Learning Forum

[m.kobyshcha]

I am using Ansys Mechanical Enterprise 2023R2 to radially compress a polymer stent using a crimper, which consists of 8–16 planar contact surfaces that radially compress the scaffold (see screenshot 1). For the crimper I use Structural Steel from the library. Finite element analysis was performed on a quarter of the model, applying appropriate symmetry boundary conditions. The nodes on the symmetry planes were fixed in the direction perpendicular to that plane. I am using the Bilinear Isotropic Hardening model (see screenshot 2). The contact is set to frictionless. Previously, I encountered an error: 

Element 321 located in Body "Part 1" (and maybe other elements) has become highly distorted. You may select the offending object and/or geometry via RMB on this warning in the Messages window. 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. Named Selections for the offending element can be created via the Identify Element Violations property on the Solution Information Object.

But after using the tips in the error and watching this video: "https://www.youtube.com/watch?v=fI2a_xP0veI&t=132s", I managed to resolve the issue.

However, new problems soon emerged: "Element 28340 has excessive thickness change," "Element 1058 (SOLID185) is turning inside out," and "Element 21380 has excessive distortion." All problems concern the stent.

Are the new errors related to the previous one?

this is what i tried (all the same actions as for the first problem):

• different mesh size
• different step size
• frictionless and frictional contact
• nonlinear mechanical mesh with linear element order
• applied the load gradually
• different thickness of crimper

I have been trying to resolve these issues on various forums for a long time, but nothing seems to work. Could you please help me?

[Sai Deogekar]

Hi, 

Looks like you have tried quite a few options to resolve this. Could you share some more details about the model?

1. The errors refer to some elements. In which region are those located?
2. What does your mesh look like in those regions?
3. How are you applying the boundary conditions to radially compress the stent?
4. How far along does the simulation get to before failing?
5. I noticed that you have 30 time steps. Is there a reason for using so many time steps?