• 한국해양공학회지
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• 제25권6호
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• pp.49-55
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• 2011

In order to analyze feasibility of replacing a conventional 6-mm Ti bar with a 5-mm bar, a series of rotating bending fatigue tests were carried out on Ti-6Al-4V bars by strengthening the fatigue performance using a special technique called UNSM (Ultrasonic Nanocrystal Surface Modification). The results of S-N curves clearly showed that the performance of the 5-mm titanium specimen was similar to that of the 6-mm specimen when the UNSM treatment was applied. The 5-mm treated specimen converged with small scattering band into the linear line of the non-treated 6-mm one. Below the fatigue life of $10^5$ cycles, the UNSM treatment did not show any significant superiority in the bending stress and fatigue life. However, over the fatigue life of $10^5$ cycles, the effect of UNSM was superior for each fatigue life, and the bending stress became longer and higher than that of the untreated one. In the case of 6-mm Ti-bar with UNSM, the fatigue limit was about 592 MPa, and there was fatigue strength increase of about 30.7% at the fatigue life of $10^4$ cycles compared to the untreated 6-mm bar. Therefore, the compressive residual stress made by the UNSM in Ti-6Al-4V increased the fatigue strength by more than 30%.

• Journal of Biosystems Engineering
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• 제1권1호
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• pp.64-72
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• 1976

This experimental work was carried out to investigate the fatigue bending strength on various shapes and sizes of notches of the domestically manufactured steel plate. The notch types tested were a circular hole, U-and V-notches. The S-N diagram for different notch shapes were discussed in relation to plan bending strength and stress concentration factor of notches .The results of the experiments are summarized as follows : (1) The difference between stress concentration factor and notch factor was greater as the radium of notch root became smaller, and these values approached to an identical value as the radium of notch root increased. (2) It was shown that the plane bending fatigue limit of bar without notch for the hotrolled steel having the tensile strength of 33.1kg/$mm^2$was 17.0kg/$mm^2$. (3) U-and V-notch had a greater effect of stress concentration factor on the endurance limit, but O-hole showed the same effect only for $\o\pm2mm$. (4) For the same radius of notch root, U-notch showed a lower value of fatigue limit compared to V-notch and O-hole.

• 한국섬유공학회:학술대회논문집
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• 한국섬유공학회 2001년도 가을 학술발표회 논문집
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• pp.409-412
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• 2001

현재의 섬유산업의 동향은 소비자의 욕구가 다양화되고 있다는 점과 고급화가 되고 있다는 점에 초점을 맞춘 의복과 고기능 및 특수기능을 가진 생활관련제품 및 첨단제품으로서 발전되고 있다는 특징을 가지고 있다. 본 연구에 사용된 water-jet loom은 air-jet loom의 제직 폭의 한계를 해결하기 위해 연구하던 체코의 기술자 V. Svaty에 의해 개발되어 졌으며, 그 이후 Murata사가 기술도입을 통하여 1960년에 일본에서 처음 제작되었고, 그 후 다수의 직기 메이커들이 개발 및 개선을 거듭하여 상업적인 생산을 본격화한 것이다. (중략)

• 오토저널
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• 제13권3호
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• pp.19-24
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• 1991

본 고에서는 자동차 안전대책중에서 One-box car의 전면충돌 안전대책에 대하여 개략적으로 소개하고자 한다. 1. 충돌기본식 1/2M$V^{2}$=F.S에서 에너지 흡수율이 frame의 변형 평균 하중과 차체 변형량에 좌우된다. 2. frame 형상은 굽힘형보다 압축형이 동일한 변형구간에서 월등한 충돌에너지를 흡수한다. 3. 압축형 frame의 에너지 흡수효과는 main-frame의 버팀강도가 e.a-frame의 변형 하중보다 강해야만 그 효과를 충분히 얻을 수 있다.

• 한국철도학회논문집
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• 제10권2호
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• pp.201-210
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• 2007

Sandwich composites made of glass fabric epoxy facesheets with aluminum honeycomb core or balsa core is considered for the structural design of bodyshell of a Korean Low Floor Bus. Initially, in order to select the optimal facesheet and core materials in design stage, the flexural response of a sandwich composite is a critical importance. In this study, theoretical formula which could easily and quickly evaluate and obtain the flexural responses such as deflection and flexural stiffness of a sandwich composite subjected to external load was established. This theory could calculate the flexural responses of sandwich composites with narrow as well as wide width and with facesheets of unequal thickness, and also distinguish between the bending and shear effects of deflection. Finite element analysis using ANSYS V10.0 was used to offer the best elements for real sandwich composites, and flexural test according to ASTM C393 was conducted to compare with the results of theoretical formula and finite element analysis. The results show that the flexural responses of sandwich composites using proposed theoretical formula is in good agreement with those of experiment and finite element method.

• 대한기계학회논문집A
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• 제32권11호
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• pp.990-996
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• 2008

Nowadays, the trend to a lightweight design accelerates the use of advanced high strength steel (AHSS) in automotive industry. Springback phenomena is a hot issue in the sheet metal forming, especially bending process using AHSS. Several analytical methods for that have been proposed in recent years. Each of method has their advantages and disadvantages. There are only a few optimal solutions which can minimize the two objectives simultaneously. In this study, an effective method optimized the multi objective value. The method by the design of experiments(DOE) and artificial neural network(ANN) was presented to compensate springback of bending parts. This method was applied to L and V bending process. The effective method could be optimized to multiple object. It was confirmed that the proposed method was more efficient than traditional manual FEA procedure and the trial and error approach for springback compensation.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2001년도 추계학술대회 논문집
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• pp.247-252
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• 2001

Recently the steel parts used at automobiles are required to be used under high stress more than ever before in need of the weight down. To achieve this requirement of a high strength steel, it must be necessary to decrease inclusion content and surface defect as like decarburization, surface roughness etc.. In this study, the surface conditions are measured to know the influence on fatigue properties by two cases of shot peening of two-stage shot peening and single-stage shot peening. And for this study, two kinds of spring steel (SUP7, 50CrV4) are used. This study shows the outstanding improvement of fatigue properties at the case of two-stage shot peening in the rotary bending fatigue test and this is assumed to be from on low stress condition, the 1st stage shot peening is not affected by nonmetallic inclusion under metal. it is possible that the 2nd stage shot peening increases the fatigue life and the high stress but that is affected by nonmetallic inclusion under metal. so far beeasily 50CrV4 have made high stress. But, results also show fatigue failures originated at inclusion near surface, and this inclusion type is turned out to be a alumina of high hardness.

• 한국해양공학회지
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• 제15권3호
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• pp.93-99
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• 2001

Recently the steel parts used at automobils are required to be used under high stress more than ever before in need of the weight down. To achieve this requirement of a high strength steel, it must be necessary to decrease inclusion content and surface defect as like decarburization, surface roughness etc.. In this study, the surface conditions are measured to know the influence on fatigue properties by two cases of shot peening of two-stage shot peening and single-stage shot peening. And for this study, two kinds of spring steel (SAE 9254, DIN50CrV4) are used. This study shows the outstanding improvement of fatigue properties at the case of two-stage shot peening in the rotary bending fatigue test and this is assumed to be from (1) on low stress condition, th 1st stage shot peening is not affected by nonmetallic inclusion under metal.(2) it is possible that the 2nd stage shot peening increases the fatigue life and the high stress but that is affected by nonmetallic inclusion under metal. (3) so far beeasily DIN50CrV4 have made high stress. But, results also show fatigue failures originated at inclusion near surface, and this inclusion type is turned out to be a alumina of high hardness.

• 한국해양공학회지
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• 제15권4호
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• pp.66-72
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• 2001

Recently the steel parts used at automobiles are required to be used under high stress more than ever before in need of the weight down. To achieve this requirement of a high strength steel, it must be necessary to decrease inclusion content and surface defect as like decarburization, surface roughness etc.. In this study, the surface conditions are measured to know the influence on fatigue properties by two cases of shot peening of two-stage shot peening and single-stage shot peening. And for this study, two kinds of spring steel (JISG4081SUP7, DIN 50CrV4) are used. This study shows the outstanding improvement of fatigue properties at the case of two-stage shot peening in the rotary bending fatigue test and this is assumed to be from on low stress condition, the 1st stage shot peening is not affected by nonmetallic inclusion under metal. it is possible that the 2nd stage shot peening increases the fatigue life and the high stress but that is affected by nonmetallic inclusion under metal. so far beeasily DIN50CrV4 have made high stress. But, results also show fatigue failures originated at inclusion near surface, and this inclusion type is turned out to be a alumina of high hardness.

• 한국재료학회지
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• 제11권3호
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• pp.221-226
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• 2001

사파이어 ($\alpha$-$Al_2$$O_3$) 단결정에 있어 basal slip (0001)1/3<1120>의 전위속도를 4점 곡강도를 이용하여, 측정하였다. 이 곡강도는 온도 $1200^{\circ}C$ 에서 $1400^{\circ}C$ 그리고 응력은 90MPa, 120MPa, 160MPa에서 행하여졌다. 전위속도는 4 점굽힘 시편의 굽힘변위속도에 의해 구하여졌다. 얻어진 전위속도를 이용하여 전위속도의 온도 및 응력 의존성에 대해 검토하였다. 전위속도의 온도의존성을 이용하여 basal slip 전위속도를 위한 활성화에너지를 구하였으며, 그 값은 대략 2.2$\pm$0.4eV이었다. 한편, 전위속도의 응력의존성을 나타내는 응력지수 m은 2.0$\pm$0.2이었다.