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Doubt on example_fatigue.py #53

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mmartini1987 opened this issue Jul 1, 2021 · 1 comment · May be fixed by #54
Open

Doubt on example_fatigue.py #53

mmartini1987 opened this issue Jul 1, 2021 · 1 comment · May be fixed by #54

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@mmartini1987
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Good morning all,
while I appreciate that WDRT is no longer being developed, I would still try to share a doubt I have related to the fatigue calculation example in example_fatigue.py.

My doubt is related to how the 1-year DEL is calculated - starting from the 1-hour DELs.

In line 40 of the code, you sum up the contributions to the 1-year DEL as:

    Feq_1y = Feq_1y + (Feq_1h[i][j]**m) * N1h * P[i][j]

where N1h is the average number of cycles in 1 hour. I wonder why you don't multiply this by 24 * 365, which is the number of hours in one year, to get the 1-year damage contribution of Feq_1h[i][j].

I came across this doubt when looking at the DEL of 1.04 MN you calculate in the example, which looks a bit low - in 8 out of 9 cells of the scatter diagram (75% of occurrences), the 1-hour DEL is higher than the calculated DEL, which makes me think that the 1-year DEL should be somehow larger than 1.04 MN.

Thanks in advance for your patience and kindness.

Best regards
Michele Martini

@j-vanrij
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j-vanrij commented Jul 2, 2021

Yes, I believe you are correct, this example contains an error. Line 40 should be:

Feq_1y = Feq_1y + (Feq_1h[i][j]**m) * N1y * P[i][j]

(Which is the same as multiplying it by 24*365, as you’ve noted.)

This would then give ~4.74 MN for the equivalent 1-year load.

Sorry for the error/confusion.

Thanks,
Jennifer van Rij

@ssolson ssolson linked a pull request Jul 6, 2021 that will close this issue
@ssolson ssolson linked a pull request Aug 3, 2021 that will close this issue
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