Difference between IFA e FEA for a frame

[Anonymous]

Good evening,
i have a question, i need to size a frame and i wanted to do it with inventor tools. I have done both an FEA and an IFA, however the results are completely different, both as regards the stresses and as regards the displacement. Which tool do you recommend me to use the most of the two?

[TheCADWhisperer]

Attach example here.

[Anonymous]

frame_upframe_downframe_constrants_forces_FEAFrame_Von_MisesFrame_DisplacementFrame_IFA_DisplacementFrame_IFA_Stress

This is my case. This is my first FEA so i want to understand many things. First of all, how to constrain external parts of the frame, because in my case I have a bolted plate with the slew bearing, and the holes are my actual constraints. All the rest of the frame is free.
In case I use the IFA, I can only put fixing constraints in the nodes of the structure, which however are not my real constraint conditions, while in the case of finite element analysis, I can put real constraints, but I don't know why, I get those stresses and Von mises is super high, in one of the holes in the plate. Could you help me understand how to do it?

[TheCADWhisperer]

You must Attach the Inventor assembly - mere images are not of much use.