Learning Forum

[Jamie Kerr]

Hi,

I’m trying to run a simulation structural on the components shown below.

The model uses beam element connection to simulate bolts (image below shows the setup of these).

When I try to run the model I’m getting the following error:

‘A solver pivot warning or error has been detected in the UX degree of freedom of node 13982 located in Backplate DIff mount|Mirror1[2]. This is usually a result of an ill conditioned matrix possibly due to unreasonable material properties, an under constrained model, or contact related issues.  Check results carefully. You may select the offending object and/or geometry via RMB on this warning in the Messages window.’

The issue node seems to change every time I generate a mesh on the components.  This time it’s on this one here:

After clearing & regenerating mesh its now here:

I will say they most commonly occur in these bolt holes. In the past I have managed to make it run, but I had to set some of the contacts to bonded.

 I’ve reached the point where I have nothing left to try to solve this problem, so your help would be really appreciated.

[Chandra Sekaran]

It is tough to pinpoint issues. The node ID in the error message may not necessarily indicate the part that has the problem. May be you can run a modal analysis on this structure. If some part is unconstrained you will get a rigid body mode and the animation will show the part flying away. Then you can look more closely at the constraints on that part.  Another thing to do is to introduce the 'contact tool' under connections and review the initial contact status.

[Jamie Kerr]

Thanks for getting back to me. I'll give this a go today and let you know the results. 

[Jamie Kerr]

Hello,

Presumably this is what you mean by 'flying away'? Whats the fix? 

Cheers,

Jamie

 

[Jamie Kerr]

Switched these supports to bonded. They didnt fly away (nothing else did either), ran the orginal model and still have the pivot error. Looks like the cotnact tool doesn't work for beams.