Help with understanding non-convergence?

User: "Wesley_Peijnenburg2"
Altair Community Member
Updated by unknown

I'm using tutorial OS-T 1394 and 1560 (V2022.1) and made a similar model from scratch to check if I understand it. Hopefully someone is willing to help with understanding a non-convergence problem?

Attached is the model, the purpose is to simulate contact between a sphere and wall (axisymmetric). 

There is a very good blog post which helped me a lot: 
https://community.altair.com/community?id=community_blog&sys_id=538764ab1b3790d4a5f742eddc4bcba4 

Thanks to the blog post I could already try the below corrections to solve it:
   - Following advice found in output file, friction has been set to zero.
   - Contact stabilisation: CNTSTB with parameters from OS-T 1560. Goal is to find stress fields, impact on energy accuracy can be accepted?
   - Tried increasing force
   - LS input DLOAD - This seems to solve warning 1955 "zero static force vector"?
   - It gives info 4936: suggested TLOAD1/TLOAD2. Indeed works fine but does not solve the issue.
   - It does seem to solve error 1996: "All entries have zero scale"
   - Error 941 now remains: non-convergent iterations

Possible reasons that I can think of:
   - Force 0.2N not properly applied?  
   - Not properly constrained?
   - Insufficient/poor elements for the wall part?
   - LGDISP needed to capture deformation? 
   - Convergence expert keeps backing off, but why? Step too large? 

Important warnings that remained: 
WARNING # 3400 - Singularity detected at following 1 DOFs.
WARNING # 6529 - The x-displacements of grids (e.g., GRID 1) on the axis of symmetry need to be constrained  ->

Many thanks in advance! 
- Wesley

Find more posts tagged with