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MODELING OF A REPULSIVE TYPE MAGNETIC BEARING FOR FIVE AXIS CONTROL INCLUDING EDDY CURRENT EFFECT
T.Ohji,S.C.Mukhopadhyay,M.I wahara,S.Yamada 전력전자학회 1998 ICPE(ISPE)논문집 Vol.- No.-
So far a single-axis controlled repulsive type magnetic bearing system have been designed and fabricated in our laboratory employing the repulsive forces operating between the stator and rotor permanent magnet for levitation. The radial axis is uncontrolled passive one The higher speed of operation is limited due to the vibration along the uncontrolled axis and the increase of control current due to eddy current interference. This paper will discuss a detailed modeling of the repulsive type magnetic bearing system for five axis control including the eddy current effect and the method of reduction of eddy current effect Simulation results using Matlab will be presented.<br/>
High strain-to-failure porous alumina ceramics with improved mechanical properties
D. Doni Jayaseelan,S. Ueno,T. Ohji,S. Kanzaki 한양대학교 세라믹연구소 2004 Journal of Ceramic Processing Research Vol.5 No.1
A pulse electric current sintering technique was employed to fabricate porous alumina from a commercially available powder. Porosity was controllable between 20 to 50% depending on the sintering temperature. The fracture strength was correlated exponentially as a function of porosity. A high strength of ~250 MPa was achieved for the specimens, which had porosity of 30 vol.%. The strain-to-failure of the porous Al2O3 ceramics increased considerably and this improves the reliability of the specimens.
Alumina/SiC 나노복합재료에서의 잔류 열응력 완화거동에 관한 연구
Y. H. Choa,K.Niihara,T. Ohji,J. P. Singh 한국분말야금학회 2002 한국분말야금학회 학술대회논문집 Vol.2002 No.1
Plastic deformation was observed by TEM around the intragranular SiC particles in the matrix for nanocomposite system. The dislocations are generated at selected planes and there is a tendency for the dislocations to form a subgrain boundary structure with low-angel grain boundaries and networks. In this study, dislocation generated in the matrix during cooling down from sintering temperatures by the highly localized thermal stresses within and/or around SiC particles caused from the thermal expansion mismatch between matrix and SiC particle was observed. In monolithic and microcomposite system. These phenomena is closely related to the plastic relaxation of the elastic stress and strain energy associated with both thermal misfitting inclusions and creep behaviors. The plastic relaxation behavior was explained by combination of yield stress and internal stress.