Steel memory 1

[DE51GNR]

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.

 

[racookpe1978]

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

Why do you think you need heat treatment?

 

[EdStainless]

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

 

[tbuelna]

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.

 

[DE51GNR]

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.

 

[metman]

DE51GNR (Industrial) (OP):

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

Design for RELIABILITY, manufacturability, and maintainability

 

[djhurayt]

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

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
[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1451335934/tips/pulled_through_to_end_of_pipe_1mm_gklm29.pdf[/url]

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

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

 

[DE51GNR]

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....?

 

[ornerynorsk]

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.

 

[metman]

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/..._87978083224_c_S&026=-99&025=c&navid=12104482

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

 

[metman]

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