• Journal of Ocean Engineering and Technology
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• v.12 no.3 s.29
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• pp.42-48
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• 1998

구형 관입시험에 의한 얼음의 균열을 연구 하였다. $-10^{circ}C$에서 S2 기둥얼음의 시편(152mm X 152mm X 152mm)에 stainless 강으로 된 구(지름 25.4mm)로 하중을 가하였다. 구형indentor는 얼음 시편의 장축인 기둥방향에 수직으로 하중을 가하였으며 이때 변위율은 0.038mm/s로 하여 단조증가 하중 시험을 하였다. 하중을 가하기 시작하면 indentor 하부에서 crushing 이 발생하고, 하중이 증가함에 따라서 방사선 균열 또는 횡균열이 성장하여 splitting 또는 spallation이 발생하였다. 단조증가 하중 때와 동일한 indentor를 사용하여 하중 및 비하중율 0.5KN/s로 맥박하중을 가할 때 이들 방사선 균열 및 횡 균열이 발생 성장하였다. 첫 맥박 하중의 크기는 1KN으로 하고 그 뒤 계속 이어지는 시험은 맥박 하중의 크기를 증가시킨 뒤 행하였으며 균열 길이는 맥박과 맥박 사이에서 계측 하였다. 기타 취성고체에서 관찰 되었던 것과 같이 방사선 균열 및 측면균열의 길이는 impression 반지름과 하나의 지수법칙이 성립함을 보여주었다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.9
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• pp.1146-1151
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• 2019

Histogram H is an x-monotone rectilinear polygon with a horizontal edge, called by a base, connecting the leftmost vertical edge and the rightmost vertical edge. Here the rectilinear polygon is a polygon with only horizontal and vertical edges and the x- monotone polygon P is a polygon in which every line orthogonal to the x-axis intersects P at most twice. Walking counterclockwise on the boundary of a histogram H yields a sequence of left turns and right turns at its vertices. Conversely, a given sequence of the turns at the vertices can be realized by a histogram. In this paper, we consider the problem of finding a histogram to realize a given turn sequence. Particularly, we will find the histograms to minimize its area and its bounding box. It will be shown that both of the problems can be solved by linear time algorithms.

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.11a
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• pp.24-25
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• 1996

• Proceedings of the Materials Research Society of Korea Conference
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• 1997.05a
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• pp.75-75
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• 1997

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.395-398
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• 2006

Forging is applied for many industrial fields. Also, it is applied to hose nipple. Stress and metal analysis is finding method of forging possibility and we predict this possibility by finite element forging analysis. But there are also many manufacturing procedure after forging, and metal texture is varied by additional heat treatment or coating. So this research is focused on the measuring and analysis of plastic residual stress distribution at overall manufacturing procedure. From raw material to final product we measured real residual stress at each manufacturing procedure by X ray diffract meter, and simulated another procedure except forging by nonlinear finite element analysis. Also we showed how Zn-Ni coating is more contributable to metal strength than Zn coating. By this research we make final conclusion that process analysis must be observed from raw material to final manufacturing state for robust design.

• Korean Journal of Materials Research
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• v.7 no.2
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• pp.129-135
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• 1997

This study has investigated the effects of aging treatment on thc nlechanical propcrries of blg-iiAl-x%nix - 0.1.2) alloys fabricated by the squeeze castmg process. The microstructurcs of as-squeeze cast were composed of pro eurectic $\alpha$ magnesium solid solution, super saturated $\alpha$ solid solution and $\beta(Mg_{17}AI_{12}$) compund. Agcd at both $200^{\circ}C$ and $240^{\circ}C$, Mg--6AixZn alloys showed the peak hardness due to the formation of $\beta(Mg_{17}AI_{12}$) precipitates. The tiiscontinuous precipitates of the lamella r\.pe are predominant at $200^{\circ}C$ aging tredrment. tvhilc. the finely dispersed continu ous precipitates were major type at $240^{\circ}C$ treatment. Mg-- GAI-xZn a1loi.s fabricated hy the squeeze casting process had the hetter combination of tensile strength and elongation compared to the conventionally cast alloys. As increascci zinc: contents. the tensile strength was increased 11y the soiid solutirin strengthening effect of zinc,.

• Journal of Korea Foundry Society
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• v.17 no.5
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• pp.419-425
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• 1997

용탕단조방법에 의해 제조된 Mg-6Al-xZn(x=0, 1, 2)합금의 기계적 성질에 미치는 시효열처리의 영향을 조사한결과 아래와 같은 결론을 얻었다. (1) 주조조직을 관찰한 결과 미세한 수지상조직을 나타냈으며 초정${\alpha}$, 과포화 ${\alpha}$, ${\beta}$상 등 세가지 상으로 구성되어 있었다. (2) Mg-6Al-xZn합금은 시효경화성을 나타내었으며 Zn의 첨가량이 증가할수록 전시효구간에서 경도값이 높게 나타났다. (3) 시효조직을 관찰한 결과 $200^{\circ}C$의 시효시에는 불연속 석출물이 대부분 차지했으나 $240^{\circ}C$의 시효온도에서는 수지상 경계에서 시작되는 미세분산된 연속석출물이 대부분 이었다. (4) $240^{\circ}C$에서 시효열처리 한 시편은 연속석출물이 석출됨으로서 $200^{\circ}C$에서의 시효열처리된 시편에 비하여 과시효되는 경향이 작았다. (5) T6열처리 후 인장시험 결과 Zn 첨가량에 따라 강도가 증가하였는데 Mg-6Al-2Zn합금의 경우 인장강도는 248.4 MPa을 나타내었으며 Zn양에 따른 연신율의 감소는 나타나지 않았다.

• Journal of the Korea Society of Computer and Information
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• v.11 no.1 s.39
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• pp.45-53
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• 2006

Finite failure NHPP models presented in the literature exhibit either constant, monotonic increasing or monotonic decreasing failure occurrence rates per fault. In this paper, Goel-Okumoto and Yamada-Ohba-Osaki model was reviewed, proposes the $x^2$ reliability model, which can capture the increasing nature of the failure occurrence rate per fault. Algorithm to estimate the parameters used to maximum likelihood estimator and bisection method, model selection based on SSE, AIC statistics and Kolmogorov distance, for the sake of efficient model, was employed. Analysis of failure using real data set, SYS2(Allen P.Nikora and Michael R.Lyu), for the sake of proposing shape parameter of the $x^2$ distribution using the degree of freedom, was employed. This analysis of failure data compared with the $x^2$ model and the existing model using arithmetic and Laplace trend tests, Kolmogorov test is presented.

• Journal of the Mineralogical Society of Korea
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• v.20 no.4
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• pp.231-245
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• 2007

The forged iron axe of the middle 3rd Century found in the No. 2 wood-framed tomb from the Hwangseongdong site, Gyeongju is rectangular on the plane level. The iron axe shines in met-allic luster, which is light grey with pale creamy tint. The result of X-ray diffraction analysis shows that the axe consists of magnetite and geothite, which can explain why the composition and texture of the original ore has been kept intact. There are fine-grained quartz, calcite, mica, magnetite, amphibole, unknown tungsten minerals, pyroxene and olivine inside the axe. Those must be the impurities that they failed to remove in the thermal treatment process. Generally, the iron axe consists mainly of pearlite texture coexisting ferrite and cementite, and show high carbon contents with homogeneous distribution. It can be interpreted the axe was carburized after the material was made to resemble pure iron. The decarbonization work didn't go well along the process marks. Crude ores of the iron axe are possible utilized by magnetite from the Ulsan mine on the basis of the occurrences and inclusions. It's estimated that the original ore was bloom produced in low-temperature reduction and formed around in $727^{\circ}C$, which is eutetic temperature.

• Journal of the Korean Society for Heat Treatment
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• v.12 no.1
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• pp.1-8
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• 1999

This study has investigated the effect of aging treatment on the microstructure and mechanical properties of Mg-6Al-xZn(x = 1.5, 2.5) alloys fabricated by the squeeze casting process. The microstructures of as-squeeze cast were composed of pro-eutectic ${\alpha}$, super saturated ${\alpha}$ and ${\beta}(Mg_{17}Al_{12})$ compound. Aged at both $200^{\circ}C$ and $240^{\circ}C$, Mg-6Al-xZn alloys showed the peak hardness due to the formation of ${\beta}(Mg_{17}Al_{12})$ precipitates. The discontinuous precipitates of the lamella type are predominant at $200^{\circ}C$ aging treatment, while the finely dispersed continuous precipitates were dominant at $240^{\circ}C$ aging treatment. Mg-6Al-xZn alloys fabricated by the squeeze casting process had the better combination of tensile strength and elongation compared to the conventionally cast alloys. As zinc contents increased, the tensile strength was increased by the solid solution strengthening effect of zinc.