Learning Forum

[Shreyas Dhake]

I am trying to test a cuboid material with an embedded spheroid object pushing against it. However after running the simulation I get the error:

A solver pivot warning or error has been detected in the UZ degree of freedom of node 6587 located in Part 1. 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.

Image of simultation:

I need help restricitng the UZ degree of freedom upon the spheroid structure. Any guidance would be appreciated.

[Armin]

Hi Shreyas,

How do you consider the interactions between the sphere and the cube? I can see that no contact pairs have been defined.

You can right-click on the "Connections" branch and then insert "Manual Contact Region". Then scope it to the associated Contact and Target surfaces of the model.

[Shreyas Dhake]

Hi Armin, 

Thank you for the reply. 

I attempted to connect the sphere to the cuboid using manual contact region to obtain the image below:

After I tried re-calculating I obtained an error on a different degree of freedom. Should I ensure all the faces except the face where the spheroid is, a fixed support as I would like to see the deformation of the spheroid against the cuboid. 

 

 

 

[Armin]

Thanks Shreyas.

Here are a couple of suggestions:

The two bodies appear to be interfering with each other. It is good practice to initiate the simulation from the time when the sphere is just touching the cube but not overlapping with it. If the sphere is embedded within the cube, make sure there is a gap in the cube that fits to the sphere. You can do these steps in CAD software like Ansys Discovery.

For the contact pairs, you need to only select the surfaces where you expect a contact to occur. For example, you can select the outer face of the sphere as "Target" and then select one face of the cube where it contacts with the sphere as the "Contact".   

[Shreyas Dhake]

Hi Armin,

Thank you for the suggestions. I shall try and implement them. 

For contact pairs you mention using the outer face of the sphere despite that half not being within the cuboid, why is this the case?