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링압축시험에서 역해석을 이용한 유동응력과 마찰상수 결정법
최영,김호관,조해용,김병민,최재찬,Choi, Y.,Kim, H.K.,Cho, H.Y.,Kim, B.M.,Choi, J.C. 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.3
An inverse analysis been applied to obtain the flow stress of the material. In this method, a ring-shaped specimen is compressed between two flat tools. This procedure employs, as the object function of inverse analysis, the balance of measured loads and reaction forces calculated by using rigid-plastic finite element method. The balance is explicit scalar function of flow stress which is a function of some unknown constants. For minimizing the balance, Newton-Raphon scheme is used. The friction factor, m, between flat tools and the specimen is determined by using friction area-divided method. The proposed method allows an accurate identification by avoiding the usual assumptions made in order to convert experimental measures into stress-strain relation. In this paper, the proposed method is numerically tested. A commercial pure aluminum was selected, as an example, to apply the method and the results are compared with stress-strain relation obtained by experiments.
Generalized Modeling Method for Compliant Mechanisms considering Rigid-body Deformations
Y. M. Choi(최영만),H. H. Lim(임현호) Korean Society for Precision Engineering 2021 한국정밀공학회 학술발표대회 논문집 Vol.2021 No.11월
The multi-rigid-body matrix method (MRBMM) is a generalized modeling method for obtaining the displacement, stress, and modal information of a compliant mechanism without performing inner-force analysis. MRBMM discretizes a compliant mechanism into flexible hinges and rigid bodies to implement a mass-spring model. The method designs the multi-body spring mechanism using coordinate transformations in a matrix form. In MRBMM, the deformations of the element assumed to be a rigid body are ignored. In some cases, such as displacement amplification mechanisms, non-negligible deformation occurs even in elements other than the flexible hinge. In this paper, we present a multi-compliant-body matrix-method that considers a rigid body as a compliant element, while retaining the generalized framework of the MRBMM. In the MCBMM, a rigid body in the MRBMM is segmented into a certain number of body nodes and flexure hinges. For bridge type displacement amplification mechanism, MCBMM yields the most accurate amplification ratio among several previous modeling methods. Finally, we confirmed that the MCBMM shows improved accuracy in estimating static and dynamic performances of compliant mechanism through an example of XY positioning mechanism with a double-lever mechanism.
초실감/고정밀 서비스를 위한 초정밀 네트워크 기술 동향
최영일,김응하,강태규,김도영,김정윤,정태식,Choi, Y.I.,Kim, E.H.,Kang, T.K.,Kim, D.Y.,Kim, J.Y.,Cheung, T.S. 한국전자통신연구원 2021 전자통신동향분석 Vol.36 No.4
To realize remote surgery from hundreds of kilometers away, a new communication environment with ultra-low latency and high-precision features is required. Thus, ultra-high precision networking technology that guarantees the maximum latency and jitter of end-to-end traffic on an Internet-scale wide area network is in development as part of 6G network research. This paper describes the current status of various networking technologies in ITU-T, ETSI, IEEE, and IETF to ensure ultra-low latency and high precision in wired networks.