• 한국공작기계학회논문집
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• 제15권5호
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• pp.104-113
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• 2006

The main objective of this study is to investigate the effect of compounded welding by using acoustic emission (AE) signals and doing a source location for weld heat affected zone (HAZ) through tensile testing. This study was carried out an SWS 490A high strength steel for electric shield metal arc welding, SMAW; $CO_2$ gas metal arc welding, GMAW($CO_2$); and gas tungsten arc welding, GTAW/TIG. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. For instance, Gutenberg-Richter magnitude-frequency relationship (G-R MFR) offers useful b-value in data analysis. Namely event identification, source location gives the X- and Y-coordinates of the AE source. And K-means clustering analysis by Euclidean distance confirmed that was powerful to source location. Generally, strength of welded metal zone was stronger than strength of base metal. As the result, confirmed certainly that fracture is produced in HAZ instead of welded metal zone from source location.

• Steel and Composite Structures
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• 제26권5호
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• pp.583-594
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• 2018

Although a lot of experimental and analytical investigations have been carried out for steel bridge piers made of SS400 and SM490, the formulas available for SS400 and SM490 are not suitable for evaluating ultimate load and deformation capacities of steel bridge piers made of high strength steel (HSS) SM570. The effect of various parameters is investigated in this paper, including plate width-to-thickness ratio, column slenderness ratio and axial compression force ratio, on the ultimate load and deformation capacities of steel bridge box piers made of SM570 steel subjected to cyclic loading. The elasto-plastic behavior of the steel bridge piers under cyclic loads is simulated through plastic large deformation finite element analysis, in which a modified two-surface model (M2SM) including cyclic hardening is employed to trace the material nonlinearity. An extensive parametric study is conducted to study the influences of structural parameters on the ultimate load and deformation capacities. Based on these analytical investigations, new formulas for predicting ultimate load and deformation capacities of steel bridge piers made of SM570 are proposed. This study extends the ultimate load and deformation capacities evaluation of steel bridge piers from SS400, SM490 steels to SM570 steel, and provides some useful suggestions.

• 보존과학회지
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• 제34권1호
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• pp.31-37
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• 2018

서천 봉선리 유적에서 출토된 목곽고의 제작 연대는 출토된 토층 및 토축부의 축조방법으로 5세기 전후로 추정되었다. 정확한 연대를 확인하고자 목곽부재 3점에 대해 위글매치를 이용한 방사성탄소연대분석을 실시하였다. 목곽부재 1(BSMG 01)의 최외각 연륜은 95.4% 신뢰구간에서 AD 431~551년, 목곽부재 2(BSMG 06)는 AD 460~570년으로 확인되었고 목곽부재 3(BSMG 12)은 AD 240~430년 또는 AD 490~510년으로 산출되었다. 목부재 3점의 공통 연대는 AD 490~510년으로 고고학적으로 추정된 연대와 일치하였으며, 위글매치를 이용한 방사성탄소연대측정의 정확성을 입증할 수 있었다.

• 한국안전학회지
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• 제34권6호
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• pp.7-12
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• 2019

Flux Cored Arc Welding (FCAW), which has been widely used in many industries, was developed in the 1950s to supplement shortcomings of the Shielded Metal Arc Welding (SMAW). FCAW has an advantage in that it can weld regardless of postures and give good quality results in the filed with many different working conditions. In this study, SM490A (rolled steel for welding structural purpose) with different thicknesses (L:25T+R:30T) were welded using FCAW. Then the mechanical properties (tension test, bending test, hardness test, impact test and macro test) were analyzed and the following conclusions were drawn. In the tensile test, it exceeds the KS standard tensile strength range (400~510) in all welding positions, which means there is a problem in the tensile force transmission performance. In the bending test, it was found that most of the specimens did not exhibit surface rupture or other defects during bending test and they exhibit sufficient toughness even after plastic deformation. In the hardness test, all the results were lower than the standard value of 350 Hv of KS B 0893, which means they have good hardness. In the impact test, all results were larger than the KS reference value of 27J. In the macro test, they showed uniform structure state by the shape of the weld, and there was risk of lamination because no internal defects, bubbles, or impurities were found on the surface of the weld.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제45회 하계 정기학술대회 초록집
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• pp.229.1-229.1
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• 2013

초격자는 동종의 III-V 삼원 합금층을 성장하는 동안 스피노달 분해(spinodal decomposition)로 인한 원자배열(atomic ordering)과 상분리phase separation)에 의해서 발생하는데 MBE (molecular beam epitaxy)과 MOVPE (metalorganic vapor phase epitaxy)를 이용하여 성장시킬 때 주로 발생한다. 본 논문에서는 성장온도에 따른 InP/GaP SPS (short-period superlattices) 구조의 광학적 특성 변화를 시료의 온도와 여기광의 세기를 이용하여 분석하였다. 시료는 MBE 장비를 이용하여 성장하였으며, SPS층은 659쌍의 GaP(2.9 ${\AA}$)과 InP(3.1 ${\AA}$)로 이루어져 있고, GaP 층을 처음에 증착한 뒤, InP 층을 증착 하였다. 성장시 온도를 $400^{\circ}C$, $425^{\circ}C$, $460^{\circ}C$ 그리고 $490^{\circ}C$로 변화를 주어 성장하였다. 이들 시료를 GT400, GT425, GT460 그리고 GT490이라 하였고 이에 대한 광학적 특성을 PL (photoluminescence)를 이용하여 분석하였다. 10 K에서 PL 피크는 GT400 시료는 634 nm, GT425 시료는 636 nm, GT460 시료는 680nm, 그리고 GT490 시료는 692 nm에서 나타났으며, GT425 시료의 PL 세기가 가장 강하게 나타나고 GT400 시료의 PL 세기가 가장 약하게 나타났다. 그러나 260 K에서 PL 세기는 GT460 시료가 가장 강하게 나타나고 GT425 시료가 가장 약하게 나타났다. 성장온도가 증가함에 따라 밴드갭이 감소하는 것은 특정 성장온도($460^{\circ}C$) 이상에서 LCM (lateral composition modulation)이 형성되는 것으로 설명할 수 있다. GT400 시료와 GT425 시료의 PL 피크가 1.94 eV와 1.95 eV로 비슷하고, GT460 시료와 GT490 시료의 PL 피크가 1.82 eV과 1.79 eV로 비슷하게 나타난 것은 $460^{\circ}C$이상에서 성장한 시료에서 LCM 구조 형성으로 설명할 수 있다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.714-719
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• 2002

In The Great Hanshin-Awaji Earthquake, the general yield brittle fractures were observed in beam-column connections of steel building frames. Among many influencing factors which affect the general yield brittle fracture, it can be considered that fracture toughness has substantial effects. Some studies are making clear the required toughness for the base metal and the weld metal, but general values are not proposed. Moreover, it seems that it is also important to pay attention to the toughness decrease in the weld heat affected zone (weld HAZ), because the toughness decrease occurs in the HAZs of mild steel. In this paper, the relationship between toughness of simulated HAZs of "the rolled steels for building structures (SN)" and the weld heat-input limit of the SN steel are investigated, in an attempt to provide the required toughness for HAZs. The relationships between the increase of the hardness value and toughness, and changes of microstructure after weld heat-input are also discussed. The main results are summarized as follows. 1) The SN400B can keep its toughness at higher heat-inputs compare to the SN490Bs. 2) The steel grade, which becomes harder than other steel grades at the same heat-input, has smaller absorbed energy and smaller limit of heat-input. 3) The weld heat-input limit of the SN400B and the SN490B are proposed separately for some required toughness values.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2005년도 생물공학의 동향(XVI)
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• pp.490-490
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• 2005

• Tuberculosis and Respiratory Diseases
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• 제43권4호
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• pp.487-490
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• 1996

• Tuberculosis and Respiratory Diseases
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• 제45권3호
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• pp.483-490
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• 1998

• Macromolecular Research
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• 제15권6호
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• pp.487-490
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• 2007