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

At each of the points of interse-tion by a ray of exciting forces
with the graph of natural frequencies resonance will occur.
these modes "bursts" are observed, .i.e., sharp increase in
and an increase in stresses.
In
amplitudes
An analysis of the frequency characteristic shows which harmonies
of forced vibrations will be dangerous and makes it possible to
soundly implement the design of a turbine node so as to avoid
dangerous resonance modes.
The following practical methods of combatting resonance modes
in
blades exist.
1. Elimination of the dangerous exciter harmonics. This can
sometimes be done by a small structural alteration of the turbine
unit. Let us assume that dangerous harmonic k = 4 (based on the number
of racks). If we change the number of racis, increasing it, for
example, to 5, then the dangercus harmonic disappears.
2. To build the resonance frequency out of the blade, i.e.j to
change the inherent angular velocity w.c.
certain variation in
This can be done by a
the blade's dimensions, however, so as not to
disturb the gas-dynamic characteristics of the turbine and not to
make a basic alteration of the turbine stage. It is possible, for
example,
in
webs,
to use hollow blades, to cut the angle of the blade foil
the periphery near the trailing edge, to use blades with band
to combine blades into groups by connectors or'to cast blades
with band webs in
groups.
All these measures allow the redistribution of mass and the
rigidity of the blade foil and, consequently, a variation in wc'
3. The damping of blade vibrations. There are several methods
of damping vibrations in elastic systems based on energy dispersion
of a vibrating blade. This involves primarily damping in the blade
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