interpretation analysis modal structure labile

[delphy90]

hello to all I have here a new question that I hope to be able to solve with you.
I have a 2d component to simulate with patran. I impose my constraints but, in the analysis phase, nastran sends me the following error:

user fatal message 9050 (subdmap sekrrs)
run finishedd two to overdo pivot ratios in matrix kll.
user action: constrain mechanisms with spci or suporti entries or specify param,bailout,-1 to continue the run with mechanisms.

I realized that the structure is labile and that you have to better set the constraints. I carry out the modal analysis and known that the first frequency has too high value.
how do I understand how to change constraints according to the results of modal analysis? better yet, how can I interpret modal analysis?
I trust in your help. Thanks

 

[Onda]

If you do a modal of a single rigid body, you get that the first six frequencies are about null and correspond to the 6 degrees of body freedom. if your body is poorly bound, the way (or ways) you find are shifts in the direction of lability, whether they are translations or rotations. so you have a graphic representation of how the bond is missing.
Just do the modal and do the lplt of the results, in case animando

 

[delphy90]

the modal analysis of which we are the 103 or the 111?
Specifically, how do I lplt the results?

 

[Onda]

if you do the Sol 103 with patran with the basic settings, you should pull out the autovalues of the solution that are precisely the various modal deformities or movements if the model is not bound

 

[delphy90]

I still don't understand one thing..I have to set a particular frequency range for the Sol 103?

 

[Onda]

if you have free ways your frequency range is around 0. otherwise they are the own frequencies of the piece.

I can't give you numbers because I have no idea what models.

if the goal is to see the lability, if you put between 0 and 10 go great.

 

[delphy90]

Thank you very much tomorrow I try to make the simulation at the pc

 

[delphy90]

I simulated the component in a range between 0 and 50 and found the first 6 frequencies. you place the results below:
What can I deduct from this data according to you?

 

[Onda]

that the model has a lability as the first frequency is nothing
if you make a plot of the model, animated see how it moves and understand why it is labile

 

[delphy90]

Since I feel an ignorant goat in interpreting animated graphics (which I keep not understanding), can I find lability directly from the .f06 file?

 

[Onda]

You can't.

It is not that it tells you which knot is labile, it simply shows you how it moves. And you should understand that.
If you want, do a bdf zip file and I can take a look at it.

 

[delphy90]

I'm just sending you the bdf file? I'll tie it up or send it to you by e-mail?

 

[Onda]

attach it in a zip file to the discussion so it is available for everyone.
just the launch bdf

 

[delphy90]

View attachment analisi_modale.7zI don't really know how to thank you!! !

 

[Onda]

is labile around the x axis
you have bound only on movements and not on rotations on a straight
therefore the model is free to rotate on that straight.
You don't have to turn the modal.
you must at least add a constraint to x rotation on the knots where you put the constraints otherwise it will never turn

 

[delphy90]

:36_1_4: how did you understand??? If he's gonna take me back another time, how can I figure it out from the animation alone?

really thank you for the support! ! !

 

[Onda]

I opened the model and looked at how you bound it.
I didn't even upload the results.

 

[delphy90]

Can I show you another piece nicely? This is the famous door on which a series of concentrated forces act.
static analysis tells me that the structure is labile but modal analysis brings me frequencies close to zero. therefore in theory it is not lability. or as usual I folded....
View attachment analisi_modale.7z

 

[Onda]

but there is the same mistake before!!
you have bound along a line with constraints only in xyz and therefore lacks rotation along the bond line.
this time is in y and not in x.

But you could try to think before asking identical questions!

 

[delphy90]

That's exactly what I can't understand..why also bind rotation along the bond line?
Is a door that I roar right around y...se block those rotations as the door moves? I was taking into account the conponent in reality