Abnormal distortion on shell element (S4R) under Abaqus explicit compression? 1

[yinan]

Hi everyone, I have a question that has been bothering me for a month.

In Abaqus Explicit, I used shell (S4R) to simulate a compression experiment. I chose 'general contact' with 'all* with self' for the contact settings. However, there is a distortion as shown in the picture starting at the step 0.

I have tried many solutions but none have worked, such as controlling hourglassing and changing mass scaling. It seems that the problem lies in the contact setting of 'all* with self', because if I manually add the surface pairs that will come into contact during compression, such distortions do not occur. But adding contact pairs one by one really takes time. How could I set up the contact while keeping All* with self?

I really appreciate if you have

time to look at my issue!

 

[FEA way]

Hard to say without the file but double-check your mesh. You may have something like overlapping faces meshed with shell elements. Run a frequency analysis on this mesh. And check all the warning messages in your simulation.

 

[yinan]

Hi FEA way,

Thank you very much for your reply! I have double checked the mesh quality and also geometry including overlapping faces. I guess the issue should most likely lie in the "All* with self" contact. Because the weird distortion happens at step 0 only where there is no small vertex-hexagon (the weakest place).

 

[FEA way]

Can you share the .inp or .cae file ? General contact itself shouldn’t cause this unless the mesh is very fine and the automatic surface thickness reduction fails to prevent self-intersections.

 

[yinan]

Hi FEA way,

Thank you very much for taking time on my model!

 

[yinan]

If you need cae file, here is the 2020 version.

 

[FEA way]

As I suspected, you have duplicated faces in that core. You will see this if you use the Remove Selected tool from the Display Group toolbar, set it to Faces and hide one of these faces - the other one will still be visible.

 

[yinan]

Thank you so much! That is the reason!