Learning Forum

[akhilagarthade]

Hello,

I am working on shell model with Face/edge and edge/edge contacts and get following error:

"An internal solution magnitude limit was exceeded. (Node Number 15030, Body Part 15, DOF UZ) Please check your Environment for inappropriate load values or insufficient supports.  You may select the offending object and/or geometry via RMB on this warning in the Messages window.  Please see the Troubleshooting section of the Help System for more information."

All are bonded contacts with MPC, no gap and no penetration. Closed contacts. There are few Body-Body revolute joint and one Body-Ground Spherical joint. Load is 2G acceleration.

Tried command ncnv,,1e30 but still doesn`t work.

I had no luck finding answer for such error with bonded contact but friction less contact have solutions. 

I cant add more constraints, please let me know how to resolve this issue.

[akhilagarthade]

I kept Weak Spring: program controlled and run was successful, BUT...

There are few face/edge contacts which looks they are breaking contact in animation. I ran Modal before static and in that also it seems like loosing contact ( Animation was at True Scale ).

I checked contact status and they are Closed, Penetration = 1e-13, Geometric gap = 1e-14, I have used tolerance value = 0.127 mm. Everything looks perfect in Initial contact results but still it looks losing contact.

Please let me know solution.

[peteroznewman]

Please use the Insert Image button on the reply toolbar and show an image of the Modal solution first natural frequency.  Is the frequency approx. zero?  Look at the Deformation, which part is red?  That is the part that is not connected.

[akhilagarthade]

First 8 natural frequencies are ZERO. This is strange I guess, because as per my knowledge first 6 natural frequencies should be zero.

 I checked all red parts and are having perfect Closed contact

[peteroznewman]

Can you show an image of the Modal Deformation?

Also, please delete the two posts in the discussion that is not yours.

[peteroznewman]

If your structure is grounded, no frequencies should be zero.

If your structure is floating in space, like a satellite, then the first 6 natural frequencies will be zero and mode 7 is the first bending mode.

[akhilagarthade]

There is one spherical joint between Body - Ground, so I think that makes my structure grounded.

Actually I am working professional so can't share image of structure but I will share one the problematic part

[akhilagarthade]

     

 

here are the images. 1st is actual part. 2nd & 3rd are deformation at different frequencies. 4th are 20 mode shape frequencies. And Contact region 273 is number for this part. Edge of small shaft as contact and plate surface as target.

There are few more parts like this which animate as breaking contact in modal. Also this small shaft is attached to another shaft with Revolute joint, where this small one is Scope reference and other is Mobile reference and of course these two are not in touch or contact with each other.

And also gives error as explained in my very first message.

 

[peteroznewman]

A part has 6 degrees of freedom (DOF).  When all 6 DOF are constrained, then the structure is grounded.

A spherical joint constrains 3 translational DOF leaving 3 rotational DOF free. That means the structure is not grounded.

Do you have a commercial ANSYS license?  If that is a current license with paid up maintenance, you can get technical support from the local distributor who sold your company the license. This website is for Students to get technical support because they are using the free Student license.

[akhilagarthade]

Yes we have paid license. I can get help from tech support.

While searching answer on google and Ansys forum I end up here. This is quite urgent and it is weekend hence though no support available.

But Peter can you please share some idea? It will be very helpful. In previous models also I faced same insufficient support error but had given extra support fo the sake of it but in this model can`t give extra support. 

[peteroznewman]

You need 3 points of support, you have 1 point holding XYZ to zero.

At a point some distance along the X axis, add a displacement BC that sets YZ to zero.

At another point some distance along the Y axis, add a displacement BC that sets Z to zero.

Now you have constrained 6 DOF.  You can do a different pattern if you want to choose points spaced along Z from the spherical joint.

[akhilagarthade]

I forgot to mention, along with Spherical join, there are six wheels constrained in Y direction and One wheel of it also constrained in X direction. Constraints are given with Remote displacement to keep rotations free.

[peteroznewman]

So if you drag and drop the six wheel displacements from the Static Structural to the Modal analyisis, you should not get any zero frequency modes. Is that true?

[akhilagarthade]

It should be, I will try that. Currently in Modal the only constraint is spherical joint. Other constraints I mentioned are used in static.

[akhilagarthade]

So I observed strange behavior. Instead of considering Surface of that small shaft as a Scope ref for revolute joint , I applied at circular edge of plate and can now see that no contact loosing behavior.

But applied weak spring to overcome insufficient support error only to find that weak spring has considerable force reaction. So I think I have to extra support.

[peteroznewman]

I can't help if you can't show the geometry.

[akhilagarthade]

It is okay, I will get help from tech support. And will post here with answer if I get any. 

Thank you for your kind response.