• Journal of the Korean Society of Safety
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• v.15 no.1
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• pp.140-145
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• 2000

This paper was composed with fatigue test of the cruciform specimens, as load carrying and non-load carrying type. It also has performed computational analyses for geometric condition of the fillet welding bead. As test results, the effect of stress ratio in the specimen was insignificant. Stress ranges were varied with R=0.1~0.2. The fatigue cracks that were found in the load carrying type specimens and most specimens welded with contact were developed at the end of welds. The fatigue strength of specimen that have fractured in maternal plate was found about ${\Delta}\sigma_c$=63.5MPa. It's about 24% less than that of the non-load carrying type specimens having about ${\Delta}\sigma_c$=83.8MPa. A category of the Fatigue design specifications which provide for cruciform details was defined grade C as a stress of the maternal member. And then, the fatigue strength to be transformed into the maternal stress was found about 78.27 MPa, it tends to be less than that of allowable fatigue strength.

• Plant Journal
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• v.9 no.4
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• pp.31-36
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• 2013

In order to extend a hot gas parts replacement cycle of a gas turbine, blade row 1 from low pressure turbine, which has a significant impact on the cycle, has been selected from stored set after one cycle use. Taking into account the status of the first stage moving blade in LP turbine operated more than 27,000 equivalent operating hours(EOH) and the replacement cycle in the same type of gas turbine, the replacement of the high temperature components installed on the GT, a study subject, can be extended from 24,000 to 27,000 EOH.

• Journal of Welding and Joining
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• v.14 no.2
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• pp.19-27
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• 1996

재료의 표면개질은 표면층의 조직변화에 대한 개질법과 표면피복에 의한 개질 법으로 나눌 수 있다. 조직변화에 의한 개질법으로는 침탄, 질화, 이온주입 및 금속 확산 등이 있고, 표면피복에 의한 개질법으로는 도장, 도금, 육성용접, 물리증착(PVD) 및 화학증착(CVD) 등이 있는데, 용사법은 표면피복에 의한 개질법에 속한다. 용사기술 은 비교적 최근에 발달된 표면피복 기술로서 그림1과 같이 플라즈마, 가스화염 또는 아크열원을 이용하여 금속 또는 비금속 재료를 용융 혹은 반용융 상태로 모재에 고속 도로 분사하여 충돌 적층시켜 피복하는 공정으로 다른 표면개질기술에 비해서 여러 가지 잇점을 가지고 있다. 이것은 거의 모든 재질의 모재(금속, 세라믹, 유기재료 등) 에 대해 피막의 형성이 가능하고, 용사재료의 종류도 다양하다(금속, 합금, 각종 세라 믹, 플라스틱, 각종 복합재료 등). 또한 노재크기의 제한이 없고, 대형의 재료에 대해 서 한정된 부위의 피복이 가능하며, 모재의 열영향이 적고, 피막의 형성속도가 다른 피막법에 비해 빠른 장점을 가지고 있다. 그 예로 알루미나(Al$_{2}$O$_{3}$)를 피복할 경우 화학증착(CVD)법에 의해서는 피막형성 속도가 약 2 * $10^{-4}$mm/min 인데 비해 용사법에 의해서는 약 7.5 * $10^{-1}$mm/min로 매우크다. 이와같은 많은 장점을 갖고있는 용사법을 이용한 표면개질에 대해 본 기술보고에서 서술하고자 한다.

• Korean Journal of Soil Science and Fertilizer
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• v.26 no.1
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• pp.1-9
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• 1993

A study was carried out to investigate the genesis and mineralogical characteristics of clay minerals in three different types of soil derived from the gray shale distributed in Kyeongbuk Province in Korea. The soils have been developed from parent materials of residuum (Daegu series, Sirye series), colluvium(Banho series), and alluvium (Bigog series) of the same origin of parent rock with a topographical sequence. The investigation mainly focussed on the mineralogical aspects of primary minerals of asnd and silt fractions, identification and quantification of clay minerals, and characterization of hydroxy-interlayered mineral (HIM) along with their chemical composition. The identification was done through analyses of chemical, X-ray diffraction, and thermal methods. The major clay minerals in the soils are illite, vermiculite, kaolin and HIM, while chlorite and mixed layer minerals such as illite/chlorite and illite/vermiculite were coexisted as a subsidiary minerals. The distribution of clay minerals, however, varies according to the location and types of parent material. In the soils derived from the parent material of residuum, the upper soil (Daegu series) shows higher of 2:1 type minerals such as illite, vermiculite, and HIM than 1:1 type mineral rich in the lower soil(Sirye series). Soils developed from the parent material of colluvium and alluvium were high in illlte and mixed layer minerals, but low in HIM compared with the residual soils. The predominant weathering sequence of the clay minerals in each soil could be inferred as follows according to the minerlogical distribution and quantification of clay minerals : Daegu series, illite ${\rightarrow}$ vermiculite ${\rightarrow}$ HIM ; Sirye series, vermiculite ${\rightarrow}$ kaolin minerals ; Banho sereies and Bigog series, illite ${\rightarrow}$ illlte/vermiculite and/or illite/chlorlte mixed layer ${\rightarrow}$ vermiculite.

• Journal of the Korean Society for Nondestructive Testing
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• v.17 no.1
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• pp.1-10
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• 1997

In this paper, the effects of temperature change (low and high temperature) on the impact damages of CFRP laminates was experimentally studied. Composite laminates used for this experiment are CF/epoxy orthotropic laminated plates, which have two-interfaces $[0^{\circ}\;_6/90^{\circ}\;_6]s$ and $[0^{\circ}\;_4/90^{\circ}\;_4]s$. And CF/PEEK orthotropic laminated plates, which have two-interfaces $[0^{\circ}\;_4/90^{\circ}\;_4]s$. And, this study aims experimentally to present the interrelations between the impact energy vs. impact damages (i.e. delamination area and matrix crack) of CFRP laminates (CF/epoxy, CF/PEEK) subjected to FOD(foreign object damage) under low and high temperatures. A steel ball launched by the air gun collides against CFRP laminates to generate impact damages.

• Journal of Energy Engineering
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• v.18 no.1
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• pp.49-55
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• 2009

Occurrence of hydrogen embrittlement could be one of the main obstacles for using structural equipment under hydrogen environment. It is required to develop assessment methods of hydrogen embrittlement for the metals used in production, storage, transmission and application utilities of hydrogen. The most probable method of hydrogen mass transmission is using existing natural gas pipeline. Base or weld part of the pipeline can be damaged by mixed gas of hydrogen in the pipeline. In this study small punch (SP) testing was employed to evaluate the hydrogen embrittlement behavior for a line pipe steel (API X65) with electrochemically hydrogen charged specimens. Results showed that the SP test can be a good candidate test method for hydrogen damage evaluation method. Strength of steel is known to be decreased with the level of hydrogen charging. However, for API X65 steel base metal need in this study, the effect of hydrogen to strength was not significant. It can be negligible regardless of the hydrogen contents in the steel. With this test different strength levels with various hydrogen charging conditions were observed. It can also be anticipated that more sensitive evaluation of material behavior be obtainable by the SP test method.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.41-44
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• 2008

본 연구에서는 고분자 전해질 연료전지용 금속분리판의 전기화학적 부식을 방지하기 위한 금속 첨가 DLC(Diamond-like-carbon) 표면처리 방법을 개발하였으며, stainless steel 304를 모재로 하여 텅스텐 첨가 DLC, 티타늄 첨가 DLC, 몰리브덴 첨가 DLC 금속분리판을 제작하였다. 제작된 금속분리판을 이용하여 내구성 평가,전기화학적 부식 특성, 성능평가 및 접촉저항 특성 등을 평가하였다. 전기화학적 부식특성의 경우 각각의 분리판에 대해 6.69, 1.2, 1.0 ${\mu}A/cm^2$로 모재인 STS 304의 25 ${\mu}A/cm^2$의 부식전류밀도에 비해 우수한 부식특성을 보였다. 또한 초기 성능에서 몰리브덴 첨가 DLC 분리판의 경우 300 mA/$cm^2$에서 0.757 V로 측정되었으며, 이는 graphite 분리판 측정 결과인 0.758 V와 유사한 성능을 보였다. 또한 내구성 평가에서 초기 성능 대비 성능 감소율이 10% 감소하는데 소요된 시간은 graphite 분리판의 경우 2,000시간으로 나타났으며, 몰리브덴 첨가 DLC 분리판의 경우 1,700시간으로 측정되었다. 1,500시간 까지의 성능 감소율은 grphite,텅스텐 첨가DLC,티타늄 첨가DLC, 몰리브덴 첨가 DLC 분리판 순으로 각각에 대해 37.7, 60.3, 92.8, 45.7 ${\mu}V$/hr로 나타났다.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.4
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• pp.409-417
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• 2014

Since the oil price has been significantly jumped for recent some years, the diesel engine of the merchant ship has been mainly used the heavy oil of low quality. Thus, it has been often exposed to severely corrosive environment more and more because temperature of the exhaust gas in a combustion chamber is getting higher and higher with increasing of using the heavy oil of low quality. As a result, wear and corrosion of most parts surrounded with combustion chamber is more serious compared to the other parts of the engine. Therefore, an optimum weldment for these parts is very important to prolong their lifetime in a economical point of view. In this study, four types of filler metals such as Inconel 625, 718, 1.25Cr-0.5Mo and 0.5Mo were welded with SMAW and GTAW methods in the forged steel which would be generally used with piston crown material. And the corrosion properties of weld metal, heat affected zone and base metal were investigated using electrochemical methods such as measurement of corrosion potential, anodic polarization curves, cyclic voltammogram and impedance etc. in 35% H2SO4 solution. The weld metal and base metal exhibited the best and worst corrosion resistance in all cases of filler metals. In particular, the weld metal welded with filler metals of Inconel 718 revealed the best corrosion resistance among the filler metals, and Inconel 625 followed the Inconel 718. Hardness relatively indicated higher value in the weld metal compared to the base metal. Furthermore, Inconel 625 and 718 indicated higher values of hardness compared to 1.25cr-0.5Mo and 0,5Mo filler metals in the weld metal.

• Journal of the Korean Magnetics Society
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• v.11 no.1
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• pp.1-7
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• 2001

We investigated to DC magnetic characteristics, the dependence of annealing temperature on the crystal grain and the crystalline orientation for grain-oriented silicon ribbon with 100 $\mu\textrm{m}$ final thickness manufactured by three times cold rolling method using the hot-rolled silicon steel plate as a raw material. The growth of (110)[001] Goss texture were almost observed in the whole area of the sample. The values of the saturation magnetic flux density B$\sub$s/ and the average ${\alpha}$ angle have 1.9 T and 4.6 degrees respectively. From this result we could be confirmed that the three times cold rolling method has a possibility of manufacture for oriented ultra-thin silicon ribbons much more simple and cheeper than the existing oriented silicon steel manufacturing method by means of more simplified producing process.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.04a
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• pp.103-104
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• 2007

Cr-Mo-Si-N 코팅막은 AISI D2 모재와 Si 모재위에 $Ar/N_2$ 혼합기체를 사용하여 AIP (arc ion plating) 방법과 마그네트론 스퍼터링 (DC magnetron sputtering) 방법을 결합시킨 하이브리드 코팅시스템을 이용하여, 증착하였다. XRD, HRTEM, XPS 등의 분석장비를 이용하여 Cr-Mo-Si-N 코팅의 미세구조를 관찰하였다. Cr-Mo-Si-N 코팅의 경도는 Si함량이 12.1 at.%에서 약 50 GPa의 최고치를 나타냈으며, 평균 마찰계수는 Si 함량이 증가할수록 감소하였다.