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1

Wpływ naprężeń wstępnych na wybrane obliczane parametry drganiowe maszyn elektrycznych

Maniara R., Kardas D.

Energetyka

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2009

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nr 9

592-598

PL

Duże siły i amplitudy drgań występujące w pobliżu lub stanie rezonansu są niebezpieczne dla maszyn elektrycznych. Naprężenia dynamiczne towarzyszące drganiom przy częstotliwościach rezonansowych prowadzą do zniszczenia zmęczeniowego. Dlatego maszyna elektryczna powinna być tak zaprojektowana, aby uniknąć pracy w pobliżu rezonansu, a więc jej częstotliwości drgań własnych powinny znajdować się w bezpiecznej odległości od częstotliwości sił wymuszających. Zaprezentowano wpływ naprężeń wstępnych na częstotliwość drgań własnych wybranego węzła konstrukcyjnego maszyny elektrycznej.

EN

High vibration forces and amplitudes occurring in the resonance state or close to it, are dangerous for electric machines. Dynamic stresses, accompanying the vibrations close to resonance frequencies, lead to fatigue failure. That is why an electric machine must be designed in order to avoid occurring of working vibrations close to the resonance state – it means that the frequency of its free vibrations must be in a safe distance from frequencies of exciting forces. Presented is an influence of initial stresses on free vibration frequency of a selected constructional node of an electric machine.

2

On plane waves in an isotropic linear thermoelastic solid with initial stresses

Singh B.

International Journal of Applied Mechanics and Engineering

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2006

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Vol. 11, no 4

957-963

EN

The plane wave propagation in a homogenous isotropic, thermally conducting elastic solid under normal initial stresses is studied with two thermal relaxation times. Three types of plane waves, quasi-P, thermal and quasi-SV waves, are shown to exist. The dependence of the velocities of these plane waves on the direction of propagation is shown graphically for different combinations of normal initial stresses.

3

Propagation and attenuation of seismic body waves in initially stressed dissipative medium

Dey S., Dutta D.

Acta Geophysica Polonica

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1998

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Vol. 46, nr 3

351-366

EN

The paper discussed the effect of initial stresses on the propagation and attenuation of seismic body waves in a dissipative medium. The study reveals that the presence of initial stresses has strong effect in the propagation and attenuation of seismic waves. The velocity of waves depends on the direction of propagation and pure longitudinal and transverse waves are available only in the direction of initial stress and perpendicular to it. In other directions, a longitudinal wave is accompanied by some rotation and a transverse wave by some dilatation. The study also shows that the presence of compressive initial stress increases the velocity of longitudinal wave but diminishes that of trahsverse wave. It is also observed taht the loss of longitudinal wave due to dissipation is maximum in the initially stress-free case and decreases as the initial stress increases. In the case of SV wave, the presence of initil stresses decreases the loss factor upto the point when the direction of propagation makes an angle of 55° with the direction of initial stress, and then increases.