Modal analysis differences

[Joerg_Grossmann]

Hi all,

I have a fully uncontrained model with i take a modal analysis to do a free-free analysis (see Section 21). in the FEA -Programm of inventor professional the result of the first six ridig body modes are 0. This is correct. If I take Nastran In-CAD only the first 3 (T1,T2,T3) rigid modes are zero or < 1E-03 Hz., the 3 translative modes (R1,R2,R3) are not zero. What is the problem? I attach the out-file of NASTRAN to this post

Regards

[shigeaki.k]

Hello @Joerg_Grossmann,

are you able to show the screenshots of the rigid body modes?

Regards,

Shigeaki K.

[Joerg_Grossmann]

Hello,

from which program? NASTRAN In-CAD or Inventor ?

Regrads

[shigeaki.k]

Hello @Joerg_Grossmann

Both would be nice. Then comparison can be made.

Regards,

Shigeaki K.

[shigeaki.k]

Hi @Joerg_Grossmann,

I am also happy to grab the files from you so I can run them on my side?

Regards,

Shigeaki K. 

[Joerg_Grossmann · Accepted solution]

Do you have an transfer folder for my model ?

[shigeaki.k]

Hi @Joerg_Grossmann,

could you try the following?

• Use a smaller mesh size.
• Activate "continuous meshing". We made a similar model on our side and this seems to help. I was under the impression that this is more for shell meshing but I will follow this up separately with the other engineers. 

I will also send you an email via the support portal with instructions on how to attach file(s).

Regards,

Shigeaki K.

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[shigeaki.k · Accepted solution]

Hi @Joerg_Grossmann, 

could you please try with the contact type set to "offset bonding"? You can leave the other settings in the dialogue box as they are.

Regards,

Shigeaki K.

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