×
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

Steel memory

Steel memory

Steel memory

(OP)
Hi all,
Wondering if someone can help.
If you can picture a strip of steel about 6mm wide x 1-2mm thick x 250mm long.
It is flat half way along(125mm)and then curves down at a constant radius like a quadrant of a circle.
Now that needs to be the original shape of it.
What I need to do is insert it (quadrant end first) through a straight tube (16mm bore x 200mm long)
So it needs to be flexible enough to almost flatten out to go through the tube and come out the other end returning to original shape.
I hope this is understandable.
I need to know what spec steel to use and if or what heat treatment is needed.

RE: Steel memory

Draw what you think you want get OUT after the wrapping (bending?).

Why do you think you need heat treatment?

RE: Steel memory

If you are going to deform it and expect it to return then you cannot exceed the yield strength. I didn't draw this part but it sounds like it is way above that level. This is tight bend radius.
Think of it this way, if you have a flat part and bend it in this radius would you expect it to spring right back straight?
Calculate the stress involved, and then we can see if this is even possible.
You would be helped with a material with a lower modulus (Ti, Al, Cu, Mg) and very high strength (steel, Ni alloys, Ti alloys, BeCu), and making the part thinner (to reduce stress).

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

RE: Steel memory

Based on your description, a constant radius quadrant of this strip (ie. a 90deg sector) having a 125mm circumferential length would mean a radius of around 79.6mm in the formed condition. I don't think any normal metal alloy will do what you are asking. The only metal alloy I can think of that might work is something like Nitinol. But it would require being heated to return it to its original shape.

RE: Steel memory

(OP)
Thank you for the replies.
I have tried to attach a sketch, hopefully it has uploaded OK.
Basically the metal strip that can be less than 1mm thick if it has to be, needs forming to the shape on left of picture.
It needs to flex to push through tube (right in pic)and then return to formed shape (left of pic) when it comes out.
Please note that the scale of picture is not perfect.

RE: Steel memory

DE51GNR (Industrial) (OP):

What prevents you from inserting the metal strip from the straight end?

Design for RELIABILITY, manufacturability, and maintainability

RE: Steel memory

If I am understanding you correctly, like tbuelna said it looks like your formed part will have a centerline radius of approx. 79.73mm
https://res.cloudinary.com/engineering-com/image/upload/v1451335800/tips/inserted_up_to_bend_1mm_oif8j9.pdf

Once you pull the straight end of you part through to the end of the pipe your centerline radius will have to flatten to 141.64mm radius (provided bend flattens uniformly
https://res.cloudinary.com/engineering-com/image/upload/v1451335934/tips/pulled_through_to_end_of_pipe_1mm_gklm29.pdf

Then once the entire rolled section is in the pipe it will have flattened the radius even more to a 268.12mm radius
https://res.cloudinary.com/engineering-com/image/upload/v1451336060/tips/roll_pulled_just_into_pipe_1mm_o4dtlk.pdf

I realize this doesn't give you the material but it does you you’re geometry change that your part will need to experience during this pull through operation

RE: Steel memory

(OP)
Metman, either way it needs virtually flatten and then return to hook shape.

djhurayt, that is what the metal strip needs to do, thank you for taking the time to create the drawing.

Any ideas? can it be done? or will I need to resort to a different metal or different material; ie fibreglass, plastic....?

RE: Steel memory

Thinking along the lines of a constant force spring, your 1-2 mm thickness might be a bit too much. If you can live with thinner spring stock, it should be achievable.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

RE: Steel memory

Ornery hit the nail on the head: Here is a link to a negator, constant force spring. A tape measure is a constant force spring.

http://www.mscdirect.com/browse/tn/Motion-Control-...

This is a strain based issue so what Ed Stainless said about modulus of elasticity is the only property you are concerned with along with thickness. Modulus of elasticity will not change with heat treatment but yield strength determines how tight of radius you can bend before permanent deflection occurs,

DESIGNER: You said, "Basically the metal strip that can be less than 1mm thick if it has to be, needs forming to the shape on left of picture."

Design for RELIABILITY, manufacturability, and maintainability

RE: Steel memory

In the link above this, MSC #: 02018463, looks maybe in the general size range you need. For $8 you could make a test.


Design for RELIABILITY, manufacturability, and maintainability

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