• Journal of Welding and Joining
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• 제29권5호
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• pp.99-105
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• 2011

In this study, effect of Si content on nugget diameter in electric resistance spot welded dual-phase(DP) steel was investigated. The cold rolled DP steels with different Si content (0.5, 1.0, 1.5, 2.0 wt.%) were used and thickness of those sheet was 1.2mm. With increasing Si content, nugget diameter was increased at the same welding current. This is attributed to increase of heat input result from high resistivity. Also, nugget diameter was increased with an increase in Si content for the same heat input. For this reason, the melting point of DP steel is lowered with an increase in the Si content. And solid DP steel can easily be transformed to a liquid phase because the low melting point. Finally, a prediction formula for the nugget diameter(N.D.) could be obtained in terms of heat input(Q) and melting point(M.P) as follows: N.D.(mm) = 0.11Q(J) - 0.0031 M.P.($^{\circ}C$) + 0.32.

• 국제강구조저널
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• 제18권4호
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• pp.1139-1152
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• 2018

Many studies on the application of stainless steels as structural materials in buildings and infra-structures have been performed thanks to superior characteristics of corrosion resistance, fire resistance and aesthetic appeal. Experimental investigation to estimate the ultimate strength and fracture mode of the fillet-welded connections of cold-formed austenitic stainless steel (STS304L) with better intergranular corrosion resistance than that of austenitic stainless steel, STS304 commonly used has carried out by authors. Specimens were fabricated to fail by base metal fracture not weld metal fracture with main variables of weld lengths according to loading direction. All specimens showed a block shear fracture mode. In this paper, finite element analysis model was developed to predict the ultimate behaviors of welded connection and its validity was verified through the comparison with test results. Since the block shear behavior of welded connection due to stress triaxiality and shear-lag effects is different from that of bolted connection, stress and strain distributions in the critical path of tensile and shear fracture section were investigated. Test and analysis strengths were compared with those by current design specifications such as AISC, EC3 and existing researcher's proposed equations. In addition, through parametric analysis with extended variables, the conditions of end distance and longitudinal weld length for block shear fracture and tensile fracture were suggested.

• The Plant Pathology Journal
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• 제27권3호
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• pp.232-341
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• 2011

Pink snow mold, caused by Microdochium nivale, is a major disease on cool season turfgrasses in golf courses in northern Unites States. The relative susceptibility of 17 commercial cultivars of three bentgrass species (creeping, colonial and velvet bentgrass) to Microdochium nivale and the aggressiveness of M. nivale eight isolates obtained from infected turfgrasses on golf courses in Wisconsin were evaluated under controlled conditions. For the field trial, susceptibility of 2 year-old 12 commercial bentgrass cultivars was evaluated after inoculating three M. nivale isolates in the fields. There were significant differences in disease severities among the three bentgrass species, particularly between tetraploids (creeping and colonial) and diploid (velvet) species, and among cultivars within each species, indicating that there are varying levels of susceptibility in species and cultivars to M. nivale. Host resistance by days of cold hardening was confirmed, by detecting the resistance by 30 days of cold hardening treatments. In field trial, susceptibility of 12 bentgrass cultivars was highly correlated to the results obtained from growth chamber experiments. The positive correlation of the susceptibility between growth chamber experiments and field trials demonstrates that the growth chamber method is a useful technique for saving time, space and labor to evaluate efficiently pink snow mold susceptibility of bentgrass cultivars. This study could be applied to evaluating susceptibility of bentgrass to pink snow mold and also predicting a prospective evaluation of bentgrass cultivars to pink snow mold in fields in a breeding program.

• 한국건축시공학회지
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• 제20권1호
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• pp.35-41
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• 2020

외단열 마감 공법에서 사용되는 얇은 바름재는 아크릴 에멀젼을 주 소재로 한 마감재이다. 본 연구에서는 실란 개질 아크릴 에멀젼과 실리카 분산아크릴 에멀젼을 치환하였을때 특성을 평가하였다. 실험결과, 실란 개질 아크릴 에멀젼은 인장강도 개선에는 큰 효과는 없었으나 부착강도, 물흡수계수, 온냉반복저항성의 성능 개선에 효과적인 것으로 나타났다. 실리카 분산 아크릴 에멀젼은 인장강도 개선에 효과적이며, 10%의 치환율에서는 부착강도, 물흡수계수, 온냉반복저항성의 성능 개선에 효과적인 것으로 나타났다. 이를 통해 아크릴 에멀젼의 성능을 향상할 수 있는 복합 에멀젼을 제조할 수 있는 것으로 판단되었다.

• 아시안잔디학회지
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• 제7권1호
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• pp.19-30
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• 1993

Experiments were conducted to investigate propagation, shade tolerance, cold resistance and growth rate of evergreen ground cover plants ; Vinca minor K , Ajuga reptans L., Ophiopogon japonicus ker. f nanus hort , and Hedera helix.. The results were as follows : 1.It is convenient to use the growing case for rice seed to grow and transplant Vinca minor seed-ling. The most proper density of transplanting Vinea was 180 plants per 1m$^2$. At the end of growing season, the coverage came up to 90% The rooting ability of Hedera helix was best to cut from April to May (temperature 15~23˚C). The seedling length of Parthenocissus quinguefohlia were irregular and ranged from 5 cm of 200cm. 2. Ajuga reptans L., Ophiopogon j. and Vinca minor L. grew better under 50% light intensity than full sunlight. Particularly, under full sunlight and aestival high temperature, there were a few withering plants in Ajuga reptans L. , and V Vilica minor L. 3. Of Vinca minor K., Ajuga reptans L. , Ophiopogon japonicus ker. f. nanus hort. and Hedera helix. acclimatized in open field, where temperature was from -7~8˚C. There were few plants had damage in low temperature incubator to -16˚C after field acclimatization. 4.Tendrils of Parthenocissus quinguefolia strongly clung to the wire netting stone fence but intruded into the gap and cranny of the precast concrete fence and so clung to, so that it needed to install the bending net on the precast concrete fence.

• 대한금속재료학회지
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• 제47권8호
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• pp.482-487
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• 2009

In order to investigate the effects of intermediate heat treatment between cold rolling passes on the hardness and corrosion properties of a Zr alloy incorporating Nb (Zr-1.49Nb-0.38Sn-0.20Fe-0.11Cr) strip, three different intermediate heat treatment processes ($580^{\circ}C{\times}4hrs$, $600^{\circ}C{\times}2hrs$ and $620^{\circ}{\times}1hrs$) were designed based on a recrystallization map and an accumulated annealing parameter. Test samples from the different processes were investigated by a hardness test, corrosion test, and microstructure analysis and appropriate heat-treatment conditions were thereupon proposed. The sample subjected to an intermediate heat treatment of $580^{\circ}C{\times}4hrs$ was harder than that undergoing $600^{\circ}C{\times}2hrs$ and $620^{\circ}C{\times}1hr$ while the corrosion resistance of the sample that received an intermediate heat treatment of $580^{\circ}C{\times}4hrs$ was superior to that of the other specimens. Considering the trade-off of hardness and corrosion resistance, an intermediate heat treatment process of $600^{\circ}C{\times}2hrs$ is proposed to improve the manufacturing process of the alloy strip.

• Journal of the Korean Wood Science and Technology
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• 제46권2호
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• pp.155-165
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• 2018

The objective of the research was to evaluate the effect of particle pre-treatment on physical, mechanical, and durability of jatropha fruit hulls (JFH) particleboard. The pre-treatments included were immersing in cold water, hot water, and acetic acid solution. After each treatment, the particles were dried up to 3% moisture content. Urea-formaldehyde (UF) resin was used to fabricate particleboards with board size, thickness and density target of 25 cm by 25 cm, 0.80 cm, and $0.70g/cm^3$, respectively. Board pressed at $130^{\circ}C$ for 10 minutes, and $25kg/cm^2$ pressure. The evaluation of particleboard followed the JIS A 5908-2003. Whilist their resistance to subterranean termite test (mass loss, mortality, antifeedant value and feeding rate) refers to the Indonesian standard (SNI 01.7207-2006). The physical and mechanical properties of particleboards showed that all pre-treatments decreased the pH of particles. Overall, all particle immersing treatments resulted of better physical and mechanical properties of particleboard than those of untreated ones. The acetic acid treatment resulted the best physical and mechanical properties of particleboard. Based on the mass loss of JFH particleboard, hot water and acetic acid treated particleboards were classified into weak resistance to subterranean attack. The other two treatments were classified into very weak resistance. Hot water treated particleboard provided the highest mortality and antifeedant as much as 87.40% and 34.20%, respectively. Based on antifeedant classification, hot water treated particleboards were classified into moderately strong resistance, while other treatments were categorized into weak resistance. The lowest feeding rate value ($45.30{\mu}g/termite/day$) was attained by hot water treatment.

• 한국건설순환자원학회논문집
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• 제6권3호
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• pp.79-87
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• 2011

고로슬래그를 다량으로 혼입한 콘크리트를 동절기에 시공할 경우에는 배합에 따라서 응결과 경화가 현저히 지연되어 초기동해를 받을 위험성이 높다. 따라서 이 연구에서는 동절기에 고로슬래그를 다량으로 혼입한 콘크리트가 재령 초기에 동결을 받은 경우를 상정하여 초기동해가 콘크리트의 압축강도와 동결융해 저항성에 미치는 영향을 검토하였다. 그 결과, 고로슬래그를 다량으로 혼입한 콘크리트는 초기동해를 받음으로써 압축강도와 동결융해 저항성 모두가 현저히 저하되고, 고로슬래그를 혼입하지 않은 일반콘크리트에 비해서 특히 동결융해 저항성이 크게 저하되는 것으로 나타났다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.68-68
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• 2009

최근에 자동차 차체 경량화를 목적으로 개발된 고장력강의 용접품질 향상을 위해 인버터 DC 점용접기가 많이 사용되어지고 있다. 본 연구에서는 국내에서 개발된 인버터 DC 용접기를 사용하여 자동차용 590MPa 고장력 냉연강판(CR, SPFC 590RA)과 아연 도금 강판 (GA- EZFFC 590RA)의 용접품질을 평가하였다. 용접에 사용된 기본 조건은 인장 전단 시험을 통하여 결정하였으며, 동저항, 압흔 자국과 너겟 지름, 인장강도와의 관계를 통계적 방법으로 분석하였으며, 이를 활용하여 고장력 강판의 동저항과 압흔 자국에 따라 너겟 지름과 용접강도를 예측하는 비파괴적 용접 품질 평가 방법을 제시하였다.

• 한국표면공학회지
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• 제49권2호
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• pp.202-210
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• 2016

This study was intended to investigate the effect of the amount of magnesium addition and heat treatment in the Al-Mg coating film in order to improve corrosion resistance of aluminum coating. Al-Mg alloy films were deposited on cold rolled steel by physical vapor deposition sputtering method. Heat treatment was fulfilled in an nitrogen atmosphere at the temperature of $400^{\circ}C$ for 10 min. The morphology was observed by SEM, component and phase of the deposited films were investigated by using GDLS and XRD, respectively. The corrosion behaviors of Al-Mg films were estimated by exposing salt spray test at 5 wt.% NaCl solution and measuring polarization curves in deaerated 3 wt.% NaCl solution. With the increase of magnesium content, the morphology of the deposited Al-Mg films changed from columnar to featureless structure and particle size was became fine. The x-ray diffraction data for deposited Al-Mg films showed only pure Al peaks. However, Al-Mg alloy peaks such as $Al_3Mg_2$ and $Al_{12}Mg_{17}$ were formed after heat treatment. All the sputtered Al-Mg films obviously showed good corrosion resistance compared with aluminum and zinc films. And corrosion resistance of Al-Mg film was increased after heat treatment.