• KSCE Journal of Civil and Environmental Engineering Research
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• v.8 no.2
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• pp.135-145
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• 1988

This study deals with the prediction of crack propagation in concrete mortar subjected to static and dynamic load. Total 54 CLWL-DCB(Crack-line-loaded-double-cantilever beam) concrete mortar specimens were tested to measure crack growth using ASTM 561-80. Main variables were sand to cement ratio and water to cement ratio. The resulting load(P)-COD(Crack Opening Displacement; $2V_1$) curves and COD-CTOD (Crack Tip Opening Displacement; $2V_2$) curves were analyzed to calculate effective crack length and physical crack length by way of ASTM 561-80 proposed. Replica crack length were also obtained directly during the test. The differences in crack propagation between under static load and under dynamic load were investigated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.77-86
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• 1989

A modified $C^{*}$ integral as load parameter in creep fracture is proposed considering the effect of crack growth. It is shown that the parameter does not depend on crack velocity. By performing experiment using STS 304 stainless steel at 600.deg.C the validity of the parameter is investigated. The results show that the parameter is a good measure as a load parameter in creep fracture and the rate of crack tip opening displacement can also be a creep load parameter for STS 304 at 600.deg. C.C.

• Journal of the Korean Geosynthetics Society
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• v.10 no.3
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• pp.1-8
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• 2011

This paper presents the performance evaluation of asphalt pavement reinforced with fiber sheet type of geosynthetics and observations conducted to evaluate the practical efficiencies and performance of overlay asphalt pavement reinforced with geosynthetics. In this study, performance evaluation were performed for the six section of construction site. The performance indcators of asphalt pavement reinforced with geosynthetics has been collected Automatic Road Analyzer (ARAN), Falling Weight Deflectometer (FWD) and have been analyzed for rutting, cracking ratio, falling weight and international roughness index. As a result of performance evaluations, geosynthetics reinforced asphalt pavement is sigficant effect on increasing a cracking resistance than the non-reinfroced asphalt pavement, also rutting and crak is slowly increase as incerasingly performance period.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1568-1575
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• 1990

Fatigue crack growth behavior was investigated in the center cracked plate of KS SB41 steel and the relation between the crack growth rate and various mechanical parameters was studied at small scale yielding, large scale yielding and full scale yielding. The crack opening ratio U was about 0.6-0.8 and had the larger value in the case of load control than that of strain control. Effective stress intensity factor range, .DELTA.K$_{eff}$ and J integral range, .DELTA.J were obtained from the notion of crack opening, and the crack growth rate was expressed with these values. The value of J integral range increased rapidly at stress ratio, R=0 in full scale yielding of load control test. COD value also increased rapidly with the increase of ligament net stress at large scale yielding of load control test.t.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.6
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• pp.191-197
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• 2006

This study is to establish a standardization of injection system by inorganic material for crack repair of tunnel concrete structures. For this various surveys and experiments were carried out as followed. The first we surveyed capability of injection and crack pattern of concrete structures in site. and second we analyzed the relationship between crack width and volume of injection, and decided pressure and volume of injection. Finally we evaluated the relationship between crack width and volume of injection with kind of concrete structures, and between required time for injection and crack width with thickness of structure. From these surveys and experiments, we cleared the relationship between crack patterns and injection technologies such as volume, pressure of injection and required time for injection with kind of structure.

• Journal of the Microelectronics and Packaging Society
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• v.8 no.3
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• pp.25-30
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• 2001

The stress intensity factors for edge cracks located at the bonding interface between the semiconductor chip and the adhesive layer subjected to a uniform transverse tensile strain are investigated. Such cracks might be generated due to a stress singularity in the vicinity of the free surface. The boundary element method (BEM) is employed to investigate the behavior of interface stresses. The amplitude of complex stress intensity factor depends on the crack length, but it has a constant value at large crack lengths. The rapid propagation of interface crack is expected if the transverse tensile strain reaches a critical value.

• Journal of Welding and Joining
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• v.4 no.3
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• pp.13-25
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• 1986

철강 구조물의 용접기술에 있어 용접부의 신속성을 좌우하는 가장 중요한 요소는 용접균열에 관한 문제와 용접본드부의 취화에 관한 문제로 요약될 수 있다. 일반적으로 용접부 및 그 근방의 금속은 국부적으로 매우 높은 온도까지 급열된 후 급냉되므로, 용접부에서 각종균열의 발성 위험성이 높아지고 용접본드부를 취화하여 파양인성의 저하를 초래하게 된다. 따라서 이러한 문 제점을 극복하기 위해서는 재료의 선택이나 설계, 시공, 검사의 각 단계에서 충분한 검토가 필 요하다. 특히 최근 들어 이전보다 높은 강도의 고장력강재가 널리 사용되고 구조물의 대형화에 따라 구속조건이 증대되며 구조물의 사용 조건은 더욱 가혹 화함에 따라 상술한 문제점은 더욱 중요시되고 있다. 철강 용접부에 발생하는 균열은 용접시공시 발생되는 균열과 용접완료후 구 조물 사용중에 발생되는 균열로 대별될 수 있다. 용접시공중 발생되는 균열은 용접열싸이클로 인해 생성되는 조직, 석출물등의 치금학적 요인과 잔유응력 또는 구속응력등의 역학적 요인이 중첩됨으로서 발생된다. 또한 사용중 발생되는 균열은 상기의 두 가지 요인이외에 환경적 요인이 첨가되어 발생된다고 볼 수 있다. 이상과 같은 용접균열을 방지하기 위해서는 실 구조물 용접 조립시의 각종 조건을 재현한 시험법을 통해 용접균열 발생의 한계조건을 정량적으로 분석할 필요가 있다. 이러한 균열 시험의 결과, 적정한 용접 시공 조건이 도출될 수 있기 때문이다. 이와 같은 필요성에 의해 지금까지 다수의 용접균열 시험법에 관한 연구가 행하여져 왔고 그 중에는 각 국가의 협회나 학회의 규격으로 확립된 것도 많으며 국제규격으로 되어 있는 것도 있다. 본 고에서는 각종균열들에 대한 지금까지 밝혀진 기구들에 대해 해설하고, 그 각각에 적용되고 있는 시험법들에 대해 소개하고저 한다.C1지구의 공업.생활용수는 103units, 33units로 배분되고, 하류지구에 304units로 배분되었다. 따라서 용도별로 물배분하므로서 금호강 하루지역에 더욱 많은 물을 배분할 수 있음을 알았다.통해서 수위-유량관계(rating curve)를 규명하였다. 시험지구의 관개효율 및 용수손실 규명 등에 관한 기본자료를 수집하기 위해서는 계측시스템의 운영은 장기간으로 지속 되어야 한다며, 전기전도도와 토양수 농도, 전기전도도와 함수량의 관계를 이용한 천이상태의 오염원 농도 측정방법을 개발하였다. 특히 제안식에서는 한계함수량의 개념을 도입하여 전기전도도와 함수량관계를 추정하므로 추정식의 실험값 반영 정도를 증가시켰다. 본 연구에서 제안된 식을 이용하여 추정된 전기전도도와 함수량관계는 다른 제안식에 비하여 개선된 결과를 보여 주었고, 본 연구에서 개발한 오염원 농도 측정법을 이용하여 측정한 결과 함수량이 0.15이하에서는 측정오차가 크지만 함수량이 0.15이상일 경우 매우 좋은 결과를 보였는데 질량평형을 검토한 결과 약 5-10%의 오차율을 보였다. 따라서 본 논문에서 개발된 천이상태의 오염원 농도측정법은 용존 오염물질의 이송에 관한 정확한 실험을 제공할 것으로 판단된다.며, 수질 보전적-환경 보전 차원에서 저수관리 체계를 확고히 할 수 있는 방안을 강구하여야 할 것이다.펄스주입법에 의해 증착된 박박은 강유전성 이력을 나타내었다.지역과 비도시지역을 비교하는 조사 연구가 필요하며, 이러한 조사결과를 바탕으로 자녀의 식습관에 대한 교육을 위한 교재, 교구의 개발과 영양, 식습관 교육프로그램의 개발을 통해 가정과 학교에서 부모와 교사가 자녀의 식생활 지도 관리를 돕고 가정과 교육기관이 연계한 교육 프로그램이 활성화 될 수 있도록 지속적인 관심을 기울여 나가야 할 것이며, 이에 따른

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.7
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• pp.1575-1581
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• 2005

Recently, further study is being done on the affect of crack on concrete structure and many people have made every endeavor not to leave it unsettled but to minimize it by repair works. In this paper we propose the image processing method that do not remain manual but automatically process the length, the direction and e width of cracks on concrete surface. First, we calibrate light's affect from image by using closing operation, one of morphology methods that can extract the feature of oracle and we extract the edge of crack image by sobel mask. After it, crack image is binarized by iteration binarization. And we extract the edge of cracks using noise elimination method that use an average of adjacent pixels by 3${\times}$3 mask and Glassfire Labeling algorithm. on, in this paper we propose an image processing method which can automatically measure the length, the direction and the width of cracks using the extracted edges of cracks. The results of experiment showed that the proposed method works better on the extraction of concrete cracks. Also our method showed the possibility that inspector's decision is unnecessary.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.593-599
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• 2022

In this study, a crack monitoring system capable of detecting cracks based on image processing techniques was developed to effectively check cracks, which are the main damage of concrete structures, and a program capable of imaging and analyzing cracks was developed using machine vision. This system provides objective and quantitative data by replacing the appearance inspection that checks cracks with the naked eye. The verification of the development system was applied to the construction site of a self-healing concrete water tank to monitor the crack and the amount of change in the crack width according to age. In the case of crack width detected by image analysis, the difference from the measured value using a digital microscope was up to 0.036 mm, and the crack healing effect of self-healing concrete could be confirmed through the reduction of crack width.

• Journal of the Korean Geotechnical Society
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• v.23 no.9
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• pp.29-37
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• 2007

The experiments have been conducted on Kaolinite in laboratory to investigate the development of shrinkage cracking and propose a simple model. Image analysis method consisting of control point selection(CPS) technique is used to process and analyze images of soil cracking captured by a digital camera. The distributions of crack length increment and crack area increment vary as a three-step process. These steps are regarded as stages of soil cracking. They are in turn primary crack, secondary crack and shrinkage crack stages. In case of crack area, the primary and secondary stages end at normalized gravimetric water content(NGWC) of 0.92 and 0.70 for different specimen thicknesses respectively. In addition, the primary stage in case of crack length also ends at NGWC of 0.92 while the secondary stage stops at NGWC of 0.79, 0.82, and 0.85 for the sample thicknesses of 0.5, 1.0, and 2.0 cm respectively Based on the experimental results, the distributions of crack length increment and crack area increment appear to be linear with a decrease of NGWC. Therefore, the development of shrinkage cracking is proposed typically by a simple model functioned by a combination of three linear expressions.