Environmental Engineering Reference
In-Depth Information
According.to.Bok,.v.=.0,.while.according.to.Fokht.,.v.=.1. 10 .Fokht's.hypoth-
esis.concerning.the.proportionally.of.the.nonelastic.stress.to.the.frequency.is.
not.conirmed.by.experiment,.while.the.Bok's.hypothesis.is.in.better.agree-
ment.with.experimental.results,.at.least.in.a.rather.wide.range.of.frequencies.
Golfman 8 .shows.the.critical.damping.coeficient,.δ,.for.iberglass.for.differ-
ent.angles.relative.to.a.warp/ill.directions..The.critical.damping.coeficient.
also.has.been.determined.in.the.process.of.determining.the.free.vibration.of.
the.patterns..The.coeficient.of.internal.friction.λ.was.found.in.the.process.of.
testing.the.iberglass.for.durability.
The. ability. of. ultrasonic. waves. to. travel. in. a. web. direction. over. a. mini-
mum.time.was.also.established.by.Golfman. 11
The.velocity.of.ultrasonic.waves.propagation.was.determined.as:
.
V 0 .=.L/t.10 3 .=.L.f.10 3 ..
(5.46)
where:
L.is.the.length.between.the.two.acoustic.heads;
t.is.the.time.taken.for.the.ultrasonic.oscillations.to.reach.from.one.head.to.
the.other;
f.is.the.frequency.of.ultrasonic.wave.propagation.
In.the.real.dynamic.conditions,.the.internal.friction.that.results.from.these.
actions.has.some.delay.to.ultrasonic.wave.propagation.
.
V d .=.L.f.10 3 λ..
(5.47)
The.velocity.of.ultrasonic.waves.in.lattice.structures.will.be:
.
V.=.V 0 .-.V d .=.L.f.10 3 (1.-.λ)..
(5.48)
We.determined.that.the.modulus.of.elasticity.under.angle.α.as:
..
Eα=.V 2 α ρ(1.-.μ μ )..
(5.49)
The. transverse. displacement. S. for. a. rotor. blade. in. the. polar. coordinates.
can.be.determined.as: 9
2
2
2
2
S
Sx
x
+
S
R
+
S
.
.
(5.50)
R
0
m
=
F
2
2
2
2
t
θ
Here:
m.is.a.mass.of.rotor.blade;
F.are.the.outside.forces.,.F.=.(L.-.D.-.W.sin.θ).sinΩt;
Sx,.S R ,.S θ. are.the.transverse.displacements.in.the.polar.coordinates.
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