Shape-memory-alloy00

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shape memory alloy
 * (SMA) is a material that have a memory, it's memory save it's shape in it under only one condition in another condiation it will have many shapes.
 * there are 2 phase to the material:-
 * 1) martensite :-in this phase the material will be in low temp, it have monoclinic crystal structure.
 * 2) austenite:- in this phase the material will be in high temp, it have cubic crystal structure.



History

The first steps towards the discovery of the shape-memory effect were taken in the 1930s. According to Otsuka and Wayman , ( A. Ölander ) discovered the pseudo elastic behavior of the Au-Cd alloy in 1932. ( Greninger & Mooradian ) (1938) observed the formation and disappearance of a martensitic phase by decreasing and increasing the temperature of a Cu-Zn alloy. The basic phenomenon of the memory effect governed by the thermoelastic behavior of the martensite phase was widely reported a decade later by ( Kurdjumov and Khandros ) (1949) and also by Chang and Read (1951).[1]

The nickel-titanium alloys were first developed in 1962–1963 by the United States Naval Ordnance Laboratory and commercialized under the trade name Nitinol (an acronym for Nickel Titanium Naval Ordnance Laboratories). Their remarkable properties were discovered by accident. A sample that was bent out of shape many times was presented at a laboratory management meeting. One of the associate technical directors,( Dr. David S. Muzzey ), decided to see what would happen if the sample was subjected to heat and held his pipe lighter underneath it. To everyone's amazement the sample stretched back to its original shape.

Manufacture

Shape-memory alloys are typically made by casting, using vacuum arc melting or induction melting. These are specialist techniques used to keep impurities in the alloy to a minimum and ensure the metals are well mixed. The ingot is then hot rolled into longer sections and then drawn to turn it into wire.

The way in which the alloys are "trained" depends on the properties wanted. The "training" dictates the shape that the alloy will remember when it is heated. This occurs by heating the alloy so that the dislocations re-order into stable positions, but not so hot that the material recrystallizes. They are heated to between 400 °C and 500 °C for 30 minutes. Typical variables for some alloys are 500 °C and for more than 5 minutes.

They are then shaped while hot and are cooled rapidly by quenching in water or by cooling with air.

Materials

Alloys of metals having the memory effect at different temperatures and at different percentages of its solid solution contents. Ag-Cd 44/49 at.% Cd Au-Cd 46.5/50 at.% Cd Cu-Al-Ni 14/14.5 wt.% Al and 3/4.5 wt.% Ni Cu-Sn approx. 15 at.% Sn Cu-Zn 38.5/41.5 wt.% Zn Cu-Zn-X (X = Si, Al, Sn) Fe-Pt approx. 25 at.% P Mn-Cu 5/35 at.% Cu Fe-Mn-Si Pt alloys Co-Ni-Al Co-Ni-Ga Ni-Fe-Ga Ti-Pd in various concentrations Ni-Ti (~55% Ni) Ni-Ti-Nb Ni-Mn-Ga

Applications:


 * Aircraft

Boeing, General Electric Aircraft Engines, Goodrich Corporation, NASA, and All Nippon Airways developed the Variable Geometry Chevron using shape-memory alloy that reduces aircraft's engine noise.

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> There have also been limited studies on using these materials in robotics, for example the hobbyist robot Stiquito (and "Roboter frau Lara"[7]), as they make it possible to create very light robots. Weak points of the technology are energy inefficiency, slow response times, and large hysteresis. > > Nitinol wire is also used in and in a few magic tricks, particularly those involving heat and shapeshifting.
 * Robotics

THIS FRAU LARA ROBOT

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Medicine

Shape-memory alloys are applied in medicine, for example, as fixation devices for osteotomies in orthopaedic surgery, in dental braces to exert constant tooth-moving forces on the teeth.

The late 1980s saw the commercial introduction of Nitinol as an enabling technology in a number of minimally invasive endovascular medical applications. While more costly than stainless steel, the self expanding properties of Nitinol alloys manufactured to BTR (Body Temperature Response), have provided an attractive alternative to balloon expandable devices in stent grafts where it gives the ability to adapt to the shape of certain blood vessels when exposed to body temperature. On average, 50% of all peripheral vascular stents currently available on the worldwide market are manufactured with Nitinol.



SEE THAT

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MY VISION IN THE FUTURE THAT WE CAN MAKE A MOTOR IT'S MECHANICS AND MOVEMENT DEPEND ON THIS MATERIAL SEE THIS VIDEO IT CAN BE EASILY TO SEE THAT IF WE HAD TO CYLINDERS WITH 2 PISTON WE CAN ATTACH THEM TO AHAND OF (SMA) THAT CAN PUSH OR PULL IT LIKE THIS IMAGE

THAT'S MY DESIGN & MY VISION COME FROM THIS VIDEO

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THANKS

REFRENCES & WEB SITES


 * 1) wikipedia Shape-memory_alloy
 * 2) smart.tamu.edu
 * 3) YOU TUBE