Environmental Engineering Reference
In-Depth Information
k /k
+
µ
x
y
xy
χ
=
1
+
µ
k /k
xy
x
y
.
.
(5.63)
Here:.k
x
.and.k
y
.=.sensitivity.coeficients.in.x,.y.directions.was.determined.
by.calibrated.iberglass.specimens..Normal.and.shear.stresses.acting.in.root.
sections.will.be.determined.with.inluence.coeficient.χ.Equation.(5.63).
(
)
σ
= A E
ε
1 -
µ χ ε χ µ
-
(
-
x
x
x
xy
y
yx
.
.
(5.64)
(
)
σ
=
A E
ε
1 -
µ χ ε χ µ
-
(
-
y
y
y
yx
x
xy
-
1 -
1
µ χ
χ
(
)
xy
= G
2
45
τ
ε
ε
+
ε
xy
xy
x
y
+
1 -
µ χ
xy
.
)
.
(5.65)
Coefficient A
=
(
)
(
2
1 -
µ µ
1
-
χ
xy
yx
Modulus.of.elasticity.E
x
,.E
y
,.G
xy
,.and.Poisson.ratios.μ
xy
.and.μ
yx
.was.prede-
termined.on.the.iberglass.specimens;.deformations.ε
x
,.ε
y
,.and.ε
45
.was.mea-
sured.when.load.reached.the.beginning.of.failure.
A. power. wind. turbine. blade. with. resistance. strain. gauges. is. shown. in.
Figure 5.2.
Stresses.for.wind.turbine.blades.in.x,.y.directions.(see.Figure 5.2).can.be.
calculated.using.Equation.(5.64).
Here:.μ
xy
,.μ
yx.
coeficients.of.Poisson's.ratio
ρ.is.density.of.hybrid.materials.(80.percent.iberglass.and.20.percent.car-
bon.iber);
ω.is.a.velocity.of.rotation.blade.(22-25.m/s,.see.Chapter.2,.rotor.design);
K.is.a.coeficient.of.proile.
Following.Golfman,
17
.coeficient.of.proile.has.been.found.as:
2
λ
α β
e
27
16
K
=
k
.
.
(5.66)
(
)
-
Here:.e
k
.
is.a.maximum.thickness,.λ.is.coeficient.of.anisotropy,.relations.of.
longitudinal.stiffness.to.transverse.stiffness;
E + G
E + G
xy
xy
λ =
..
.
(5.67)
xz
xz
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