sin αst

The stresses are summarised and compared to the limit states in table E.10.
Compressionparallel
to grain
[MPa]
Compressionperpendicular
to grain
[MPa]
Shear
parallel to
grain
[MPa]
Shear
perpendicular
to
grain
[MPa]
STRUCTURAL ANALYSIS OF BLADES
Tension
perpendicular
to
grain
[MPa]
Tension
parallel to
grain
[MPa]
Limit state stress 4.9 0.54 0.96 0.27 0.32 9.0
Design stress 5.7 0.14 0.20 0.05 0.15 0.25 0.22 0.32 6.3
Table E.10: Summary of results and comparison to limit states
The limit state for compression parallel to grain is exceeded by 16%. The location of the
maximum compressive stress is shown on figure E.11.
Figure E.11: Position of maximum compressive stress
The maximum stress is highly local as less than 0.01% of the element volume has a com-
pression stress that exceeds the limit state. The limit state is not exceeded in the cross-
section at the blade root, which is the cross section that the loads are originally derived for
in accordance with IEC 61400-2. When further taking into account the high material safety
factor of 10, due to lacking S-N curves, it is considered acceptable that the limit state is
exceeded by 16% for this load case.
159