Numerical singularity issue

[mapi]

Hi,
I encouter a problem.

In msg file, it says:

SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE 191 D.O.F. 3 RATIO = 6.85800E+11

I wonder what can cause such singularity problem and I don't know what is wrong with my UEL code.

Thanks.

 

[corus]

Probably infers rigid body motion in dof 3.

corus

 

[mapi]

Right. There is rigid body motion.

So how do we give such boundary condtions:

Five nodes on a circle(2D), these five nodes can only move toward the center of circle--there is only radial displacement and no tangential displacement (no rotation). Suppose that we fix one node, how about other nodes? How to apply BCs?

 

[corus]

Fix any one node in dof 3.

corus