• Journal of Welding and Joining
• /
• v.25 no.4
• /
• pp.9-14
• /
• 2007

선박의 고강도화 및 극후물화가 진행됨에 따라 선체 구조물의 파괴 특성에 대한 관심이 높아지고 있으며, 최근 균열정지의 관점에서 취성균열 정지특성에 대한 연구가 활발히 이루어지고 있다. 기존의 연구결과에 따르면 65mmt 이상의 극후물 용접부에 대해서 취성균열 정지특성의 저하가 발생할 가능이 있다고 보고되고 있으며, 취성균열 정지특성이 우수한 강재의 개발 이외에 용접부 보강재의 부착, 보수 용접 실시 등 개선 방안을 마련하기 위한 다양한 연구가 진행되고 있다. 그러나 극후물 용접부 취성균열 전파기구에 관한 규명은 현재 전무한 실정이며, 강재 두께의 영향 이외에 용접 입열량 용접부 잔류응력 등의 효과가 복합적으로 검토되어야 한다. 아울러 극후물 용접부 균열정지 파괴인성의 평가, 대형파괴시험을 대체할 소형시험법의 개발 및 검증 등에 관한 연구가 요구된다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2020.11a
• /
• pp.996-999
• /
• 2020

노후 선박의 증가로 선체 검사의 필요성이 높아지고 있다. 하지만 선체 벽면의 균열을 찾고 보수하는 작업은 위험성이 높고 효율성이 낮다. 이에 본 논문에서는 선체의 벽면에 진공 흡착하여 장애물에 부딪히지 않고 선체 벽면을 이동하면서 균열을 탐지하는 로봇을 개발하였다. 선체 균열탐지 로봇은 선체뿐만 아니라 사람이 직접 균열을 찾기 힘들거나 위험한 곳에 유용할 것이며 균열로 인한 선박 사고 발생을 줄여줄 것으로 기대된다.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.3
• /
• pp.84-89
• /
• 2018

Recently, study on self-healing materials have been performed to increase the life by repairing the damage of structures themselves, which are difficult to repair or require high maintenance costs. A water permeability test has been widely used for the evaluation of self-healing performance. However, in the self-healing performance test method, the initial crack width of the concrete greatly affects on the self-healing performance but it does not have a consistent standard. Therefore, in this study, the correlation between crack and permeability and that between time and permeability were analyzed based on crack width and permeability. In addition, since the initial crack width measured by optical microscope is not reliable, the value is derived from the Poiseuille flow and the tendency of time-permeability and time-crack width are analyzed.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1998.05b
• /
• pp.350-355
• /
• 1998

본 논문은 다양한 파괴역학 해석방법을 이용하여 원주방향 관통균열이 존재하는 탄소강 및 스레인레스강 배관의 하중 지지능력을 예측하기 위한 것이다. 이를 위해 실제적인 기본모델과 배관 및 균열의 형상, 재료물성치를 변화시킨 가상적인 특정모델을 대상으로 순수 굽힘하중 작용조건에서의 공학적 해석 및 유한요소해석을 수행하였으며, 타당성 검토를 위해 문헌에 제시된 실험결과와 비교하였다. 비교결과, 예측한 하중 지지능력은 각 평가방법 뿐만 아니라 배관 및 균열의 형상, 재료특성 등에 따라서도 차이를 보였으나, 전반적으로는 실험결과에 비해 보수적인 결과를 제시하는 것으로 나타났다.

• Journal of the Korea Concrete Institute
• /
• v.15 no.1
• /
• pp.1-10
• /
• 2003

The purpose of this study is to evaluate the capacities of repaired structural walls with different shear span ratios(1, 2, 3). Experimental tests were carried out. In this study three isolated large-scale wall specimens were made. The original wall specimens were tested until the drift reaches more than 3%. The region of the damaged specimen with the crack larger than 0.2 mm is replaced by new concrete. Also, severly distorted reinforcements were also replaced by new reinforcements. The crack smaller than 0.2 mm was cured by epoxy resin. Because of the space limitation of the laboratory the dimensions of all walls are the same. The shear-span ratio was controlled by the combination of axial and lateral force using the special test setting. All specimens were tested using the incremental quasi static cyclic load until failure occurs. Test results show that strength of repaired walls was almost equivalent to that of original walls. However, deformation capacities of repaired wall specimens are inferior to the original wall specimens.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2008.05a
• /
• pp.379-385
• /
• 2008

콘크리트 건물의 보수 작업은 표면에 발생하는 균열을 정확하게 계측함으로써 비용적인 측면과 안전성이 결정된다. 하지만 표면에 발생한 균열은 대부분 점검자에 의해 수작업으로 계측되기 때문에 시간적 측면에서 비효율적이다. 따라서 본 논문에서는 콘크리트 슬래브 표면에 발생한 균열의 밝기와 밀도 그리고 면적 특징을 이용한 균열 검출 기법을 제안한다. 제안된 균열 검출 방법은 콘크리트 슬래브 표면의 명암도와 위치 정보를 ART2 기반 양자화에 적용한 후, 균열과 인접한 배경간의 명암도 차이를 이용하여 균열과 인접한 배경을 분리한다. 균열과 인접한 배경이 분리된 영상에서 형태학적인 정보를 이용하여 세부적인 잡음을 제거한 후에 최종적으로 균열 영역을 검출한다. 실제 콘크리트 균열 영상을 대상으로 실험한 결과, 다양한 콘크리트 균열 영상에서 기존의 방법보다 균열 검출 성능이 개선되었음을 확인하였다.

• Journal of the Korea Concrete Institute
• /
• v.15 no.3
• /
• pp.462-469
• /
• 2003

This paper presents an experimental study on the potential durability enhancement of infrastructures repaired by a sprayed high ductile fiber-reinforced cementitious composite (ECC). For this study, a PVA-ECC which exhibits sprayable properties in the fresh state and tensile strain-hardening behavior in hardened state was sprayed and tested. The experimental results show that the sprayed ECC exhibits mechanical properties with strain capacity comparable to the cast ECC with the same mix design. During loading, the crack widths of ECC are tightly controlled with an average of 30${\mu}m$. It is also revealed that when sprayed ECC is used as a repair material, ductility represented by deformation capacity at peak load of repaired beams in flexure are obviously increased in comparison to those of commercial prepackaged mortar (PM) repaired beams. In addition to high delamination resistance, the significant enhancement of energy absorption capacity and crack width control in ECC repair system suggest that sprayed ECC can be effective in extending the service life of rehabilitated infrastructures.

• 한국도로학회지:도로
• /
• v.14 no.1
• /
• pp.21-24
• /
• 2012

• Journal of the Society of Naval Architects of Korea
• /
• v.29 no.2
• /
• pp.79-91
• /
• 1992

This paper develops the compliance approach to the problem of load sharing between a cracked plate and a patch used to bridge the crack. The theory is validated by using calculated stress intensity factors for the patched and unpatched case to reduce experimentally observed growth rates to common base, Calculations are then made on the effect of patch dimension on fatique life technique. The optimum design of the patch considered the life expectancy and fracture strength of the cracked structure can be performed simply by using this technique.

• Journal of the Korea Concrete Institute
• /
• v.14 no.5
• /
• pp.766-773
• /
• 2002

The failure phenomenon of overlaid concrete structures, such as surface crack, and peel-off failure, shear bond failure in the end contact zone, was investigated due to humidity changes. To investigate this failure phenomenon, the surface tensile stress, and the shear stress, the vertical tensile stress in the contact zone were analysed using the non-linear stress-strain relationship of material such as strain-hardening- and strain-softening diagrams. Overlay thickness and overlay material were the main variables in the analyses. It is assumed that the initial surface humidity of overlaid concrete structures was 100％ r.H. With a atmospheric humidity of 55％ r.H. and two load cases for drying(LCI), curing and drying(LC2), the stress states of overlaid concrete structures were calculated. The result shows that only fictitious cracks occurred in the overlay surface of CM2O, ECM25, and no shear bond failure occurred in the contact zone without CM2O. The peel-off failure was proved to be the main cause of the damage in the overlaid concrete structures. Only for overlay thickness of 1cm occurred no peel-off failure in the case of drying after a long-term public use(LC1). In the case of curing and drying during overlay work(LC2) occurred the peel-off failure within 1.5days for all the overlaid concrete structures.