Analysis of dynamic characteristics of fluid force induced by labyrinth seal

Flow patterns of the labyrinth seal are experimentally investigated for making a mathematical model of labyrinth seal and to obtain the flow induced force of the seal. First, the flow patterns in the labyrinth chamber are studied on the circumferential flow using bubble and on the cross section of the seal chamber using aluminum powder as tracers. And next, the fluid force and its phase angle are obtained from the measured pressure distribution in the chamber and the fluid force coefficients are derived from the fluid force and the phase angle. Those are similar to the expression of oil film coefficients. As a result, it is found that the vortices exist in the labyrinth chambers and its center moves up and down periodically. The pressure drop is biggest in the first stage of chambers and next in the last stage of chambers

Charge Ordering in alpha-(BEDT-TTF)2I3 by synchrotron x-ray diffraction

The spatial charge arrangement of a typical quasi-two-dimensional organic conductor alpha-(BEDT-TTF)2I3 is revealed by single crystal structure analysis using synchrotron radiation. The results show that the horizontal stripe type structure, which was suggested by mean field theory, is established. We also find the charge disproportion above the metal-insulator transition temperature and a significant change in transfer integrals caused by the phase transition. Our result elucidates the insulating phase of this material as a 2k_F charge density localization.Comment: 8 pages, 5 figures, 1 tabl

EBSD-assisted fractographic analysis of crack paths in magnesium alloy

 Magnesium (Mg) alloys are attractive as structural materials due to their light weight and high specific strength. It is well known that Mg alloy has hexagonal close-packed (HCP) structure and only basal slipor twinning can operate during plastic deformation because critical resolved shear stresses of the other slipsystems such as pyramidal or prismatic slips are much higher than the basal slip. Thus sometimes characteristicfracture surfaces are formed during stress corrosion cracking (SCC) or fatigue crack propagation (FCP) in Mgalloys, where many parallel lines are formed. These lines are different from so-called fatigue striations, becausethey are formed even under sustained load condition of SCC. Consequently, electron back scattered diffraction(EBSD) technique was applied on the fracture surface, and the formation mechanism of parallel lines wasinvestigated. EBSD-assisted fractography had revealed that the characteristic parallel lines were formed due tothe operation of basal slips, not twining. It is considered that hydrogen-enhanced localized plasticity (HELP)mechanism had been activated under corrosive environment