The strngth of a memory wire coil

[alan2here]

I wondered if this materal.

 

http://www.mutr.co.uk/product_info.php?cPath=418_464&products_id=1151

 

Could be tightly coiled in a cointainer, then have heat such as (for simplicity) boiling water added into the container then the force to straighten the wire would be verry strong with potentally intresting applications.

Edited June 10, 2009 by alan2here

[Ndi]

Memory stuff works by deforming objects before their (English limitation here) permanent destruction point. As a result, heating does nothing more than reverting to whatever shape it was in before.

 

Think of it as a frozen spring. You tug, you freeze. It remains like that. Let it warm up and it slowly reverts to its initial state. Sum of all available energy is same as the one put into it to deform it - no energy is gained or lost (ideally) - just stored.

 

As for coiling into a barrel to make it blow, we have better ways, hydraulic being one - especially with mechanical advantage.

 

Article also suggests sprinkler systems (we already have bi-metal ones for that) and bi-metals work almost as well if ones needs a simpler open-close action.

 

While interesting as a material because Titanium has cool properties like being implantable, we have several other "memory" materials that are widespread and pretty cool. Shrink wrap for one.

 

I wonder how they heat mounted braces to 90 Celsius.

[alan2here]

I was also imagining a rapid uncoiling effect from one opening in the barrel. I see you were thinking big with a barrel :¬P

 

Thanks for the reply. Do any of the other alternatives outproform this one at such practical tempretures?

[Ndi]

We don't really like temperature-controlled stuff unless we want it temperature-controlled because the environment on Earth has such bad temper. Cars are tuned and sometimes remade (parts) for hot/cold areas, and high-low altitude because the same car could work in as low as -30C to as high as +80C in the _temperate_ area, higher in the extremes (I know that's not how hot it gets in the summer but a black car in the sun goes mighty high).

 

We usually prefer controllable stuff. Most of our locks are electrical, magnetic or a combination thereof (including mechanical). Shop tags that prevent shop-lifting have a latch inside that is unlocked by a string magnetic field and twisting, heat-tags would have come undone in China or lock up in Norway. Quick-enter and lock systems are also electromagnetic because one can lock/unlock immediately and because they fail-open with disasters, fire and emergencies. That's why they are mandatory in most emergency exits that normally lock.

 

A thermal lock would be slow, lack power (a magnetic lock with a 10W rating can hold 300Kg, dual lock high and low on a door makes it effectively locked) and could fail left in the sun (or when cold). Electromagnets have no such flaws. Correctly sealed they have 100% reliability and virtual endless lifetime (it's the case that fails). Also, it can't be damaged-shut, like with mechanical and electro-mechanical latches.

 

Also, for transport, sealing, etc we have magnetic latches - power to lock- power to unlock. This has the huge advantage that it can have a RFID smart chip in it or other auth so it only works with a known and dedicated opener. Sensitive shippings already have smart temperature sensors embedded in the product that actively log and report temperature every 5 minutes so the receiver can know if cooling failed anywhere on the way. It's used for meat, medical supplies, bio-sludge, organs, etc.

 

The thermal stuff in the article has its advantages when you need slow-moving but no-motors, like implants, especially since Ti is so well tolerated (it's virtually immune to organic juices). I still wonder how they plan on heating it to 100 or so Celsius to make it open a rib cage. Or what happens when you take a really hot shower or heat up during exercise and ... Well, no matter.

 

For one-way memory (buy it stretched, shrinks-at-home) we have long polymer (shrink-wrap, shrink-tube) that are cheap and don't revert, but nobody cares because it's so cheap you just replace it. Plus, most stuff you shrink-wrap you don't really fiddle with. Also, they plan on doing this on clothes that auto-iron with heat, as they are sold ironed. The technology exists, it's revolutionary, cool, and failed. Long polymers are uncomfortable. Plus, that's why clothes do when ironed, the heat breaks the bonds that are make in the cold (washing machine) leaning only the strong, built-in bonds. Your clothes basically have memory, it's just not that impressive. That's why in-rack steam ironing works.

 

For both way we have bi-metal which is used extensively since 300 or so years (balance pendulum clocks length) to the newer stuff like thermo-regulated stuff. All that clicks when turning on and off is most likely bi-metal: home plug-in heaters, boilers, irons, most of the old turn-dial thermostats, trip protections in electronics. It's very nice because it never fails (mechanical), it's reusable and it has hysteresis of sorts (once tripped, it takes a little while to re-do instead of locking in a click-click cycle).

 

I'm not sure what replacement you speak of. If it's opening barrels, a plain spring-lock is nice and reliable, dirt cheap, the dock workers can work it with no additional tools, no power required, works in the dark and blackouts, *and* can be overpowered with a metal rod that lives 100 years in the rain. Why touch it?