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김재민,이중건 여수대학교 1998 論文集 Vol.13 No.2
This paper presents results of dynamic analysis for a bridge in intersection part of two tunnels subjected to moving vehicle loadings. Since such a bridge system is very unusual due to the fact that it is located in tunnel, the dynamic characteristics of the structure can not be assumed as conventional one. The structure investigated in this study is a reinforced concrete bridge in the intersection part of Namsan Tunnel-1 and Tunnel-2 in Seoul. It is supported by temporary steel structure which shall be constructed during the period of replacing lining in Tunnel-2. Dynamic analysis was carried out for the system using a finite element model constructed by general purpose FE program SAP2000. For this purpose, the structure, lining of tunnels, and surrounding rock were represented bey finite elements, while the rock region is truncated and on its outer boundary viscous dampers were placed to simulate radiation of elastic waves generated in tunnels. Several types of vehicles with various driving velocities were considered in this analysis. The FE model including vehicle loadings was verified by comparing calculated peak particle velocity with the measured one. From the analysis, the impact factor for the bridge was estimated as 0.20. Therefore it has been concluded that the use of upper bound for the impact factor specified in design code is expected to be conservative for this kind of bridge system.
초음파타원진동절삭가공법에 의한 Co-Cr-Mo 합금의 경면가공
송영찬(Young Chan Song),田中健一(Kenichi Tanaka),森脇俊道(Toshimichi Moriwaki) Korean Society for Precision Engineering 2008 한국정밀공학회지 Vol.25 No.3
The biocompatibility and the fatigue strength of Co-Cr-Mo alloy are excellent, so it is used well for the material of artificial joints. The head of artificial joint needs mirror surface for reduction of abrasive resistance. Mirror finishing of Co-Cr-Mo alloy with geometrically defined single crystal diamond cutting tools is handicapped by micro chipping of tool edge. In general, it is said that the micro chipping of diamond tool is caused by work hardening of Co-Cr-Mo alloy for the cut. In the present research, mirror finishing of Co-Cr-Mo alloy by applying ultrasonic elliptical vibration cutting was carried out. The experimental results show that the micro chipping of diamond tool was suppressed and the tool wear was remarkably reduced as compared with the ordinary diamond cutting without elliptical vibration motion. It was confirmed that the good mirror surface of maximum surface roughness of 25 ㎚P-V was obtained for the cutting length of about 14 m. It is expected that mirror finishing of Co-Cr-Mo alloy can be achieved by applying ultrasonic elliptical vibration cutting practically.