topic Re: Damage plot Vibration Fatigue in Inventor Nastran Forum

Damage plot Vibration Fatigue

viktor_velichko — Mon, 29 Jun 2020 13:08:36 GMT

Hello colleagues! I am doing a vibration analysis of fatigue. And I see that damage and life are displayed unrealistic. What am I doing wrong? I followed the recommendations in the attached files.

Re: Damage plot Vibration Fatigue

John_Holtz — Mon, 29 Jun 2020 23:24:22 GMT

Hi @viktor_velichko

The short answer is the "Fatigue Setup > Event Duration" is missing. The software needs to know "how long the vibration is" so that it can convert the calculated damage to a calculated life. (Remember that the life shown in Inventor Nastran is in units of time, not the number of cycles.)

Another issue is the results file has 12 fatigue results, 6 of which appear to be reasonable and 6 which appear to be results of 0. Inventor Nastran is showing 9 of the results. Which 9 is it showing? It looks like the "Fatigue > Shell Damage" and "Fatigue > Shell Life" are correct (and maybe some other ones).

Re: Damage plot Vibration Fatigue

viktor_velichko — Tue, 30 Jun 2020 11:52:28 GMT

"The short answer is the "Fatigue Setup > Event Duration" is missing"
Yes, I missed this step. Thank you!

"It looks like the "Fatigue > Shell Damage" and "Fatigue > Shell Life" are correct (and maybe some other ones)."

It's strange, because in shell usually has different stess level on Top and Bottom face.