Fatigue life and damage scale

Hello,

I performed a fatigue analysis on a part and I don't properly understand what Optistruct is telling me. What is the damage scale indicating? On my part, I have spots with damage 104. What does this tell me?

Also, how does the life scale work? If some spot on the part has 10e-3 life, will it break immediately?

If I change the parameters of the legend while displaying life as a result type, what do I change? The number of load cycles the part can take?

Kind Regards,

Alex

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Altair Forum User

Hi Alex,

Fatigue load history consists of radom peaks which maybe difficult. OptiStruct uses Palmgren-Miner’s linear damage accumulation rule to evaluate when damage in the material occurs.

Failure is predicted when Damage is greater than or equal to ONE.

LIFE calculated depends on your input units. if applied cycle is in seconds life is in seconds, etc...

Altair Forum User

Hello Prakash,

thank you for this information!

Where do I controle the cycle in optistruct? To make the model, I followed the tutorial for 'ctrlarm' for the SN-fatigue analysis. I could not find a parameter, which would define the amount of cycles per second?

Also, I put all of the fatload into one fatevnt, are they now occuring simultaneously? How do I change the model that the loads occure one after each other? Or at last, simulate the loads independently from the other loads?

Kind regards,

Alex

Altair Forum User

Hi Alex,

I mean to say that input load vs time cycle which you provide.