WORKBENCH CONVERGENCE PROBLEM

[gwgwkar1]

Hello,

I am trying to simulate angioplasty procedure in a stenosed artery in WB.
I have designed the artery and balloon and imported them in WB.
I have set contact connection as frictionless and penalty method with FKN=0.08.
The project does not converge and the error is
''One or more elements have become highly distorted. Excessive
distortion of elements is usually a symptom indicating the need for
corrective action elsewhere. Try incrementing the load more slowly
(increase the number of substeps or decrease the time step size). You
may need to improve your mesh to obtain elements with better aspect
ratios. Also consider the behavior of materials, contact pairs,
and/or constraint equations. If this message appears in the first
iteration of first substep, be sure to perform element shape checking.''
I have read that the contact interface must have similar mesh but I do not know how to do this...
Also I managed to find the problematic elemnts by using the instructions of

http://www.padtinc.com/blog/post/20...chanical-APDL-to-Plot-Distorted-Elements.aspx

but Ineed help in correcting this problem.
Any suggestions will be accepted!!!thx in advance!!!

 

[lopessilva]

Hello,

I´m not a bio engineer, so I will tell you what I know about the error. The error you are obtaining means there is something you need to improve. Usually this error happens when the local stresses on at least one element make the element distortion very high, and the analysis can´t continue because ANSYS is unable to solve equilibrium equations for that element. Other elements can also be affected as well. This error is most likely due to:
-Mesh: try to obtain meshes with the best aspect ratios possible
- Conditions of the problem: in mechanical, it would be useful to check the loads. Usually passing the loads from concentrated to distributed can fix this error. I don´t know the equivalent to loads in your analysis
-Check constraints. The model can be insuficiently constrained. Constraint the model on areas instead on only keypoints and on regular surfaces. You should, as possible, to constraint the opposite side of the part where you are applying the load. If you are still obtaining this error after all these tries, try to do overlap operations on lines/areas and/or glue on volumes if you have several. If this still does not help, the program simply can´t solve the model with the conditions you impose. Read some papers related about your subject in order to improve the conditions you impose to ANSYS on the simulation.

Sorry for the "mechanical help", but I hope I could help you. Please let me know the outcome.






Regards,
Hugo Silva
Mechanical Eng. PhD student
Materials Eng. MSc.