×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

Solid Extruded Tube, collapsing and rippling in Dynamic Explicit Step
2

Solid Extruded Tube, collapsing and rippling in Dynamic Explicit Step

Solid Extruded Tube, collapsing and rippling in Dynamic Explicit Step

(OP)
Hi all

I have a simple analysis, where a long tube is displaced into a large tube that features a bend. The idea is to look at the stress distributions along the tube as it deforms around the bend.
I have been using a dynamic explicit step to run this, using shell geometries to date, and it runs fine. However, once I employ solid geometries, and long lengths, the tube that is being displaced "ripples" when it should just translate in one direction, and it also flattens out and collapses under itself in some way. Attached picture describes what I am finding.

Is this a product of using the dynamic explicit step? I have attached the input file, if anyone could give me some insight into what may be happening.

Regards,
Tom

RE: Solid Extruded Tube, collapsing and rippling in Dynamic Explicit Step

The element type C3D8R is quite bad when used with one element through thickness and bending deformation. Try again with C3D8I.

RE: Solid Extruded Tube, collapsing and rippling in Dynamic Explicit Step

Be careful when using C3D8I also - it is much more sensitive to aspect ratio (likes to be a perfect cube).

Check your artificial strain energy.

RE: Solid Extruded Tube, collapsing and rippling in Dynamic Explicit Step

Not sure why you need a tie constraint at all. The geometry you are working seems benign enough to let you have a continuous mesh. If you are going to be a modeler, meshing is an essential aspect that you must become good at.

Also, unless there is real need, it is better to have realistic material properties assigned to all materials in a model. So, while assuming something is rigid can be okay in some situations, it can cause other difficulties such as in contact penalty stiffness determination by the code, artificially high contact energy, etc. which can then manifest in unrealistic accelerations.

*********************************************************
Are you new to this forum? If so, please read these FAQs:

http://www.eng-tips.com/faqs.cfm?fid=376
http://www.eng-tips.com/faqs.cfm?fid=1083

RE: Solid Extruded Tube, collapsing and rippling in Dynamic Explicit Step

(OP)

Quote (IceBreakerSours)


Not sure why you need a tie constraint at all. The geometry you are working seems benign enough to let you have a continuous mesh. If you are going to be a modeler, meshing is an essential aspect that you must become good at.

So I was having difficulty meshing the transition region (sloped), with the hex elements that I used for the other 2 regions. a free tet mesh was all I was able to apply, despite numerous attempts at partitioning. As I am new to the software and am still learning, perhaps I am missing a way that I could partition this region to allow for a continuous use of a single element type?

Regards,
Tom

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!


Resources


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close