1. SEMINAR ON SHAPE MEMORY ALLOYS
SUBMITTED BY: PRABHAT KUMAR SINGH MECHANICAL-53

2. Definition of a Shape Memory Alloy
Shape Memory Alloys (SMAs) are a class of metal alloys that can recover apparent permanent strains when they are heated above a certain temperature.
They can retain their properties at high temp.

3. History Of SMA’s Discovered in 1932 By Chang and Read
In 1938, Brass (CuZn)
In 1951, Gold Cadmium (AuCd)
Buehler and co-workers discovered
Nickel-Titanium (NiTi).(1962)

4. Basic working principle
SMAs have two stable phases - the high-temperature phase, called austenite and the low-temperature phase, called martensite.
the martensite can be in one of two forms: twinned and detwinned, as shown in Figure 1.
A phase transformation which occurs between these two phases upon heating/cooling is the basis for the unique properties of the SMAs.

7. Selection Criteria of SMA’S
Range
Sensitivity
Repeatability
Linearity and Accuracy
Impedance
Nonlinearities
Static and Coulomb Friction
Frequency Response

8. Properties: A Shape Memory Alloy may be stretched up to 8% more than their original length without permanently stretching or damaging the material.

9. Types Of Shape Memory Alloys
One-way Shape Memory Alloy
Two-way Shape Memory Alloy
Types Of Alloys
NITINOL
Copper Based

10. Ni-Ti Alloy (NITINOL)
NITINOL means Nickel Titanium Naval Ordnance Laboratory and it is discovered in 1965.
Its composition is about 56% Nickel and 44% Titanium.
Nitinol “remembers” its original shape and springs back up to temperatures up to 500 degrees C. Can be strained 8 to 10 times more than spring steel without permanent deformation.

11. Physical Properties of Nitinol
Density-6.45gms/cc
Melting temperature ºc
Resistivity: 82uhom-cm
Thermal conductivity:.1wW/cm-ºc
Latent heat:5.78cal/gm
Heat capacity:0.077cal/gm-ºc
Magnetic succeptibility:3.8uemu/gm

12. Mechanical Properties of Nitinol
Ultimate tensile strenth: mpa
Typical elongation:15.5%
Yield strenth(hi temp):560
Yield strenth (low temp):100
Poission ‘s ratio:0.3
Energy conversion efficiency:5%
Work output:1 joule/gm

13. Current Application of Nitinol
It has similar properties to human hair.
Nitinol’s amazing properties allows surgeons to perform life saving operations.
Nitinol is used to:-
Seal holes in the heart
Patch up faulty blood vessels
Attach tendons to bone

14. Application of Nitinol
The ICEmobile
A Nitinol heat engine, called the Icemobile has a loop of Nitinol which you immerse in warm water, to make it spin (which then cuts up ice cubes).

15. Future application of Nitinol
Engines in cars and airplanes
Car frames
Engine cooling
Carburetor
Engine lubrication

16. LIMITATIONS OF SMA’S Heat Dissipation Stiffness/Flexibility
Relatively expensive to manufacture and machine compared to other materials such as steel and aluminum.
Most SMA's have poor fatigue properties; this means that while under the same loading conditions (i.e. twisting, bending, compressing) a steel component may survive for more than one hundred times more cycles than an SMA element.

17. ABNORMAL BEHAVIOUR OF SMA
SMA also exhibits superelastic (pseudoelastic) behavior.
SMAs deformed above a critical temperature show a large reversible elastic deformation (recoverable strains up to 10%. much exceeding the elasticity) as a result of stress-induced martensitic transformation.

18. APPLICATION OF NANOMUSCLES
An advantage to this new shape memory alloy is its’ efficiency. No other alloy or polymer can compare to its’ strength and efficiency to weight ratio.
Nanomuscles weigh just one gram but can lift grams, and are preferred to electric motors as they are far cheaper to produce.

19. Application in aircraft
Active Control and reduction of noise and vibrations in external parts.
• control of aero-acoustic excitations.
active suspension of equipment.
Shape control of aerodynamic surfaces.
• Active fluid dynamics.
• Integrated antennas and electromagnetic structures.

20. CONCLUSION
Shape memory alloys provide wide range of alloys which can be used in every field.
They allow to avoid shock loading, have simple design and are easy to operate.
IT can also used in carburetor, automobiles,engines and in aircrafts.
They are also used in combustion chamber.

21. REFERENCE
Shape Memory Applications Inc. Shape Memory Alloys. Hodgson, Darel E.; Ming H. Wu, Memory Technologies; Robert J. Biermann, Harrison Alloys, Inc.
Nickel-Titanium Shape Memory Alloys. Azom.com.
Shape Memory Alloys. TiNi Aerospace Inc <

22. REFERENCE CONTINUED…….
Shape memory alloy micro-actuators for medical applications; J. Peirs, D. Reynaerts, H. Van Brussel, K.U.Leuven - P.M.A. Celestijnenlaan 300B, 3001 Heverlee

23. THANK YOU