SHAPE MEMORY ALLOYS

1. SHAPE MEMORY ALLOYS Presented by Pradeep kumar Jaiswal Mechanical Engineering NIT KURUKSHETRA

2. Introduction Shape memory alloys (SMA's) are metals, which exhibit two very unique properties, pseudo-elasticity, and the shape memory effect. Discovered by Arne Olander in the year 1938 The most effective and widely used alloys include Ni Ti (Nickel Titanium), Cu Zn Al and Cu Al NiThe two unique properties described above are made possible through a solid state phase change, that is a molecular rearrangement, which occurs in the shape memory alloy solid state phase change is similar to a molecular rearrangement is occurring, but the molecules remain closely packed so that the substance remain solid

3. General principles • Shape memory metal alloy can exist in two different temperature dependent crystal structures (phases) called martensite (lower temperature ) and austenite ( higher temperature or parent phase ).

5. Shape Memory Effect

6. The Shape memory effect is currently being implemented in: • Coffepots • The space shuttle • Thermostats • Vascular Stents • Hydraulic Fittings (for Airplanes)

7. Pseudo-Elasticity Figure shows the process of pseudo elasticity

8. Examples of applications in which pseudo-elasticity is used are: • Eyeglass Frames • Medical Tools • Cellular Phone Antennae

9. Applications • Aircraft Maneuverability The wire on the bottom of the wing is shortened through the shape memory effect, while the top wire is stretched bending the edge downwards, the opposite occurs when the wing must be bent upwards. The shape memory effect is induced in the wires simply by heating them with an electric current

10. Hinge less shape memory alloy Flap 

11. Medical Applications • Stents • Vena-cava Filters • Dental and Orthodontic Applications

12. Bone Plates • Bone plates are surgical tools, which are used to assist in the healing of broken and fractured bones. • The breaks are first set and then held in place using bone plates in situations where casts cannot be applied to the injured area. • Bone plates are often applied to fractures occurring to facial areas such the nose, jaw or eye sockets. • Repairs like this fall into an area of medicine known as osteosynthesis.

13. Fracture repair

14. Plate and screw

15. Reconstruction of fractured face using bone plates

16. Robotic muscle • Shape memory alloys mimic human muscles and tendons very well. SMA's are strong and compact so that large groups of them can be used for robotic applications,

17. Working of SMA in a Robotic muscle

18. Advantages • Bio-compatibility • Diverse Fields of Application • Good Mechanical Properties (strong, corrosion resistant) Disadvantages • These alloys are still relatively expensive to manufacture and machine compared to other materials such as steel and aluminum. • Most SMA's have poor fatigue properties

19. Future Application • Future applications include engines in cars and airplanes and electrical generators utilizing the mechanical energy resulting from the shape transformations. • Nitinol with its shape memory property is also envisioned for use as car frames. • possible automotive applications using SMA springs include • engine cooling, carburetor and engine lubrication controls.

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