MLife-Fatigue-Number of cycles to failure

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Maryana.Berezyak
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Location: Portugal

MLife-Fatigue-Number of cycles to failure

Postby Maryana.Berezyak » Wed Mar 04, 2020 11:25 am

In Theory Manual we can find the following formulation for Ni (number of cycles to failure) calculation (picture)

I tried to find out from my research where this formulation comes from because I can't understand the 1/2 and i could not find it.(There is only reference to Annex G but that does not contain this formulation) From what I understood this formula only takes into account one slope unlike in the Eurocode.

Thank you for your help.
Attachments
Ni.jpg
Equation 2
Ni.jpg (5.13 KiB) Viewed 187 times

Jason.Jonkman
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Re: MLife-Fatigue-Number of cycles to failure

Postby Jason.Jonkman » Wed Mar 04, 2020 4:06 pm

Dear Maryana,

The 1/2 is there because the S-N curve is typically given in terms of load amplitudes (peak-to-mean) rather than load ranges (peak-to-trough) and the variable L^RF_i is a range, not an amplitude.

Best regards,
Jason Jonkman, Ph.D.
Senior Engineer | National Wind Technology Center (NWTC)

National Renewable Energy Laboratory (NREL)
15013 Denver West Parkway | Golden, CO 80401
+1 (303) 384 – 7026 | Fax: +1 (303) 384 – 6901
nwtc.nrel.gov

Maryana.Berezyak
Posts: 2
Joined: Wed Mar 04, 2020 9:52 am
Organization: self
Location: Portugal

Re: MLife-Fatigue-Number of cycles to failure

Postby Maryana.Berezyak » Fri Mar 06, 2020 10:53 am

Dear Jason,

Thank you very much for your quick answer.
Best regards,


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