are used to improve the reliability of the surface and internal defect detection for nuclear piping materials, and their field applicability and reliability is verified.

• 대한토목학회논문집
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• 제30권1A호
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• pp.53-59
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• 2010

최근 들어 적외선을 이용하여 콘크리트 구조물의 결함 또는 공동 등을 평가하려는 비파괴 연구가 활발하게 진행되고 있으며, 이는 유지관리기법의 중요한 부분을 이루고 있다. 적외선 화상분석(Infrared Thermography)을 콘크리트 표면에 적용할 경우, 콘크리트의 표면온도는 표면을 구성하는 재질과 열적특성(비열, 열전도율, 열전달율)에 따라 그 응답이 다르게 나타나게 된다. 서로 다른 배합을 가지는 시멘트 모르타르에서는 공극률이 다르게 구성되고, 표면에서 공극률의 차이는 열에 노출된 뒤, 냉각되는 과정에서 열적 거동이 다르게 평가된다. 한편 이러한 공극률은 강도 및 염화물 확산계수와 같은 역학적/내구적 특성에 영향을 주기도 한다. 본 연구에서는 외부에서 열을 가하여 측정하는 능동방식(active type)을 이용하여, 표면의 온도변화를 분석하였다. 물-시멘트비 55%와 65%인 시멘트 모르타르 시편을 제작하였으며, 공극률, 압축강도, 염화물 확산계수 등의 물리적 특성값들이 평가되었다. 이후 동일한 실내조건(온도 $20{\sim}22^{\circ}C$, 습도 55-60%)에서 적외선 화상분석 기법을 적용하였다. 시간의 경과에 따라 공극을 많이 포함하는 시편의 경우, 표면 온도가 상대적으로 증가하였으며, 온도가 일정해지는 시점(임계시점)이 단축되고 있음을 확인할 수 있었다. 이러한 특성은 콘크리트와 같이 공극과 골재를 가지고 있는 복합재료의 품질 평가에 적용할 수 있음을 시사한다. 한편 공극률과 실험상수를 고려하여, 공극률에 따라 변화하는 임계시간에 대한 계산식을 제안하였다. 본 논문에서는 시멘트 모르타르의 공극량의 변화에 따른 물리적 변화와 이에 따른 열특성 변화가 논의될 것이다.

• Journal of Biosystems Engineering
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• 제42권3호
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• pp.163-169
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• 2017

Purpose: This study was performed to evaluate the feasibility of using an infrared thermography technique for phenotype analysis of pepper seedlings exposed to a low-temperature environment. Methods: We employed an active thermography technique to evaluate the thermal response of pepper seedlings exposed to low-temperature stress. The temperatures of pepper leaves grown in low-temperature conditions ($5^{\circ}C$, relative humidity [RH] 50%) for four periods (6, 12, 24, and 48 h) were measured in the experimental setting ($23^{\circ}C$, RH 70%) as soon as pepper seedling samples were taken out from the low-temperature environment. We also assessed the visible images of pepper seedling samples that were exposed to low-temperature stress to estimate appearance changes. Results: The greatest appearance change was observed for the low-temperature stressed pepper seedlings that were exposed for 12 h, and the temperature from these pepper seedling leaves was the highest among all samples. In addition, the thermal image of low-temperature stressed pepper seedlings for 6 h exhibited the lowest temperature. Conclusions: We demonstrated that the leaf withering owing to the water deficiency that occurred under low-temperature conditions could induce an increase in temperature in plant leaves using the infrared thermography technique. These results suggested that the time-resolved and averaged thermal signals or temperatures of plants could be significantly associated with the physiological or biochemical characteristics of plants exposed to low-temperature stress.

• 비파괴검사학회지
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• 제35권3호
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• pp.193-199
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• 2015

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.

• 비파괴검사학회지
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• 제30권3호
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• pp.200-206
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• 2010

In ultrasound-excited thermography, the injected ultrasound to an object is transformed to heat and the appearance of defects can be visualized by thermography camera. The advantage of this technology is selectively sensitive to thermally active defects. Despite the apparent simplicity of the scheme, there are a number of experimental considerations that can complicate the implementation of ultrasound excitation thermography inspection. Factors including acoustic horn location, horn-crack proximity, horn-sample coupling, and effective detection range all significantly affect the detect ability of this technology. As conclusions, the influence of coupling pressures between ultrasound exciter and specimen was analyzed, which was dominant factor in frictional heating model.

• 접착 및 계면
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• 제7권4호
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• pp.10-12
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• 2006

The successful use of adhesively bonded parts depends on the defect-free bond of the components. Therefore it is necessary to detect relevant faults and defects in an early state of the production. A 100% test should be pursued, but especially at complicated structures the detection of defects is not easy. Possible testing methods, which show a high potential for the NDT of adhesively bonded parts, are thermography based NDT methods. At present mainly two different procedures of active thermography are being used: Pulse and Lock-In Thermography. With pulse thermography the examined material is warmed up with a short energy pulse (light, eddy current or ultrasonic pulse) and the heat response is recorded after a certain time. The result is an infrared image which indicates material defects in different depths. This paper presents a variety of images showing the capability of Lock-In Thermography to image subsurface defects. Several examples of adhesives joints qualify the ultrasonic Lock-In-Thermography for the in-process quality control for adhesive bonded components.

• 대한전기학회논문지:시스템및제어부문D
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• 제55권2호
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• pp.68-71
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• 2006

Active thermography has been used for several years in the field of remote non-destructive testing. It provides thermal images for remote detection and imaging of damages. Also, it is based on propagation and reflection of thermal waves which are launched from the surface into the inspected component by absorption of modulated radiation. For energy deposition, it use external heat sources (e.g., halogen lamp or convective heating) or internal heat generation (e.g., microwaves, eddy current, or elastic wave). Among the external heat sources, the ultrasound is generally used for energy deposition because of defect selective heating up. The heat source generating a thermal wave is provided by the defect itself due to the attenuation of amplitude modulated ultrasound. A defect causes locally enhanced losses and consequently selective heating up. Therefore amplitude modulation of the injected ultrasonic wave turns a defect into a thermal wave transmitter whose signal is detected at the surface by thermal infrared camera. This way ultrasound thermography(UT) allows for selective defect detection which enhances the probability of defect detection in the presence of complicated intact structures. In this paper the applicability of UT for fast defect detection is described. Examples are presented showing the detection of defects in PCB material. Measurements are performed on various kinds of typical defects in PCB materials (both Cu metal and non-metal epoxy). The obtained thermal image reveals area of defect in row of thick epoxy material and PCB.