NDE Digital Methods for Predicting Stiffness and Strength of Wind Turbine Blades - Hybrid Anisotropic Materials for Wind Power Turbine Blades - page 168

TABLE 6.3
Results.of.Static.Treatment.to.Determine.Modulus.of.Normal.Elasticity.E z
Ez*103kg/
cm 2

Empirical
Frequency

'(x)eq.
15

m 1
m 1 'x*105 'Sx*105 'x-'x1s c 2 .eq.16

3.1.3.15.3.2 .5 3.56 0.25 1.63 0.0035 3—2 .0.133

3.25.3.3.3.35 .7 1.04 0.139 6—1 .0.166

3.4.3.45.3.5 .8 3.56 0.217 9—.

-1

.0.101

3.55.3.6.3.65 .10 0.016 0.240 10—0 .0

3.7.3.75.3.8 .8 0.76 0.18 8—0 .0

3.85.3.9.4.0 .4 1.35 0.096 4—0. .0

Note: .N.=.å42;.c2.=.å0.4

We.assumed.that.the.empirical.curve.follows.the.law.of.normal.distribu-
tion. 8 .The.normal.law.of.distribution.is.given.by:

( )

2

x-a

1
2 6

. ρ ( ) x = e . (6.15)

( )

1 2 /

2 σ

2

π

where. X i . and. S. are. substituted. instead. of. “a”. and. “6,”. respectively.. With.
Equation. (6.15). and. by. substituting. experimental. results,. we. can. check.
whether. they. follow. the. law. of. normal. distribution.. We. assumed. that. the.
empirical. curve. follows. the. theory. of. normal. distribution. if. the. reliability.
testing.is.not.less.than.95.percent..Therefore,.the.probability.is.more.than.5.
percent.(0.05)..To.compare.the.experimental.and.theoretical.curves,.density.
of.probability.by.Pearson's.criterion.is.used,.which.is.given.by.the. Methods of
Statistical Treatment of the Experimental Datum . 9

e Experimental and eoretical Distribution
Modulus of Elasticity Ez

15

10

5

0

1 2 3 4

Modulus of Elasticity Ez, 10 5

5 6

Series 1 Series 2 Series 3

FIGURE 6.2
Modulus.of.elasticity.Ez.distribution.