MPC (RBE2, RBE3) sol400 NASTRAN multi step analysis

[marulanda]

Hi I'm an aeronautical engineer who work as stress analyst.
I've a problem with a non linear multi step analysis sol400 Nastran.

I've two non-linear steps, in the first there are preloaded bolts and some surface with friction.
In the second I added an inertial load.
There is a lamped mass which is linked with Rb2 and Rbe3 rigid element, to the structure.

If I run only the first step without rigid element and mass, There aren't problem. But with Mass the second step has some probleme, the mass loose its link with structure.

I've read that with nonlinear analysis, Rb2 and Bbe3 gives problems.

Is there someone who can help me please?

(I'm sorry for my english)

Thanks!

 

[aerostress82]

Rbe2 and Rbe3 don't like touching each other in some cases. Make sure they are not attached to the same nodes on your elements..

Spaceship!!
Aerospace Engineer, M.Sc. / Aircraft Stress Engineer

 

[janFEA]

Hello,
can you provide Nastran deck file (.dat)?

Jan

 

[marulanda]

The problem was the contact table in the passage from step1 to step 2, not the rbe.

thanks very much

 

[mas13]

can you give attached file for .dytr.out , .f04 and .f06 or pic of your error? may be in this discussion can give suggestion after read information from file it

 

[marulanda]

I've the same problem in another model, but in this case I cannot apply the same solution, because in the second step there aren't contacts, so I post this file.



There are two problems:

I don't know why but the second step doesn't start from the stress of the first step.

In the output file I can visualize all results of the first step but only elemnt stress on the second.

I'think that the problems are RBE elm.

I need help please, attached the file.

thanks

 

[aerostress82]

You are missing NLPARM card in step 2?

Not so sure, but this is the only thing I can think of as I can't check your model at home without any FEA software.
In the company, they won't allow me to look into this. So I'm just text reading your bdf file.

Spaceship!!
Aerospace Engineer, M.Sc. / Aircraft Stress Engineer

 

[marulanda]

Thanks for your help.

The second step is a linear analysis, I'm not sure that NLPARAM is necessary.
Do I have apply an NLPARM card in both steps?