파괴 및 비파괴 검사를 이용한 노후 교량의 교각 두부 조사

김태완,홍성남,한경봉,박선규 한국구조물진단유지관리공학회 2008 한국구조물진단유지관리공학회 논문집 Vol.12 No.2

비파괴 검사 기술은 현존하는 구조물의 진단을 위해 빈번하게 사용되었고, 사용되고 있다. 이러한 검사들로 본 연구에서 사용된 검사로는 육안적 검사, 해머 사운딩, 슈미트 해머, 그리고 토모그래피를 포함한 초음파 검사 등이 있다. 완료된 비파괴 검사 결과는 국부적으로 수행될 파괴검사의 위치를 산정하는데 사용되었다. 그래서, 압축강도, 염화물, 암석 분류 실험으로 구성된 파괴검사를 수행하였다. 비파괴검사와 파괴검사의 결과들을 종합하여 교각두부의 건전성을 평가하였다. 본 논문에서는 파괴 검사와 비파괴 검사의 적용과 해석, 그리고 이어지는 보수, 보강, 유지 결정 과정에 대해서 나타내었다. Nondestructive testing techniques have been historically and commonly used to evaluate the quality of existing concrete structures. The techniques utilized included visual inspection, hammer sounding, Schmidt hammer rebounding, and ultrasonic pulse velocity testing including tomographic imaging. Results of the nondestructive tests were used to determine areas to be tested with local destructive tests. These tests included concrete compressive strengths, chloride testing, and petrographic testing. The overall results indicate that inside core of each of the pier caps are healthy. On all of the pier caps, extensive exterior concrete layer rehabilitation needs to be completed. This paper shows the application and interpretation of common nondestructive testing techniques and the consequent repair, rehabilitation, maintenance decisions and safety assesment.

보통 콘크리트강도형 간이 인발시험법에 대한 제안

고훈범(Ko, Hune-Bum),차은호(Cha, Eun-Ho),오강환(Oh, Kang-Hwan) 대한건축학회 2017 大韓建築學會論文集 : 構造系 Vol.33 No.4

The pullout test certified by the American Society for Testing and Materials(ASTM) is known to be more reliable for estimating concrete strength under construction of concrete structures than other nondestructive testing(NDT) methods such as rebound number, penetration resistance, break-off, and ultrasonic pulse velocity. However, existing equipment needed for the pullout test, known as Lok test or Capo test, require several complex installation steps and expensive loading systems including load cell. We propose a simplified pullout test composed of a break-off type bolt, a standard bolt with a groove on the shaft, as an insert, an insert nut, and a pullout instrument without load cell. This simplified pullout test would be more beneficial due to its low cost, simplicity and convenience. To verify the advantages of the simplified pullout test, three wall specimens were tested with two types of concrete strength, 15MPa and 24MPa, using the Lok test, a general pullout test including load cell, and a simplified pullout test. It was found that the pullout force was very similar in comparison with compressive strength. Therefore, it was verified that the simplified pullout test can be used to replace the Lok test. The prediction equation of groove diameter with the concrete strength was derived as y=6.01x-17.17(y=concrete strength, x=the groove diameter of break-off bolt) through regression analysis. An allowable error can be easily maintained within the specified value if appropriate safety factors are studied and added to the prediction equation.

Patterns of Resistographs for Evaluating Deteriorated Structural Wood Members

LEE, Jun Jae,KIM, Kwang Chul,BAE, Mun Sung 한국목재공학회 2003 목재공학 Vol.31 No.6

The density and strength of wood is affected by degradations and defects, such as voids and knots. Old wooden structures such as traditional cultural properties have been deteriorated by these types of defects. They were evaluated by a visual observation that is difficult to evaluate the inner deterioration in structures. In this study, three nondestructive testing techniques were investigated to detect the wooden structural members. Ultrasonic stress wave tests, drilling resistance tests and visual inspections were used to examine the structural wood members. Patterns of Resistograph using by drilling resistance tests could indicate the features of internal wood such as voids, knots, decay, fungi, and so on. The technique just like as ultrasonic stress wave tests, however, difficult to detect exactly area where small amounts of internal deterioration in logs are. In spite of results of ultrasonic stress wave test, the internal deterioration of wooden structural members could be evaluated by the relationship between ultrasonic stress wave tests and drilling resistance tests.

Application of a compressed-sensing (CS)-based deblurring scheme to digital tomosynthesis (DTS) for improved x-ray nondestructive testing: Simulation and experimental studies

Kim, K.S.,Park, S.Y.,Kim, G.A.,Cho, H.S.,Je, U.K.,Park, Y.O.,Park, C.K.,Lim, H.W.,Woo, T.H.,Park, S.M.,Lee, H.W.,Seo, C.W. Applied Science Publishers 2016 Optics and lasers in engineering Vol.86 No.-

In this work, we investigated a compressed-sensing (CS)-based deblurring scheme for image deblurring of high accuracy in digital tomosynthesis (DTS). We implemented the proposed deblurring scheme and performed a systematic simulation to demonstrate its viability for improved x-ray nondestructive testing. We also performed an experiment by using a table-top setup which consists of an x-ray tube (90kV<SUB>p</SUB>, 6mAs) and a CMOS-type flat-panel detector having a 198-μm pixel resolution. In both the simulation and the experiment, 51 projection images were taken with a tomographic angle range of θ=60<SUP>o</SUP> and an angle step of Δθ=1.2<SUP>o</SUP> and then deblurred by using the proposed algorithm before performing the common filtered-backprojection (FBP)-based DTS reconstruction. Our results indicate that the proposed deblurring scheme appears to be effective for the blurring problems in DTS and is applicable to improve the image characteristics in the present x-ray nondestructive testing.

와전류검사 기술을 적용한 가압중수로 원전 압력관 비파괴검사

이희종(Hee-Jong Lee),최성남(Sung-Nam Choi),조찬희(Chan-Hee Cho),유현주(Hyun-Joo Yoo),문균영(Gyoon-Young Moon) 한국비파괴검사학회 2014 한국비파괴검사학회지 Vol.34 No.3

중수로 원자로는 한 개의 원자로용기로 구성된 경수로와는 달리 약 380여개의 연료채널(fuel channel)로 구성되어 있다. 연료채널을 구성하는 압력유지 기기인 압력관(pressure tube)은 지르코니움 합금(Zr-2.5wt% Nb) 재질로서 치수는 내경이 103.4 mm, 두께가 약 4.19 mm, 길이가 6.36 m인 튜브 형태의 관이다. 압력관은 내부에 핵연료 다발과 냉각재가 내장되며 압력관의 기능은 연료를 지지하고 열수송 유체인 중수(D₂O)를 이송한다. 압력관의 단순한 기하학적인 형상으로 인하여 자동화 비파괴검사가 가능하고 접근성이 우수하다. 연료 채널은 경수로형 원전과 동일하게 설치전과 운전중에 원자력안전위원회 법령 요건에 따라 주기적으로 엄격한 비파괴검사를 수행하여 건전성을 확인한다. 연료채널의 주기적 비파괴검사에는 초음파탐상 및 와전류탐상검사 기법을 적용한 체적 비파괴검사 기술이 적용된다. 이중에서 와전류탐상검사 기법은 초음파탐상검사에서 검출된 결함의 확인을 위한 보충검사기술로 적용되고 있지만 표면결함에 대한 검출능이 초음파탐상검사 기법보다 우수한 장점을 가지고 있다. 본 논문에서는 압력관 내부 표면 비파괴검사에 적용되고 있는 와전류탐상검사 기술의 압력관 내면에 발생할 수 있는 결함의 검출 및 깊이 측정 특성에 대한 연구결과를 기술하였다. 즉, 와전류검사 기술은 압력관 내면에 발생할 수 있는 아주 미세한 결함을 매우 우수한 분해능으로 검출할 수 있으므로 초음파탐상검사 결과 확인을 위한 보충기술로서 매우 유용하지만, 결함의 깊이 측정은 오차가 매우 크게 발생하므로 결함 깊이 측정에는 적합하지 않고 오직 표면결함 검출에만 적용하는 것이 바람직하다. A pressurized heavy water reactor (PHWR) core has 380 fuel channels contained and supported by a horizontal cylindrical vessel known as the calandria, whereas a pressurized water reactor (PWR) has only a single reactor vessel. The pressure tube, which is a pressure-retaining component, has a 103.4 mm inside diameter × 4.19 mm wall thickness, and is 6.36 m long, made of a zirconium alloy (Zr-2.5 wt% Nb). This provides support for the fuel while transporting the D₂O heat-transfer fluid. The simple tubular geometry invites highly automated inspection, and good approach for all inspection. Similar to all nuclear heat-transfer pressure boundaries, the PHWR pressure tube requires a rigorous, periodic inspection to assess the reactor integrity in accordance with the Korea Nuclear Safety Committee law. Volumetric-based nondestructive evaluation (NDE) techniques utilizing ultrasonic and eddy current testing have been adopted for use in the periodic inspection of the fuel channel. The eddy current testing, as a supplemental NDE method to ultrasonic testing, is used to confirm the flaws primarily detected through ultrasonic testing, however, eddy current testing offers a significant advantage in that its ability to detect surface flaws is superior to that of ultrasonic testing. In this paper, effectiveness of flaw detection and the depth sizing capability by eddy current testing for the inside surface of a pressure tube, will be introduced. As a result of this examination, the ET technique is found to be useful only as a detection technique for defects because it can detect fine defects on the surface with high resolution. However, the ET technique is not recommended for use as a depth sizing method because it has a large degree of error for depth sizing.

비파괴평가기술을 이용한 유리기지 복합재료의 손상 모니터

김정국(Jeongguk Kim),백광선(Kwangsun Baik),김원경(Weon-Kyong Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

Two types of nondestructive evaluation (NDE) methods, such as infrared (IR) thermography and acoustic emission (AE) techniques, were used for the damage analyses during tensile testing of Nextel fiber reinforced Blackglas matrix composites. During tensile testing, AE sensors and an IR camera were used for in-situ monitoring of the progressive damages of the samples. AE provided the amounts of damage evolution in terms of the AE intensity and/or energy, and the IR camera was used to obtain the temperature changes during the test. Microstructural characterization using scanning electron microscopy (SEM) was performed to investigate the fracture mechanisms and modes of Nextel/Blackglas samples. Moreover, SEM characterization results provided the substantial evidence of failure behavior, and showed comparable results with NDE signatures.

인쇄회로기판 검사를 위한 단일조사 이중에너지 엑스선 영상기법의유용성에 관한 연구

김승호,김동운,김대천,김준우,박지웅,박은평,김진우,김호경 한국방사선산업학회 2015 방사선산업학회지 Vol.9 No.3

A single-shot dual-energy x-ray imaging technique has been developed using a sandwichdetector by stacking two detectors, in which the front and rear detectors respectively producerelatively lower and higher x-ray energy images. Each detector layer is composed of a phosphorscreen coupled with a photodiode array. The front detector layer employs a thinner phosphorscreen, whereas the rear detector layer employs a thicker phosphor screen considering thequantum efficiency for x-ray photons with higher energies. We have applied the proposed methodinto the inspection of printed circuit boards, and obtained dual-energy images with backgroundclutter suppressed. In addition, the single-shot dual-energy method provides sharper-edge imagesthan the conventional radiography because of the unsharp masking effect resulting from the useof different thickness phosphors between the two detector layers. It is promising to use the singleshotdual-energy x-ray imaging for high-resolution nondestructive testing. For the reliable use ofthe developed method, however, more quantitative analysis is further required in comparisonswith the conventional method for various types of printed circuit boards.

Monitoring Fatigue Damage Evolution in Ceramic Matrix Composites

김정국(Jeongguk Kim),권성태(Sung-Tae Kwon) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.8

Infrared (IR) thermography nondestructive evaluation (NDE) technique was used for the monitoring of high-cycle fatigue damage in ceramic matrix composites (CMCs). The CMCs system was Nicalon fiber reinforced calcium aluminosilicate (CAS) glass-ceramic matrix composites designated as Nicalon/CAS. During fatigue testing, an IR camera was used for in-situ monitoring of progressive damages of Nicalon/CAS samples. Stress versus cycles to failure (S-N) curves were generated for predicting the lifetime of Nicalon/CAS composites, and the IR camera monitored the temperature changes during high-cycle fatigue testing. Microstructural characterizations using scanning electron microscopy (SEM) were performed to investigate fracture modes and failure mechanisms of Nicalon/CAS samples. In this study, the NDE technique was used to facilitate a better understanding of fracture mechanisms of Nicalon/CAS composites during high-cycle fatigue.

Electromagnetic nondestructive testing at high lift-off using a magnetic image conduit

이진이,Jongwoo Jun,김정민,Minhhuy Le 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.5

To protect sensors from the extreme environments, such as, heat, moisture, pollution and radiation, cracks must be inspected for; this can be done by measuring the distribution of magnetic fields at high lift-off through nondestructive electro-magnetic testing. However, as the intensity of an electro-magnetic field is inversely proportional to the square of the lift-off, it becomes increasingly difficult to effective inspect a crack as the lift-off increases. In this paper, a magnetic image conduit to minimize the intensity loss of an electro-magnetic field at high lift-off is proposed, and the effectiveness of a conduit for magnetic imaging is verified by means of both theoretical and experimental approaches.

초음파를 이용한 바이오시스템 계측

김기복,김만수 한국산업식품공학회 2004 산업 식품공학 Vol.8 No.1

Ultrasonic nondestructive testing is a versatile and successful technique that can be applied to a wide variety of material analysis applications. The state-of-art technology of sensors, microprocessors, and methods for signal analysis has been promising new possibilities for the application of ultrasonic techniques to non-destructive and non-hazardous testings. Ultrasonic material analysis is based on a simple principle of physics. That is, the motion of a wave is affected by the medium through which it travels. Thus, changes in one or more of four measurable parameters associated with the passage of a elastic wave through a material - time of flight, attenuation, scattering, and frequency content - would be correlated with changes in physical properties such as hardness, elastic modulus, density, homogeneity or particle size and structure. Ultrasonic techniques can be applied to various biosystems such as food, agricultural products and biological materials, owing to their nondestructive nature. In this paper, the principle of ultrasonic technique was briefly described and its applications to biosystems were reviewed.