sin αst

STRUCTURAL ANALYSIS OF BLADES
six Poisson’s ratios are independent, as the remaining depend on the other three and may
be obtained from relations found in [52]. The Poisson’s ratios used for structural analysis
are listed in table E.3 [30, p. 5-3].
�LR �LT �RT
0.328 0.292 0.382
Table E.3: Poisson’s ratios
The characteristic material properties of table E.1 are converted into limit state values
using partial safety factors of table E.4, set in IEC 61400-2. It is assumed that the material
is fully characterised, meaning that factors such as environmental effects and manufactur-
ing methods have been taken into consideration when determining the material proper-
ties.
Condition �m �f
Fatigue strength 10 1.0
Ultimate strength 1.1 3.0
Table E.4: Partial safety factors in accordance with IEC 61400-2
The limit states values are calculated as follows:
Where
fk is the characteristic material strength
�m is the partial safety factor for the material
�f is the partial safety factor for the load
The ultimate limit states are shown in table E.5.
Compression
parallel to
grain
[MPa]
Compression
perpendicular to
grain
[MPa]
�lim =
Shear parallel
to grain
[MPa]
Shear perpendicular
to
grain
[MPa]
Tension
perpendicular
to grain
[MPa]
(E.3)
Tension
parallel to
grain
[MPa]
15 1.6 2.9 0.82 1.0 27
Table E.5: Ultimate limit states for blade material
f k
� m � f
151