• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1994.04a
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• pp.3-9
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• 1994

초고강도 마레이징강의 초박판 고정밀 연소관의 유동성형공정 조건을 도출하기 위하여 치수제어 시험을 실시하고 가공열처리 공정이 적용된 연소관의 물성 및 구조시험을 통해 신뢰성을 평가하였다. 두께 0.5mm 이하인 초박판 연소관의 유동성형에서 두께증가 현상은 성형속도 0.5-0.75mm/rev에서 X롤러의 성형비를 상대적으로 10%이하로 하고. 성형반경을 4mm로 작게 함으로써 제어할 수 있었으며. 이와 같이 개발된 연소관은 인장강도가 300ksi 이상으로 크게 강화되었고, 예상 최대작동압력에 대한 안전계수가 1.3 이상으로서 구조적 안전성이 입증되었다.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05c
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• pp.335-340
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• 1996

핵융합로 제1벽 재료의 후보재로 고려되는 Fe-Cr-Mn계 스테인리스강을 진공 용해하여 이 합금의 미세 조직 및 기계적 성질 그리고 부식 특성에 미치는 Mn, W의 첨가 효과 및 소둔 열처리 온도의 효과에 대하여 실험하였다. 미세 조직 분석은 광학 현미경 관찰, XRD분석 등으로 행하였으며, 기계적 시험으로는 상온 인장 시험, 경도 시험 및 충격 시험을 행하였다. 그리고 부식 시험으로는 부식 환경을 염산과 황산으로 나누어 각 환경에서의 양극 분극 시험을 행하였다. Mn함량이 증가할수록 오스테나이트상이 증가하고 있으나, $\alpha$'마르텐사이트는 급격히 감소하는 대신$\varepsilon$마르텐사이트는 Mn함량이 20%일 때 최대간을 보인 뒤 감소하고 있다. Mn함량이 증가할 수록 또한 소둔 온도가 상승할수록 항복 강도, 인장 강도 및 경도는 감소하였으며 연신율은 증가하였다. 이러한 결과는 합금 중의 오스테나이트 및 마르텐사이트 조직의 함량과 밀접한 관련이 있는 것으로 판단된다. 한편 합금 중의 Mn함량이 증가할수록 부식 환경에 관계없이 부식 저항성의 변화는 크지 않은 것으로 나타났다. 그러나 W함량이 증가하면 환경에 관계없이 임계 전류 밀도를 감소시키나, 부동태 전류 밀도는 HCI환경에서는 감소시키고 H$_2$SO$_4$환경에서는 오히려 증가시키는 상반된 효과가 나타났다.

• 한국가스학회:학술대회논문집
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• 2003.10a
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• pp.53-58
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• 2003

API 5L X65 배관에 50mm이상의 단관을 삽입하여 용접하였을 경우, 삽입된 단관 길이 변화에 따른 용접부 기계적 특성 평가 결과를 요약하면 다음과 같다. 1. 단관삽입 용접부위의 거시적 조직관찰, 미소경도측정, 인장시험, 굽힘시험을 수행한 결과, 단관삽입 용접부의 건전성에는 문제가 없는 것으로 평가되었다. 2. 단관삽입 용접부의 원주방향 최대 인장 잔류응력의 크기는 단관 삽입 길이에 관계없이 약 150MPa로서 그리고 최대 압축 잔류응축은 약 300MPa로 측정되었다. 모재의 항복강도가 492MPa인 것과 비교하여보면 단관 삽입 용접에 의한 잔류응력의 영향은 매우 작은 것으로 평가되었다.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.564-565
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• 2011

본 연구는 154 kV, 345 kV급 초고압 케이블의 수직구간 활락 안전성에 대한 평가를 진행하였다. 안전성에 대한 평가는 유한요소해석법을 이용하여 진행하였으며, 당사에서 제작한 케이블 및 클리트에 대하여 케이블의 자중과 발열에 따른 제품 내부의 응력과 케이블의 변형량에 초점을 맞추어 비교 분석하였다. 해석 결과, 하중 및 발열에 대해 재료의 인장강도 측면에서 충분한 안전율을 가지고 있는 것으로 나타났으며, 변위 해석 또한 최대 변위 발생부가 최대 응력 발생부와 관계없는 케이블 끝단에서 나타나는 것으로 볼 때, 재료 건전성 측면에서 안전한 것으로 해석되었다. 본 연구는 향후 경사지나 수직구간의 포설 설계시 해석적 방법으로 포설 안전성을 확보하는데 기여할 수 있을 것으로 사료된다.

• Journal of the Korean institute of surface engineering
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• v.16 no.3
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• pp.108-123
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• 1983

순수 Mo와 Mo-Nb, Mo-Ta($\leq$10 at% Nb. Ta)합금을 1,500-2,06$0^{\circ}C$ 범위에서 탄소의 고용도를 연구하였다. 특수한 침탄방법으로 C2H2를 시편에 침탄한후 열처리하여 부분적으로 석출하거나 완전석출에 관계없는 화학적 분석방법으로 행하였다. 순수 Mo에서 최대탄소 고용도는 logCCmax = 7.02-9,490/T이다. Nb, Ta를 미량첨가하여 탄소의 최대 고용도는 Arrhenius 식을 적용할 수 없다. Nb-, Ta- 농도와 온도에 따라 Mo2C와 Nb-,Ta-를 함유한 여러 가지 탄화물상을 만들거나 $\alpha$고용체와 Mo가 포함된 NbC, TaC와 평형상태를 나타나기 때문이다. 실험온도 범위에서 Nb, Ta를 첨가량을 증가하면 탄화물 내부에 NbC, TaC로 석출된다. 고온에 용해된 a-고용체는 150-200 oK/Min으로 냉각하면 석출물은 결정입계나 결정내부에 나타난다. 순수 Mo에 Nb, Ta를 첨가하여도 경도, 파괴실험에서와 같이 인장강도는 크게 증가하지 않는다.

• Korean Journal of Food Science and Technology
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• v.30 no.6
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• pp.1285-1294
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• 1998

Whey powder, a by-product of milk industry, was utilized to produce biopolymer film with the combination of film matrix supporting material, sodium caseinate. Biopolymer films were prepared from whey powder-sodium caseinate mixtures at several mixing ratios. The effects of pH, plasticizers and cross-linkers on tensile strength (TS) and elongation (E) of films were investigated. The films could be formed by use of whey powder up to 70%. As the whey powder content was increased, TS of the film decreased while E increased. Films containing more than 70% of whey powder could not be formed due to the stickiness of lactose in whey powder. The optimum pH of the film solution was found to be 10. Among the plasticizers tested, sorbitol was found to be the most effective plasticizer while glycerol was inadequate for the film. Tensile strengths of films containing $30{\sim}40%$ whey powder were higher than 10 MPa with relatively high E, when the films were plasticized with 30% (w/w) and 40% sorbitol. TSs of the relatively weak films containing $50{\sim}60%$ whey powders were improved by the addition of small amount of sodium citrate for 30% sorbitol plasticized films, and by the addition of sodium chloride for 40% sorbitol plasticized films. It was concluded that up to 70% of whey powder could be utilized to produce biopolymer films by adding sorbitol and cross linkers at pH 10.

• Korean Journal of Agricultural Science
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• v.14 no.2
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• pp.345-357
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• 1987

This study was performed to obtain the basic data which can be applied to improve the early strength of concrete. The results obtained were as follows; 1. In case that water reducing-set accelerating agent was added 0.75% of the weight of cement, the weight of water was reducd 10%. And $CaCl_2$ did nearly not have an effect on the w/c ratio. 2. Compressive strength and tensile strength increased 25%, 43%, respectively, in case that $CaCl_2$ was 2.0% of the weight of cement, and showed 120%, 140%, respectively, in case that water reducing-set accelerating agent was 0.75% of the weight of cement. 3. In case of steam curing at $60^{\circ}C$, the strength increased with the ages. At $100^{\circ}C$, the increase of strength in 1 age was two times as compared with plain concrete. After 7ages, the strength was similer to plain concrete. 4. The relationship between compressive strength and tensile strength was linear and was highly significant in cases of plain concrete, $CaCl_2$ concrete, C-W concrete, steam cured concrete, respectively.

• The korean journal of orthodontics
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• v.33 no.2 s.97
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• pp.103-111
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• 2003

The Purpose of this study was to evaluate the effect of occlusion on the mechanical strength of periodontal fibers during retention periods after experimental tooth movement. In the Sprague-Dawley male rats weighing 200g or more, the ntraoral elastics were inserted into the both right and left interproximal space between upper first and second molars for tooth movement. kiter 4 days later, the left lower first, second, and third molars were extracted for differentiating the non-occlusal side from the occlusal side in the same mouth. At the same time the elastics were removed and then light cured resin was Placed in the space between upper first and second molars following undercut was made for retention bilaterally. From the beginning of retention, 7 rats were sacrificed at 0, 4, 8, 12, 16, 20 days respectively. For evaluating of magnitude on the mechanical strength of periodontal tissue, the maximal shear load of the upper first molars were measured bilateraly during extraction using Instron Universal Testing Machine. The results of this study were obtained as follows : 1. In the occlusal side, the maximal shear load was increased from no retention to retention 20 days group as time was going and statistically difference was shown from retention 12 days group (p<0.05). 2. In the non-occlusal side, the maximal shear load was increased slightly from no retention to 20 days group as time was going but there was no statistically difference (p>0.05). 3. The result compared with the maximal shear load between occlusal and nonocclusal side showed no statistically difference until retention 8 day group (p>0.05), but showed statistically difference from retention 12 day to 20day group (P<0.05). These results show that occlusion had an effect on mechanical strength of the periodontal fibers during retention periods after experimental tooth movement; therefore, it is suggested that occlusion should be considered while the retainer types and retention period are planned.

• Journal of the Society of Disaster Information
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• v.20 no.2
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• pp.411-418
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• 2024

Purpose: This study aims to develop brand new bolt fastening type of seismic retrofit using high tensile alloy materials for existing reinforced concrete columns. Method: A T-type cross-sectional seismic retrofit made of SUS304 and SS275, and the high-tensile bolt of SCM435 was analyzed for the effect of material properties on seismic performance through bending test. Result: The experiment using SUS304 shows a 7% higher maximum strength and 22% higher yield strength and shows a higher compressive stress of 360MPa. In addition, the change in the neutral axis is also smaller. Conclusion: Seismic retrofit using SUS304 is considered to be better in terms of yield strength, tensile strength, neutral axis change, and ductility, and it is considered necessary to experiment with RC column real experiments in future studies.

• Korean Journal of Agricultural Science
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• v.14 no.2
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• pp.373-383
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• 1987

No-fines concrete is concrete from which the fine aggregate fraction has been omitted. The concrete so formed, consisting only of coarse aggregate, cement, and water, has large voids uniformly distributed through its mass. This study was performed to obtain the basic data which can be applied to the use of no-fines concrete. The data was based on the properties of no-fines concrete depending upon various mixing ratios. The results obtained were summarized as follows. 1. Test result of the consistency, suitable water-cement ratio was increased with the increasing of mixing ratio. 2. At the suitable water-cement ratio, the highest strengths were showed. But it gradually was decreased with the increasing of mixing ratio and strengths are considerably lower than that of conventional portland cement concrete. 3. The relations between compressive and tensile strength were highly singnificant as a straight line shaped. The strength ratio was decreased with the increasing of mixing ratio and considerably lower than of conventional portland cement concrete. 4. Bulk density was decreased with the increasing of the mixing ratio, and was similar to that of the conventional portland cement concrete at mixing ratio 1:4. 5. The relations between strength and bulk density were highly significant as a straight line shaped. The decreasing ratio of strengths was higher than that of bulk density.