## General Mechanical

#### convergence error

• shubham14
Subscriber

I am trying to simulate 2D circle with large displacemet at top edge and fixed at bottom edge. I am getting a convergence error while enabling large deflection in ansys. i have applied displacement with the number of steps and time stepping. Can anyone suggest how will i get a converged solution. I am attaching the geometry here with boundary conditions.

• peteroznewman
Subscriber

Hello shubham,

If you scroll down a little in this Category, you will find this very relevant post.

Is the bottom of your circle really fixed or is it making contact with an object?
Does the top of your circle really have a point load at the center or is it making contact with an object?
If you are squeezing the circle between two other objects, I recommend using quarter symmetry and just drawing the top object and adding contact to the model.

Regards,
Peter

• shubham14
Subscriber

Thanks, Peter for the quick response

Yes bottom of circle is fixed and i am giving a large displacement (20% of diameter) to a small edge on top surface and i have no idea how to put time stepping and number of steps (in step controls). Maybe because of that i am getting a convergence error, and an error shows- the solution failed to solve completely at all points, partial results at some points have been able to be solved.

geometry details -

diameter - 100 mm ( on x-y plane)

top edge - 0.5 degree angle symmetry on y axis (i.e. 1 degree)

bottom edge - 20 degree angle symmetryon y axix(i.e. 40 degree)

please guide me to get a fully converged solution.

Regards,

shubham

• peteroznewman
Subscriber

shubham,

It will be difficult to achieve convergence at such a large 20% compression of this disk when holding a bottom segment of the edge fixed and having a narrow top segment with a displacement BC.

The reason is that one element will be on the BC and the next element will be free. That free element will distort so much that it fails to compute and the convergence will stop.

Are you saying that the bottom of the disk is bonded to a surface with perfectly sharp edges and the top is on a knife edge?  Is the image below the kind of deformation you are looking for?

It will be less difficult if you have contact and rigid surfaces with a corner radius where the extent of contact ends. Here is a relevant post with advice on how to get convergence to improve for a hyperelastic material. What is the material you are using?

Regards,
Peter

• shubham14
Subscriber

Yes Peter, exactly i am looking this type of deformation that you have shown above. I created material bilinear isotropic hardening material with E = 100KPa and poisson's ratio of 0.49  in ansys.

Thanks and Regards,

Shubham

• peteroznewman
Subscriber

Okay, did you make some progress after reading my post above and the discussions that I linked to?  Show me your mesh. What about not using Fixed Support and Displacement and replacing them with contact that includes a small radius at the corners.

Regards,
Peter