• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.12
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• pp.967-974
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• 2013

Recently the authors had proposed the z-pinning patch concept to simply manufacture z-pinned composite structures at industrial production site and manufactured composite single-lap shear joint specimens using the concept. Through static tensile test on the specimens they had obtained 54~68% improvement of the joint strength. As a sequential study of it, in this study, fatigue test has performed to measure an improvement of joint strength under cyclic loading. The z-pin's material is stainless steel and its surface was specially machined into zagged shapes and chemically corroded to increase the connection force with composite materials. Approximately 98~125% improvement of the joint strength under cyclic loading was obtained.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.901-910
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• 1989

Corrosion fatigue crack propagation behavior of duplex stainless steel weldments in substitute ocean water was investigated to evalulate effects of micro-structural change and residual stresses. Fatigue crack propagation rate was found influenced markedly .alpha./.gamma. phase ratio but little by residual stresses. Fatigue crack propagation rate is higher in the corrosive environment than in room atmosphere. The crack propagation rate estimated by the measurement of striation spacing was higher than that, obtained by crack length measurement in low .DELTK.K region. At hight .DELTK.K region, however, both crack propagation rates were found to be identical.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1998.11a
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• pp.9-14
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• 1998

고강도 알루미늄 합금은 기술의 진보에 따라서 이용도가 높은 매우 중요한 재료로서, 잘 알려진 적용분야로서는 항공우주산업, 고속회전체, 항공기용재 등으로 많이 사용되고 있다. 고강도 알루미늄 합금은 Al-Cu-Mg(2000 series)를 기초로 둔것과 Al-Zn-Mg-Cu(7000 series)를 기초로 둔 것등이 있다. (중략)

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2003.05a
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• pp.229-236
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• 2003

철도는 국가의 물류 및 인적자원을 수송하는 주요한 수송수단으로 1899년 9월 연장 33.2km의 경인선을 시작으로 선로가 지속적으로 증설되어 현재 총영업연장은 6,683km에 달하고 있다. 현재 국내에는 총 2,500여개소의 철도교가 있는데, 이 중에서 강교량에 대해서 연장이 차지하는 비율은 약 48%이고, 공용기간이 50년 이상인 강교량이 전체교량의 약 46%를 차지하고 있으므로 이들 강철도교는 노후화가 상당히 진행되고 있을 것으로 판단된다.(중략)

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.532-537
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• 1997

최근 세계 각 국에서는 노후된 원전의 연장운전과 관련하여 주요기기의 손상진단 또는 수명평가를 통한 지속적인 안전성 보장과 원전의 정비계획 수립, 효율적인 원전이용 등을 위하여 기기의 손상평가 및 성능감시를 수행할 수 있는 각종 감시시스템을 개발하고 있다. 국내의 경우도 발전소 가동년수 증가와 함께 안정적인 전력수급을 위해 연장운전에 대한 타당성 검토를 수행한 바 있으며, 그 후속연구도 진행될 예정으로 있어 발전소를 구성하고 있는 주요 기기의 안전성 확보와 신뢰도 향상이 요구되고 있다. 이러한 측면에서 Prototype 형태로 기기 건전성 평가에 활용할 수 있는 과도상태, 조사취화, 피로손상, 균열성장 및 부식손상 평가모듈을 개발하고, 이를 통합하여 원자력 발전소 종합 진단감시시스템을 구축하였다.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.17-22
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• 2007

Low-cycle environmental fatigue tests of cast austenitic stainless steel CF8M at the condition of fatigue strain rate 0.04%/sec were conducted at the pressure and temperature, 15MPa, $315^{\circ}C$ of a operating pressurized water reactor. The used test rig was limited to install an extensometer at the gauge length of the cylindrical fatigue specimen inside the small autoclave. So the magnet type LVDT's were used to measure the fatigue displacement at the specimen shoulders inside the high temperature and high pressure water autoclave. However, the displacement and strain measured at the specimen shoulders is different from the one at the gauge length for the geometry and the cyclic strain hardening effect. FEM calculated the displacement and the strain of the gauge length from the data measured at the shoulders. Tensile test properties in elastic and plastic behavior of CF8M material were used in the FEM analysis. A series of low cycle fatigue tests simulating the cyclic strain hardening effect verified that the FEM calculation was well agreed with the simulated tests. The process and method developed in this study would be so useful to produce reliable environmental fatigue curves of CF8M stainless steel in pressurized water reactors.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.2
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• pp.177-185
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• 2008

Low-cycle environmental fatigue tests of cast austenitic stainless steel CF8M at the condition of fatigue strain rate 0.04%/sec were conducted at the pressure and temperature, 15MPa, $315^{\circ}C$ of a operating pressurized water reactor (PWR). The used test rig was limited to install an extensometer at the gauge length of the cylindrical fatigue specimen inside a small autoclave. So the magnet type LVDT#s were used to measure the fatigue displacement at the specimen shoulders inside the high temperature and high pressure water autoclave. However, the displacement and strain measured at the specimen shoulders is different from the one at the gauge length for the geometry and the cyclic strain hardening effect. Displacement of the fatigue specimen gauge length calculated by FEM (finite element method) used to modify the measured displacement and fatigue life at the shoulders. A series of low cycle fatigue life tests in air and PWR conditions simulating the cyclic strain hardening effect verified that the FEM modified fatigue life was well agreed with the simulating test results. The process and method developed in this study for the environmental fatigue test inside the small sized autoclave would be so useful to produce reliable environmental fatigue curves of CF8M stainless steel in pressurized water reactors.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.3
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• pp.333-338
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• 2013

The compressive residual stress and fatigue behavior of shot peened alloy 600 under a high-temperature environment is investigated in this study. Alloy 600 is used in the main parts of nuclear power plants, and the compressive residual stress induced by the shot peening process is considered to prevent SCC (stress corrosion cracking). To obtain practical results, the fatigue characteristics and compressive residual stress are evaluated under the actual operating temperature of a domestic nuclear power plant, as well as a high-temperature environment. The experimental results show that the peening effects are valid at a high temperature lower than approximately $538^{\circ}C$, which is the threshold temperature. The fatigue life was maintained at temperatures lower than $538^{\circ}C$, and the compressive residual stress at $538^{\circ}C$ was 68.2% of that at room temperature. The present results are expected to be used to obtain basic safety and reliability data.

• Korean Journal of Environment and Ecology
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• v.10 no.2
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• pp.191-204
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• 1997

Eight major trails of Soraksan National Park were selected to investigate the use impacts on environmental edterioration of trail according to the different amount of use. The entire width, bare width, maximum depth and slope of trail as the trail condition surveyed at the total of 188 points were significantly greater on the more heavily-used trail. Major deterioration types of trail were root-exposure, widening, rock-exposure, divergence in order of frequency. And trail conditions of edteriorated points were significantly different from those of non-deteriorated points. The damaged area more severe than Class 4 on trail reached about 10,864m$^{2}$ in total, and especially about 4,560m$^{2}$ in the section between Huiunkak Shelter-Munomigogae trail. The dominant trees of trail edge vegetation were be Quercus mongolica in upper layer, but in lower lauer Carpinus laxiflora, Lespedeza maximowiczii for valley and Carpinus laxiflora, Ghododendron mucronulatum var. cilatum, Tripterygium regelii for ridge.. Especially coverage and number of individuals was highest on Munomighgae-Taech'ongbong trail of the largest use of amount, and each trail was dissimilar in species composition of lower layer of edge vegetation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.14 no.6
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• pp.26-34
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• 2000

The considerations for remaining life of ACSR (Aluminum Stranded Conductors Steel Reinforced) in transmission lines have become gradually important to hold reliability and stability of power supply. The remaining life of ACSR exposed to the atmosphere for a long period may rely on deterioration caused by environmental indices such as atmospheric corrosion, galvanic corrosion, crevice corrosion and fatigue corrosion. One of reduction of useful life in overhead transmission lines built on the ridge of mountain is often caused by forest fires.This paper deals with investigation of strength deterioration performance of ASCR due to fires through several testing and analyzing data for tension load and extension of blazed ACSR. Test samples are ACSR 480[$\textrm{mm}^2$] conductors, which are artificially fired to regular durations. Mechanical properties such as tension load and extension for fired ACSR conductors are tested and estimation functions for mechanical performances corresponding to fire duration are determined. As a result, it can be verified that both tension load and extension of ACSR are reduced by increasing fire duration. Hence, it is obvious that ACSR due to forest fires may lead to mechanical deterioration.