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


Compression of UHMW sheet in bend

Compression of UHMW sheet in bend

Compression of UHMW sheet in bend

We are bending a 12"x5"x.125" UHMW extruded sheet around a 4.5" radius. When we do so, the sheet seems to compress and the overall length decreases by 1.8%.
Is that really what is happening or is there something obvious we are missing?
If it is compressing, over time will the material creep and grow any significant amount?

Once bent the 12" dimension forms almost a half circle.
We restrain it firmly to shape as it is quite stiff.
We see the same compression even when we have heat formed the material to near net shape prior to fitting (low heat on the outside face of the sheet).

RE: Compression of UHMW sheet in bend

How are you bending it? Cold mechanical bending can be done in a slip roll, between a couple of dies, or perhaps by twisting the ends. Adding heat would primarily reduce load required to form and reduce springback. when a beam is bent, the inside is in compression, but the outside is in tension, and the center is at zero stress, save for a small shear in thin sections. In the theory, the center plane, called the neutral axis, does not change length. Could this be due to friction with your forming tool? Try lubrication the dies. You may not want to do this in production for contamination reasons, but try it as a diagnostic exercise to see if it is the problem. Also, if you heat from the outside while bending over a cold mandrel, the mandrel will act like a heat sink, and the part will never be heated to a uniform temp. Try preheating your tooling, then heat the blank from both sides. Again, maybe not practical in production, but perhaps useful in diagnosing your problem

Rick Fischer
Principal Engineer
Argonne National Laboratory

RE: Compression of UHMW sheet in bend

Also, try annealing the stock before you cut the 12" length.

Rick Fischer
Principal Engineer
Argonne National Laboratory

RE: Compression of UHMW sheet in bend

When we bent it just used heat on one side and let it curl from the stress.
But the part is smaller whether we pre bend or not.
To install we just strap it to the curve.

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!


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