stent crimping of nitinol quarter model abaqus

• Sep 22, 2022

• #2

FEA way

Mechanical

Nov 13, 2018

5,144

Are equations constraints necessary in your case ? Can't you use symmetry boundary conditions or cyclic symmetry ? It would be much easier and less prone to errors if applicable to your model.

 

Upvote 0 Downvote

• Sep 23, 2022

• Thread starter
• #3

Josh1313998

Student

Feb 15, 2022

10

Hi, im using cyclic BCs to mimic symmetry and the equation constraint is only to map all nodes of the crimptool to one point for easy RF extraction. does that make sense?

 

Upvote 0 Downvote

• Sep 23, 2022

• #4

FEA way

Mechanical

Nov 13, 2018

5,144

I would try without that equation to avoid overconstraint - using just the cyclic symmetry interaction.

 

Upvote 0 Downvote

• Sep 26, 2022

• Thread starter
• #5

Josh1313998

Student

Feb 15, 2022

10

Thanks so much for your time and help. unfortunately this doesnt seem to solve my issue.
could you think of any other reasons? would sharing an inp help?

 

Upvote 0 Downvote

• Sep 28, 2022

• #6

FEA way

Mechanical

Nov 13, 2018

5,144

Yes, it will be easier to help if you share the .cae or .inp file.

 

Upvote 0 Downvote

• Sep 28, 2022

• Thread starter
• #7

Josh1313998

Student

Feb 15, 2022

10

[link file:///C:/Josh_Abaqus/RF-crimp-models/12-copy-shell/continuos-strut-design/NoEQNconstraintandbcsaresymmbcs.inp]Link[/url]
[link file:///C:/Josh_Abaqus/RF-crimp-models/12-copy-shell/continuos-strut-design/thickness030newmesh.inp]Link[/url]

The first link shows the newer design inp which i created to reduce regional stress concentrations but doesnt seem to be doing so and the second one is an older design where it ran pretty ok. the problem is it is quite noisy, has high stress concentrations and most importantly the RF values im getting are too high especially for the new design.

 

Upvote 0 Downvote

• Sep 28, 2022

• Thread starter
• #8

Josh1313998

Student

Feb 15, 2022

10

"C:\Josh_Abaqus\RF-crimp-models\12-copy-shell\continuos-strut-design\NoEQNconstraintandbcsaresymmbcs.inp"
"C:\Josh_Abaqus\RF-crimp-models\12-copy-shell\continuos-strut-design\thickness030newmesh.inp"
I cant seem to attach the links so that you can open them . is there a way to do so on this?

 

Upvote 0 Downvote

• Sep 28, 2022

• #9

FEA way

Mechanical

Nov 13, 2018

5,144

There is an Attachment bar at the bottom of the reply window. There use the "Click Here to upload your file to ENGINEERING.com" option and upload the file from your computer.

 

Upvote 0 Downvote

• Sep 28, 2022

• Thread starter
• #10

Josh1313998

Student

Feb 15, 2022

10

here is the 1st one where the only probelmes are folding in of parts of the stent, high regional von mises and noisy/high reaction forces

 

 https://files.engineering.com/getfile.aspx?folder=f03a7594-5fc4-482a-b642-833f8bca7cf9&file=thickness030newmesh.inp

Upvote 0 Downvote

• Sep 28, 2022

• Thread starter
• #11

Josh1313998

Student

Feb 15, 2022

10

Here is the newer design using fillets that i am trying to use

 

 https://files.engineering.com/getfile.aspx?folder=525bbd2d-5e53-4900-8c2f-fe640b1233d5&file=NoEQNconstraintandbcsaresymmbcs.inp

Upvote 0 Downvote

• Sep 28, 2022

• Thread starter
• #12

Josh1313998

Student

Feb 15, 2022

10

this picture shows the folding in of the ends of the struts i have referenced as well as the high von mises stress values.

 

 https://files.engineering.com/getfile.aspx?folder=b8250ec1-42fb-422d-901c-bfcb669cd05a&file=frontviewofstentwithstressconc.PNG

Upvote 0 Downvote

• Sep 30, 2022

• #13

FEA way

Mechanical

Nov 13, 2018

5,144

Here are a few remarks after looking at your model:
- you are using fixed incrementation within a dynamic explicit step - is there a reason for it ? The use of automatic incrementation is advised in the majority of cases.
- your general contact domain is limited to one selected surface pair - it's not wrong but make sure that no other contact (like self contact) can occur in this case
- did you check the global energies in the model ? Do they all look correct ? Also, I've noticed that you limited the energy output to just two energies. It would be good to include other types as well - for verification purposes. In Abaqus/Explicit analyses it's really important.
- if you encounter some noise in results, consider increasing output frequency or using built-in filters
- prescribed velocity (with smooth step amplitude) might be better than prescribed displacement in the case of Abaqus/Explicit analysis

 

Upvote 0 Downvote

• Oct 7, 2022

• Thread starter
• #14

Josh1313998

Student

Feb 15, 2022

10

Thanks a million! i have taken these into account but still no joy unfortunately. The only problem im really having now is the high reaction forces.is there anything else that could induce this?

 

Upvote 0 Downvote

• Oct 9, 2022

• #15

FEA way

Mechanical

Nov 13, 2018

5,144

What are the expected reaction forces and how did you estimate them ? Also, what's the quantitative difference between them and the values from the analysis ?

 

Upvote 0 Downvote

• Oct 10, 2022

• Thread starter
• #16

Josh1313998

Student

Feb 15, 2022

10

so from literature similar crimps would generate 30-80 N of radial reaction force which im getting from my one quarter model so i must multiply the 40 n im getting by four to get the real values of the radial reaction force of the whole stent.. im extracting this by using an equation constraint to map a reference point to all nodes on the crimptool and plotting the reaction force of the reference point in the field output.

 

Upvote 0 Downvote