강판형의 덮개판 형상에 따른 피로특성

정영화,홍성욱,김익겸,정진석,Jung, Young Hwa,Hong, Sung Wook,Kim, Ik Gyeom,Jung, Jin Suck 한국강구조학회 2000 韓國鋼構造學會 論文集 Vol.12 No.2

이 연구에서는 덮개판 형상이 피로특성에 미치는 영향을 정량적으로 평가하기 위해서 강교량을 구성하는 구조세목 중 덮개판 필렛용접부를 대상으로 일련의 피로실험을 실시하였다. 피로실험결과 덮개판 형상에 따라 피로강도에 다소 차이를 나타내고 있었으나 국내 및 외국의 피로설계기준을 만족함을 알 수 있었다. 또한 비치마크실험결과로부터 피로균열 발생점은 용접지단부의 형상에 밀접하게 관련되어 있음을 확인할 수 있었으며, 용접지단부의 여러 곳에서 동시다발적으로 발생한 피로균열이 반타원형의 표면균열의 형태로 성장하고 이 균열이 서로 합체되어 관통균열의 형태로 성장함으로써 결국 파단에 이르렀다. 한편, 파괴역학적 해석결과로부터 기존의 제안식 및 유한요소해석에서 구한 균열보정 계수 중기하학적형상보정계수가 가장 지배적임을 알 수 있었으며, 피로균열성장속도와 유한요소해석에서 구한 응력확대계수범위 사이의 관계로부터 덮개판 필렛용접부의 피로수명을 산정 할 수 있었다. In this study, A series of fatigue tests have been performed on the fillet welded joints of cover plates in steel plate girders in order to quantitatively assess the fatigue characteristics according to the shapes of cover plates. From the results of fatigue tests, it has been shown that the fatigue strengths were slightly different according to their shapes, but satisfied the fatigue design curves in Korea and other countries. Also, from the results of beachmark tests, it has been confirmed that the points of fatigue crack initiation were closely related to the shapes of weld bead toes, and fatigue cracks simultaneously initiated from several points in weld bead toes have been grown as semi-elliptical surface cracks, and these cracks have been coalesced each other, and grown as through thickness cracks, and finally reached to fracture. Besides, from the results of fracture mechanics approaches, stress gradient factors were the most dominant factors among crack correction factors obtained from the existing equations and finite element analysis, and the fatigue life on fillet welded joints of cover plates could be estimated using the relations between fatigue crack growth rate and stress intensity factor range obtained from finite element analysis.

강판항(鋼板桁) 덮개판 형상에 따른 피로균열성장특성

정영화,김익겸,정진석,이형근,Jung, Young-Hwa,Kim, Ik-Gyeom,Jung, Jin-Suck,Lee, Hyung-Koon 강원대학교 산업기술연구소 1999 産業技術硏究 Vol.19 No.-

When a variety of repeated loads are given, most steel structures failed in much lower level of loads than static failure loads. In addition, bridge always includes the internal defects or discontinuities. from these, fatigue cracks initiates and can lead to sudden failure. Thus, in this study, tensile specimens by the cover plate shapes were used as the test specimens. The fatigue test was performed by constant amplitude fatigue loading and beach mark. From the results of this study, each specimen's fatigue section was observed. in addition, stress intensity factor at crack tip was calculated by using the Green's function which applied to discontinuous section where causing stress concentration. Therefore, the fatigue life of structural detail was investigated by adopting the theories of fracture mechanics. each specimen's crack shape is a semi-elliptical surface crack or center crack sheet, stress gradient correction factor, Fg is the most subjective of all stress intensity correction factors and fatigue life should be predicted by previous proposed function and finite element analysis.

지간장에 따른 강판형 철도교의 피로피해도 평가

정영화,김익겸,김지훈,남왕현,Jung, Young-Hwa,Kim, Ik-Gyeom,Kim, Ji-Hun,Nam, Wang-Hyone 강원대학교 산업기술연구소 1999 産業技術硏究 Vol.19 No.-

Steel railway bridge gets vibration from moving load ; additionally, this kind of moving load is going to be a sufficient reason, which causes fatigue damage to steel railway bridge. Fatigue damage and stress curve were raised by moving load depends on span length in steel railway bridge. In other words, stress curve appears index regarding every axial load in short span, but self weight lets stress curve's change decrease in proportion to increasing span length. Thereby, we have studied that how the steel railway bridge appear fatigue damage in proportion to span length of steel railway bridge. Dynamic strain was measured in 4 steel plate-girder railway bridge during the trains was passing, which is located on the line of Kyoung-chun railway. And time history response analysis has been done in order to ensure actual survey. The results of this study show the decreased of the fatigue damage in steel railway bridge according to length of span. This paper ends is bases research of fatigue design in steel railway bridges according to span length.

한국산 저장식품응애 1미기록 종(Suidasia medanensis Oudemans, 1924)에 대한 보고

정영화,홍신지,이원구,Jung, Young-Hwa,Hong, Shin-Ji,Lee, Won-Koo 한국응용곤충학회 2010 한국응용곤충학회지 Vol.49 No.4

2008년에서 2009년 저장식품응애에 대하여 조사하던 중, 꼬마뿌리응애(Suidasia)속의 Suidasia medanensis Oudemans, 1924가 한국 미기록 종으로 확인되어 그 형태학적 특징을 보고한다. One of stored food mites, Suidasia medanensis Oudemans, 1924 is first reported form Korea after the stored food surveys in 2008 and 2009. The morphological characteristic is given.

TIG처리에 따른 하중비전달형 필렛용접부의 피로특성

정영화,경갑수,홍성욱,김익겸,남왕현,Jung, Young Hwa,Kyung, Kab Soo,Hong, Sung Wook,Kim, Ik Gyeom,Nam, Wang Hyone 한국강구조학회 2000 韓國鋼構造學會 論文集 Vol.12 No.5

이 연구에서는 하중비전달형 필렛용접부를 대상으로 순수휨상태에서 TIG 처리에 따른 피로강도 향상정도 및 피로특성을 정량적으로 평가하기 위해서 4점 휨실험을 실시하였다. 피로실험결과 용접후처리를 실시하지 않은 시험체는 국내 외에서 규정하는 피로강도등급을 만족하고 있고 TIG 처리한 시험체는 용접후처리를 실시하지 않은 시험체보다 $2{\times}106$회 피로강도가 상회하는 것을 알 수 있었다. 또한 비치마크실험결과 피로균열은 용접지단부의 비드접선각도 및 곡률반경이 최소로 되는 점에서 다발적으로 발생하며, 반타원형 균열로 성장, 합체되어 파단에 이르는 것을 확인할 수 있었다. 한편 유한요소해석결과 용접지단부의 응력집중계수는 용접지단부의 비드접선각도 및 곡률반경과 밀접한 관계가 있으며, 이 중에서 곡률반경이 용접지단부의 응력집중계수에 보다 큰 영향을 미치는 것을 알 수 있었다. 한편 파괴역학적 해석결과 a/t가 0.4 이하인 경우에 기하학적형상보정계수가 균열보정계수에 가장 지배적인 영향을 미치는 인자임을 알 수 있었다. 또한 유한요소해석결과로부터 산정한 응력확대계수범위와 피로균열성장속도의 관계식으로부터 피로수명을 비교적 정확하게 산정할 수 있었다. In this study, the 4-point bending test has been performed in order to estimate the effect of TIG-dressing on fatigue strength and fatigue characteristics quantitatively for non load-carrying fillet welded joints subjected to pure bending. As a result of fatigue tests, fatigue strength of as-welded specimens has been satisfied the grade of fatigue strength prescribed in specifications of domestics and AASHTO & JSSC, and fatigue strength at $2{\times}106cycles$ of TIG-dressing specimens has been increased compared with as-welded specimens. As the result of beachmark tests, fatigue cracks have been occurred at several points, where the radius of curvature and flank angle in the weld bead toes are low, and grown as semi-elliptical cracks, then approached to fracture. As a result of finite element analysis, stress concentration factor in weld bead toes has been closely related to the flank angel and radius of curvature, and between these, the radius of curvature has more largely affected in stress concentration factor than flank angle. As a result of fracture mechanics approaches, the crack correction factor of test specimens has been largely affected on stress gradient correction factor in case a/t is below 0.4. From the relations between stress intensity factor range estimated from FEM analysis and fatigue crack growth rate, fatigue life has been correctly calculated.

韓國農地法制의 史的 展開와 展望

鄭永和(Jung, Young-Hwa) 한국법사학회 1996 法史學硏究 Vol.17 No.-

참가사리 분획물의 암 예방효과

정영화(Young?Hwa Jung),정복미(Bok?Mi Jung),신미옥(Mi?Ok Shin),배송자(Song?Ja Bae) 한국식품영양과학회 2006 한국식품영양과학회지 Vol.35 No.4

본 연구에서는 해조류 중 홍조류에 속하는 참가사리를 추출, 분획하여 항발암효과를 측정하였다. 참가사리 분획물을 4종의 암세포주 HT29, HepG2, MCF-7 및 B16-F10에 처리하였을 때 암세포 증식억제실험을 한 결과 대장암세포주인 HT29의 경우 GTMM층과 GTMB층에서 농도의존적인 효과가 나타났으며 첨가농도 150 ㎍/mL에서 각각 93.64%와 74.14%의 수치를 보였다. 간암세포주인 HepG2의 경우 150 ㎍/mL 첨가 시 GTMM층과 GTMB층이 각각 95.97%, 81.78%의 높은 증식억제효과를 보였으며 유방암세포주인 MCF-7에서는 GTMM층이 120 ㎍/mL과 150 ㎍/mL 첨가농도에서 각각 88.50%와 91.82%의 높은 암세포증식 억제효과를 나타냈다. 피부암세포주인 B16-F10은 다른 세포주에 비해 미약하나 역시 GTMM층이 최종첨가농도에서 86.20%의 억제를 나타내었다. 이와 같이 4종의 암세포주의 증식억제는 전반적으로 GTMM층과 GTMB층에서 높은 효과가 나타남을 알 수 있다. 한편 Western blot analysis를 통해 간암세포주인 HepG2에서 GTMM층의 처리에 따른 pro-apoptosis Bcl-2 family의 발현증가를 볼 수 있었으며, PARP 분절과 연관된 caspase-3, 7의 활성화를 확인할 수 있었다. 이처럼 GTMM층은 apoptosis의 작용에 의한 세포사멸을 유도하며, 이러한 apoptosis의 기전으로는 최소한 caspase의 활성화에 따른 절단 PARP 단백질의 증가, Bad, Bax 등의 apoptosis 관여인자가 작용하고 있음을 확인할 수 있었다. HepG2를 이용한 quinone reductase 유도활성여부를 측정한 결과 GTMM층이 45 ㎍/mL 및 60 μg/mL의 시료첨가농도에서 대조군에 비해 각각 2.34, 2.86배의 QR유도활성을 나타내었으며, GTMB층의 경우 최종첨가농도인 60 ㎍/mL에서 2.04 배의 효소활성을 나타내었다. In this study, we investigated anticarcinogenic effects of extracts from Gloiopeltis tenax (GT). GT was extracted with methanol (GTM), which was then further fractionated into four fractions by using solvent fractionation method, affording methanol (GTMM), hexane (GTMH), butanol (GTMB) and aqueous (GTMA) soluble fractions. We determined the cytotoxic effects of these fractions on cancer cells by MTT assay. Among various fractions of GT, the GTMM showed the strongest cytotoxic effect at concentration of 150 ㎍/mL, displaying 95.97% on HepG2 cell lines and 93.64% on HT?29 cell lines, respectively. And, the anti?proliferative effect of GT was accompanied by a marked in increase of levels of Bad, Bax, Bok and Bak protein and activation of caspase?3, caspase?7 and PARP protein. Also, we observed quinone reductase (QR) induced effects in all fraction layers of GT on HepG2 cells. The QR induced effects of the GTMM and GTMB on HepG2 cells at concentration of 60 ㎍/mL showing inductive indexes of 2.86 and 2.04 compared to the control value of 1.0.

하중비전달형 필렛용접부의 피로강도 향상법에 관한 연구 (2) : TIG 처리에 따른 영향

정영화(Jung Young Hwa),경갑수(Kyung Kab Soo),홍성욱(Hong Sung Wook),김익겸(Kim Ik Gyeom),남왕현(Nam Wang Hyone) 대한토목학회 2000 대한토목학회 학술발표회 논문집 Vol.2000 No.1

합성섬유를 혼입한 콘크리트의 강도 및 내구특성

정영화(Jung Young Hwa),이주형(Lee Ju Hyung),홍창우(Hong Chang Woo),이정호(Lee Jung Ho) 강원대학교 산업기술연구소 1998 産業技術硏究 Vol.18 No.-

Concrete structures has been deteriorated by poor environment. This study was conducted to evaluate durability of concrete which are increasingly demanded recently. Therefore, the research of durability must be executed for application of Polypropylene fiber reinforced concrete real structures. Concrete durability properties incorporating Polypropylene fiber was performed with the variable of Fiber contents, Fiber type and Target strength. specimens were made and subjected to durability and strength tests. The results show that strength of concrete is increased the Fiber content increase, Mono-Filament fiber and Polypropylene fiber reinforced concrete makes improved durability properties.

국부가열을 이용한 면외거셋의 피로강도 향상

정영화(Jung Young Hwa),남왕현(Nam Wang Hyone),장동휘(Chang Dong Huy) 강원대학교 산업기술연구소 2001 産業技術硏究 Vol.21 No.1

This study is finding the most appropriate model of kangwondo watershed. To synthesize each hydrograph, It is found to several parameters which are used in existing hydrographes. then the synthestic hydrograph is compared and investigated wish many hydrographes of the rivers in kanwondo. These methods, Nakayasu, Clark, SCS are used to calculate the run-off of this watershed. When the calculated run-off is compared with real rating-curves, then it is found that the SCS method using the Clark’s concentrantion time is the best way on this area having large watershed, long river length and gentle water slope, the Nakayasu method is more suitable on this area having small watershed, short river length and steep water slope. Also it is founded from analyzing run-off hydrographes, peak run-off and peak time that the Clark’s method applied Kirpich’s concentration time way is suitable in the area of kanwondo.