×
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

How to bend tube to evaluate stress?

How to bend tube to evaluate stress?

How to bend tube to evaluate stress?

(OP)
Am a newbie to Cosmos and want to perform a 90 degree bend on a straight extrusion to evaluate the stress or distortion at the inner radius (if any).  

Besides fixing one end of the extrusion, I am not sure which other restraint to apply to perform a 90 degree bend?

Please advise.

RE: How to bend tube to evaluate stress?

Use quarter symmetry and restrain both symmetry faces. Apply a presrcibed displacement to the free end to bend it.

corus

RE: How to bend tube to evaluate stress?

(OP)
What displacement method should I apply to the free end for bending?  I tried to apply a restraint on the free end with reference to an axis and a 1.5 radian (to make the free end rotate 90 degrees about the axis), but it didn't quite work.  It keeps prompting to turn on large displacement flag.  If I pressed 'yes', the static study will fail.  If 'no', it gave some result but only with a slight bend and nowhere near 90 degrees.  

RE: How to bend tube to evaluate stress?

Do what Corus says and use 1/4 symmetry to cut down the model size for starters...

I suspect that you will definitely need to perform this as a large-displacement (non-linear) analysis, so you will have to have the large displacement flag on.

I'm not all that conversant with COSMOS (we only have the linear-static bundle here and use ABAQUS for everything else smile), but could you create a rigid (non-deformable) roller to bend the extrusion round with a prescribed displacement (as Corus suggests) on the free end.  Or use another rigid surface to 'push' the free end round the roller?

Martin

RE: How to bend tube to evaluate stress?

This is a nonlinear analysis (not to be confused with large displacement), you will need advanced professional for a legitimate analysis, as you are interested in behavior well beyond the yield point of the material.

RE: How to bend tube to evaluate stress?

Try a smaller displacement value to see if you get an answer with large displacement switched on. The radius of the bend might be a good estimate of the translation needed. I don't see why the job failed though as you're applying a prescribed displacement rather than a force which might cause instability problems.

corus

RE: How to bend tube to evaluate stress?

I agree with Mech151, it is essential to consider this as a non-linear analysis.

The material's yield and plastic deformation stress/strain behaviour are key to analyzing this problem.

Also, the final inner distortion of the tube will depend on how you model the bending dies and what assumptions are made for clamping and friction.  Also, springback may be significant as well.

ERT
http://www.akeng.com

RE: How to bend tube to evaluate stress?

Thanks ERT,
I would add the following:  
1.  For such a large displacement, your model is probably experiencing element locking (deformed elements exceed geometry limits).  
2.  Even better than an analysis for this problem would be to talk to a fabricator (tube bender).  They will be able accurately predict the distortion that you will see.  Depending on the radius of the bend, they may take counter measures like filling the tube with sand.  We use a couple of good tube benders, let me know if you would like contact information.

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