• Title/Summary/Keyword: Internal defects

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VISUALIZATION OF INTERNAL DEFECTS IN PLATE-TYPE NUCLEAR FUEL BY USING NONCONTACT OPTICAL INTERFEROMETRY

  • Park, Seung-Kyu;Park, Nak-Gyu;Baik, Sung-Hoon;Kang, Young-June
    • Nuclear Engineering and Technology
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    • v.45 no.3
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    • pp.361-366
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    • 2013
  • An imaging technique to visualize the internal defects in a plate-type nuclear fuel specimen was developed by using an active optical interferometer for a nondestructive quality inspection. A periodic thermal wave having a sinusoidal intensity pattern induced a periodical strain variation for the specimen. The varying strain image was acquired using an optical laser interferometer. The strain distribution over the internal defects will be distorted in an acquired strain image because a part of the thermal wave will be reflected from these defects during propagation. In this paper, internal defects were efficiently visualized by sequentially accumulating the extracted defect components. The experimental results confirmed that the developed visualization system can be a valuable tool to detect the internal defects in plate-type nuclear fuel.

Shape-Simplification Analysis Model for Fatigue Life Prediction of Casting Products Considering Internal Defects (내부 결함을 고려한 주조 제품의 피로수명 예측을 위한 결함 형상단순화 해석모델)

  • Kwak, Si-Young;Kim, Hak-Ku
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.10
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    • pp.1243-1248
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    • 2011
  • Internal defects are a major concern in the casting process because they have a significant influence on the strength and fatigue life of casting products. In general, they cause stress concentration and can be a starting point of cracks. Therefore, it is important to understand the effects of internal defects on mechanical properties such as fatigue life. In this study, fatigue experiments on tensile specimens with internal defects were performed. The internal defects in the casting product were scanned by an industrial CT scanner, and its shape was simplified by ellipsoidal primitives for the structural and fatigue analysis. The analysis results were compared with experimental results for casting products with internal defects. It was demonstrated that it is possible to consider internal defects of casting products in stress and fatigue analysis. The proposed method provides a tool for the prediction of the fatigue life of casting products and the investigation of the effects of internal defects on mechanical performance.

Nondestructive Internal Defects Evaluation for Pear Using NIR/VIS Transmittance Spectroscopy

  • Ryu, D.S.;Noh, S.H.;Hwnag, H.
    • Agricultural and Biosystems Engineering
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    • v.4 no.1
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    • pp.1-7
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    • 2003
  • Internal defects such as browning of the flesh and blackening and rot of the ovary of pear can be easily developed because of the inadequate environmental conditions during the storage and distribution of fruit. The quality assurance system for the agricultural product is to be settled in Korea. All defected agricultural products should be excluded prior to the distribution to enhance the commercial values. However, early stage on-line defect detection of agricultural product is very difficult and even more difficult in a case of the internal defects. The goal of this research is to develop a system that can detect and classify internal defects of agricultural produce on-line using VIS/NIR transmittance spectroscopy. And Shingo pear, which is one of the famous species of Korean pear, was used for the experiment. Soft independence modeling of class analogy (SIMCA) algorithm was employed to analyze the transmittance spectroscopic data qualitatively. On-line classification system was constructed and classification model was developed and validated. As a result, the correct classification rate (CCR) using the developed classification model was 96.1 %.

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Research on the Non-Contact Detection of Internal Defects in a Rail using Ultrasonic Waves (비접촉 초음파 방식의 철도레일 내부결함 검출에 관한 연구)

  • Han, Soon Woo;Cho, Seung Hyun;Kim, Joon Woo;Heo, Tae Hoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.617-625
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    • 2012
  • Non-contact detection of internal defects in a rail using ultrasonic waves is discussed in this paper. Cracks in a rail may be a cause of a serious railway accident such as derailment if left undetected. Concurrent rail inspection method based on ultrasonic testing using piezoelectric transducers has several limitations as it should keep physical contact with the rail. This work suggests a non-contact detection of internal defects in a rail using ElectroMagnetic Acoustic Transducers (EMAT) which can produce and measure ultrasonic waves in a rail without any couplant. The EMATs for rail inspection are designed and fabricated and their working performance is verified through a series of experiments on various types of internal defects in test rails. The effect of lift-off between the transducers and the rail on the generated signals is also discussed.

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Internal Defects Inspection of Die-cast Parts via the Comparison of X-ray CT Image and CAD Data (CAD 데이터 및 엑스레이 CT이미지 비교를 통한 다이캐스팅 부품의 내부 결함 검사방법)

  • Hong, Gyeong Taek;Shim, Jae Hong
    • Journal of the Semiconductor & Display Technology
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    • v.17 no.1
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    • pp.27-34
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    • 2018
  • Industrially, die-casting products are formed through casting, and so the methods to inspect the defects inside them are very restrictive. External inspection methods including visual inspection, sampling judgment, etc. enables researchers to inspect possible external defects, but x-ray inspection equipment has been generally used to inspect internal ones. Recently, they have been also applying three-dimensional internal inspections using CT equipment. However, they have their own limitations in applying to the use of industrial inspection due to limited detection size and long calculation time. To overcome the above problems, this paper has suggested a method to inspect internal defects by comparing the CAD data of the product to be inspected with the 3D data of the CT image. In this paper, we proposed a method for fast and accurate inspection in three dimensions by applying x-ray inspection to find internal defects in industrial parts such as aluminum die casting products. To show the effectiveness of the proposed method, a series of experiments have been carried out.

Research on the Non-Contact Detection of Internal Defects in a Rail Using Ultrasonic Waves (비접촉 초음파 방식의 철도레일 내부결함 검출에 관한 연구)

  • Han, Soon-Woo;Cho, Seung-Hyun;Kim, Joon-Woo;Heo, Tae-Hoon
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.22 no.10
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    • pp.1010-1019
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    • 2012
  • Non-contact detection of internal defects in a rail using ultrasonic waves is discussed in this paper. Cracks in a rail may be the cause of a serious railway accident such as derailment if left undetected. Concurrent rail inspection method based on ultrasonic testing using piezoelectric transducers has several limitations as it should keep physical contact with the rail. This work suggests a non-contact detection of internal defects in a rail using ElectroMagnetic Acoustic Transducers (EMAT) which can produce and measure ultrasonic waves in a rail without any couplant. The EMATs for rail inspection are designed and fabricated and their working performance is verified through a series of experiments on various types of internal defects in test rails. The effect of lift-off between the transducers and the rail on the generated signals is also discussed.

Development of Digital-Image-Correlation Technique for Detecting Internal Defects in Simulated Specimens of Wind Turbine Blades (풍력 블레이드 모의 시편의 내부 결함 검출을 위한 이미지 상관법 기술 개발)

  • Hong, Kyung Min;Park, Nak Gyu
    • Korean Journal of Optics and Photonics
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    • v.31 no.5
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    • pp.205-212
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    • 2020
  • In the performance of a wind turbine system, the blades play a vital role. However, they are susceptible to damage arising from complex and irregular loading (which may even cause catastrophic collapse), and they are expensive to maintain. Therefore, it is very important both to find defects after blade manufacturing is completed and to find damage after the blade is used for a certain period of time. This study provides a new perspective for the detection of internal defects in glass-fiber- and carbon-fiber-reinforced panels, which are used as the main materials in wind turbine blades. A gap or fracture between fiber-reinforced materials, which may occur during blade manufacturing or operation, is simulated by drilling a hole 5 mm in diameter in the middle layer of the laminated material. Then, a digital-image-correlation (DIC) method is used to detect internal defects in the blade. Tensile load is applied to the fabricated specimen using a tensile tester, and the generated changes are recorded and analyzed with the DIC system. In the glass-fiber-reinforced laminated specimen, internal defects were detected from a strain value of 5% until the end of the experiment, while in the case of the carbon-fiber-reinforced laminated specimen, internal defects were detected from 1% onward. It was proved using the DIC system that the defect was detected as a certain level of strain difference developed around the internal defects, according to the material properties.

Analysis of Impact Behavior of Al-Alloy Castings Considering Internal Defects (내부 결함을 포함한 주조 알루미늄 합금의 충격 거동 해석)

  • Jo, Seong-Woo;Kwak, Si-Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.36 no.12
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    • pp.1599-1604
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    • 2012
  • In general, internal defects, such as shrinkage in casting, cause stress concentration and can be a starting point for cracks. Therefore, it is important to understand the effects of internal defects on the mechanical properties including the impact behavior. This study aim is to evaluate the effects of internal casting defects on the impact performance of Al-alloy castings. Both an experimental method and computational analysis were used to achieve the research objective. The internal defects in the casting were scanned using an industrial CT scanner, and their shape was simplified using ellipsoidal primitives for impact analysis. The good agreement between the experimental and computer simulation results verified the reliability of the proposed computational method for the FEA of casting components with internal defects.

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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    • 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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