Air Temp Nitinol

[sm0ky2]

I guess they already hooked it up to rats
https://www.ncbi.nlm.nih.gov/m/pubmed/9659619/

[memoryman]

Not sure what you base your numbers on.
If someone wants to experiment, I have ~900 ft of 0.016" dia Nitinol for sale; shape change temp ~40C. If interested, send a pm.
Flexinol is different from Nitinol in performance; my application was as an actuator, using pulsed current.

[sm0ky2]

memoryman

this thread Gadgets first reply #1
Quote
This type of Nitinol wire can lift 30 pounds 30 inches with just a 30 degree F shift in tempature differential
end quote

Seems a big movement of a heavy weight at a small temperature differential ?

if accurate

do you have any data
respectfully
Chet K

Several top research facilities have quotes 55-75 tons per sq inch, with temps slightly above
room temperature. (70-90F)
The stress state was inconveniently low temp for me personally
Seemed as if the best of these heat reactive alloys is actually powered
by "cold".


Ideally we sacrifice raw power for a trained reactive temperature that is
1) room temperature on the cold side
And
2) not too high on the hot end of things, such as to be easily attainable.


The double-training techniques are interesting because we can set two points
A hot configuration and a cold configuration, making an ideal actuator for oscillatory action.

[sm0ky2]

thermal conversion efficiency would have to be more than
100% efficient for us to use "cold power".
In more detail: we would have to compensate for the energy
we consume while creating the cold situation. Wether it is a refrigerated
fluid, or dry ice, liquid nitrogen, etc.
these systems themselves being less than100% efficient


So to be 'useful' as a thermo-mechanical generator
We need the cold side to be ambient, or within a range we
can sustain with minimal energy input. The hot side therefore
being the driving force of the differential.
These alloys have significantly lower force per mass ratios.
Something like 8lbs per 4% stress.
[why 4%?  This is the limitation of degradation, stresses of greater
than 4% can lead to limitations on the sustainable lifetime of the alloys.
  Within the 4% stress range, prototype engines have sustained billions
of cycles.]


[edit:  sorry forgot a detail- that 8lbs was for the hot side reaction
a 0.5 mm wire coiled spring
      Something like 9 inches in total length. Active temp cold stress (70F)
   Hot memory (110F).]


The memory curie point to train these is something like
916F
And involves locking them in position and repeatedly heating
Then quickly cooling ( ice bath)

[memoryman]

I have actually trained my own springs using a small oven (max 1,000degC). The cooling cycle does not have to involve ice water.