• Journal of Aerospace System Engineering
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• v.18 no.3
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• pp.17-26
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• 2024

Aircraft engines are exposed to high temperatures, high pressures, and stress caused by the rotation of the turbine shaft during flight. These loads can result in microcracks both on the inside and outside surfaces of the structure. Consequently, this can lead to structural defects and negatively impact the lifespan of the parts. To proactively prevent these defects, a finite element analysis is carried out to identify cracks. However, this process is time-consuming and requires significant effort due to the repetitive nature of crack modeling. This study aims to develop a crack modeling method based on the finite element model. To achieve this, the Constrained Delaunay Triangulation (CDT) technique is employed to triangulate the space while considering limitations on point connections. The effectiveness of this method is validated by comparing stress intensity factors for semi-elliptical cracks in plates and cylindrical vessels. This approach proves to be a valuable tool for crack analysis studies.

• JOURNAL OF ELECTRICAL WORLD
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• no.6 s.138
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• pp.89-92
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• 1988

변압기 1차측에는 과부화 보호를 위한 고압 컷 아웃이 사용되고 여기에 텐션형 퓨즈가 장착되어 있다. 고압 컷 아웃은 전류개폐능력 관계로 300kVA 이하인 변압기에 사용된다. 변압기 운전중은 고압 컷 아웃의 내부점검을 할 수 없기 때문에 통상은 눈으로 외시점검을 하는 것이 일반적이다. 고압 컷 아웃의 사고로는 퓨즈 용단, 애자부의 균열, 오손 등으로 인한 지락이나 접촉 칼날부의 접촉 불량, 본체의 파손 등이 있다. 이러한 사고를 사전에 발견하기는 곤란한 경우가 많은 것 같다. 이러한 사고를 사전에 발견하기는 곤란한 경우가 많은 것 같다. 다음은 고압 컷 아웃이 파손해서 정전된 사례이다.

• Korean Journal of Construction Engineering and Management
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• v.16 no.3
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• pp.143-151
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• 2015

The Crack, occurred in the concrete structure, is a major cause of function deterioration such as strength, durability and waterproof. Therefore the need for crack reduction will continue as long as there is concrete structure. But, it is not easy to reduce or prevent crack cause of impact factor of it. There are so many factors of crack such as material, construction and maintenance environment, and structure, and these are acting in combination. So, this study derives a correlation between the cracks and members through reviewing member crack occurred. And member's attribute, related crack, is analyzed by it. It consider that the basic attribute of member is similar when its requirements are similar. Through this study, therefore, foundation of countermeasure of crack will be provided by prediction of crack shape through member's attribute.

• KIPS Transactions on Software and Data Engineering
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• v.10 no.5
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• pp.161-168
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• 2021

Cracks affect the robustness of infrastructures such as buildings, bridge, pavement, and pipelines. This paper presents an automated crack detection system which detect cracks in diverse surfaces. We first constructed the combined crack dataset, consists of multiple crack datasets in diverse domains presented in prior studies. Then, state-of-the-art deep learning models in computer vision tasks including VGG, ResNet, WideResNet, ResNeXt, DenseNet, and EfficientNet, were used to validate the performance of crack detection. We divided the combined dataset into train (80%) and test set (20%) to evaluate the employed models. DenseNet121 showed the highest accuracy at 96.20% with relatively low number of parameters compared to other models. Based on the validation procedures of the advanced deep learning models in crack detection task, we shed light on the cost-effective automated crack detection system which can be applied to different surfaces and structures with low computing resources.

• Journal of Korean Tunnelling and Underground Space Association
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• v.4 no.4
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• pp.287-300
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• 2002

Composition Presplitting Angle Cut (COPA-Cut) is a newly developed blasting method for tunnel excavation. Contrary to existing methods, COPA-Cut first creates presplitting by tension crack in cut. In this study, field tests measuring the advance efficiency, noise and ground vibration were performed in order to verify the presplitting effect. To compare the economy and workability, tests were simultaneously performed by COPA-Cut and existing method on the same condition. Results show that COPA-Cut increased advance efficiency and decreased noise and ground vibration. Also, it was confirmed that COPA-Cut is superior to existing method in terms of economy, workability and quality control.

• Proceedings of the KWS Conference
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• 2010.05a
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• pp.56-56
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• 2010

최근 강구조물의 건설이 지속적으로 증가되어 왔다. 또한 강구조물의 유지관리 및 안전성에 대한 관심이 급증하고 있다. 시설물의 안전성 확보는 대형사고의 사전 예방, 공용 중 갑작스런 가동 중지에 의하여 발생되는 비용증가를 사전에 차단 할 수 있다는 점에서 그 중요성은 매우 크다고 할 수 있다. 또한 각종 구조물은 열악한 사용조건, 고온, 고압, 고속, 대형화됨에 따라 일단 사고가 발생 했을 경우 대형사고의 위험이 예상되므로, 제작시 검사의 강화뿐만이 아니라 공용 중 구조물의 안전성을 진단 할 수 있는 모니터링 체계의 확립이 필요한 시점이다. 현재 국내에서 강구조물들의 균열 모니터링 시스템에 관한 연구는 매우 미흡한 실정이며, 현재 사용되고 있는 비파괴검사 방법은 UT와 RT등이다. 이러한 방법들은 많은 시간과 경비가 소요되며 또한 거대구조물 혹은 사람의 접근이 어려운 곳에는 적용하기가 힘들다. 또한 주기적인 검사 작업으로 인한 막대한 시간과 비용의 손실이 발생되고 있으며 초기 결함을 조기에 인지하지 못함으로써 적절한 보수 보강 대책이 이루어지지 않아 보수 보강 비용의 증대를 초래한다. 더욱이, 결함이 진전된 이후에도 이것을 인지하지 못하여 적절한 대응을 하지 않는다면 대형사고로 이어질 수도 있다. 따라서 강구조물에 대한 효율적인 유지관리가 가능하고, 초기결함으로부터 균열이 진전하여 붕괴되는 사고를 미연에 방지하며 초기에 보수보강 작업을 수행함으로써 보수보강 비용도 절감 할 수 있는 모니터링 시스템의 개발이 요구되고 있다. 이러한 모니터링 시스템의 개발은 기술적 측면에서 강구조물의 효율적인 유지 관리 노하우를 얻을 수 있으며 경제 산업적 측면에서는 보수 보강 비용 및 불필요한 주기적 점검 비용을 절감 할 수 있다. 이 연구에서는 전위차법을 이용하여 강구조물의 필렛 용접부에서의 균열진전양상을 파악하고 정량화를 통해 필렛용접부의 잔여수명을 예측하였다.

• Journal of the Korea Computer Graphics Society
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• v.28 no.2
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• pp.1-9
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• 2022

In this paper, we propose a vector-based augmentation technique that can generate data required for crack detection and a ConvNet(Convolutional Neural Network) technique that can learn it. Detecting cracks quickly and accurately is an important technology to prevent building collapse and fall accidents in advance. In order to solve this problem with artificial intelligence, it is essential to obtain a large amount of data, but it is difficult to obtain a large amount of crack data because the situation for obtaining an actual crack image is mostly dangerous. This problem of database construction can be alleviated with elastic distortion, which increases the amount of data by applying deformation to a specific artificial part. In this paper, the improved crack pattern results are modeled using ConvNet. Rather than elastic distortion, our method can obtain results similar to the actual crack pattern. By designing the crack data augmentation based on a vector, rather than the pixel unit used in general data augmentation, excellent results can be obtained in terms of the amount of crack change. As a result, in this paper, even though a small number of crack data were used as input, a crack database can be efficiently constructed by generating various crack directions and patterns.

• Composites Research
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• v.27 no.6
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• pp.219-224
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• 2014

Nancomposites manufacture has been developed rapidly, because of reinforcing effects of CNT in terms of mechanical, electrical and thermal properties. In this study, 10 wt% CNT paste was fabricated with good dispersion state and easy processability. Damage sensing and reinforcing effect of CNT paste were investigated in nanocomposites. 10 wt% CNT paste exhibited better tensile and flexural properties than those of general 1 wt% CNT nanocomposites. To observe the healing effect of CNT paste, a crack was made artificially with 30wt% CF30wt%/PP composites, and the CNT paste was filled inside the crack. The damage sensing of CNT paste in CF30wt%/PP composites was investigated by electrical resistance measurement and mechanical tests. CNT paste exhibited good reinforcing effect in mechanical properties of CF30wt%/PP composites, and this reinforcing effect was getting better with larger cracks. The reason was because CNT paste had good interfacial adhesion with CF30wt%/PP composites to resist crack propagation. In electrical resistance measurement, there was a jump in electrical resistance signal at the adhesion interface. The jumping signal could be used to predict fracture of CF/PP composites. CNT nanocomposites for damage sensing had crack reducing effect and damage detection using electrical resistance method.

• Journal of Korean Tunnelling and Underground Space Association
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• v.5 no.3
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• pp.251-260
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• 2003

Tunnel blasting has been performed with V-cut to investigate the characteristics. Blasting vibrations were measured at two directions, the proceed direction and side direction. Propagation characteristics were determined by regression analysis; square root scaled distance and cube root scaled distance with maximum charge per delay of the blast. Testing result, The cross point was 62m in the allowable vibration velocity of 3mm/sec and 46m in 5mm/sec. Also, vibration level with measuring point was highest and decayed fastest, adapting to cube root scaled distance, for the proceed direction on ground.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.2 s.21
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• pp.1-7
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• 2006

Recently, the massive concrete structures have been increasingly built in Korea. Many reinforced concrete structures have been reported to suffer from cracking in construction stages due to heat of hydration arising from mass concrete. This cracking may cause some serious durability problems and thus reduces the safety and service life of the structures. In this study, the stresses, strains, and temperatures were measured and the crack widths and crack Patterns were also observed in the footing and abutment structures. And the causes and mechanism in thermal cracking in the footing and abutment structures are thoroughly analysed. The comparisons of test results with analysis have been made. Efficient crack control techniques were developed form the experimental and analytical studies.