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Active Contributor
nosborne
Posts: 30
Registered: ‎12-19-2011
Accepted Solution

Warning Message on Linear Static Analysis with Gap Elements

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12-19-2012 08:48 AM

Warning: Solution is possibly unstable (Pmax/Pmin = 2.4326E+19).


I have a plate element model that has gap and boundary elements in it also (see attached image). I get the above warning when I run the analysis but the solution converged and the displacement results all appear to be normal. The reaction forces add up also. Should I be concerned ? What does the warning mean and why would I get it ?

Thanks for any help.

 

 

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Distinguished Contributor
madg1
Posts: 108
Registered: ‎03-16-2012

Re: Warning Message on Linear Static Analysis with Gap Elements

12-19-2012 10:44 AM in reply to: nosborne

you can look at the nodes where the max and min stiffness values i guess

madg1
ASIMM 2012
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Valued Mentor
AstroJohnPE
Posts: 498
Registered: ‎08-30-2012

Re: Warning Message on Linear Static Analysis with Gap Elements

12-19-2012 06:33 PM in reply to: nosborne

If the displacements and reaction forces are correct, then the other results should be okay, but be sure to check them carefully.

 

Plate elements have a very small stiffness in rotation about he axis noral to the element. This is probably where the minimum stiffness occurs. If the maximum stiffness occurs at the boundary element (1D or 3D Spring Support in the ribbon interface) or gap element, you can control the stiffness. It may be possible to lower the stiffness to avoid the warning message.

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

16 years experience with Simulation Mechanical
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Active Contributor
nosborne
Posts: 30
Registered: ‎12-19-2011

Re: Warning Message on Linear Static Analysis with Gap Elements

12-20-2012 05:55 AM in reply to: nosborne

Both of the maximum and minimum stiffness values are on plate elements. The maximum is listed as a TX DOF and the minimum is an RX DOF. I assume that the directions are based on the global coordinate system and that would mean the minimum is the rotation around the axis normal to the plate element. Some of the software I have worked with previously does not include that DOF in the stiffness ratio calculations so it doesn't produce a warning.

 

Thanks for the help John.

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