NDE Digital Methods for Predicting Stiffness and Strength of Wind Turbine Blades - Hybrid Anisotropic Materials for Wind Power Turbine Blades - page 175

where:
h.is.a.parameter.of.length.propagation.of.the.ultrasonic.wave;
ρ.is.the.density.of.composites.(for.iberglass.1.998.g/cm 3 );
C.is.the.velocity.of.ultrasonic.propagation(.m/sec).

By.replacing.the.stress.function.from.Equation.(6.21),.the.results.are.seen.
in.Equation.(6.23):

2

d
dx

2

σ x Q = = Q h C ρ

11 11 x

2

d
dy

2

σ y Q = = Q h C ρ

2

. . (6.23) 22 22 y

2

2

d
dy

2

τ xy Q = = Q h C ρ

12 12 xy

2

If.the.mechanical.deformation.is.equal.to.zero,.it.is.only.considered.under.
thermal.stresses. 11
The.equation.for.thermal.stresses.would.become:

. σ ij =Q ij .α ij .T. (6.24)

where:
α.is.the.coeficient.of.temperature.expansion;
T.is.the.temperature.gradient.

Q ij .are.the.stiffness.constants.that.can.be.determined.using.an.NDE.method.
for.velocity.propagation. 4
For.the.orthotropic.nose,.thermal.radial.stresses.are:

E

1

σ = -Q α T = α T

11 11 11 11

1 - µ µ

.

12 21

.

while.the.thermal.tangential.stresses.are:

E

. (6.25)

2

σ = -Q α T = α T

. .

22 22 22 22

1 - µ µ

12 21

Here:
E 1 ,.E 2 .are.the.moduli.of.normal.elasticity.in.the.radial.and.tangential.directions;