용접부의 표면피로균열 수명 평가에 관한 연구

朴庚銀,鄭鎭成,李龍福 弘益大學校 科學技術硏究所 1995 科學技術硏究論文集 Vol.6 No.-

In this study, to evaluate the fatigue life of surface crack in welding material general structural rolled steel(SS400) was used and welding was performed by MIG butt process. After that, it was machined the same pattern`s initial surface flaw on each welding zone divided by welding metal zone(WM), heat affected zone(HAZ), base metal zone(BM) and boundaries. Using this specimen it could be well evaluated the fatigue life in welding zone. The result are summarized as follows: 1. In each welding zone surface fatigue crack varies from initial aspect ratio of two to semicircle shape at first, after that the aspect ratio of it is reduced gradually. Aspect ratio indicates largely in order of the boundary of HAZ and BM, BM and HAZ, the boundary of WM and HAZ and WM. 2. Surface fatigue crack growth rate is larger in surface direction compare with depth direction at first and it shows that approaches in two direction during fatigue crack propagate continuously. Fatigue crack growth rate indicates largely in order of the boundary of HAZ and BM, BM and HAZ, the boundary of WM and HAZ, and WM. 3. Fatigue life indicates largely in order of WM, the boundary of WM and HAZ, HAZ, BM and the boundary of HAZ and BM. 4. The ratio of initial life to fatigue life indicates largely in order of HAZ, the boundary of HAZ and BM, BM, the boundary of WM and HAZ, and WM. It belongs to 34% to 58% in welding zone.

보건관리 대행사업 이후 작업환경 수준의 변화

박복현,김화성,이용진,안규동,이병국 순천향대학교 산업의학연구소 1999 순천향산업의학 Vol.5 No.1

This study was performed to evaluate the threshold limit values(TLVs) exceeding rates and periodical changes based on the results from work environmental measurement for 40 factories applied health service program, located in Cheonnan area, from 1995 to 1997. The obtained results were as follows; 1. The hazaed frequency in environmental monitoring were noise(865, 34.4%), illumination(804, 31.9%), dust(205, 8.1%), organic solvent(371, 14.7%), lead(114, 4.5%), and specific chemicals(31, 1.2%), heavy metal(127, 5.0%) in order. 2. The order of TLVs exceeding rate of hazardous agents by type of industries were cement-related manufacture(42.3%), fiber industry(40.0%), food stuff industry(24.3%), metal work industry(21.8%), electronics manufacture (9.9%), other industries(10.2%), chemical industry(7.9%). 3. The mean exceeding rates of hazard by type of industry were 29.5% in noise, 27.3% in dust, 25.8% in specific chemicals, 10.2% in solvent and 7.9% in lead, but none in heavy metal. 4. The average of standardized values of noise divided by TLV were decreased in food stuff industries and chemical industries, but not changed in fiber and cement-related industries. While, the average of standardized values of organic solvents divided by TLVs were decreased in electronic manufacturing industries and other industries.

T형 합성보의 스터드 쉬어 콘넥더의 내력에 관한 연구

박복만,정구섭,최승용,김복순 명지대학교 공학기술연구소 1993 공학기술연구소 논문집 Vol.8 No.-

This study summarizes the results of tests on 18 Two-slab push out specimens. The main purpose of the investigation was to evaluate the capacity and behavior of stud shear connectors embedded in the normal concrete(F_c=173∼295㎏/㎠). Two different diameters(Φ16mm,Φ13mm) of steel shear connectors welded on T-shpaed steel were used for push out specimens. The following conclusions were drawn from this study. 1. The shear strength(q_u) of stud shear connectors embedded in concrete was influenced by the cross sectional area of the steel shear connector(A_s), concrete design strength(F_c) and elastic modulus of the concrete(E_c). The emperical function described the test results. q_u = 0.3A_s√FcEc 2. The maximum loads in this study were reached at slips varing from 1.5mm to 4.0mm 3. The webs of T-shaped steels welded by the steel shear connectors were safe under t≥d/2. Where t is the thickness of the webs, d, the diameter of stud shear connector.

방사화 분석법을 통한 방사선량 및 포획단면적 개념 이해

박상태,김용복,육근철,이희복,김준태,정기주 공주대학교 과학교육연구소 2003 과학교육연구 Vol.34 No.-

중성자 방사화법은 여러 가지 물질의 특성을 규명하는데 매우 유용한 방법이다. 기본적으로 이러한 방법은 매우 간단하다. 임의의 시료를 저속 중성자에 조사시키면, 그 시료는 방사능을 띄게 되고 시료로부터 나오는 β^+, β^-, 그리고 γ선의 선량을 측정하거나 시료의 반감기를 측정하면, 시료를 구성하고 있는 물질의 구성성분이나 그 농도를 알아낼 수 있다. 본 연구에서는 금 박막을 방사화시킴으로서 열중성자 선량값으로 1426.68 ± 11.62n/㎠ㆍsec를 얻었다. 또한, ^55Mn의 열중성자 포획 단면적은 13.79±0.45bam 이었는데 이는 Table of Isotope에 제시된 값과 매우 잘 일치하였다. 본 연구의 실험기법은 일반적으로 널리 알려진 방법이지만, 학생들이 쉽게 접할 수 있는 실험이 아니기 때문에 '선량' 또는 '단면적' 등돠 같은 물리 개념을 가르치는데 유용하게 사용될 수 있을 것으로 기대된다. Neutron activation is very powerful technique for identifying characteristics of many elements. Basically the technique is quite simple. A sample is irradiated by slow neutrons and becomes radioactive. By measuring the β^+s, β^-s, γs and half-life of the resulting sample, the elemental constituents of the sample and their relative concentrations can be identified. In this studies, thermal neutron flux was 1426.68 ± 11.62 n/㎠ ·sec from Au activation analysis. Thermal neutron capture cross section for ^55Mn was 13.79 ± 0.45 barn, it is a good agreement with Table of Isotope data. Technique of this measurement is not special, but can be used usefully for physics concepts learning such as flux and cross section.

CMP 공정에서 결함밀도 감소를 위한 POU 슬러리 필터의 특성과 탈이온수의 고분사법에 의한 패드수명의 개선

박성우,김철복,정소영,서용진 대불대학교 2001 論文集 Vol.7 No.1

As the integrated circuit device shrinks to smaller dimensions, chemical mechanical polishing (CMP) process has been widely used to planarize dielectric layers, which was required for the global planarization of inter-metal dielectric (IMD) layer with free-defect. However, as the IMD layer gets thinner, micro-scratch lead to severe circuit failure which affect yield. CMP slurries can contain particles exceeding 1 ㎛ in size, which could cause micro-scratches are generated by agglomerated slurry, solidified and attached slurry in pipe line of slurry supply system. To prevent agglomerated slurry particle from inflow, we installed 0.5 ㎛ point of use (POU) filter, which is depth-type filter and has 80% filtering efficiency for the 1.0 ㎛ size particle. In this paper, we have studied the relationship between defect generation and polished wafer counts to understand the exact efficiency of the slurry filtration, and to find out the appropriated pad usage. Our experimental results of micro-scratch formation, it is shown that slurry filter plays an important role in determining consumable pad lifetime. The filter lifetime is dominated by the defects. We have concluded that slurry filter lifetime is fixed by the degree of generating defects, and it is impossible to prevent defect-causing particles perfectly through the depth-type filter. Thus, we suggest that it is necessary to optimize the slurry flow rate, and to install the high spray bar of de-ionized water (DIW) with high pressure, to overcome the weak-point of depth type filter.

십자형 필렛 용접부의 피로강도 평가에 관한 연구

朴商洽,朴仁圭,李龍福,南炳燦 弘益大學校 科學技術硏究所 1999 科學技術硏究論文集 Vol.10 No.1

Fabrication by welding may result in stress concentration regions in the joints and it may be caused by weld imperfections on geometrical discontinuities. Thus, fatigue strength of welded details was essential for fatigue design of welding structures. In this study, constant amplitude fatigue tests on load-carrying fillet welded specimen carried out, and fatigue strength were evaluated. Also, in this investigation an attempt is made to develop a new analytical model to predict the fatigue crack propagation life of fillet welded cruciform joints of SWS 490B steels containing lack of penetration defects with more accuracy. From the result of this study, fatigue crack growth characteristics of load-carrying fillet welded cruciform joints, containing lack of penetration defects are found to be influenced by the weld size and geometry.

저항방사열계 적외선 감지기 제조를 우한 바나듐 산화막의 전기적 특성 및 유전 특성

박재홍,최용남,최복길 공주대학교 생산기술연구소 2000 論文集 Vol.8 No.-

For fabrication of bolometric infrared detector, thin films of vanadium oxide(VO_x) was deposited by r.f. magnetron sputtering from V_2O_2 target in 10% gas mixture of argon and oxygen, and in-situ annealed in vacuum with different temperatures and times. Crystal structure and surface morphology of films were characterized through XRD and SEM. In order to measure the current-voltage characteristics, temperature dependence of conductance, and dielectric properties of vanadium oxide, Al/VO_x/Al sandwich devices structure was adopted. The films prepared below 200℃ were amorphous, and those prepared above 300℃ were polycrystalline. Above 3×10^4V/cm conduction of vanadium oxide is limited by space charge formed near eletrode. Conduction mechanisms above 10^5V/cm are due to Schottky emission and Fowler-Nordheim tunneling effects. Resistance and capacitance of grain boundary are decreased with increasing annealing temperature. Oxygen vacancy is related to the localized state and non-stoichiomeric of vanadium oxide.

저항방사열계 적외선 감지기 제조를 위한 바나듐 산화막의 전기적 특성 및 유전 특성

박재홍,최용남,최복길 공주대학교 생산기술연구소 2000 論文集 Vol.8 No.-

For fabrication of bolometric infrared detector, thin films of vanadium oxide(VO_(X)) was deposited by r.f. magnetron sputtering from V_(2)O_(5) target in 10% gas mixture of argon and oxygen, and in-situ annealed in vacuum with different temperatures and times. Crystall structure and surface morphology of films were characterized through XRD and SEM. In order to measure the current-voltage characteristics, temperature dependence of conductance, and dielectric properties of vanadium oxide, Al/VO_(X)/Al sandwich devices structure was adopted. The films prepared below 200℃ were amorphous, and those prepared above 300℃ were polycrystalline. Above 3×10^(4)V/cm conduction of vanadium oxide is limited by space charge formed near electrode.? Conduction mechanisms above 10^(5)V/cm are due to Schottky emission and Fowler-Nordheim tunneling effects. Resistance and capacitance of grain boundary are decreased with increasing annealing temperature. Oxygen vacancy is related to the localized state and non-stoichiomeric of vanadium oxide.

HDPE 관의 TEE 성형에 대한 유한요소해석

박용복,송두호 朝鮮大學校 機械技術硏究所 2004 機械技術硏究 Vol.7 No.2

고밀도 폴리에틸렌(HDPE) 파이프 중 TEE 성형 공정이 강소석 유한요소해석 툴인 DEFORM을 이용하여 해석되었다. 많은 HDPE 파이프 중 TEE는 주관을 가지관과 연결하여 온수의 유동방향을 변화시키는데 사용된다. HDPE 파이프는 온수의 온도를 유지하기 위한 절연재로서 사용된다. HDPE 파이프에 대한 TEE 성형과 맞대기 용접 공정은 기존의 압출용접 공정에 비해 용접부의 강도를 향상시키는 개성된 공정이다. 초기의 구멍 형상과 같은 설계 인자들이 실험과 해석을 통하여 얻어졌고, 실제 제조공정에 적용되었다. TEE forming process on HDPE(High Density PolyEthylen) pipe has been analyzed by using rigid plastic finite element analysis code. DEFORM. TEE of HDPE pipes is necessary to connect a main pipe with a branch pipe and change the flow direction of hot water. A HDPE pipe is used as insulator to maintain the temperature of hot water. TEE forming and butt welding process on a HDPE pipe is a updated process improving the strength of welding part compared to conventional extrusion welding process. The design parameters, such as an initial hole, shape have been obtained from the experiment and rigid-plastic finite element analysis, which is applied to the actual manufacturing process.

김미료 소재로서 Di-D-Fructofuranose Dianhydride3의 물리 및 생리적 특성

박정복,김소자,최용진 한국미생물생명공학회 ( 구 한국산업미생물학회 ) 1996 한국미생물·생명공학회지 Vol.24 No.5

충치 원인균인 Streptococcus mutans와 유용 장내 세균인 각종 Bifidus 균주 증식에 미치는 di-D-fructofuranose dianhydrideIII(DFAIII)의 효과를 조사 분석하여 DFAIII의 생리 효과를 간접적으로 분석하였다. DFAIII는 Arthrobacter sp. A-6 토양 분리균이 생산하는 inulin fructotransferase(depolymerizing)을 이용, inulin을 분해하여 다량 생산한 다음 gel filtration 과정을 거쳐 순수 분리 정제하였다. 정제 DFAIII는 pH 2.5, 130℃에서 15분 가열 처리에 의해 약 35%의 분해율을 보이는 반면 sucrose는 완전히 분해되었으며, pH 5.5, 140℃ 처리 조건에서는 거의 분해되지 않는 매우 높은 열 안정성을 나타내었다. 또한 충치 유발의 중요 기준이 될 수 있는 S. mutans 증식 효과도 fructose와 sucrose는 물론이고 시판 올리고당보다도 훨씬 낮았다. 반면, Bifidus 균에 대한 증식 효과는 균주에 따라 다소의 차이는 있었으나 증식을 전혀 보이지 않았던 E. coli에 비해 뚜렷한 증식 촉진효과를 나타내었다. BL 배지에서의 Bifidus longum과 E. coli의 혼합 배양에 있어서도 Bifidus longum의 경우에서는 선택적으로 뚜렷한 증식 촉진 효과를 보였으나 E. coli의 증식은 오히려 억제됨을 확인하였다. 이상의 실험 결과를 종합 분석해 본 결과 DFAIII는 매우 우수한 생리 효과를 기대할 수 있는 감미료 소재중의 하나인 것으로 평가되었다. Some physical and physiological properties of di-D-fructofuranose dianhydrideIII(DFAIII), as a new sweetener, were investigated via in vitro experiments. The disaccharide was prepared by decomposing inulin with inulin fructotransferase(depolymerizing) from Arthrobacter sp. A-6. DFAIII had more excellent heat and acid stability than sucrose. This was one of the most desirable properties especially for the oligomer types of sweetener. DFAIII showed the least pH drop in the Streptococcus mutans culture, compared with the other saccharides examined. This indicates that the sugar will be fairly effective for prevenreas, E. coli did not show growth promotion in the DFAIII-containing medium. In the co-culture of Bifidus longum and E. coli in the BL medium, Bifidus longum had a selective growth while the growth of E. coli appeared rather to be inhibited.