Using Mlife for a lifetime fatigue estimation

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Julius.Scherf
Posts: 7
Joined: Thu Jun 18, 2020 6:10 am
Organization: TU Darmstadt
Location: Germany

Using Mlife for a lifetime fatigue estimation

Postby Julius.Scherf » Thu Jun 18, 2020 10:11 am

Hi everyone,

I want to use MLife to determine the fatigue lifetime for the 5MW NREL
turbine.
So far, I have run test 18 without problems. After reading up in the forum,
I've to download MLife to do fatigue estimations, but I can't find the
corresponding link.
Can somebody help me?

Thanks and best wishes,
Julius

Jason.Jonkman
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Location: Boulder, CO
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Re: Using Mlife for a lifetime fatigue estimation

Postby Jason.Jonkman » Thu Jun 18, 2020 11:47 am

Dear Julius,

A similar question was asked and answered in my post dated Jun 17, 2020 in the following forum topic: viewtopic.php?f=4&t=805&start=30.

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

Julius.Scherf
Posts: 7
Joined: Thu Jun 18, 2020 6:10 am
Organization: TU Darmstadt
Location: Germany

Re: Using Mlife for a lifetime fatigue estimation

Postby Julius.Scherf » Thu Jun 18, 2020 1:25 pm

Thank you for your quick reply. That helps a lot.

Best wishes,
Julius

Julius.Scherf
Posts: 7
Joined: Thu Jun 18, 2020 6:10 am
Organization: TU Darmstadt
Location: Germany

Re: Using Mlife for a lifetime fatigue estimation

Postby Julius.Scherf » Fri Jul 03, 2020 5:54 am

Hi Jason,

I managed to run the mlife_certification_test file provided by mlife.
Now I want to adjust the input files in such a manner that I can determine the lifetime of the 5MW NREL turbine for all three cases specified in the IEC-61400 standard.
1. To do so, do I have to modify the DLC data files, or do I have to import the data files from FAST?
2. I'm wondering how I can plot the corresponding Wöhler curve?

Best wishes,
Julius Scherf

Jason.Jonkman
Posts: 4866
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Using Mlife for a lifetime fatigue estimation

Postby Jason.Jonkman » Fri Jul 03, 2020 8:58 am

Hi Julius,

I'm not sure what you mean by "DLC data files". Are you referring to the FAST time-series output files?

MLife will not plot the S-N curve for you, but you can plot it yourself using the values of L_Ult, L_MF, and m using equation (2) from the MLife Theory Manual: https://drive.google.com/file/d/1d7uWya ... sp=sharing.

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

Julius.Scherf
Posts: 7
Joined: Thu Jun 18, 2020 6:10 am
Organization: TU Darmstadt
Location: Germany

Re: Using Mlife for a lifetime fatigue estimation

Postby Julius.Scherf » Mon Jul 06, 2020 4:12 am

Hi Jason,

thank you for your quick reply.
The Problem concerning the DLC files solved itself.
But regarding the S-N curve, I have a question. I understand that I can calculate the number of cycles using equation (2) with L_Ult and L_MF provided by MLife, but I'm not sure about L_i^RF. Can I understand it as such that it represents the standard deviation from each load case?


Best wishes,
Julius Scherf

Jason.Jonkman
Posts: 4866
Joined: Thu Nov 03, 2005 4:38 pm
Location: Boulder, CO
Contact:

Re: Using Mlife for a lifetime fatigue estimation

Postby Jason.Jonkman » Mon Jul 06, 2020 6:56 am

Dear Julius,

L^RF_i is the cycles load range about a fixed mean value. The S-N curve is a plot of L^RF_i (S) versus N_i (N).

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

Julius.Scherf
Posts: 7
Joined: Thu Jun 18, 2020 6:10 am
Organization: TU Darmstadt
Location: Germany

Re: Using Mlife for a lifetime fatigue estimation

Postby Julius.Scherf » Tue Jul 07, 2020 3:12 pm

Dear Jason,

thank you. I appreciate your effort.

Best wishes,
Julius


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