Contact Surfaces Error

[SciFiMind]

Hello,
I am new to Abaqus and this is my first project, however i do have a very experianced analyst helping me. I am trying to model a steel plate (yellow) screwed on the nonlinear cast iron base (green). We are doing this by modelling the threaded area as smooth cylinders and a high friction contact pair. We are interested in the filleted/undercut area between the two parts, which keeps failing on prototype parts.

***WARNING: SOLVER PROBLEM. NUMERICAL SINGULARITY WHEN PROCESSING NODE 12040
D.O.F. 2 RATIO = 1.21704E+010.

We have been getting this error for two nodes on the inside face of the yellow part, approximate location shown as red dot. Orginally we got this error on the first step and he informed me this was due to the yellow part flying away before making contact, so we added springs and reduced the intial time interval. Now the first step runs fine but we get the same error message in the second step. We are confused becasue he said the springs usually solve the problem and we are confused as to why we are only get this error on two of the hundreds of nodes on the inner face. Thanks for the help

Myles F.
Design Analysis Intern
Case New Holland

 

[corus]

I don't think the node numbers themselves are important, other than that they lie on the surface. The important thing is that dof 2 is noted as being the problem. In your model this is tangential to the surfaces so the two can, in theory, slide apart. I don't know what your 1st step is but it'd be best to restrain some part in the 2 direction, prevent rotation, and press the two together using friction, rough. Then release the fixed displacements you've applied, and apply your loads. You can forget your springs then.
Also, I'd try and mesh it with hex bricks and use linear elements. They behave better in contact.

corus