• 대한전자공학회논문지SD
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• 제48권3호
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• pp.18-24
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• 2011

본 논문에서는 double boss 구조의 저압용 압력 센서의 다이아프램 브리지 모서리에 홈을 형성함으로서 압력센서의 내압특성을 향상시킬 수 있음을 확인하였다. 저압용 실리콘 압력센서에서는 일반적으로 boss구조가 널리 사용되고 있으나 칩에서의 제한된 다이아프램의 사이즈와 두께로 인하여 좋은 감도를 얻을 수는 없다. 특히, double boss구조는 다이아프램의 브리지 모서리 응력이 크게 작용함에 따라서 크랙이 생겨 다이아프램의 파괴가 진행되어 센서의 감도는 우수하지만 동작영역의 범위가 줄어들어 신뢰성에 문제가 있다는 단점을 가진다. 기존 double boss구조 압력센서 다이아프램 브리지에 모서리 홈의 길이를 $0.5{\sim}10{\mu}m$로 변화시키며 ANSYS 시뮬레이션을 시행하여 다이아프램 브리지 모서리와 브리지의 가장자리 그리고 압저항 소자가 위치하는 곳의 최대응력을 확인하였다. 그 결과 브리지 모서리의 길이가 6${\mu}m$이상인 경우, 브리지 모서리에서 발생하는 응력은 압저항 소자에 작용하는 응력보다 적다.

• 한국재료학회지
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• 제24권10호
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• pp.520-525
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• 2014

Effects of Cu and B on effective grain size and low-temperature toughness of thermo-mechanically processed high-strength bainitic steels were investigated in this study. The microstructure of the steel specimens was analyzed using optical, scanning, and transmission electron microscopy; their effective grain size was also characterized by electron back-scattered diffraction. To evaluate the strength and low-temperature toughness, tensile and Charpy impact tests were carried out. The specimens were composed of various low-temperature transformation products such as granular bainite (GB), degenerated upper bainite (DUB), lower bainite (LB), and lath marteniste (LM), dependent on the addition of Cu and B. The addition of Cu slightly increased the yield and tensile strength, but substantially deteriorated the low-temperature toughness because of the higher volume fraction of DUB with a large effective grain size. The specimen containing both Cu and B had the highest strength, but showed worse low-temperature toughness of higher ductile-brittle transition temperature (DBTT) and lower absorbed energy because it mostly consisted of LB and LM. In the B-added specimen, on the other hand, it was possible to obtain the best combination of high strength and good low-temperature toughness by decreasing the overall effective grain size via the appropriate formation of different low-temperature transformation products containing GB, DUB, and LB/LM.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 춘계학술대회 논문집
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• pp.129-135
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• 2004

This study was to evaluate the effect of carbon content on metallic change and fatigue characteristics with Fe-29% Ni-17% Co, low heat expansion alloy, widely using electronic components, precision machines, and sealing with glass and metal etc. The steels were fabricated with variation of carbon content, 0, 0.03, 0.06, 0.1, and 0.20% with VIM and tensile test and fatigue test were performed to achieve the above purpose. The more carbon content, the higher hardness value and yield strength. But elongation of 0.03%C, 0.06%C, and 0.10%C specimen decreased about 2.2%, 1.5% and 0.8% respectively mote than that of the base metal. Especially the strength and elongation of 0.20%C specimen increased simultaneously about 14.4% and 7.5%. Fatigue life of 0.03%C specimen decreased but the more carbon content, the higher fatigue life over 0.06% carbon content more than that of base metal.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2005년도 추계학술대회 논문집
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• pp.336-339
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• 2005

API steel is used for line-pipe to transport the oil and natural gas. As the recent trends in the development of API steel are towards the use of larger diameter and thicker plate, many researches have been studied to achieve higher strength, higher toughness and lower yield ratio in API steel. However, the strength of API steel after pipe forming is changed depend on the competition of the Bauschinger effect and work hardening. So, the purpose of this study is to investigate the influence on the Bauschinger effect for API steel by addition of V and Cu which are formed the precipitations for higher strength in API steel. The results are that the addition of V considered as a ferrite stabilizer and Cu considered as a austenite stabilizer decreases and increases the Bauschinger effect for API steel respectively.

• Computers and Concrete
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• 제16권3호
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• pp.467-485
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• 2015

This paper presents a comprehensive work on determination of yield base shear coefficient and displacement ductility factor of three to eight story actual reinforced concrete buildings, instead of using generic frames. The building data is provided by a walkdown survey in different locations of the pilot areas. Very detailed three dimensional models of the selected buildings are generated by using the data provided in architectural and reinforcement projects. Capacity curves of the buildings are obtained from nonlinear static pushover analyses and each capacity curve is approximated with a bilinear curve. Characteristic points of capacity curve, the yield base shear capacity, the yield displacement and the ultimate displacement capacity, are determined. The calculated values of the yield base shear coefficients and the displacement ductility factors for directions into consideration are compared by those expected values given in different versions of Turkish Seismic Design Code. Although having sufficient lateral strength capacities, the deformation capacities of these typical mid-rise reinforced concrete buildings are found to be considerably low.

• 한국주조공학회지
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• 제18권4호
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• pp.364-372
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• 1998

Effects of Si and Ca additions on the mechanical properties of AM60 based Mg alloys have been investigated. Hardness of the AM60 based Mg alloys reached a maximum value after aging for approximately 33 hours but the amount of hardness increase was negligible. The poor age hardening response of the alloys was due to low Al content, which implies that Al content must be >6 wt.% to observe age hardening effect. The tensile and yield strength increased with increasing Al, Si, and Ca content but elongation decreased with increasing Al and Si content. The best mechanical properties obtained in AM 40-2.5Si-0.2Ca alloy after T4 heat treatment were as follows; tensile strength 193.4 MPa, yield strength 79.2 MPa, and elongation 11.2%. High temperature property obtained from creep test was also improved by introducing $Mg_2Si$ which has high hardness, high melting temperature and low thermal expansion coefficient.

• Journal of Welding and Joining
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• 제33권5호
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• pp.31-34
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• 2015

Microstructure and tensile property in the weld heat-affected zone (HAZ) of austenitic Fe-Mn-Al-C low density steels were investigated through transmission electron microscopy analysis and tensile tests. The HAZ samples were prepared using Gleeble simulation with high heat input welding condition of 300 kJ/cm, and the HAZ peak temperature of $1200^{\circ}C$ was determined from differential scanning calorimetry (DSC) test. The strain- stress responses of base steels showed that the addition of V improved the tensile and yield strength by grain refinement and precipitation strengthening. Tensile strength and elongation decreased in the weld HAZ as compared to the base steel, due to grain growth, while V-added steel had a higher HAZ strength as compared than V-free steel.

• 한국철도학회논문집
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• 제9권6호
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• pp.695-700
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• 2006

This study investigates the effects of the material properties and the fatigue behavior in the SM490A material specimens due to the low-temperature atmosphere. In the fatigue behavior, the low-temperature affects the fatigue life. As the temperature get low, the fatigue limit increase, also As the yield strength and the tensile strength increase, the impact absorbed energy decrease. The difference of fatigue lift represents to normal distribution and it is larger between the room temperature and the low temperature, but in the result of the cumulative density function, the effect of temperature is not too large on it.

• Structural Engineering and Mechanics
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• 제78권4호
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• pp.473-484
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• 2021

Similar to other structures, ultimate strength values showing the maximum load that the structure can resist without damaging has great importance on ships. Therefore, increasing the ultimate strength values will be an important benefit for the structure. Low carbon steels used in ships due to their low cost and good weldability. Improving the ultimate strength values without interfering with the chemical composition to prevent of the weldability properties of these steels would be very beneficial for ships. Grain refinement via severe plastic deformation (SPD) is an essential strengthening mechanism without changing the chemical composition of metallic materials. Among SPD methods, equal channel angular pressing (ECAP) is one of the most commonly used one due to its capacity for achieving bulk ultrafine-grained (UFG) materials. When the literature is examined, it is seen that there is no study about ultimate strength calculation in ships after ECAP. Therefore, the mean purpose of this study is to apply ECAP to a shipbuilding low carbon steel to be able to achieve mechanical properties and investigate the alteration of ship hull girder grillage system's ultimate strength via finite element analysis approach. A fine-grained (FG) microstructure with a mean grain size of 6 ㎛ (initial grain size was 25 ㎛) was after ECAP. This microstructural evolution brought about a considerable increase in strength values. Both yield and tensile strength values increased from 280 MPa and 425 MPa to about 420 MPa and 785 MPa, respectively. This improvement in the strength values reflected a finite element method to determine the ultimate strength of ship hull girder grillage system. As a result of calculations, it was reached significantly higher ultimate strength values (237,876 MPa) compared the non-processed situation (192,986 MPa) on ship hull girder grillage system.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.434-437
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• 2006

Due to the shape of spindle with small diameter and heavy section, rapid cooling is difficult. It is difficult to fabricate the tapered wheel bearings with fine microstructure. Thus, their mechanical characteristics, such as yield strength and fatigue resistance, decrease. Producing the tapered wheel bearings with good workability during orbital forming after hot forging, hot forging process with several process parameters was optimized by means of statistical technique of Six-Sigma scheme. As a result, the lower heating temperature is, the lower the hardness and yield strength of forgings are. Also, the faster conveyer velocity is, the lower the hardness and yield strength of forgings are. To avoid therefore occurrence of the surface rupture during orbital forming, the heating temperature should be controlled as low as possible and the conveyer velocity should be controlled as fast as possible.