Fatigue Analysis

[Sajjad2164]

Hello, friends!

I have encountered an issue when I was trying to simulate the fatigue of the internal equipment of a reactor. I'm wondering that I should do fatigue analysis for each part or for the whole assembly?
Because in the assembly, we have bolt loads and I am not sure if I should apply bolt loads to the assembly or not.
Thanks
Sajjad

 

[TGS4]

Why wouldn't you want to include the bolt loads in the assembly. If they do not change, then there is no stress range. If they do change, then you would want to know.

 

[Sajjad2164]

Thanks, TGS4!
I applied the bolt load to the assembly and recorded the results. I was asking because I was wondering how I should do the fatigue analysis. I mean, should I analysis the parts separately, or apply the load combinations to the assembly and then extract the results. The latter I believe, is more reasonable.
There's another question:
In NB-3216 (Derivation of Stress Differences), two types of principal stress directions are mentioned, NB-3216.1 Constant principal Stress direction and 2) Varying Principal Stress Direction.
How I should identify these two?