1. SMART MATERIALS GOPINATH.M M.Tech Istyr AUTOMOTIVE COMPENENTS
11/12/2018

2. DEFINITION:
Smart materials are materials that have one or more properties that can be significantly changed in a controlled fashion by external stimuli, such as stress, temperature, moisture, pH, electric or magnetic fields.
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3. TYPES OF SMART MATERIALS
Piezoelectric materials
Shape memory alloys
Magnetostrictive materials
Magnetic shape memory alloys
pH-sensitive polymers
Halo chromic
Chromogenic systems
Photomechanical materials
Self-healing materials
Thermoelectric materials
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4. PIEZOELECTRIC MATERIALS:
Materials that produce a voltage when stress is applied.
Since this effect also applies in the reverse manner, a voltage across the sample will produce stress within the sample.
Suitably designed structures made from these materials can therefore be made that bend, expand or contract when a voltage is applied.
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5. SHAPE MEMORY ALLOY AND SHAPE MEMORY POLYMERS :
Materials in which large deformation can be induced and recovered through temperature changes or stress changes (pseudo elasticity).
The large deformation results due to martensitic phase change.
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6. HALOCHROMIC MATERIALS:
Materials that change their colour as a result of changing acidity.
One suggested application is for paints that can change colour to indicate corrosion in the metal underneath them.
DIELECTRIC ELASTOMERS (DEs) :
Smart material systems which produce large strains (up to 300%) under the influence of an external electric field.
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7. Change color in response to electrical, optical or thermal changes.
CHROMOGENIC SYSTEM:
Change color in response to electrical, optical or thermal changes.
These include electrochromic materials, which change their color or opacity on the application of a voltage (e.g. liquid crystal displays).
Thermochromic materials change in colour depending on their temperature.
Photochromic materials, which change colour in response to light—for example, light sensitive sunglasses that darken when exposed to bright sunlight.
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8. MAGNETOCALORIC MATERIALS:
Compounds that undergo a reversible change in temperature upon exposure to a changing magnetic field.
THERMOELECTRIC MATERIALS:
Materials to build devices that convert temperature differences into electricity and vice-versa.
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9. TEMPERATURE RESPONSIVE POLYMERS:
Materials which undergo changes upon temperature.
PHOTOMECHANICAL MATERIALS:
Change shape under exposure to light.
SELF-HEALING MATERIALS:
The intrinsic ability to repair damage due to normal usage, thus expanding the material's lifetime
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10. MAGNETIC SHAPE MEMORY ALLOY:
Materials that change their shape in response to a significant change in the magnetic field.
pH-SENSITIVE POLYMERS:
Materials that change in volume when the pH of the surrounding medium changes.
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11. SHAPE MEMORY ALLOY (SMA)
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12. DEFINITION:
A group of metallic alloys which shows the ability to return to their original shape or size (ie., alloy appears to have memory) when they are subjected to appropriate thermal procedure (heating / cooling) are called shape memory alloy (SMA)
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13. Intelligent materials Adaptive materials
SMAs ALSO CALLED:
Shape shifters
Active materials
Smart materials
Intelligent materials
Adaptive materials
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14. SPECIAL FEATURES:
At lower temperature, they have a plastic nature and they can be deformed with the application of a force.
At high temperature they behave like metals and hence induced strain is not recoverable.
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15. Easily deformable phase which exists at low temperature(monoclinic).
PHASES OF SMA’s
Two solid phases
MARTENSITE:
Relatively soft .
Easily deformable phase which exists at low temperature(monoclinic).
AUSTENITE:
Crystal structure at high temperature.
High degree of symmetry (cubic).
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16. TYPES OF SHAPE MEMORY ALLOYS: One –way shape memory alloy:
Exhibits shape memory effect only upon heating .
Two –way shape memory alloy:
Exhibits shape memory effect during both cooling and heating
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17. They have the properties of both metals and ceramics.
EXAMPLES:
They are intermetallic compounds having super lattice structures and metallic –ionic- covalent characteristics.
They have the properties of both metals and ceramics.
Ni – Ti alloy (Nitinol)
Cu – Al – Ni alloy
Cu – Zn –Al alloy
Au – Cd alloy
Ni – Mn – Ga alloy
Fe based alloy
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18. Prepared in vacuum or in a inert gas atmosphere
HOW SMA PREPARED:
Prepared in vacuum or in a inert gas atmosphere
Reason : due to its high reactivity of the titanium present in the compound
Methods: Plasma arc melting, Electron beam melting, Vacuum induction etc.
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19. Twinned martensite becomes deformed martensite at low temperature while loading.
When heated, deformed martensite becomes austensite (shape recovery) and upon cooling gets transformed to twinned martensite.
SMA’s exhibits changes in electrical resistance, volume and length during the transformation with temperature.
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20. PSEUDOELASTIC EFFECT:
Pseudo elasticity occurs in shape memory alloys when the alloy is completely composed of Austensite .
Pseudo elasticity occurs without a change in temperature.
The load on the SMA is increased until the austenite becomes transformed into Martensite simply due to the loading.
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21. This pseudo elastic effect is also called as super elasticity.
The loading is absorbed by the softer martensite, but as soon as the loading is decreased the Martensite begins to transform back to Austensite.
This pseudo elastic effect is also called as super elasticity.
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22. HYSTERSIS:
Hysteresis is generally defined as the difference between the temperature at which the material is 50% transformed to austensite upon heating and 50% transformed to martensite upon cooling. The difference can be upto 20 – 30OC.
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23. PROPERTIES OF Ni – Ti ALLOY: It has high shape memory strain (8.5%).
The density is 6.45 gm/cm3.
It is more flexible
It has high melting point (1300OC)
The transformation temperature varies between -200OC and 110OC.
It has high thermal stability.
It has high corrosion resistance.
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24. APPLICATIONS OF SMA’s: Micro valve (Actuators) Toys and novelties
The thermal conductivity ranges from 8.5(Martensite) to 18 (Austensite) WOC/m.
It has very high yield strength of about 70 to 140 Mps in Martensite form and about 200 to 700 Mps in Austensite form.
APPLICATIONS OF SMA’s:
Micro valve (Actuators)
Toys and novelties
Antenna wires
Thermostats
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25. Artificial hearts and dental Orthodontic applications Eye glass frame
Medical field
Blood dot filters
Artificial hearts and dental
Orthodontic applications
Eye glass frame
Cryofit hydraulic couplings
Springs, shock absorbers, and valves
Stepping motors
Titanium – aluminum SMA
AUTOMOTIVE COMPONENTS
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26. SNAP ON PIEZOELECTRIC MATERIALS:
The best-known application is the electric cigarette lighter:
Pressing the button causes a spring-loaded hammer to hit a piezoelectric crystal, producing a sufficiently high voltage electric current that flows across a small spark gap, thus heating and igniting the gas.
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27. The portable sparkers used to light gas grills or stoves work the same way, and many types of gas burners now have built-in piezo-based ignition systems.
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28. THANK “U”
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