• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.933-936
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• 2008

모르타르에 2 %이내의 합성섬유를 혼입함으로써 콘크리트의 수십, 수백 배에 달하는 인장변형률 경화거동을 보이는 ECC가 기존 연구에 의해 개발되었으며, ECC를 구조부재에 사용할 경우, 구조물의 성능개선이 매우 커질 것으로 판단된다. 그러나 ECC를 사용한 구조물을 설계할 때 중요한 요인인 ECC의 인장거동 관계 예측에 대해서는 많은 연구가 이루어지지 않았으며, 특히 보다 실제적인 인장거동 관계를 예측하기 위해서는 섬유분산성 등 실제의 균열면응력-변위 곡선을 고려한 연구가 필요하다. 따라서, 이 연구에서는 ECC의 인장거동 관계를 예측할 수 있는 기법을 제시하였다. ECC의 인장거동 예측방법은 초기균열강도, 인장강도, 인장변형률을 구하는 과정으로 구성되는데, 보다 합리적이고 실제적인 ECC의 인장거동 예측을 위하여 균열면응력에서 가교작용에 기여하는 유효섬유의 개수를 섬유의 기울어진 각도와 섬유사이의 간격에 따라 예측하였다. 또한 극한인장변형률 예측을 위하여 화상처리기법을 사용하였다. ECC의 인장실험결과와의 비교를 통하여 예측방법의 타당성을 평가하였다.

• 한국안전학회지
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• 제33권4호
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• pp.90-97
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• 2018

As the result(also after it's been carried out the damping force test with 800ea lateral dampers of 50ea trainset from entering heavy maintenance workshop to implement heavy maintenance inspection cycle, there were 86.25%(650ea) which were out of $350kg{\pm}15%$ of the standard value of damping force compared to the reference value. After the implementation of heavy maintenance inspection cycle, it's been examined damping force test with total samples 32ea(samples 8ea per a trainset) from actual running EMU 4ea trainset. As the result, percent defective was 84.4%(27ea), which was a very high level. System. The lateral damper's the failure cause of damping force defective was oil leakage caused by tearing crack of oil seal and foreign material in oil iron 473 ~ 1932 times higher than that of new oil, copper 36 ~ 98 times higher than that of new oil reduced oil amount cycling damping valve. It resulted from the change cause of damping force. In the static analysis on the shape of lateral damper oil seal's the existing and improved product, the stress of the improved product was smaller than that of the existing product. In the fatigue analysis, the existing product showed a low life in the upper area. However, in case of the improved product, it could be confirmed that the destruction did not occur up to the specified 1.0e + 006 cycles and the lifetime was further improved in most areas.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2007년도 추계 학술논문 발표대회
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• pp.71-74
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• 2007

With the changes of times the building materials tend to extend the demand for application under the special environment. Since high-ductile mortar is developed, the building materials show excellent performance like toughness, compression, tensile, and bending, etc. in the general concrete from the existing brittle point. And, recently they are widely used as repairing and reinforcing materials both at home and abroad because they are recognized as excellence like durability and fire-resistance. However, it is in a situation of creating problems in durability because it frequently happened deterioration of buildings that have already repaired and reinforced at a time when it requires reconstruction of recently deteriorated construction structure recently. Therefore, in this study improved with a more repair Material development and reinforcement of the second high-ductile mortar products for a variety of basic materials were presented want, research plans used include traditional repair materials and the newly developed PCM (polymer cement mortar) structural reinforcement type indicated that comparison. PCM analysis in order to present a rate depending on the types fiber 0, 1.2 and 2.0(%) at three levels and mixture water according to ratios of weight to Plain in the 2.0 and 1.85(kg) at two levels is set, the results were as follows. 1) This study has shown that PCM had excellent strain hardening behavior at the same time that the bending stress increased according to the fiber contents. 2) This study has shown that it had the durability performance due to the high substance transmission according to the fiber contents.

• 수산해양교육연구
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• 제28권6호
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• pp.1549-1560
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• 2016

Today, all the countries of the world newly recognize importance of sea, which are focused on efforts for security of marine territory and fishes resources. Many of the coastal state, to strengthen the rights of their own country EEZ, marine survey and continental shelf development, travels through such maritime jurisdiction in the territorial sovereignty and the EEZ overlaps, deepening complex interests between neighboring countries cooperation activities of the fierce competition, the domestic and foreign been has been carried out. Under such circumstances, is devastated coastal of China, our territorial waters and EEZ has been violated more and more, in spite of the powerful crackdown maritime public power, illegal fishing more resistance intensified. They tend to be gradually organization, collectivization and atrocities. Currently, illegal fishing of Chinese fishing boats in the West Sea of Korea, including the waters near Yeonpyeong Island is prevalent as operating in the coast of the country. Furthermore regrettable one is illegal on a scale and the situation where South Korea of scale of damage caused by it have not been accurately grasp of the operation, but that there is damage of Korea official duty enforcement to crack down the increase to illegal operations year after year have occurred. Violent, illegal fishing of Chinese fishing boats, in order to eradicate the operations of insane at our sea, we investigated to the infringement situations of fisheries resources by multiple fields. each of problems presenting a specific preservation plan in accordance with the function and role of the maritime enforcement organization and other government organization the point. at the same time we will try to seek measures such as a scheme that it is possible to increase the capacity.

• 한국해안·해양공학회논문집
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• 제23권4호
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• pp.285-291
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• 2011

이 연구에서는 신형소파블록을 대상으로 실험 및 수치해석을 수행하여 역학적 성능을 평가하고 적절한 보강재의 배근에 따른 구조성능 향상 효과를 검토하였다. 수치해석을 통하여 신형소파블록에 인장응력이 발생하는 위치와 크기를 예측하여 보강재를 설계하였다. 보강재로는 일반 철근 및 해양환경에 적합하도록 부식과 피로에 장점을 지닌 섬유보강재(FRP)를 사용하였다. 실험을 통하여 보강재가 없는 무근 신형소파블록의 파괴하중은 350 kN으로 소파블록의 자중에 비하여 6.2배로 나타났으며, 철근이나 FRP보로 보강한 실험체는 모두 실험의 최고하중인 900 kN 이상의 강도를 보였다. 위험단면을 통과하는 보강재의 개수는 시공의 편의를 위해서는 굵은 지름의 단일 보강재를 사용하는 것이 유리하지만 가는 지름의 보강재 여러 개를 사용하여 균열 폭을 감소시키는 것이 바람직하다는 결과를 얻었다.

• KIEAE Journal
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• 제10권5호
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• pp.115-121
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• 2010

Lime was the solidifier mostly used at the fields of construction and civil works in the past. however, the development of Portland cement remarkably reduced the use of it. Recently as the concernment on circumstances gets higher, lime wined attention again as an eco-friendly material and was used at earth-using construction. This study examined the physical and chemical capacity of lime complexes with lime capacity improved, and performed fundamental study on the way to concretize by mixing it with earth. As a result, lime complex pressure strength was lower than cement pressure strength but it showed the possibility that its strength was improved by W/B control. The measurement of XRD after paste formation confirmed a compound generated by the reaction of Ca2+ion and Si, Al, and Fe from pozzolan reaction. A earth wall experiment by using lime complexes and earth showed that the higher, WB or the lower the quantity of unit combined materials, the lower the pressure strength was. The maximum pressure strength was maximum 11MPa when the quantity of unit combined materials was 450. It is because the composed earth particles had a high content of micro powder less than silt, so a lot of combination are demanded to secure fluidity. As a result of peptization experiment, after hardening, the material was not dissolved, which informed of the possibility of use as an outer subsidiary material. If the material is hardened by mold formation method, natural hardening crack appears. Cast expresses smart surface quality and enables to design for multiple purpose. The result shows the possibility of construction of low-story structures by using earth wall made of lime complexes and earth.

• Nano
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• 제13권11호
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• pp.1850126.1-1850126.10
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• 2018

Flexible strain sensors, as the core member of the family of smart electronic devices, along with reasonable sensing range and sensitivity plus low cost, have rose a huge consumer market and also immense interests in fundamental studies and technological applications, especially in the field of biomimetic robots movement detection and human health condition monitoring. In this paper, we propose a new flexible strain sensor based on thick CVD graphene film and its low-cost fabrication strategy by using the commercial adhesive tape as flexible substrate. The tensile tests in a strain range of ~30% were implemented, and a gage factor of 30 was achieved under high strain condition. The optical microscopic observation with different strains showed the evolution of cracks in graphene film. Together with commonly used platelet overlap theory and percolation network theory for sensor resistance modeling, we established an overlap destructive resistance model to analyze the sensing mechanism of our devices, which fitted the experimental data very well. The finding of difference of fitting parameters in small and large strain ranges revealed the multiple stage feature of graphene crack evolution. The resistance fallback phenomenon due to the viscoelasticity of flexible substrate was analyzed. Our flexible strain sensor with low cost and simple fabrication process exhibits great potential for commercial applications.

• 대한금속재료학회지
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• 제47권9호
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• pp.542-549
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• 2009

Zr-based amorphous alloy matrix composites reinforced with tantalum continuous fibers were fabricated by the liquid pressing process, and their anisotropic mechanical properties were investigated by tensile and compressive tests of $0^{\circ}$(longitudinal)-, $45^{\circ}$-, and $90^{\circ}$(transverse)-orientation specimens. About 60 vol.% of tantalum fibers were homogeneously distributed inside the amorphous matrix, which contained a small amount of polygonal crystalline particles. The ductility of the tantalum-continuous-fiber-reinforced composite under tensile or compressive loading was dramatically improved over that of the monolithic amorphous alloy, while maintaining high strength. When the fiber direction was not matched with the loading direction, the reduction of the strength and ductility was not serious because of excellent fiber/matrix interfacial strength. Observation of the anisotropic deformation and fracture behavior showed the formation of multiple shear bands, the obstruction of crack propagation by fibers, and the deformation of fibers themselves, thereby resulting in tensile elongation of 3%~4% and compressive elongation of 15%~30%. These results suggest that the liquid pressing process was useful for the development of amorphous matrix composites with excellent ductility and anisotropic mechanical properties.

• 한국압력기기공학회 논문집
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• 제17권2호
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• pp.145-156
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• 2021

Ultrasonic Nanocrystal Surface Modification (UNSM) is a peening technology that generates elastic-plastic deformation on the material surface to which a static load of a air compressor and a dynamic load of ultrasonic vibration energy are applied by striking the material surface with a strike pin. In the UNSM-treated material, the structure of the surface layer is modified into a nano-crystal structure and compressive residual stress occurs. When UNSM is applied to welds in a reactor coolant system where PWSCC can occur, it has the effect of relieving tensile residual stress in the weld and thus suppressing crack initiation and propagation. In order to quantitatively evaluate the compressive residual stress generated by UNSM, many finite element studies have been conducted. In existing studies, single-path UNSM or UNSM in a limited area has been simulated due to excessive computing time and analysis convergence problems. However, it is difficult to accurately calculate the compressive residual stress generated by the actual UNSM under these limited conditions. Therefore, in this study, a minimum finite element peening analysis area that can reliably calculate the compressive residual stress is proposed. To confirm the validity of the proposed analysis area, the compressive residual stress obtained from the experiment are compared with finite element analysis results.

• 콘크리트학회논문집
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• 제21권3호
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• pp.327-335
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• 2009

지진이 빈번하게 발생하는 지역에서는 비내진상세구조물은 지진 발생시 연약층을 형성하고 취성적 붕괴를 일으키게 된다. 그러나, 기존 구조물을 해체하고 내진상세 구조물을 신축하는 방법은 건설폐기물, 환경오염 및 민원 등 여러가지 문제들을 가지는 등 비경제적 방법이라 할 수 있다. 따라서 기존 구조물이 내진성능을 만족하도록 내진보강에 관한 많은 연구가 이루어졌으며, 이러한 내진보강방법에는 끼움벽, 철골브레이스, 연속벽, 부벽, 날개벽, 기둥/보의 자켓팅 등이 있다. 이 중 끼움벽 골조는 큰 변형과 접합부에서의 회전이 발생하는 골조와, 비교적 작은 변형에서도 전단파괴를 야기하는 끼움전단벽 등 복합적인 거동특성을 나타낸다. 따라서, 이러한 시스템의 거동특성은 개개의 골조나 벽에서 나타나는 거동특성과 매우 다르게 된다. 본 연구에서는 끼움벽의 내진성능을 평가하고자 하였으며, 손상에너지의 효과적 흡수를 위해 변형경화형 시멘트 복합체 (SHCC)를 사용하였다. 실험은 1/3 축소모형의 끼움벽을 반복가력하는 것으로 계획하였다. 실험 결과, SHCC 끼움벽에서는 섬유의 가교작용을 통해 시멘트 복합체 내 응력을 재분배함으로써 미세균열이 발생하였으며, 강도 및 에너지소산능력이 우수한 것으로 나타났다.