NDE Digital Methods for Predicting Stiffness and Strength of Wind Turbine Blades - Hybrid Anisotropic Materials for Wind Power Turbine Blades - page 176

μ 12 .μ 21 .are.Poisson's.ratio.of.material—the.irst.symbol.designates.the.direc-
tion. of. force,. the. second. symbol. designates. the. direction. of. trans-
verse.deformation;
α 1. α 22. are.the.coeficients.of.thermal.expansion.in.the.radial.and.tangential.
directions;
T.is.the.temperature.gradient.

The.differential.equation.of.heat.conductivity.without.the.exothermic.reac-
tion.of.curing.of.the.nose.cap.is.as.follows:

2

dT
dt

d T
dr

+ 1

r * dT

. = β . (6.26)

2

dr

where:
t.is.the.time.of.curing;
R,.r.are.the.outside.and.middle.radius.of.the.nose.cap;
β.is.the.coeficient.of.thermal.conductivity.

Thus,.in.selecting.the.boundary.conditions.for.Equation.(6.26),.T(r,0).=.0;.
T(R,t).=.bt;.b.is.the.velocity.of.curing.(cooling).process.
The.irst.approach.to.the.solution.of.Equation.(6.27).is:

2 2

bR β t r

R

1 4

T(r,t) = ∗ - 1 -

.

.

(6.27)

β

2 2

R

The.gradient.of.temperature.T.during.the.period.of.curing.(cooling).may.
be. responsible. for. the. geometrical. parameters. of. the. nose.cap,.the. thermal.
conductivity.of.the.epoxy.resins,.and.the.velocity.of.curing.b.
We.also.must.look.at.the.stress.components.for.a.rotating.shell.that.can.be.
designated.following.Timoshenko's 16. studies.and.results.
Here:
R o ,.R i ,.r.are.the.outside,.inside,.and.middle.radius.of.the.nose.cap;
ρ.is.the.density.of.material;
ω.is.a.velocity.of.rotation.and.replaced.in.Equation.(6.27).to.Equation.(6.30).

In.Figure.6.1.are.wind.turbine.blades.with.the.installed.surface.ultrasonic.
transducers..We.used.Panametrics.Technology.contact.transducers.with.low.
frequencies. of. 50. KHz. (X1021),. 100. KHz. (X1020). and. 180. KHz. (X1019).. The.
high.voltage.pulse.receivers,.such.as.Panametrics.5058PR,.also.were.used.
In.measuring.the.temperature.gradients,.infrared.thermometers.were.used.
and.the.intensity.of.the.radiation.created.by.the.infrared.camera.was.a.func-
tion. of. the. temperature. gradient.. The. infrared. thermometers. simply. mea-
sured.the.intensity.of.radiation.and,.thereby,.measured.the.temperature..The.