Free Energy Machines

[Eleven11]

Free Energy Nitinol Heat Machines invented in the early 1970's

I had heard about "memory metal" before but this is the first time I've seen it put to use in a motor. This is really an amazing invention. I wonder why nothing ever came of it.

http://www.youtube.com/watch?v=oKmYqUSD ... vfFFVwc%3D (http://www.youtube.com/watch?v=oKmYqUSDch8&feature=plcp&context=C4b28a3fVDvjVQa1PpcFNYvQMlvXPbha7nhMKjk2ci 4rRTvfFFVwc%3D)

[urbanfarmer]

Sounds promising. How durable is this alloy?

[Eleven11]

Good question... The video said that the metal became stronger as it was used in the heat engines... A sort of annealing maybe?

I don't know much about it but doing a bit of reading, I found this...

http://en.wikipedia.org/wiki/Nickel_titanium


Limitations

Fatigue failures of nitinol devices are a constant subject of discussion. Because it is the material of choice for applications requiring enormous flexibility and motion (e.g., peripheral stents and heart valves), it is necessarily exposed to much greater fatigue strains than are other metals. While the strain controlled fatigue performance of nitinol is superior to all other known metals, fatigue failures have been observed in the most demanding applications. There is a great deal of effort underway trying to better understand and define the durability limits of nitinol.

Nitinol is half nickel, and thus there has been a great deal of concern in the medical industry regarding the release of nickel, a known allergen and possible carcinogen.[12] (Nickel is also present in substantial amounts in stainless steel and cobalt-chrome alloys.) When properly treated (via electropolishing and/or passivation), nitinol forms a very stable protective TiO2 layer that acts as a very effective and self-healing barrier against ion exchange. It has been repeatedly shown that nitinol releases nickel at a slower pace than stainless steel, for example. With that said, very early medical devices were made without electropolishing, and corrosion was observed. Today's nitinol vascular self-expandable metallic stents, for example, show no evidence of corrosion or nickel release, and the outcomes in patients with and without nickel allergies are indistinguishable.

There are constant and long-running discussions regarding inclusions in nitinol, both TiC and Ti2NiOx. All metals contain inclusions, and nitinol cannot be melted without inclusions—they are omnipresent. The size, distribution and type of inclusions can be controlled to some extent. Theoretically, smaller, rounder and few inclusions should lead to increased fatigue durability. All studies done to date, however, have failed to show measurable differences.[13][14]

A major limitation to further use of nitinol has been its difficulty to weld, both to itself and other materials. In the past ten years, laser welding nitinol to itself has become a relatively routine process. More recently, strong joints between NiTi wires and stainless steel wires have been made using nickel filler. More research is ongoing into other processes and other metals nitinol can be welded to.[15]

Recent advances have shown that processing of Nitinol can expand thermomechanical capabilities; allowing for multiple shape memories to be embedded within a monolithic structure.[16] Research on multi-memory technology is on-going and promises to deliver enhanced shape memory devices in the near future.

The attached file discusses fatigue due to corrosion but not much about mechanical fatigue. In general though, I read that it is more durable than any other metal.