What type of metal can bend repeatedly without breaking?

Just design it so that stress stays elastic.. After that take cyclic fatigue into consideraton..

Some spring steel flat might be a good start..

Thanks... Would spring steel hold its shape in order to hold the pad on my knee until I wanted to unbend it to take it off?

Use a beanbag, can fill it with metal shot if you like (but popcorn works just as well).

Are you looking for support or protection?

Metals thick enough to provide support won't be flexible enough to do this.

Now if you're looking for protection then I would go with something like fine ring chain mail. Or woven metal fabric.

You've asked a simple question that may have a surprisingly complex answer. What Kristian is talking about is metal that can be given a shape and then can bend within its spring limits. Like any spring, after you bend it, it snaps back to its original shape. You need metalworking equipment to get the initial shape to fit around your knee. I don't think that's what you want.

It sounds like you want something that you can bend to shape, probably by hand, and then un-bend to take it off. That sounds like the bendable metal splints that the military uses for temporarily splinting bone breaks,etc. They're available on the consumer market. Just Google "bendable metal splint," probably without the quote marks.

Underlying your question is what kind of metal can stand being bent back and forth, holding its shape after each bend, but which will allow you to shape it as you need to around your knee. Unless you're into the engineering of things, buying a bendable metal splint probably is the best place for you to start.

Metals break after repeated bending into new shapes, unless they're springs and they don't get bent into a new "set" shape. But you probably want a new "set" shape each time you put it on or take it off. Finding the right metal, of the right stiffness, strength, and re-bend-ability (not really a word ) is problematic. But with the bendable splints, the makers have worked out all of those issues for you.

They may not be the right stiffness. I have no idea. And even they will have a limited number of times you can bend and re-bend them. They may be very capable of handling the re-bending, but they aren't meant to be re-used multiple times. Still, they may have the best properties you'll find for what you want.

Good luck.

There is no metal that will do this forever. But soft aluminum wire is pretty good, and cheap. Art stores sell such wire for use as armatures in plaster sculpture.

Black or galvanized iron wire is also pretty good, in the thicker grades. McMaster-Carr is a good source.

You will also need wirecutting pliers and a file (to smooth the cut ends of the wire).

Joe Gwinn

Thanks so much to all of you for the ideas...

And used much like the OP's application in the toobers in the toy "Toobers & Zots."

A hinged type.

Nexxxxxxxxxt!

-- Shake off all the fears of servile prejudices, under which weak minds are servilely crouched. Fix reason firmly in her seat, and call on her tribunal for every fact, every opinion. Question with boldness even the existence of a God; because, if there be one, he must more approve of the homage of reason than that of blindfolded fear. -- Thomas Jefferson

Excellent advice. Pure lead is pretty good too. If you are old enough to remember the flexi-curve rulers used by draughtsmen, these had two thin strips of spring steel, one each side of a square lead core (the whole lot encased in PVC). The sheet lead used for roof "flashing" is pretty ductile.

e:

Well, there aren't any other wiseasses around today, so I better mention:

Ga (Gallium metal)

Gallium will deform indefinitely, because (in contact with a knee) body hea= t will melt it.=20

What's wrong with plain ol' ordinary off-the-shelf knee pads?

Thanks, Rich

I have no experience with memory metal, but I thought you could deform that and then heat it and it would return to its original shape.

Dan

Fill a bag with coffee. Wrap it around you knee. Pull a vacuum in the coffee bag. It should lock into position. To release, release the vacuum.

Pulling a vacuum in the bag will lock all the coffee grinds together.

Hey Alyson,

Coiled extension springs will do this quite well. Not sure I'd want to kneel directly on them though, but padded both sides should work. If they are in a flexible tube they won't "catch" on anything either.

In that case, why not just go with mercury, already melted. You ought to be more sensible about these things! Obviously, strips of gold, the most malleable metal, would be the best thing to use. I think a cross-section of about 1/8" x 1/2" would be good, because that's about the size used for aluminum strips in temporary casts or braces for wrists, elbows, etc., and gold, silver, and aluminum all have about the same Young's modulus.

e:

Ours just had a spring holding the lead and the metal strips.

Pure gold shouldn't work harden. Karl

If you're looking to bend the metal to fit a knee then straighten it then b= end it again, it depends on how sharp the bend is and how many cycles you n= eed. A wire coat hanger will if the bend is not sharp go through a surpris= ing number of cycles before it fails, but eventually it will.

You might want to consider a friction-based approach. Google "joby gorilla= pod" for one example.

If you're willing to go with a process and not a product, get some 10-gage = or 12-gage copper electrical wire from Home Depot or wherever and anneal it= after every use--you can anneal it with a burner on a gas stove--just get = it red hot and throw it in a bucket of water. Cut a bunch of extras and do= a week's worth at a time.

If you want to get fancy there might be a way to do what you want to with n= itinol.