topic Re: frame analysis instability type 3 in Inventor Forum

frame analysis instability type 3

Anonymous — Wed, 20 Apr 2016 06:34:35 GMT

I have run a car chassis through frame analysis. I get a solver message instability type 3 at node 108 in direction RZ. When I change the beam model tolerance from 2 to 20 or 50 ul, I simply get the same message for a different node. Instability 3 occurs at nodes on very short members, I have removed these members and changed the design but I still get instability messages. I dont know if they are harmless warning messages or if the results produced are incorrect. any advice would be appreciated.

Re: frame analysis instability type 3

JDMather — Wed, 20 Apr 2016 09:37:40 GMT

Attach your assembly here.

Re: frame analysis instability type 3

Anonymous — Wed, 20 Apr 2016 16:19:29 GMT

here is the chassis

Re: frame analysis instability type 3

JDMather — Wed, 20 Apr 2016 16:21:52 GMT

Not sure you are ready for analysis.

No parts?

Re: frame analysis instability type 3

Anonymous — Wed, 20 Apr 2016 19:22:38 GMT

here is the part

Edited by request
Discussion_Admin

Re: frame analysis instability type 3

Anonymous — Wed, 20 Apr 2016 19:23:08 GMT

and the rest

Edited by request
Discussion_Admin

Re: frame analysis instability type 3

JDMather — Wed, 20 Apr 2016 18:32:30 GMT

I think I have this figured out.

Step 1 was to read the error messages.

So, I will want to find out which frame members were not converted to Beams.

And I will want to find Node 112.

Re: frame analysis instability type 3

Anonymous — Wed, 20 Apr 2016 18:37:40 GMT

hi, yes i see that the 3d sketch i was given has some lines only 2 mm long. when i used insert frame, these were not put in and the gap was so small i could not see anything missing. i am going to re do the sketch and i should be fine. but can i ask if i have curved frame members will frame analysis bring up the instability message again and should i ignore it

Re: frame analysis instability type 3

JDMather — Wed, 20 Apr 2016 18:54:05 GMT

Based on that information I turn on the visibility of the Node Lables

Right click on the Node 112 and select Find in Window.

I see that there are several nodes in this area not conneced by rigid links.

The missing beams are associated with the curved frame members.

Manually add the missing Rigid Links where the curved frame members should connext to the rest of the beams.

Note that I changed the colors of the Rigid Links to red to make them stand out better for visibility.

Re: frame analysis instability type 3

Anonymous — Wed, 20 Apr 2016 19:05:58 GMT

i should be ok from now. thank you very much for your help

Re: frame analysis instability type 3

JDMather — Wed, 20 Apr 2016 19:09:36 GMT

Well I had trouble for some reason manually adding the Rigid Link to the left side. On the right side it was easy.

I'll go back and check again if you continue to have trouble.

Re: frame analysis instability type 3

Anonymous — Wed, 20 Apr 2016 19:11:50 GMT

is it possible for you to remove the chassis and wishbone assembley and part from this page please

Re: frame analysis instability type 3

JDMather — Wed, 20 Apr 2016 19:22:03 GMT

I don't work for Autodesk - but I notified the forum moderator that you would like the files removed.

This is a public user-to-user forum, so be careful about what you share.

Re: frame analysis instability type 3

Discussion_Admin — Wed, 20 Apr 2016 19:25:26 GMT

@Anonymous wrote:

is it possible for you to remove the chassis and wishbone assembley and part from this page please

I edited these files out per your request

Thanks for the heads up @JDMather

Thanks
Discussion_Admin

Re: frame analysis instability type 3

Anonymous — Wed, 20 Apr 2016 19:40:22 GMT

thank you