Learning Forum

[seol7281]

Hello. 

I am working on a static structural project, and it appears that the solver won't work due to the pivot errors. 

One of the errors goes: Solver pivot warnings or errors have been encountered during the solution.  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.

And the another goes: A solver pivot warning or error has been detected in the UZ degree of freedom of node 1460 located in Solid. 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.

 

I have uploaded the file, so please take a look.

What I'm focusing on at the moment is "B" system, where "A" system contains a slight geometric modification from "B". The errors appear in both systems, so those modifications do not seem to be the reasons.

Force is acted on a single (fixed) point of the structure that somewhat resembles a cup we use for drinking, and the entire structure theoretically shares the direction of the displacement. The last part of the boundary condition is represented in the displacement section.

The error messages suggest few ideas, and the only suggestion probable is the one about the underconstrained model. Material property does not seem to be problematic, and there is no contact at all. Possibility of this being an underconstrained model is considered in system "C", where the scope of the constant displacement is the entire structure. "C" does not give out any errors, but the solution for the Equivalent stress is zero everywhere, which I intuitively declare untrue.

Please let me know if you understand what is the problem with "B" or "C'. Thank you for answering.

[SaiD]

Hi,

Due to company policies, Ansys employees cannot download any attachments. You may use the "Insert Image" option to insert inline images in your posts if need be.

Pivot error generally occurs when you have rigid body motion in the model i.e. the model is not constrained sufficiently and hence can translate or rotate in some direction without undergoing any deformation. Based on the second message it looks like the model can undergo rigid body translation in z-direction. So you need to add/alter boundary conditions to prevent this.

Can you share images showing how the boundary conditions are applied?

Sai