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AKHIL A R

081ME103

III MECHANICAL-A

POWER GENERATION USINGSHAPE MEMORY ALLOYS

IN POWER PLANTS

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What is a SMA? 

yArne Olanders two very unique

properties-

y Pseudo-elasticity,y Shape memory effect. 

y The most effective and widely

used alloys include NiTi (Nickel -

Titanium), CuZnAl, and CuAlNi. 

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Working of a SMA y In most shape memory alloys, a temperature

change of only about 100 C is necessary to initiatethis phase change.

y The two phases-

yMartensite,

yAustenite.

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SHAPE MEMORY EFFECT

y Below Mf temperature

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PSUEDO ²ELASTICITY 

y Above Af  temperature.

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ApplicationsyBio-compatibility

y Diverse Fields of Application

y Good Mechanical Properties (strong, corrosion

resistant)

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Inspiration !

y Technology emerging in the field of automobile -GM

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My Idea !

y Energy generation from the exhaust of power plants

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SHAPE MEMORY ALLOYS

y Ag-Cd 44/49 at.% Cd

y Au-Cd 46.5/50 at.% Cd

y Cu-Al-Ni 14/14.5 wt.% Al and 3/4.5 wt.% Ni

y

Cu-Sn approx. 15 at.% Sny Cu-Zn 38.5/41.5 wt.% Zn

y Cu-Zn-X (X = Si, Al, Sn)

y Mn-Cu 5/35 at.% Cu

y Ni-Ti (~55% Ni)y Ni-Ti-Nb

y Ni-Mn-Ga

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WHY NITINOL?

y It has very good electrical and mechanical properties,

y long f atigue lif e, high corrosion resistance. 

y A Nitinol wire 0.6 mm in diameter can lift as much as 7.2

kgs.y Nitinol also has the resistance properties which enable it to

be actuated electrically  by joule heating.

y In most cases, the transition temperature of the SMA is

chosen such that room temperature is well below thetransformation point of the material.

y actuator, sensor, and heater all in one material.

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NITINOL

Physical Properties of Nitinol

� Density: 6.45gms/cc

� MeltingTemperature: 1240-1310° C

� Resistivity (hi-temp state): 82 µohm-cm

� Resistivity (lo-temp state): 76 µohm-cm

�Thermal Conductivity: 0.1 W/cm-° C

� Heat Capacity: 0.077 cal/gm-° C

� Latent Heat: 5.78 cal/gm; 24.2 J/gm

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Mechanical Properties of Nitinol

� Ultimate Tensile Strength: 754 - 960 Mpa

�Typical Elongation to Fracture: 15.5%

�Typical Yield Strength (hi-temp): 560 MPa,

�Typical Yield Strength (lo-temp): 100 MPa,

�Approximate Elastic Modulus (hi-tem): 75 GPa,

�Approximate Elastic Modulus (low-temp): 28 Gpa,�Approximate Poisson's Ratio: 0.3

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Operational conditions

yPulling starts at 68o C

yPulling finishes at 78o C

y

Relaxation starts at 52o

CyRelaxation finishes at 42o C

yEffective transition temperature at 70o C

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Conclusion .

yMethod of energy conservation.

yRe-utilization of the exhaust temperature.

y Increasing the overall efficiency of the plant.