• Journal of Korean Association for Spatial Structures
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• v.8 no.2
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• pp.55-62
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• 2008

Membrane structures are now used in various ways throughout the world with the merits of free shape, lightness, durability, sunlight transmittance and homogeneous material. The development of new membrane material opened up new possibility for the design of new building structures. Recently it was mainly used PVC, PVF, PVDF, PTFE, ETFE membrane for using the roofing material of membrane structures. Some problems of membrane materials have fire proofing, lack of strength, self cleaning capacity, tear resistance, durability, heat insulation, sound insulation and elasticity. For the solution of this problems, it will be tested the mechanical properties of membrane material about tensile strength, tearing resistance, etc.

• Magazine of the Korea Concrete Institute
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• v.9 no.6
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• pp.175-183
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• 1997

경제성장에 따른 항만구조물의 건설 및 유지관리에 관한 관심이 급격히 고조되고 있다. 이러한 항만구조물은 해양환경에 노출되어 콘크리트에 매입된 철근의 부식을 야기시키는 요인에 접해있다. 한편, 콘크리트 내부의 염분침투는 매입철근의 부식을 가속화시켜 콘크리트 구조물의 내구성에 상당히 큰 피해를 입힐 수 있다. 본 연구의 목적은 여러 가지 방식제를 사용함과 동시에 물/시멘트을 달리한 실험변수를 이용한 시험체에 대한 부식평가 및 매입철근의 적절한 부식방지 기법의 개발에 있다. 해양환경 조건을 simulation한 해수 및 담수 순환장치를 이용한 실내 시험체의 철근 부시도 평가 및 항만현장에 직접 거치된 시험체 등 다양한 조건하의 2년간의 실험이 현재 진행 중에 있다. 40주에 걸쳐 간헐 침투되는 해수조건에서 60개의 콘크리트 시험체의 철근 부시도 평가결과를 기초하여 180여개의 콘크리트 시험체를 새로이 제작하여 Half-Cell Test를 통한 Instant-Off Potential, Current Method를 통한 Corrosion current, Chloride Content 및 시험 종료후 시험체를 파쇄하여 부식된 철근의 무게측정등을 통하여 거동 및 부식을 예측.평가하고 이를 통한 부식방지기법을 개발하고자 한다.

• KEPCO Journal on Electric Power and Energy
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• v.4 no.1
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• pp.19-24
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• 2018

The long-term research and development for the production of domestic blades has been consistently performed. As the direct and indirect results of its nationwide technologies in precision casting have been improved as well as maintenance costs for turbine machinery has been reduced. Whereas, there are still not a few concerns about the reliability of newly manufactured blades in spite of the quality certificate in metallurgical and mechanical properties. A spin tester is a machine that gives centrifugal loading to a rotating part, and its practical application is the overspeed test that is usually used to check the quality of products. A new spin rig has been constructed in KEPCO Research Institute for the purpose of evaluating the reliability of blades. In this paper, the test methodology for low cycle fatigue damage mechanism as well as the overspeed test for newly developed blades is described, and their reliability is evaluated too.

• The Journal of Engineering Geology
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• v.20 no.3
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• pp.311-318
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• 2010

We performed laboratory measurements of the mechanical properties and slake durability of Cretaceous shale from the Hwasun area, Korea, including highly weathered and fresh samples, yielding ranges of specific gravity of 2.14-2.88, dry density of 1.86-2.83(g/$cm^3$), water content of 0.12-6.36 (%), porosity of 1.33-20.49 (%), and absorption ratio of 0.51-8.5 (%). The absorption ratio shows a strong linear relation with porosity, expressed as Ab = 0.44P-0.09 (Ab: absorption ratio, P: porosity). Values of the slake durability index ($Id_2$) and point load intensity index ($Is_{(50)}$) of highly weathered to fresh shale are 90.07-99.33 (%) and 10.8-90.2(kg/$cm^2$), respectively. $Id_2$ is linearly related to $Is_{(50)}$, expressed as $Is(50)=1E-07e^{0.2033Id_2}$(kg/$cm^2$)($r^2=0.69$). This equation is a useful tool for estimating the $Id_2$ value for shale in the Hwasun area.

• The Journal of Engineering Geology
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• v.23 no.4
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• pp.341-352
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• 2013

The physical and mechanical properties of red shale and black shale exposed in the Daegu area were investigated in tests conducted to determine unit weight, absorption ratio, porosity, ultrasonic velocity, unconfined compressive strength, point load strength, slake durability index, and deterioration characteristics. XRD, XRF, and SEM analyses were also performed on the shale specimens. While the unit weights of the two shales were similar, the absorption ratio and porosity were higher in the red shale than in the black shale. Despite the higher porosity of the red shale, the ultrasonic velocity, compressive strength, and point load strength were higher in the red shale, which is an unexpected result that may be due to the presence of fine laminations in the black shale. The deterioration rate, as determined from the point load strength and the slake durability index, increased with increasing immersion time and with the acidity of the immersion liquid. The deterioration rate was higher for the red shale than for the black shale because of the higher porosity of the former.

• Journal of the Korea Concrete Institute
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• v.26 no.4
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• pp.517-524
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• 2014

Nitrite-Type hydrocalumite (calumite) is a material that can adsorb chloride ions ($Cl^-$) that cause corrosion of reinforce bars and liberate the nitrite ions ($NO_2{^-}$) that inhibit corrosion in reinforced concrete. In this study, polymer-modified mortars using two types of epoxy resin with calumite are prepared with various polymer binder-ratios of 0, 5, 10, 15, 20% and calumite contents of 0, 5%. The specimens are tested for chloride ion penetration, carbonation, drying shrinkage and corrosion inhibition. As a result, the chloride ion penetration and carbonation depth of PMM using epoxy resin somewhat increases with increasing calumite contents, but those remarkably decreases depending on the polymer-binder ratios. The 28-d drying shrinkage shows a tendency to decrease with increasing polymer-binder ratio and calumite content. Unmodified mortars with calumite content of 5% did not satisfy quality requirement by KS. However, it was satisfied with KS requirement by the modification of epoxy resin in cement mortar. On the whole, the carbonation and chloride ion penetration depth of epoxy-modified mortars with calumite is considerably improved with an increase in the polymer-binder ratio regardless of the calumite content, and is remarkably improved over unmodified mortar. And, the replacement of the portland cement with the calumite has a marked effect in the corrosion-inhibiting property of the epoxy-modified mortars.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.9-17
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• 2012

Concrete sewage culvert shows degradation with time since it is always exposed to various harmful ions, and deterioration of concrete culvert propagates to structural safety problems. After reclamation, maintenance for concrete sewage culvert is very difficult so that high durable and structural performance are essential for the sewage concrete culvert. Recently polymer concrete has been used to improve mechanical properties and durability performance. In this paper, engineering properties are evaluated for sewage culvert made with polymer concrete, and leakage and adhesive strength between joints are evaluated with small-scale models. The polymer sewage culvert shows high compressive strength over 100MPa with low water permeability and chloride penetration. Furthermore, high resistances to chemical and biological attack are evaluated. Through tests for leakage and adhesive, unification of joints is verified with evaluation of no leakage and high adhesive strength. Precast polymer sewage culvert in this paper can be actively used for severe conditions like sewage lines.

• Aerospace Engineering and Technology
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• v.13 no.2
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• pp.1-6
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• 2014

Power system of the tilt-duct VTOL aerial robot has been developed. This paper focuses on the power train with small liquid-type engine for the R/C boat and presents the test results with design procedures. The hardware aspects of the power system include details about the hardware configurations for the interfaces with the vehicle. The ground test and tether test for measuring the thrust performance of vehicle and evaluating the endurance of power train carried out.

• Aerospace Engineering and Technology
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• v.6 no.2
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• pp.236-244
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• 2007

The 40% scaled vehicle of Smart UAV has been developed for the investigation of basic flight characteristics and the verification of flight control algorithm. The similar gimbal hub and drive train with the full scale UAV were implemented and a forced air cooling reciprocating engine was installed. The various kind of tests were conducted for the major components of the vehicle. The important performance and mechanical endurance of the fabricated vehicle were identified by ground and hovering test.

• Journal of the Korean institute of surface engineering
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• v.29 no.3
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• pp.176-185
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• 1996

플라즈마 용사된 열벽코팅의 수명을 평가하기 위하여 여러가지 양의 CeO$_2$(16,18,20,22,24 그리고 26 wt.% CeO$_2$)를 포함하는 지르코니아 코팅에 대한 상분석이 행하여 졌다. 플라즈마 용사된 후 16 및 18 wt.% CeO$_2$를 포함하는 지르코니아 코팅에서는 비평형 tetragonal 상 만이 생성되었으나 20-26 wt.% CeO$_2$를 포함하는 지르코니아 코팅에서는 비평형 tetragonal 및 cubic 상의 혼합상이 관찰되었다. 열순환 산화시험 동안에는 비평형 tetragonal 및 cubic 상은 평형 tetragonal 및 cubic 상으로 변태하였다. 평형 tetragonal 상의 일부는 열순환 산화시험의 냉각과정 중에 monoclinic 상으로 변태하였다. 그리고 16 wt.% CeO$_2$를 포함하는 지르코니아 코팅은 다른 조성의 지르코니아 코팅보다 열순환 산화시험 동안 더 많은 monoclinic 상이 생성되었으며 세라믹 코팅 수명이 짧았다.