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표면조도 특성에 따른 저항 점 용접성 평가 및 너깃 형성 고찰
김기홍,최영민,김영석,임영목,유지훈,강남현,박영도,Kim, Ki-Hong,Choi, Yung-Min,Kim, Young-Seok,Rhym, Young-Mok,Yu, Ji-Hun,Kang, Nam-Hyun,Park, Yeong-Do 대한용접접합학회 2008 대한용접·접합학회지 Vol.26 No.5
With the increased use of surface textured steel sheet in body-in-white assembly, resistance spot weldability of these steels is considered to be an important subject. This study evaluated nugget formation and weldability by measuring dynamic resistance with various weld pressure, current, and weld time for steel sheet with two different surface roughnesses. The surface roughness for T-H steel ($R_{a}=1.70\;{\mu}m$) was higher than that for T-L steel ($R_{a}=1.33\;{\mu}m$), and resulted in increased contact resistance and heating for T-H steel spot welding. Therefore, at low weld current and weld cycle ranges, the T-H steel showed better weldability over the T-L steel. The evaluations of weld interface showed that the fusion zone in the T-H steel sheet was continuous in contrast to discontinuous fusion zone for T-L steel sheet at the same welding conditions. A comparison of dynamic resistance and tensile-shear strength (TSS) between T-H and T-L steel sheet suggested that high surface roughness provided larger heating at early cycle of welding and larger TSS.
가압력 변화에 따른 표면조도처리 강판의 저항 점 용접성 비교
박상순,박영도,김기홍,최영민,임영목,강남현,Park, Sang-Soon,Park, Yeong-Do,Kim, Ki-Hong,Choi, Yung-Min,Rhym, Young-Mok,Kang, Nam-Hyun 대한용접접합학회 2008 대한용접·접합학회지 Vol.26 No.2
With the development of surface roughness textured steel for automotive body-in-white assemble, one of key issues is to understand the role of the surface roughness in textured steel sheets. To investigate effect of surface roughness on weldability in prepared steels, electrode force was varied. Steel sheets (T-H) with high surface roughness ($Ra\;=\;1.94\;{\mu}m$) reduced electrode life. It was attributed to the higher contact resistance at the electrode-sheet interface in the presence of the high surface roughness. The increased electrode diameter decreased current density, therefore reducing weld electrode life due to small weld button size. When an increased electrode force was used, a significant increase in the electrode life was observed in welding of high surface roughness steel sheet. This study suggested that contact resistance at the electrode-sheet interface was the dominant factor, as compared to the sheet-sheet interface for determining electrode life in welding of surface roughness textured steel.
일반 폐경 여성을 대상으로 한 폐경과 호르몬 대치용법에 대한 인식도 조사
장윤석,김재원,김정구,김석현,최영민,신창재,문신용,이진용 대한폐경학회 1995 대한폐경학회지 Vol.1 No.1
Hormone replacement therapy(HRT) has an established role in reducing the cardivascular risk and in preventing osteoparosis. But compliance with HRT is not good as expected. We assessed menopausal women's attitudes toward menopause and HRT to find some fators th;t might increase its use. Questionnaires were provided to the members of two churches located in Seoul and three hundred seven women responded. During menousal period, sixty eight women(22.1%) had suffered from fractures, 54(17.6%) cerebrovasscular accident, 45(14.7%) cardiac disease. More than three quarters (75.9%) of menopausal women had already experinced postmenopausal symptoms but only 55 patients(14.2%) among them had seeked medical advices. The impartant sources of information on HRT were friends(43.7%), television(24.1%) in order of frequency. Among medical doctors, gynecologists were the leading one who recommended HRT(66.7%). Sixty four(20.8%) of menopausal women had taken HRT but around 5% among them were current HRY users at the time of survey.Most menopausal women(74.8%) did not perceive menopause as a medical condition. But interestingly, one hundred two(40%) of 255 respondents knew the effectiveness of HRT in preventing ostoporosis. More than one half (59.4%) of the respondents were worried about increased risk of cancer development by HRT. Our data suggest that a systematic educational approach is required to influence menopausal women's willingness to take HRT, and that their fears about cancer sholud be resolved to increase the compliances