2. OUTLINE
• Introduction of shape memory alloys
• History of shape memory alloys
• Types of shape memory alloys
• Characteristics of SMA
• Types of SMA behavior
• Properties ,Advantages,Disadvantages of SMA
• Conclusion
• References
3. INTRODUCTION OF SMA
• Shape memory alloy is an alloy.
• SMA a is one the type of smart materials.
• Shape Memory Alloys are materials that “remember” their original
shape.
• If deformed, they recover their original shape upon heating.
• They can take large stresses without undergoing permanent
deformation.
• They can be formed into various shapes like bars, wires, plates and
rings thus serving various functions.
4. HOW DO THEY WORK
• We all know the most common phase changes:
• SMAs shape changes based on a solid state phase transformation.
The transition from one form of crystalline structure to another creates the
mechanism by which the shape change occurs in SMAs. This change
involves transition from a monoclinic crystal form (martensitic) to an
ordered cubic crystal form (austenite).
5.
6. HISTORY OF SHAPE MEMORY ALLOYS
• 1938: Arne Olande observed shape and recovery ability of Au-Cd alloy.
• 1938: Greninger and Mooradian observed the formation and disappearance of
martensitic phase by varying the temperature of a Cu-Zn alloy.
• 1962-63: William j.Buehler and Frederic. Wang observed the shape memory
effect in Nickel and Titanium alloy at the United States Naval Ordnance
Laboratory.
• Nitinol – Nickel Titanium Naval Ordnance Laboratories.
• where the two elements are present in roughly equal atomic percentages e.g.
Nitinol 55, Nitinol 60.
7. TYPES OF SHAPE MEMORY ALLOYS
One-way Shape Memory Alloy
Two-way Shape Memory Alloy
Types Of Alloys
NITINOL
Copper Based
9. PROPERTIES OF SMA
• The copper-based and Ni-Ti-based shape-memory alloys are considered to be engineering
materials.
• These compositions can be manufactured to almost any shape and size.
• The yield strength of shape-memory alloys is lower than that of conventional steel, but some
compositions have a higher yield strength than plastic or aluminum.
• The yield stress for Ni Ti can reach 500 MPa.
• The maximum recoverable strain these materials can hold without permanent damage is up to
8% for some alloys.
• This compares with a maximum strain 0.5% for conventional steels.
10. ADVANTAGES OF SMA:
• Very high power/weight ratio comparatively
• Accessible voltages can accomplish Thermo elastic transformation
• Higher strain recovery
• Higher strength
• Compactness, allowing for reduction in overall actuator size.
• Noiseless and silent operation
• High corrosion resistance
11. LIMITATIONS OF SMA:
• Heat Dissipation, need Mechanism for cooling
• Less Stiffness / high Flexibility
• Relatively expensive to manufacture and machine compared to other
materials such as steel and aluminum.
• Most SMA's have poor fatigue properties ( a steel component may
survive for more than one hundred time more cycles than an SMA
element. )
12. APPLICATIONS OF SMA
Aircraft
To reduce engine noise, some designers install chevrons onto
engines to mix the flow of exhaust gases and reduce engine noise.
Automotive
13. APPLICATIONS:
• Robotics
- Recently, a prosthetic hand was introduced by Loh et al. that can almost replicate the motions of
a human hand
• Civil Structures
SMAs find a variety of applications in civil structures such as bridges and buildings. One such
application is Intelligent Reinforced Concrete (IRC), which incorporates SMA wires embedded within
the concrete.
14. APPLICATIONS
Piping
The first consumer commercial application was a shape-memory coupling for piping.
e.g. oil line pipes for industrial applications, and water pipes.
Use of memory alloys for coupling tubing: A memory alloy coupling is expanded (a) so it fits over the tubing
(b). When the coupling is reheated, it shrinks back to its original diameter (c), squeezing the tubing for a tight
fit.
Medicine
Stent- A reinforced graft for vascular application to replace or repair damaged arteries (25mm diameter)
15. APPLICATIONS:
• Optometry:
Eyeglass frames made from titanium-containing SMAs are marketed
under the trademarks Flexon and TITANflex.
These frames are usually made out of shape-memory alloys that have their
transition temperature set below the expected room temperature.
This allows the frames to undergo large deformation under stress, yet
regain their intended shape once the metal is unloaded again.
16. CONCLUSION:
o The many uses and applications of shape memory alloys ensure a bright future for
these metals.
o Research is currently carried out at many robotics departments and materials science
departments.
o With the innovative ideas for applications of SMAs and the number of products on the
market using SMAs continually growing, advances in the field of shape memory
alloys for use in many different fields of study seem very promising.
17. REFERENCES
• Shape Memory Alloy, BTP Report by Saurabh Maghade and Sahil Agarwal.
• http://www.stanford.edu/~richlin1/sma/sma.html
• www.wikipedia.org
• Hodgson DE, Wu MH, Biermann RJ. (1990) Shape memory alloys. ASM Handbook:
ASM International. pp. 897–902
• Wilkes, K. E.; Liaw, P. K.; Wilkes, K. E. (2000). "The fatigue behavior of shape-memory
alloys". JOM 52 (10): 45
• Wu, S; Wayman, C (1987). "Martensitic transformations and the shape-memory effect in
Ti50Ni10Au40 and Ti50Au50 alloys". Metallography 20 (3): 359.
