Design and Stress Analysis of Extraterrestrial ... - The Black Vault

I -I S89. 10
,413(0.142)406
1,4.1o-• 8 )107571.1
hence
(aci= 286 0 rad/s
Blade Vibration frequency is
fc]= -- 2n =456 vib/s
The effect of revolution on the natural
frequency of a blade
In practice the frequency of natural vibrations in a rotating
blade is determined according to the frequency of a nonrotating
blade with a correction for rotation.
in
As has already been mentioned in
the stress analysis of a blade
a 1votating blade under the action of centrifugal forces moment
appears which strives to straighten the bent blade during its
vibration
(see Fig. 3.20). This is equivalent to ztiffening a blade, due
to which the natural frequency of a rotating blade increases.
Particularly strong is
the effect of centrifugal loifces on the
lowest natural frequency (corresponding to th-.
'Lrst jending form).
The effect on the other frequencies is less substantial. Therefore,
it is of interest to calculate this lowest natural. frequency with
the effect of centrifugal forces taken into account.
LA ad/cen (1)
Fig. 3.28. The dependence of
the natural frequency of a blade
on the angular velocity of
rotc: rotation.
KEY: (1) rad/s.
we
279
0 Wm9x t pad/cem