Earticle

본 연구는 도로 하부에 설치된 노후 철근콘크리트(RC) 암거를 대상으로 코어 압축강도 기반 비파괴시험(NDT) 보정기법을 적용하여 구조성능 평가의 신뢰성을 검토하였다. 현장 조사 결과 비파괴시험 추정강도가 코어 압축강도 대비 다소 높은 값으로 나타났으며, 보정계수를 적용함으로써 추정값과 실측값 간의 차이를 감소시켜 구조성능 평가의 신뢰성을 향상시킬 수 있음을 확인하였다. 구조물의 전반적인 내구성 상태는 양호하나 일부 특정 구간에서 균열, 누수, 이음부 변형 등의 국부적 손상이 관찰되었으며, 이는 철근콘크리트 암거의 재료 열화보다 지반의 부등침하와 밀접한 관련이 있는 것으로 분석되었다. 향후 연구에서는 다양한 형식의 암거 구조물을 대상으로 장기 모니터링 자료와 지반 거동 분석을 함께 적용하여 비파괴시험 보정기법의 일반화 가능성을 검증할 필요가 있으며, 지반침하에 따른 구조물의 물리적 변화와 구조적 거동 간의 정량적 관계를 고려한 통합 평가 모델이 개발될 경우, 지하시설물의 유지관리 효율성 향상에 기여할 수 있을 것으로 기대된다.

This study evaluates the reliability of structural performance assessment for an aged reinforced concrete (RC) culvert installed beneath a roadway by applying a core compressive strength–based calibration method to nondestructive testing (NDT). Field investigation results showed that the strength estimated from nondestructive testing was slightly higher than the measured core compressive strength. By applying a calibration coefficient, the discrepancy between the estimated and measured strengths was reduced, thereby improving the reliability of the structural performance assessment. Although the overall durability condition of the structure was generally sound, localized defects such as cracks, leakage, and joint displacement were observed in certain sections. These defects were found to be more closely related to differential ground settlement than to the material deterioration of the RC culvert. The development of an integrated assessment model that considers the quantitative relationship between ground settlement and structural behavior is expected to improve the maintenance efficiency of underground infrastructure.

Wood defect is due to the physiological process, genetic factor or affected by the external environment in the growth period. These defects will reduce the utilization value of wood. However, it is very difficult to determine whether there are defects exist, and the degree of defects. Therefore, the effective detection of wood defect information is particularly important. A new wood defect detection method by using RBF neural network was proposed in this paper. The new RBF defect detection method can be divided into the following main steps: (1) Detect wood defects by using X-ray nondestructive testing technology. (2) Deal with defect images by using digital image processing technology. (3) Analyze the information of different defects, and extract the characteristic value of wood defects. (4) Then, the RBF neural network model was constructed. (5) Finally, the RBF neural network is trained with the known samples and simulated with the unknown samples. The experimental results shown that the RBF neural network method was effectively detect the two typical wood defects. This method provides an important theoretical basis to realize the wood defect automatic detection.

The hatching eggs in 4-16 days incubation were from incubator of 38.5℃ to 22℃ for natural cooling and the time series images were acquired by thermal imaging technology. Analyzing the cooling curve and the cooling area and region growing, ellipse fitting, morphological processing and other methods were used to extract eggs region of interest; time series images superposition and contrast enhancement were used to raise the temperature close to the different categories of eggs gray differences; the ratio of gray value≦150 and entire ROI area was seen as characteristic parameters and the decision threshold was set according to minimum error rate Bayes rule. The non-fertilized eggs in incubating 4 days was 89.6% overall recognition and the dead embryo eggs in incubating 16 days was 96.3% overall recognition. Research showed that thermal imaging technology combined image processing technology can achieve non-destructive testing of hatching eggs activity.

원전 부지에 저장중인 방사성폐기물을 처분장에 인도하기 전에 폐기물의 물리·화학적 특성이 인수기준에 적합한지를 검사해야 한다. 검사하는 방법 중 비파괴 검사방법에 대해 조사하였는데, 조사결과 X-ray를 이용한 비파괴 방법을 적용하면 인수검사 항목 중‘드럼내 내용물 검사’,‘ 유리수 및 채움율 정량검사’를 할 수 있는 것으로 나타났다. 본 논문에서는 먼저 X-ray 장비의 원리와 시스템 선정 시 고려해야 할 사항들에 대해 간략하게 살펴 본 후 X-ray 장비를 이용하여 검사해야 할 드럼들의 특성을 분석하였다. 분석한 특성들은 드럼의 종류, 드럼의 규격, 드럼내 내용물의 종류 등이었고 이들 특성자료를 이용하여 검사에 필요한 X-ray 소요에너지를 계산하였다. 계산 결과 드럼 크기가 320 ℓ 이하인 드럼을 검사하기 위한 소요에너지는 3 MeV 이하로 나타났으며 경제성 및 실현가능성 측면에서 450 keV 장비와 3 MeV 장비를 조합하거나 단독으로 사용하는 것이 바람직하고 이 때 450 keV 장비를 이용하여 검사가 가능한 저밀도 드럼수는 2006년 12월 저장기준으로 42,327 드럼, 3 MeV 장비를 이용하여 검사가 가능한 드럼 수는 18,105 드럼으로 나타났다. 검사를 수행하는 주체, 장비 구매 방안 등에 따라 4가지 검사 시나리오를 수립하고 이에 대해 경제성 및 적용 가능성을 분석한 결과 최적의 검사시나리오는 인수기준, 처리 및 처분장 인도에 대한 폐기물 발생자의 정책 등에 영향을 받는 것으로 나타났다. 예를들어,‘ 유리수’,‘ 채움율’에 대한 정량분석과‘내용물 확인’을 모두 해야 할 경우에는 밀도가 상대적으로 낮은 폐기물이 담겨있는‘저밀도 드럼’의 검사를 위해 450 keV 이동형 장비 2대를 구입하여 자체 검사하고‘고밀도 드럼’은 외주로 검사하는 것이 바람직할 수 있다. 반면‘내용물 확인’만을 비파괴 검사항목으로 할 경우에는 450 keV 급 이동형 장비 1대면 연간 13,000 드럼을 검사할 수 있는 것으로 나타났다.

The physical and chemical properties of radioactive waste drums, which have been temporarilystored on site, should be characterized before their shipment to a disposal facility in order to provethat the properties meet the acceptance guideline. The investigation of NDT(Nondestructive Test)method was figured out that the contents in drum, the quantitative analysis of free standing waterand void fraction can be examined with X-ray NDT techniques. This paper describes thecharacteristics of X-ray NDT such as its principles, the considerations for selection of X-ray system,etc. And then, the waste drum characteristics such as drum type and dimension, contents in drum,etc. were examined, which are necessary to estimate the optimal X-ray energy for NDT of a drum.The estimation results were that: ®Á the proper X-ray energy is under 3 MeV to test the drums of320 ߧ and less; ®Ë both X-ray systems of 450 keV and/or 3 MeV might be needed consideringthe economical efficiency and the realization. The number of drums that can be tested with 450keV and 3 MeV X-ray system was figured out as 42,327 and 18,105 drums (based on storage of2006. 12), respectively. Four testing scenarios were derived considering equipment procurementmethod, outsourcing or not, etc. The economical and feasibility assessment for the scenarios wasresulted in that an optimal scenario is dependent on the acceptance guide line, the wastegenerator's policy on the waste treatment and the delivery to a disposal facility, etc. For example, itmight be desirable that a waste generator purchases two 450 keV mobile system to examine thedrums containing low density waste, and that outsourcing examination for the high density drums,if all NDT items such as quantitative analysis for 'free standing water' and 'void fraction', andconfirmation of contents in drum have to be characterized. However, one 450 keV mobile system seems to be required to test only the contents in 13,000 drums per year.

Most manufacturing processes, including welding, create residual stresses. Residual stresses can reduce material strength and cause fractures. For estimating the reliability and aging of a welded structure, residual stresses should be evaluated as precisely as possible. Optical techniques such as holographic interferometry, electronic speckle pattern interferometry (ESPI), Moire interferometry, and shearography are noncontact means of measuring residual stresses. Among optical techniques, ESPI is typically used as a nondestructive measurement technique of in-plane displacement, such as stress and strain, and out-of-plane displacement, such as vibration and bending. In this study, ESPI was used to measure the residual stress on the welded part of butt-welded American Society for Testing and Materials (ASTM) A36 specimens with $CO_2$ welding. Four types of specimens, base metal specimen (BSP), tensile specimen including welded part (TSP), compression specimen including welded part (CSP), and annealed tensile specimen including welded part (ATSP), were tested. BSP was used to obtain the elastic modulus of a base metal. TSP and CSP were used to compare residual stresses under tensile and compressive loading conditions. ATSP was used to confirm the effect of heat treatment. Residual stresses on the welded parts of specimens were obtained from the phase map images obtained by ESPI. The results confirmed that residual stresses of welded parts can be measured by ESPI.

Nondestructive testing activities in Korea are summarized. Past programs and the future direction in NDT research and development are presented. Korean NDT personnel qualification system is compared with the US system. Training program, NDT services, and professional societies are also explained.

이 글에서는 비파괴검사개론에 관하여 알아보았다. 1. 비파괴검사의 의의 1.1 비파괴검사의 역사 1.2 비파괴검사의 원리 1.3 비파괴검사의 목적과 역할 1.3.1 품질관리 1.3.2 생산원가의 절감 1.3.3 품질의 평가 1.3.4 점검 1.4 비파괴검사자의 역할 2. 비파괴검사자의 방법 2.1 방사선투과시험 2.1.1 직접촬영법 2.1.2 투시법 2.1.3 전자사진법 2.1.4 계기법 2.2 초음파탐상시험 2.2.1 음향검사와 초음파탐상 2.2.2 초음파의 성질과 종류 2.2.3 접촉매질 2.2.4 초음파 탐상 방법 2.2.5 초음파 탐촉자 2.3 자기탐상시험 2.3.1 자기탐상 원리 2.3.2 자기탐상 방법 1) 자장측정 탐상법 2) 자기기록 탐상법 3) 탐사 코일법 4) 자분탐상시험 2.3.3 자분탐상시험 2.4 침투탐상시험 2.4.1 침투탐상시험의 원리 2.4.2 침투탐상시험법의 기본 1) 침투탐상시험의 종류 2) 현상체의 종류 2.4.3 침투탐상시험의 장단점 2.5 전자유도시험 (와전류탐상법) 2.5.1 와전류의 발생과 탐지 2.5.2 와전류의 탐지 2.5.3 와전류 탐촉자 2.5.4 와전류 탐상시험의 적용과 장단점.

This paper describes a new magnetization method for non-destructive testing with magneto-optical sensor (denoted as MO sensor) which have the following characteristic : high observation sensitivity, independence of the crack orientation, and precise imaging of a complex crack geometry such as multiple cracks. When a magnetic field is applied normally to the surface of a specimen which is significantly larger than its defects, approximately the same magnetic charge per unit area occurs on the surface of the specimen. If there is a crack in the specimen, magnetic charge per unit area has the same value at the bottom of the crack. The distribution of the vertical component of the magnetic flux density, B$\_$Z/, is almost uniform over the no-crack area (denoted as B$\_$Z,BASE/), while the magnetic flux density is smaller in the surroundings of the crack(denoted as B$\_$Z,CRACK/) If B$\_$Z, BASE/ is a bit larger than the saturated magnetic flux density of the MO sensor (B$\_$s/) , then small magnetic domains occur over the crack area and a large domain over the non-crack area because B$\_$Z,CRACK/ is smaller than B$\_$s/.

An experimental study of an eddy current nondestructive testing system to measure dimensions of cylindrical metallic rods, such as cross-sectional area or diameter, is presented. Impedance characteristics of a solenoid sensor, which are generally based on Maxwell's equations in electromagnetic field, are briefly discussed for inspecting geometrical parameters of the coil sensor and testing materials. A measurement system for detecting the diameter of the metallic rod is implemented. This instrument has capabilities for detecting the sensor output signals and estimating demensions of the testing material, continuously. As a result, it was shown that the eddy current sensor with an encircling coil could estimate the diameter of metallic rod. The implemented measurement system gives accurate information for inspecting the dimension of conducting rod with good sensitivity.

In this paper, the necessity of developing effective nondestructive testing and monitoring techniques for the evaluation of structural integrity and performance is described. The evaluation of structural integrity and performance is especially important when the structures and subject to abrupt external forces such as earthquake. A prompt and extensive inspection is required over a large area of earthquake-damaged zone. This evaluation process is regarded as a part of performance-based design. In the paper, nondestructive testing and monitoring techniques particularly for concrete structures are presented as methods for the evaluation of structural integrity and performance. The concept of performance-based design is first defined in the paper followed by the role of evaluation of structures in the context of overall performance=based design concept. Among possible techniques for the evaluation, nondestructive testing methods for concrete structures using radar and a concept of using fiber sensor for continuous monitoring of structures are presented.

Ground Penetrating Radar (GPR) with 1 GHz antenna has been used to locate a steel bar embedded inside laboratory-prepared mortar specimens. Four mortar specimens are made with the dimensions of 100 cm (length) x 100 cm (width) x 14 cm (depth). One specimen had no bars and the other three specimens had a Dl9 steel bar at 4, 6. and 8 cm depth. As a part of the experimental work, the dielectric constants of mortar specimens are measured during curing. As the curing time increased. the dielectric constant decreased with decreasing moisture content inside the specimen. The steel bar embedded inside mortar specimens has been successfully identified in all three cases. The results using signal processing scheme developed in this study significantly improved the output of a commercially available radar system.

The spin valve tunneling magnetoresistance (SV-TMR) sensor performance is analyzed using Stoner-Wohlfarth model for the detection of eddy current signals in nondestructive testing applications. The SV-TMR response in terms of the applied AC magnetic field dominantly generates the second harmonic amplitude in hard axis direction. The second harmonic eddy current signal detection using SV-TMR sensor shows higher performance than that of the coil sensor at lower frequencies. The SV-TMR sensor with high sensitivity gives a good solution to improve the low frequency performance in comparison with the inductive coil sensors. Therefore, the low frequency eddy current techniques based on SV-TMR sensors are specially useful in the detection of hidden defects, and it can be applied to detect the deeply embedded flaws or discontinuities in the conductive materials.

To ensure the reliability of ultrasonic nondestructive testing techniques for modern structural materials, the effects of anisotropy and inhomogeneity and the influence of non-planar component geometries on ultrasonic wave propagation have to be taken into account. In this article, fundamentals and applications of two analytical approaches to three-dimensional elastic beam field calculation are presented. Results for both isotropic materials including curved interfaces and for anisotropic media like composites are presented, covering field profiles for various types of transducers and the modeling of time-dependent rf-signals.

지능형 초음파 탐상 시스템은 재래식 초음파 탐상시험에서 주된 논란의 대상이 되는 검사의 객관성과 신뢰성, 그리고 일반화된 검사자료의 데이터베이스화 문제를 해결할 수 있는 해법으로 제시 되었다. 또한 이 시스템은 검사의 자동화(혹은 간이자동화)를 통해 검사자에 의해 수작업으로 작성되던 피검체 및 결함관련 정보를 자동으로 계산하고 데이터베이스화함으로써, 열악한 검사환경에서도 최선의 능률을 제공할 수 있는 기반을 제공한다. 본 논문에서는 지능형 시스템의 개발을 위해 필요한 요소기술과 개발된 시스템의 전반에 관하여 논한다.

음향방출기술(acoustic emission technology)은 종래의 기존 비파괴검사법과는 달리 가동중인 설비의 건전성을 평가할 수 있으며 실시간으로 설비 상태의 진단이 가능한 실시간 감시기법이다. 즉 기존 비파괴검사법과는 달리 가동중인 설비에 대해 원격으로 결함을 탐지하고 결함 위치를 판정할 수 있는 연속감시 기능을 가진 비파괴 신기술로 최근 연구개발이 활발히 진행되고 있는 방법이다. 이러한 장점 때문에 대형 산업설비의 각종 기기들에 대한 감시 및 진단에 활용하고 있으며, 그 활용도가 점점 확대되고 있는 추세에 있다. 특히 종합적인 산업설비로 구성되어 있는 발전설비의 진단과 감시에 가장 효과적인 방법이라 할 수 있겠다. 본 논문에서는 원자력 화력 수력발전소 등의 발전설비에 대해 현재 적용중인 음향방출기술과 새로운 적용기술에 대해 서술하였다.

Diagnosis f structural integrity is the basis for correct treatment of and countermeasures against progressive structural abnormalities. An exact diagnosis is at present the most reliable means for determining the soundness of structures during power plant operations. Acoustic emission(AE) technology has recently strengthened its application base, and practitioners' understanding of the technique's fundamentals. This paper presents the results of a survey and assessment on AE monitoring applications in nuclear, fossil and hydraulic power plant. The main objective of this paper was to obtain information on various applications of AE technology in electric power plant.