세립형 고강도강의 건축구조 적용에 관한 연구

장인화,임성우,오상훈 대한건축학회 2003 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.23 No.2(구조계)

As the structure becomes larger and longer-spanned nowadays, the need for more strong and reliable structural material becomes greater. In order to apply newly developed high strength steel to the building structure, adaptability of the current building codes to the design with high strength steel was reviewed. According to the experimental results conducted, applying current building codes for the design of the structure with high strength steel up to 600 MPa will be safe. Earthquake response analysis and experimental tests was conducted for the flexible-stiff mixed structure, which was proposed by Akiyama. The flexible-stiff mixed structure, is proved to be the promising structure to improve the safety and cost competitiveness of the high strength steel structure.

모래-세립분 혼합토에 대한 반복전단강도특성 평가

김욱기,김동욱,이준용,김주형 한국지반공학회 2012 한국지반공학회논문집 Vol.28 No.7

In most design codes, soils are classified as either sandy or clayey soils, and appropriate design equations for each soil type are used to estimate their soil behaviour. However, sand-fine mixtures, which are typically referred to as intermediate soils, are somewhere at the middle of sandy or clayey soils, and therefore a unified interpretation of soil behaviour is necessary. In this paper, a series of cyclic shear tests were carried out for three different combinations of sand-fine mixtures with various fines content. Silica-sand mixture and fines (Iwakuni natural clay, Tottori silt, kaolinite)were mixed together with various mass ratios, while paying attention to the changes of void ratios expressed in terms of sand structure. The cyclic shear strengths of the mixtures below the threshold fines content were examined with the increasing fines contents. As a result, as the fines contents increased, their cyclic deviator stress ratios decreased for dense samples while it increased for loose samples. Additionally, cyclic deviator stress ratio of the mixtures was estimated using the concept of equivalent granular void ratio.

유한요소법을 이용한 세미 파인-블랭킹 금형 해석에 관한 연구

이상훈,송기환,손창우,서형진,서태일,Lee, Sang-Hun,Song, Gi-Hwan,Son, Chang-Woo,Seo, Hyoung-Jin,Seo, Tae-Il 한국금형공학회 2016 한국금형공학회지 Vol.10 No.1

Metal sheet forming has been commonly used as the core technology in manufacturing parts of automobiles. It guarantees the highest production rate due to the process of mass production employing the press die. For precision of the product, the accuracy of the molds and its mechanic structures are considered as essential factors. One of these is fine blanking, which is utilized for the production of the metal sheet spring, with which clear sheer surfaces can be achieved in one operation from the materials. However, the current designs of press dies perform the forming analysis with the molds of rigid body, so they are focused on weight lightening by a rule of thumb. Therefore, this paper practice structural analysis about developing the semi fine-fine blanking technology. The semi fine-blanking can be run through the combination of the hydraulic cylinders and normal presses, so this paper analyze the amount of deformation according to the oil pressure. In addition, based on the plasticity of 50CrV4, the materials of the mold parts, the structural analysis and life analysis are proceeded, so they are expected to be useful as data for manufacturing the mold.

Adaptive fluid-structure interaction simulation of large-scale complex liquid containment with two-phase flow

Park, Sung-Woo,Cho, Jin-Rae Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.41 No.4

An adaptive modeling and simulation technique is introduced for the effective and reliable fluid-structure interaction analysis using MSC/Dytran for large-scale complex pressurized liquid containment. The proposed method is composed of a series of the global rigid sloshing analysis and the locally detailed fluid-structure analysis. The critical time at which the system exhibits the severe liquid sloshing response is sought through the former analysis, while the fluid-structure interaction in the local region of interest at the critical time is analyzed by the latter analysis. Differing from the global coarse model, the local fine model considers not only the complex geometry and flexibility of structure but the effect of internal pressure. The locally detailed FSI problem is solved in terms of multi-material volume fractions and the flow and pressure fields obtained by the global analysis at the critical time are specified as the initial conditions. An in-house program for mapping the global analysis results onto the fine-scale local FSI model is developed. The validity and effectiveness of the proposed method are verified through an illustrative numerical experiment.

Adaptive fluid-structure interaction simulation of large-scale complex liquid containment with two-phase flow

Sung-Woo Park,Jin-Rae Cho 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.41 No.4

An adaptive modeling and simulation technique is introduced for the effective and reliable fluid-structure interaction analysis using MSC/Dytran for large-scale complex pressurized liquid containment. The proposed method is composed of a series of the global rigid sloshing analysis and the locally detailed fluid-structure analysis. The critical time at which the system exhibits the severe liquid sloshing response is sought through the former analysis, while the fluid-structure interaction in the local region of interest at the critical time is analyzed by the latter analysis. Differing from the global coarse model, the local fine model considers not only the complex geometry and flexibility of structure but the effect of internal pressure. The locally detailed FSI problem is solved in terms of multi-material volume fractions and the flow and pressure fields obtained by the global analysis at the critical time are specified as the initial conditions. An in-house program for mapping the global analysis results onto the fine-scale local FSI model is developed. The validity and effectiveness of the proposed method are verified through an illustrative numerical experiment.

Comparative Study of Tetrahydrothiophene and Thiophene Self Assembled Monolayers on Au(111): Structure and Molecular Orientation

Ito, Eisuke,Hara, Masahiko,Kanai, Kaname,Ouchi, Yukio,Seki, Kazuhiko,Noh, Jaegeun Korean Chemical Society 2009 Bulletin of the Korean Chemical Society Vol.30 No.8

Surface structure and molecular orientation of self-assembled monolayers (SAMs) formed by the spontaneous adsorption of tetrahydrothiophene (THT) and thiophene (TP) on Au(111) were investigated by means of scanning tunneling microscopy (STM) and carbon K-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. STM imaging revealed that THT SAMs have a commensurate (3 ${\times}\;2\sqrt[]{3}$) structure containing structural defects in ordered domains, whereas TP SAMs are composed of randomly adsorbed domains and paired molecular row domains that can be described as an incommensurate packing structure. The NEXAFS spectroscopy study showed that the average tilt angle of the aliphatic THT ring and $\pi$-conjugated TP ring in the SAMs were calculated to be about $30^o\;and\;40^o$, respectively, from the surface normal. It was also observed that the $\pi$* transition peak in the NEXAFS spectrum of the TP SAMs is very weak, suggesting that a strong interaction between $\pi$-electrons and the Au surface arises during the self-assembly of TP molecules. In this study, we have clearly demonstrated that the surface structure and adsorption orientation of organic SAMs on Au(111) are strongly influenced by whether the cyclic ring is saturated or unsaturated.

Comparative Study of Tetrahydrothiophene and Thiophene Self-Assembled Monolayers on Au(111): Structure and Molecular Orientation

Eisuke Ito,Masahiko Hara,Kaname Kanai,Yukio Ouchi,Kazuhiko Seki,노재근 대한화학회 2009 Bulletin of the Korean Chemical Society Vol.30 No.8

Surface structure and molecular orientation of self-assembled monolayers (SAMs) formed by the spontaneous adsorption of tetrahydrothiophene (THT) and thiophene (TP) on Au(111) were investigated by means of scanning tunneling microscopy (STM) and carbon K-edge near edge X-ray absorption fine structure (NEXAFS) spectroscopy. STM imaging revealed that THT SAMs have a commensurate (3 × 2√3) structure containing structural defects in ordered domains, whereas TP SAMs are composed of randomly adsorbed domains and paired molecular row domains that can be described as an incommensurate packing structure. The NEXAFS spectroscopy study showed that the average tilt angle of the aliphatic THT ring and π-conjugated TP ring in the SAMs were calculated to be about 30o and 40o, respectively, from the surface normal. It was also observed that the π* transition peak in the NEXAFS spectrum of the TP SAMs is very weak, suggesting that a strong interaction between π-electrons and the Au surface arises during the self-assembly of TP molecules. In this study, we have clearly demonstrated that the surface structure and adsorption orientation of organic SAMs on Au(111) are strongly influenced by whether the cyclic ring is saturated or unsaturated.

울트라 파인 플라이 애시를 사용한 초속경 LMC의 공극구조 특성

최판길,박원일,윤경구,이봉학 한국방재학회 2010 한국방재학회논문집 Vol.10 No.2

초속경 LMC(Very-Early Strength Latex-Modified Concrete ; VES-LMC)는 작업성, 강도발현 및 장기 내구성 측면에서 콘크리트 타설 후 3시간 이내에 교통개방을 가능하게 할 목적으로 개발되었고, 교량바닥판 긴급보수 공사에 유용하게 사용되고 있다. 그러나 초속경 LMC에서 라텍스의 사용이 콘크리트의 내구성은 향상시키지만 다량의 갇힌 공기를 양산한다는 단점이 있다. 따라서 취약한 공극구조를 개선하기 위해서는 특별한 방법이 필요하며, 본 논문에서는 울트라파인 플라이 애시가 사용되었다. UFFA VES-LMC의 공기량은 재령 1일에 포졸란 반응의 대부분이 발생하여 재령 1일 공기량이 경화전 공기량보다 저하되었다. 또한 재령 28일 공기량은 재령 1일 공기량의 공극구조와 동일하게 나타나, 포졸란 반응에 의해 콘크리트의 전체 공기량이 감소함을 확인하였다. 수산화칼슘의 첨가는 200이하 크기의 연행공기를 현저하게 증가시키고, UFFA를 15%이상 사용하면 간격계수를 200 이하까지 확보할 수 있어 VES-LMC의 공극구조 개선에 매우 효과적인 것으로 나타났다. Very-early strength latex-modified concrete (VES-LMC) was developed with a focus on workability, strength development and long-term durability that would allow for opening a bridge to traffic only 3 hours after concrete placement, which would be useful when repairing concrete bridge deck overlays. However, even though usage of latex in VES-LMC improves the durability, it has a disadvantage that it produces lots of entrained air. Therefore, specific plan is necessary since it is weak for freezing and thawing in air-void structure. In the present study ultra-fine fly ash (UFFA) was used. Test results are follows ;Air content of VES-LMC UFFA (VES-LMC using UFFA) concrete was decreased since major pozzolan reaction was happened in one day. It was also found that total air content of concrete was decreased with pozzolan reaction since air content in 28 days was the same with one day air content. The addition of calcium hydroxide increased entrained air which is smaller than size of 200. It was effective to improve the air-void structure of VES-LMC since spacing factor can be confirmed as smaller than size of 200 using more than 15% of UFFA.

미세기포 세척장비를 이용한 도로시설물 염화칼슘의 제거

박일건,이준형,박형준,김현진,김흥래,조일형 한국응용과학기술학회 2019 한국응용과학기술학회지 Vol.36 No.4

본 연구는 도로시설물의 염화칼슘 제거를 위한 미세기포 세척장비의 최적 운용조건에 대하여 성능평가를 수행하였다. 실험에 사용된 미세기포의 직경은 196.6±100.6nm 에 1.36×108개/ml의 농도를 나타낸다. 세척장비의 분사장치에 대한 실험 성능결과, 100bar의 분사압력에서 100cm, 150cm 분사거리에약 93%, 91%의 세척효율이 나타나는 것으로 확인되었다. 미세기포 생성(순환)횟수를 2-6회로 증가시킴에 따라 최소 1%에서 7%까지 염화물 제거율이 높아짐을 확인하였다. 미세기포 생성 공기유량을 4 ml/min에서 0.5 ml/min으로 낮춤에 따라 세척효율이 최대 30%까지 증가하는 것이 확인되었다. 일반 상수도와 미세기포의 세척효율은 미세기포가 일반상수도 보다 세척효율이 25% 높게 나타났다. This study was conducted to evaluate the optimal operating condition of ultra-fine bubble washing machine for removing calcium chloride from road concrete structure. The diameter of the ultra-fine bubble was measured to 196.6 ± 100.6 nm and the ultra-fine bubble concentration was measured to 1.36 × 108 cell/ml. As a result of the performance on the spray device of the washing machine, it was confirmed that the washing efficiency of 93% and 91% appeared at 100cm and 150cm of injection distance at 100bar injection pressure. By increasing the ultra-fine bubble generation cycles from 2 to 6, the chloride removal rate increased from 1% to 7%. As the ultra-fine bubble generation air flow was lowered from 4 ml/min to 0.5 ml/min, it was confirmed that the washing efficiency increased up to 30%. The washing efficiency of ultra-fine bubble water was 25% higher than normal water.

생체용 Ti₁-x-Zrx합금의 기계적 성질과 내부식성

정종현,백승남,노학,고영무 대한치과기재학회 1998 대한치과재료학회지 Vol.25 No.1

While titanium and its alloys has been well studied for a long time, new interest in these materials and their properties has arisen in recent years with respect to their application as biomedical metallic materials. For practical purposes, the following performances are essential for biomaterials. (1) low specific gravity (2) high corrosion resistance (3) good biostability and biocompatibility (4) sufficient mechanical properties (5) non-toxicity To develop biomedical implant materials having all the properties mentioned above, new titanium-zirconium alloys were prepared in this study. Mechanical properties and corrosion resistance were then investigated for as-cast and as-homogeneized Ti₁_x-Zrx alloys in order to reveal their possible use for biomaterials. From the experiments, the following results are obtained: 1. No martensite structure are observed in the specimens made of pure Ti and Zr. In contrast them, Ti-Zr alloys containing 18wt%Zr, 24wt%Zr and 48wt%Zr show a kind of martensite structure regardless heat treatment. 2. Fineness of structures for as-cast-alloys seems to vary with alloy composition. Ti-Zr alloy containing 48wt%Zr shows the finest microstructure. 3. Hardness of Ti-Zr alloys shows continuous change through the system and the alloys containing 48 to 60wt%Zr indicate higher hardness compared with those of pure Ti and other alloys. It is well known that hardness is usually changed with substitutional atoms, and effect of solute atom on hardness is greatest with an equi-atomic composition. The greatest hardness which was obtained in Ti-Zr alloys containing 48 to 60wt%Zr is therefore reasonable. Also, enhanced hardness can be explained on elastic interaction between dislocation and substitutional solute atoms in crystal structure and on fineness of structure. 4. Pure Ti and Zr alloys containing 6wt%Zr, 12wt%Zr, 18wt%Zr, 36wt%Zr show better corrosion resistance compared with those of pure Zr, stainless steel(SUS 316L) and the Ti-Zr alloy containing 48wt%Zr. 5. Comparing hardness, microstructure and corrosion of Ti₁_x-Zrx alloys, no large differences between as-cast and as-homogenized alloys are seen.