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  • Inorganic Chemistry  (1)
  • fluid forces  (1)
  • steady-state response  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Steady-state vibrations of an elastic beam on a visco-elastic layer under moving load (2000)
    Springer
    Archive of applied mechanics 70 (2000), S. 399-408 
    Details
    ISSN: 1432-0681
    Keywords: Key words Moving load ; wave radiation ; steady-state response ; dispersion curves ; critical velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary  The steady-state response of an elastic beam on a visco-elastic layer to a uniformly moving constant load is investigated. As a method of investigation the concept of “equivalent stiffness” of the layer is used. According to this concept, the layer is replaced by a 1D continuous foundation with a complex stiffness, which depends on the frequency and the wave number of the bending waves in the beam. This stiffness is analyzed as a function of the phase velocity of the waves. It is shown that the real part of the stiffness decreases severely as the phase velocity tends to a critical value, a value determined by the lowest dispersion branch of the layer. As the phase velocity exceeds the critical value, the imaginary part of the equivalent stiffness grows substantially. The dispersion relation for bending waves in the beam is studied to analyze the effect of the layer depth on the critical (resonance) velocity of the load. It is shown that the critical velocity is in the order of the Rayleigh wave velocity. The smaller the layer depth, the higher the critical velocity. The effect of viscosity in the layer on the resonance vibrations is studied. It is shown that the deeper the layer, the smaller this effect.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004199900071
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  • 2
    Electronic Resource
    Electronic Resource
    Fluid-Damping Controlled Instability in Tube Bundles Subjected to Air Cross-Flow (1998)
    Springer
    Flow, turbulence and combustion 61 (1998), S. 285-300 
    Details
    ISSN: 1573-1987
    Keywords: tube bundle vibrations ; cross-flow ; instability ; pressure measurements ; fluid forces ; correlation length ; fluid damping effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract There are different excitation mechanisms that cause fatal damages due to undesirable vibrations in heat exchanger tube bundles subjected to cross-flow. One of them is the fluid-damping-controlled instability (galloping) that is characterised by a sudden appearance of large amplitudes of the tubes exclusively in cross-flow direction. This paper reports on investigations using an experimental set-up in a wind tunnel where the galloping mechanism in a tube bundle can be observed as an isolated phenomenon. The apparatus allows to realise several tube bundle configurations and geometry's of real heat exchangers. The position of a flexible test tube with a linear iso-viscoelastic mounting inside the tube array is variable. The test tube is equipped with dynamical pressure sensors which are placed directly under pressure holes inside the tube. For the investigation of the acting fluid forces the non-stationary pressure distribution is measured simultaneously at 30 points on the circumference in mid plane and at 15 points in line along the tube together with the tube motion. The acting fluid forces are determined by integration of the whole pressure field process. The study gives insights into the effect of the fluid-damping-controlled instability that is still not fully understood. Moreover, a flow visualization gives an impression of the mechanism at relevant Reynolds-numbers. The results show that in case of instability due to galloping the correlation length of the forces acting along the tube axis increases suddenly to large values. The fluid forces are correlated well for the whole tube when galloping is dominant. The exciting fluid forces show harmonic character and lead to a classical resonance behaviour. Instead of a simple free vibration test in vacuum or still air, which is done mostly for fluid excited structures, the damping coefficient of the oscillating system is determined under operating conditions on the basis of the measured fluid forces. A comparison of the results with those of a free vibration test in still air is shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009984505200
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  • 3
    Electronic Resource
    Electronic Resource
    Die Darstellung und die Eigenschaften der Silber(III)-oxidphase (1963)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 322 (1963), S. 286-296 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: From AgNO3, AgF, and AgClO4 solutions, silver(III) oxide phases have been prepared by anodic oxidation. These are steel-gray, magnetite-like octahedra having a cubic face-centered unit cell (a = 9.842-9.890 Å).All the specimen obtained differ from the ideal composition Ag2O3, as analysis and pyenometric measurements show; they are supposed to be Ag2O3 defect compounds being only stable in the presence of foreign anions and Ag(I)ions (approximate formulae: Ag3+5 Ag+2O8NO3; Ag2(O, F)3; the perchlorate-containing phase has no stoichiometric composition). Their chemical properties and thermal decomposition are described.The alleged oxide Ag4O5 (SELBIN and USATEGUI) does not exist.
    Notes: 1. Es wurden aus AgNO3-, AgF- und AgClO4-Lösungen höhere Silberoxidpräparate durch anodische Oxydation dargestellt. Diese bestehen alle aus stahlgrauen, magnetitähnlichen Oktaedern, die Kantenlänge der kubisch flächenzentrierten Zelle ist a = 9,842-9,890 Å.2. Die Präparate wurden analysiert; ihre Dichte wurde gemessen und daraus der Zelleninhalt in Atomen bestimmt. Daraus geht hervor, daß das Gitter defekt ist. Die Zusammensetzung der nitrathaltigen Verbindung ist mit guter Annäherung Ag7NO11 oder Ag3+5 Ag+2O8NO3. Die fluorhaltige Phase kann als Ag2(O, F)3 formuliert werden, die perchlorathaltige hat keine stöchiometrische Formel.3. Alle diese Oxide stellen eine kubisch flächenzentrierte Phase mit der „idealen Zusammensetzung“ Ag2O3 dar, die aber nur in Gegenwart von Fremdanionen stabil ist und in welcher Ag3+ und Ag+-Ionen in verschiedenen Proportionen vorliegen.4. Die chemischen Eigenschaften werden beschrieben und die thermische Zersetzung (mit Derivatogrammen) wurde eingehend studiert.5. Das von SELBIN und USATEGUI angegebene Oxid „Ag4O5“ existiert nicht.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19633220508
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