• The Optical Journal
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• s.99
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• pp.64-68
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• 2005

유리나 파인 세라믹 등의 경취 재료를 연삭한 뒤의 특징은 지립의 최대 절입 깊이가 충분히 작은 경우, 바꿔말하면 파괴 단위가 극히 작은 경우에는 연성 모드적 연삭이 되고, 또 반대로 큰 경우에는 취성 모드적 연삭이 된다는 것이다. 보통 연성 모드적 연삭은 다듬질 연삭에, 그리고 취성 모드적 연삭은 조연삭에 적용되는 경우가 많다. 따라서 여기서는 치수·형상 정밀도를 유지하고 동시에 여분의 가공 공차를 매우 능률적으로 제거하는 것을 목적으로 한 경취 재료의 조면 연삭 기초에 대해 소개한다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.05a
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• pp.40.2-40.2
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• 2009

일반적으로, 극미세 공정조직은 높은 강도를 나타내지만 낮은 연성을 가지는 단점을 보이고 있다. 극미세 공정합금의 연성을 증대시키고자, 상대적으로 연한 고용체 또는 경한 금속간 화합물을 마이크로 크기의 초정상으로 형성시키는 연구가 활발히 진행 되어지고 있다. 이러한 마이크로 크기의 초정상은 극미세 공정합금의 연성을 증가시키기에는 효과적이지만, 강도가 큰 폭으로 낮아지는 손실을 나타내고 있다. 최근, 공정조직 만으로 이루어진 극미세 공정합금의 연성을 증대시키고자, 공정조직의 형상 및 구성상을 조절하는 등의 연구가 발표되어지고 있다. 본, 연구에서는 Ti-, Mg-계 합금에 양극화 공정조직을 유도하여 극미세 공정조직 양극화 Ti-, Mg-합금을 개발, 이러한 불균일성을 내포한 양극화 공정조직이 극미세 공정조직 양극화 Ti-, Mg-합금의 기계적 성질에 미치는 영향을 체계적으로 연구하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6A
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• pp.513-523
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• 2010

For continuous I-girder bridges, a large negative bending moment is generated near pier region so that plastic hinge is first formed at this point. Then, the bending moment is redistributed when the I-girder has enough flexural ductility (or rotational capacity). However, for I-girder with high strength steel, it is known that the flexural ductility is considerably decreased by increasing the yield strength of material. Thus, it is necessary to conduct a study for guaranteeing proper flexural ductility of I-girder with high-strength steel. In this study, the evaluation of flexural ductility of negative moment region of I-girder with high strength steel where yield stress of steel is 680 MPa is presented based on the results of finite element analysis and experiment. From the results, it is found that the flexural ductility of the I-girder is significantly reduced due to the increase of elastic deformation and the decrease of plastic deformation ability of the material when the yield strength increases. In this study, the method to improve the flexural ductility of I-girder with high strength steel is proposed by an unequal installation of cross beam and an optimal position of cross beam is also suggested. Finally, the effects of the unequal installation of cross beam on the flexural ductility are discussed based on the experimental results.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.1
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• pp.108-115
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• 2020

In this study, the flexural performance of Highly Ductile Cement Composites(HDCC) mimicking boundary conditions of shellfish skin layer was evaluated. To improve ductility by mimicking the boundary skin layer structure of shellfish, the method of stratification by charging between precast panels using HDCC and the method of distributing PE-mesh to the interface surface were applied. Evaluation of flexural performance of layered cement composite materials mimicking boundary conditions of shellfish skin layer resulted in increased ductility of all test specimens applied with stratified cross-section compared to typical bending test specimens. The layered method by inserting PE-mesh showed excellent ductility. This is most likely because the inserted PE-mesh made an interface for separating the layers while the HDCC pillars in the PE-mesh gave adhesion between layers.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.2 s.54
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• pp.206-214
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• 2009

Due to its outstanding feature, FRP is used widely for the material of strengthening in USA and Japan recently, and there have been active researches in korea as well. This study evaluates the behavior and ductility of each structure experiment using EBR and NSMR strengthening method with different AFRP types and strengthening area. There was the biggest increase in the load when the strengthening area is expanded showing a brittle aspect, and eventually the immature failure occurred. With regard to the methods, it is found that the NSMR method is more effective to strengthen the structure, and the uneven surface causes ductile failure.

• Journal of the Society of Disaster Information
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• v.13 no.4
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• pp.491-498
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• 2017

The primary objective of this research is to develop a rutting performance prediction model of flexible pavement. Extensive laboratory testings were conducted to achieve the objective. A new test method employing repetitive axial loading with confinement was also adopted to estimate the rutting performance of asphalt concrete in the research. The rutting prediction model employes a layer-strain theory. The required rutting coefficients for the prediction model were determined through the laboratory rutting characterizations of the asphalt concrete layer materials. Within the limits of this study, a laboratory rutting prediction model of flexible pavement using repetitive axial loading test was presented. It is noted that the developed rutting prediction model simulates propery the behaviors of flexible pavement layer materials.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.243-244
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• 2010

Reinforced concrete beam are very diverse materials that are used to bending reinforcement. Recently the case of FRP flexural reinforcement is actively being used is an excellent weight - rigidity. However, use of FRP bending reinforcement in brittleness material properties of concrete in an actual field application causes destruction of detachment and attachment is being considered as a major cause of destruction. For hybrid laminating plates, tensile and three-point bending tests were performed considering various designs and fabricating methods for hybrid FRP plates. Tensile property of each test specimen was investigated and the research parameter of hybrid laminating plates considered here is the combining ratio of fiber to aluminum contents.

• Composites Research
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• v.27 no.6
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• pp.236-241
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• 2014

This paper aims to evaluate material property variation of polymer concretes under ultra-violet exposure condition. The components and mixing ratio of the polymer composite specimens were determined by the previous research results. The equivalent UV exposure time was calculated with the consideration of the power of metal halide lamp and maximum 3 years were selected for the experiments. From the tests, it was found that the generated heat during UV exposure affected much the material properties of polymer concrete by means of post cure. As a result, the compressive strength increased and ductility factor decreased.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.75-75
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• 2010

기존 할로겐프리 제품은 PVC와 비교하여 유연성이 크게 떨어져 PVC 사용에 대한 규제가 강화되고 있음에도 불구하고, 이를 쉽게 대체하기 곤란하다는 문제점이 있다. 이에 할로겐프리 재료만 사용하여 고난연성, 예를 들면 UL 1581 에 따른 VW-1 규정을 충족하는 고난연성을 가지면서도 경도가 낮아(경도 70수준, Shore A) 재질의 유연성이 확보된 고분자 재료를 개발하는 것이 요구된다. 실험 결과로부터 인장강도 11[Mpa], 신장율 720[%], 가열후 인장강도 잔율 90[%], 가열후 신장잔율 88[%], 산소지수 38.0, 수직난연시험 합격, 경도(Shore A) 70, 백화현상이 나타나지 않는 등 우수한 특성을 보였다.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.157-157
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• 2003

TiAl 금속간화합물은 저밀도, 고용융점 및 우수한 고온강도 둥의 여러 장점을 지녀 고온의 열악한 부식성 분위기에 노출되는 가스터빈, 자동차 엔진부품 등에 사용하기 위해 최근 활발한 연구가 진행되고 있다. 그러나 이 합금의 실용화에 장애가 되는 가장 큰 문제점은 나쁜 저온인성, 고온가공의 어려움 및 고온에서의 나쁜 내산화성이다. 일반적으로 V는 상온연성을 증진시키지만 내산화성을 감소시키고, Nb는 상온연성과 내산화성을 증진시키는 원소이다. 또한 Mo는 강도와 연성을 증진시킨다. 이들 첨가원소의 산화특성을 비교분석하기 위하여 고온산화실험을 실시하고, 산화막의 구조, 산화막의 종류 및 형성과정을 SEM/EDS, EPMA 및 XRD을 이용하여 조사하였다.