Input parameters for MCrunch

Hi all,

I am trying to calculate the lifetime of differents parts of the wind turbine.
I am generating Data files via FAST.
I tried to use the MLife tools but the program doesn’t work (same issues as this topic : [url]http://forums.nrel.gov/t/problems-running-mlife-without-matlab/1540/4])

So i am using MCrunch and by reading the Theory and the User manual, I had several questions.

  1. I assumed that the number of rainflow channels is the same number as the number of channels that I select from the Data files, is that the case ?

  2. How to determine the number of seconds by rainflow counting period ?

  3. How to calculate the Rayleigh average Wind speed ?

  4. I also assumed that the WS min is the minimum Wind speed of the Data files and the WSDel is the difference bewteen the Rayleigh average wind speed and the maximum wind speed mean of our Data files, are my assumptions right ?

  5. How do we determine the BinWidth of every single input channels ?

  6. When I am trying to launch the lifetime calculation with the Data files “DLC2.3_1.out” “DLC2.3_2.out” “DLC2.3_3.out” of the CertTest files, I have the message error “First input can not be read” that occurs do you know why I have this error ?

  7. As I am new to materials science, I wondered to know how is it possible to estimate the lifetime of a Wind blade and the lifetime of another part of the wind turbine (like the tower for instance) with the same precision by only providing his shear force and moments (with his LUlt and TypeLMF) ?

Thanks in advance for your helps,
Alexandre
ETIENNE

For the question 6) I found the solution, we just have to put the parameter “BinMeans” to false and keep the “DoLife” parameters to true.
But now I have some results that I found unusual (for instance as LifeTime damage about 10^(-18) kN).
Thus I wanted to know if it is possible to have a lifetime estimation of the blade with MCrunch ? The documentation doesn’t tell anything about it but I wanted to know if it is possible to have it.

Best regards,
Alexandre
ETIENNE

Hi Alexandre,

Here are my answers to your questions:

  1. You can choose any subset (or all) of the output channels to process for fatigue.

  2. RF_Per is the period (inverse of frequency) of the constant-amplitude cycles that you wish to calculate damage-equivalent loads (DELs) for. RF_Per = 1 s (1 Hz) is common.

  3. The Rayleigh-average wind speed could be based on site conditions or by an assumed IEC wind class.

  4. When weighting the datasets with the wind speed probability distribution, you specify a number of wind speed bins to bin the datasets into based on the minimum wind speed (WSmin) and the bin width (WSel).

  5. If you are binning cycles, you should understand the max-min range of your data in order to choose an appropriate bin width.

  6. MLife does support fatigue lifetime calculations.

  7. When processing loads (forces/moments) for fatigue instead of stresses, the S-N curve is defined in terms of highest load the cross section can withstand before failure, as discussed in our FAQ: nwtc.nrel.gov/FAQ#TypeLMF.

I hope that helps.

Best regards,

Dear Jason,

Thanks for your replies,
I appreciate you took your time to answer my questions.

Best regards,
Alexandre
ETIENNE