You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
5.3 Self Weight loading<br />
The bending moment at the blade root due to self weight loading can<br />
dominate the stresses at the blade root. Because the turbine is<br />
rotating the bending moment is a cyclic load with a frequency of<br />
f = ω / 2π<br />
. The maximum self-weight bending moment occurs when a<br />
blade is horizontal.<br />
Fig. 26<br />
Bending moment at root of blade due to self weight<br />
M<br />
sw<br />
=<br />
R<br />
∫<br />
rmin<br />
m(<br />
r)<br />
g(<br />
r − rmin<br />
) dr<br />
where m(r) is the mass of the blade per unit length. This is a<br />
tangential (edge-wise) bending moment and therefore the maximum<br />
bending stress due to self-weight is given by:<br />
σ<br />
M sw b<br />
max, sw =<br />
I NN 2<br />
Simplified method: split blade into elements, assume each element<br />
has uniform self weight.<br />
24
Change language