Random Response Fatigue Analysis Damage co-relation

Question

Hii everyone,

I'm try to co-relate the damage evaluation given by hyperlife tool with hand calculations,

I computed Random Response fatigue analysis, imported into hyperlife tool,

I'm using stress combination Vonmisses, Mean stress Goodman,Layer worst, Type of loading Random (PSD Stress) Damage model THREE,

I have assigned SN Curve, and Total duration is 18000s,  computed Damage.

I have few doubts from here, The max RMS stress i got is 194.5 M Pa in Z1 layer, the *rfout of the damage results, it shows the stress amplitude as 194.9 M Pa which is greater than actual,

I want to calc Number of cycles applied ,thats is nzcross*Total duration, nzcross is sqrt(m0/m2) should i calc these moments for input curve or output curve of the max element.

Can you tell me how to calc these moments, if i try reverse engg, the moments i should get are very less.

Pls I need this Urgently,

Thank you

Mintu · Answer

yes, @solon, i used that card to get moments in the punch file,

2D elements, but when i try to cal the number of cycles using sqrt(m2/m0)*T the cycles doesn,t match for given by Hyperlife tool, and as I said theres also this little variation in stress its using to cal from the actual maximum stress shown.

Can you show step by step calc if possible.

solon · Answer

Hello, you can export the PSD moments in your random analysis run with STRESS(PSDM)