power generation using shape memory alloys
TRANSCRIPT
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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