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원자력발전소 운전환경에서 SA508 Gr. 1A 저합금강의 피로 수명 분석
이용성,김태순,이재곤,Lee, Yong Sung,Kim, Tae Soon,Lee, Jae Gon 한국압력기기공학회 2010 한국압력기기공학회 논문집 Vol.6 No.1
Fatigue has been known as a major degradation mechanism of ASME class 1 components in nuclear power plants. Fatigue damage could be accelerated by combined interaction of several loads and environmental factors. However, the environmental effect is not explicitly addressed in the ASME S-N curve which is based on air at room temperature. Therefore many studies have been performed to understand the environmental effects on fatigue behavior of materials used in nuclear power plants. As a part of efforts, we performed low cycle fatigue tests under various environmental conditions and analyzed the environmental effects on the fatigue life of SA508 Gr. 1a low alloy steel by comparing with higuchi's model. Test results show that the fatigue life depends on water temperature, dissolved oxygen and strain rate. But strain rate over 0.4%/s has little effect on the fatigue life. To find the cause of different fatigue life with ANL's and higuchi's model, another test performed with different heat numbered and heat treated materials of SA508 Gr. 1a. On a metallurgical point of view, the material with bainite microstructure shows much longer fatigue life than that with ferrite/pearlite microstructure. And the characteristics of crack propagation as different microstructure seem to be the main cause of different fatigue life.
플립칩의 반복 굽힘 시험 시 파손 특성에 관한 실험적 연구
이용성,정종설,김홍석,신기훈,Lee, Yong-Sung,Jeong, Jong-Seol,Kim, Hong-Seok,Shin, Ki-Hoon 한국생산제조학회 2009 한국생산제조학회지 Vol.26 No.3
In general, circuit board assemblies experience various mechanical loadings during assembly and in actual use. The repeated cyclic bending can cause electrical failures due to circuit board cracks, solder interconnects cracks, and the component cracks. In this paper, we report on the failure characteristics of semiconductor chips under the repeated cyclic bending. We first describe a new 4-point bending tester, which is developed according to JEDEC standard No. 22B113. The performance of the tester is then estimated through actual experiments. Test results reveal that the cracks first occur on the outer balls around 20,000 cycles and gradually propagate to the inner balls where cracks are found around 70,000 cycles.
Lysobacter capsici YS1215를 이용한 뿌리혹선충(Root-knot nematode)의 생물학적 방제
이용성(Yong-Sung Lee),박윤석(Yun-Suk Park),김선배(Sun-Bae Kim),김길용(Kil-Yong Kim) 한국토양비료학회 2013 한국토양비료학회지 Vol.46 No.2
The experiments were carried out to investigate the biocontrol potential of Lysobacter capsici YS1215 on root-knot nematode and to characterize its lytic enzyme activities. L. capsici YS1215 showed chitinase and gelatinase activities on the medium containing 0.5% chitin or 0.5% gelatin as substrates. Cell growth of L. capsici YS1215 was highest at 6 days, and the highest activities of chitinase (4.0 unit ml<SUP>-1</SUP>) and gelatinase (7.43 unit ml<SUP>-1</SUP>) were observed on 3 and 5 days after incubation, respectively. To investigate the effect of L. capsici YS1215 on tomato growth and nematode infection, the plants in pot trial were treated with bacterial culture (BC), half of bacterial culture (HBC), only bacterial medium (BM), tap water (TW) and commercial nematicide (CN). HBC treatd plants showed the higher shoot fresh weight and dry weight on 5<SUP>th</SUP>week after incubation while BM, HBC and BC had consistently higher values than TW at 9<SUP>th</SUP> week. HBC appeared to be the highest shoot fresh length at 9<SUP>th</SUP> week. Both CN and BC showed lower number of egg mass, root gall, and population of juveniles in soil compared to BC, HBC, BM and TW. These results suggest that L. capsici YS1215 with its strong ability of lytic enzyme production can be one of the most significant candidates for biocontrol agents against root-knot nematodes.