• 문화기술의 융합
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• 제10권3호
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• pp.845-849
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• 2024

현재 도시철도 레일의 노후화로 인한 레일표면결함이 증가하고 있으나 국가에서 제정된 궤도성능평가에 관한 세부지침에서 레일표면손상을 기술자의 육안, 간단한 측정 도구로 점검을 수행하는 실정이다. 주기적인 선로순회작업 및 육안점검을 통해 레일표면의 결함을 발견하는 것은 매우 중요하다. 그러나 점검자의 주관적 판단에 의해 레일표면의 결함의 경중을 평가하는 것은 레일 내부의 손상을 예측하기에 상당한 제약이 따른다. 본 연구에서는 레일표면손상에 따른 레일내부 균열특성에 관한 연구로서 현장측정에서는 레일표면 손상개소를 선정하여 가속구간 및 제동구간의 노후레일 시료를 채취하여 레일표면손상 상태를 평가하고자 전자주사현미경(SEM)을 이용하여 균열특성을 분석하였다. 분석결과, 주행 중인 열차로 인해 발생하는 균열 메커니즘과 레일표면방향으로 올라오는 각도로 균열이 발생하는 가속구간의 균열특성을 실험적으로 입증하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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• pp.183-186
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• 1995

Most defects in the cement concrete pavement take place mainly on the joints. These corner cracks don't happen as often as others relatively. it happens continuously. In order to analyze the structural behavior of the corner cracks, The finite element structural analysis was performed on the representative section of the cement concrete pavements using JSLAB which uses FEM analysis method. On plain cement concrete pavements, The result shows that loading not only on the joints but also on the center of slab brings out the maximum stress on the corner of slab and it is expected to make the corner cracks.

• Korean Chemical Engineering Research
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• 제52권5호
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• pp.587-591
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• 2014

고급 홍삼의 생산 수율을 증가시키는 제어 방법에 관한 실험을 수행하였다. 수삼에서 홍삼을 만드는 과정 중 수증기로 수삼을 찌는 증삼 공정에서 동체균열, 내공, 내백 등이 발생하는데 이는 홍삼의 품질을 저하시키는 원인이 된다. 고급 홍삼의 수율을 증가시키기 위해서는 이런 불량 요인을 최소화하는 방법이 필요하다. 최근까지 대부분의 증삼 공정의 제어는 증삼 과정의 필수 인자인 온도만을 조절하거나 온도와 압력을 동시에 조절하여 제어하는 방법이 연구되었다. 그러나 이는 불량 요인을 최소화하는 목적에 적합하지 못한 것으로 보인다. 이와 달리, 본 연구에서는 기존의 홍삼 제조 방식을 토대로 $96{\sim}99^{\circ}C$의 온도를 유지하면서 수삼의 무게 제어를 통하여 불량 요인을 최소화하는 제어 방법을 제시한다. 무게 제어를 적용한 실험 결과 증삼 과정 후 수삼의 동체균열의 불량요인이 줄어드는 것을 확인할 수 있었다.

• 한국건설관리학회논문집
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• 제23권5호
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• pp.23-33
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• 2022

공동주택의 하자소송 금액에서 가장 많은 비율을 차지하고 있는 균열하자는 하자판정 기준이 명확하지 않아 판결에 따라 하자에 관한 판단이 엇갈리고 있다. 균열하자 판결금액 대부분을 차지하는 층간균열은 균열의 폭이나 상태와 관계없이 모두 하자로 판정되는 추세이며, 보수공법 또한 대부분 일률적으로 정해지고 있다. 이는 균열하자 판정의 기준이 되는 국토교통부의 하자판정기준과 법원에서 기준을 삼는 건설감정실무의 기준이 일치하는 않는 문제에서 출발한다. 법령의 개정과 법원감정실무지침서의 개정 등을 통해 모든 이해관계자가 적용할 수 있는 하자판정 기준의 수립이 필요하다. 또한, 층간균열 보수공법 기준은 층간균열의 폭과 상태에 따라 공법을 적용할 필요성이 있다. 균열에 대한 하자판정과 보수공법적용을 합리화한다면 소송에만 의존하는 현재의 하자분쟁 추세를 바꿀 수 있는 계기가 될 수 있을 것이다.

• International Journal of Precision Engineering and Manufacturing
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• 제5권3호
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• pp.11-18
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• 2004

In this paper, the classification of artificial defects in semiconductor packages is studied by using pattern recognition technology. For this purpose, the pattern recognition algorithm includes the user made MATLAB code. And preprocess is made of the image process and self-organizing map, which is the input of the back-propagation neural network and the dimensionality reduction method, The image process steps are data acquisition, equalization, binary and edge detection. Image process and self-organizing map are compared to the preprocess method. Also the pattern recognition technology is applied to classify two kinds of defects in semiconductor packages: cracks and delaminations.

• Structural Engineering and Mechanics
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• 제52권5호
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• pp.1019-1032
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• 2014

Rails are key elements in railway superstructure since these elements receive directly the train load transmitted by the wheels. Simultaneously, rails must provide effective stress transference to the rest of the track elements. This track element often deteriorates as a consequence of the vehicle passing or manufacturing imperfections that cause in rail several defects. Among these rail defects, transverse cracks highlights and are considered a severe pathology because they can suddenly trigger the rail failure. This study is focused on UIC-60 rails with transverse cracks. A 3-D FEM model is developed in ANSYS for the flawless rail in which conditions simulating the crack presence are implemented. To account for the inertia loss of the rail as a consequence of the cracking, a reduction of the bending stiffness of the rail is considered. The numerical models have been calibrated using the first four bending vibration modes in terms of frequencies. These vibration frequencies have been obtained using the Experimental Modal Analysis technique, studying the changes in the modal parameters of the rails induced by the crack and comparing the results obtained by the model with experimental results. Finally, the calibrated and validated models for the single rail have been implemented in a complete railway ballasted track FEM model in order to study the static influence of the cracks on the rail deflection caused by a load passing.

• 한국철도학회논문집
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• 제10권1호
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• pp.1-6
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• 2007

Railway wheels in service are regularly checked by ultrasonic testing, acoustic emission and eddy current testing method and so on. However, ultrasonic testing is sometimes inadequate for sensitively detecting the cracks in railway wheel which is mainly because of the fact of crack closure. Recently, many researchers have actively fried to improve precision for defect detection of railway wheel. The development of a nondestructive measurement tool for wheel defects and its use for the maintenance of railway wheels would be useful to prevent wheel failure. The induced current focusing potential drop(ICFPD) technique is a new non-destructive tasting technique that can detect defects in railway wheels by applying on electro-magnetic field and potential drops variation. In the present paper, the ICFPD technique is applied to the detection of surface and internal defects for railway wheels. To defect the defects for railway wheels, the sensor for ICFPD is optimized and the tests are carried out with respect to 4 surface defects and 6 internal defects each other. The results show that the surface crack depth of 0.5 mm and internal crack depth of 0.7 mm in wheel tread could be detected by using this method. The ICFPB method is useful to detect the defect that initiated in the tread of railway wheels

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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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.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1996년도 추계학술대회 논문집
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• pp.444-449
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• 1996

The semiconductor, which is precision product, requires many inspection processes. The surface conditions of the semiconductor chip affect on the functions of the semiconductors. The defects of the chip surface are cracks or voids. As general inspection method requires many inspection procedure, the inspection system which searches immediately and precisely the defects of the semiconductor chip surface is required. We suggest the detection algorithm for inspecting the surface defects of the semiconductor surface. The proposed algorithm first regards the semiconductor surface as random texture and point spread function, and secondly presents the character of texture by linear estimation theorem. This paper assumes that the gray level of each pixel of an image is estimated from a weighted sum of gray levels of its neighbor pixels by linear estimation theorem. The weight coefficients are determined so that the mean square error is minimized. The obtained estimation window(two-dimensional estimation window) characterizes the surface texture of semiconductor and is used to discriminate the defects of semiconductor surface.

• 대한기계학회논문집A
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• 제21권7호
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• pp.1097-1105
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• 1997

Because of the existence of stress interaction field made by other defects and propagating cracks, the structure may be weakened. Therefore in this study, the crack behavior in the interaction field made by two different cracks is studied experimentally. In the experiment, vertical distance between two cracks and applied stress are varied to make different stress interacted field. In addition, the effect of plastic zone is used to examine crack propagation path and rate. Three types of crack propagation in the interacted field were found, and crack propagating path and rate of two cracks were significantly changed according to different applied stress as each crack propagates. And the results are attributed to the effect of the size and shape of the plastic zone.