Learning Forum

[bolbol]

Hello,

I'm trying to solve a contact between two bodies (ring and flat surface) but got the following errors.

Attached also the log file for solution information

[peteroznewman]

Under Analysis Settings, change Auto Time Stepping to On.

• Set the Initial Substeps to 100


• Leave the Minimum Substeps at 1


• Set the Maximum Substeps to 200.

If the above is insufficient to achieve convergence, change the Solver to Direct.

Do you have the Symmetry BC properly configured?

[bolbol]

 

Yes, it's activated as shown.

 

[bolbol]

 

Also, I have the following B.C

[bolbol]

 Moreover fixed support on the bottom face and cylindrical support on the inter face of the ring.

I think the only option left is to change the solver to Direct, correct?

P/s. sorry to answer in multiple replies like that, the forum didn't accept it in one reply.

[peteroznewman]

• You are showing the time steps for step 2. What happens in step 1? Is the error occurring in step 1 or step 2?


• You show the faces for Symmetry, but not the axis direction, check that is correct.


• You should add a second Symmetry Plane through the center in the width direction to prevent the ring from moving axially. This will probably fix the error.


• You have a Moment load, but that is not a Symmetric load. Remove that.


• Change to the Direct solver.

[bolbol]

 - The 1st step is a few iterations without applied load, no error occurs.

- Symmetry normal to X-axis, So, I guess it's correct.

- I have already cylindrical support for the inner surface of the ring as shown in the previous replies, would I suppress it or leave it and create what you suggested?

- I'll suppress it to check the solution but how to add the moment? In this case, do I have to cancel the symmetry and make it full geometry?

[peteroznewman]

The Cylindrical support prevents the Bearing Load from having any effect. Cylindrical support does not support the axial direction. The second symmetry condition will do that. Delete the Cylindrical support and add the second symmetry condition

You can't have a moment and the first symmetry condition, they are incompatible. Once you delete that, you need to add a constraint in that direction.  Try solving without the moment initially.

[bolbol]

Thank you, I'll go with these suggestions but I'm a bit confused.

If cylindrical support doesn't work the axial direction, what is meant by these 3 directions in the picture?

[peteroznewman]

Sorry, I missed that Cylindrical Support includes Axial support (it didn't use to in older versions). However, you don't have axial support in the best way, the entire inner face is fixed which prevents Poisson's ratio expansion due to the applied bearing force.

If you put in a symmetry plane to support the axial direction, then the inner face is free to expand with Poisson's ratio effect when the bearing force is applied.

[bolbol]

Hello again,

A quick follow up for the results

I did as suggested in the previous replies, errors and unrealistic still occur.

the upper ring flew away in the 2nd step and when I checked the information log, I found this error.

Is it because the constrains not enough? Should I use the cylindrical support again?

[peteroznewman]

Did you turn on Auto Time Stepping?

Did you set the Initial Substeps to 100?

[bolbol]

Yes, it's On.

And for the initial time step, it's 200.

[peteroznewman]

Insert a Contact Tool under the Connections folder. Evaluate Initial Contact Status. The frictional contacts must be Closed. If it is Near Open with a tiny Gap, then in the Contact Details, set the interface to Adjust to Touch.

[bolbol]

Adjust to Touch is selected

and here is a screenshot of the evaluation.