**JVA Abstract**

### Transverse Vibration of a Rectangularly
Orthotropic Spinning Disk -

Part II:
Forced Vibration and Critical Speeds
** **

A. Phylactopoulos and G.G. Adams

Summary

The transverse forced vibration of a rectangularly orthotropic
spinning disk is investigated. The disk is subjected to a constant
stationary point-load. Although the deflection of an
*isotropic* disk under these loading conditions is
time-invariant in a space-fixed coordinate system, the *
orthotropic* disk undergoes time-dependent oscillatory motion.
This phenomenon occurs as a result of the continually changing
orientation of material properties with respect to the load. The
disk deflection under-the-load is determined as a function of time.
Also the deflection along a disk radius and circle containing the load
are determined at a fixed instant of time.
The occurence of critical speeds is also investigated. Without
damping, virtually any angular speed of the orthotropic disk is found
to be critical. This behavior is due to the occurence of more than one
Fourier component in each of the eigenfunctions of the free vibration
problem. With damping included, a large amplitude response is found at
a speed much less than the lowest classical critical speed of an
isotropic disk.

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