BY,
SHEBINA. A
ROLL NO:
15
Materials that respond to a stimulus in the
form of a mechanical property change such
as a dimensional or a viscosity change.
Eg: Simple amplifier ( converts low energy signal
into high power signal)
Transducer( energy of the amplified control
signal is converted into work)
Actuator Material Classes
Actuator Materials
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Shape Memory Alloys
Magnetostrictive Materials
Piezoelectric & Electrostrictive Materials
Electrorheological & Magnetorheological
Fluids
Shape Memory Alloys
• Ability of material to regain its original
shape when heated to a temp, after being
deformed at a lower temp.
• Shape memory effect occurs in a no: of
alloys, which undergo a special type of
transformation called the ‘
• SMAs are useful for actuators as they
change
shape
 tiffness
 osition
 atural frequency and
 ther mechanical characteristics
in response to temp or electromagnetic
fields. The diverse applications for these
metals have made them increasingly
important
Types:• Copper - aluminium - nickel
• Copper - zinc - aluminium
• Iron - manganese - silicon
(nitinol) – most useful
• Ni-Ti has
that this
alloy exhibits above transformation temperature
~ for a single cycle max 8%
~ for 10,000 cycles 4%
30 to 50degree celsius
~ austenite 100 micro ohms*cm
~ martensite 80 micro ohms*cm
< 1.002
3.06
(youngs Modulus)
~ austenite 83GPa
~ martensite 28 to 41 Gpa
Applications…
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Automobile transmissions
Shock Absorbers
Small Pumps
Window Openers
Automotive
AerospaceMedical
consumer
• Materials which change shape
when placed in magnetic field.
Result of re-orientation of the
magnetic
domains, which produces
internal strain in the material
• Utilised in switches and sensors
~ materials of fixed structure
 metal, ceramic and polymeric composites
 Elastomers filled with ferromagnetic material
powders (carbonyl iron)
 Solid magnetocaloric materials
~ Materials of variable internal structure
 MR Fluids
 Ferro Fluids
 Porous materials saturated with MR Fluids
Electrical energy
mechanical energy
• Giant Magnetostrictive Materials such as rare
earth-iron feature magnetostrains two orders
of magnitude larger than Ni
• Terfenol – D : commercially available
• Positive microstrains of 1000 to 2000ppm are
reported to terfenol-D
• NiMnGa alloys offering a microstrain up 6%
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Young's modulus- 2.5-3.5x1010 N/m3
Tensile strength- 28MPa
Compressive strength- 300MPa
Density- 9250kg/m3
Strain- 0.6%
• Force : offer large force
• Voltage : Its is adjusted by no:of
turns in the coil. With high current
and large section wires, required
magnetic field produced with low
voltage
Applications
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Active noise and vibration cancellation
Sonar
Fuel injection
Medical
Nozzle anti-clogging system (paper)
Screening applications
Metals casting industry
• Sonar transducers – very high power
transducers, long range transmissions
and communication applications
• Hydraulic valves – high speed valves
• Inchworm motors – in low frequency
sound transducers
• Materials that exhibit an electrical polarization
with an applied mechanical stress
• 2 types
~ piezoceramic
 relatively stiff
 Large piezoelectric constant
~ piezopolymer
 Relatively flexible
 Large voltage capacity
Property
Curie temp
(degree Celsius)
Young's modulus
(N/m2 )
Piezoelectric
constant
Maximum
electric field
PZT
(Lead Zirconate Titanate)
PVDF
(PolyVinylidene Floride)
212
100
59.51
310
21210
2310
.41
4010
• A change in dimensions of material
due to the application of electric field
• Non – linear response
• No hysteresis
• A quick response time
• Higher displacements with good
reproducibility
~ APPLICATIONS
• Micro positioned
• Adaptive optics
• Rheology is the science of the flow and
deformation of matter. i.e., response of the
matter to a force or stress
• Viscous fluid can be altered by ER fluids by
application of electric field. Response time is
typically a millisecond
• Colloidal suspensions of dielectric solids in
non-conducting liquids
• In absence of electric field, colloidal
suspension
–fine
particle,
uniformly
distributed
• Electric field applied – dielectric particles
causes the particles to align with the
electric field, causes them to adhere to
adjacent particles which join to form fibrils
• Fibrils modifies the viscosity of fluid
• When electric field is removed, alignment
disappears
Applications
• Tunable shock absorbers used in sports
equipment
FACTORS CONSIDERED FOR ACTUATOR
MATERIALS
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Actuation voltage
Speed of actuation
Actuation force
Stored energy
Electrical resistivity
Mechanical quality factors
Resistance to fracture
Young’s modulus
Density
Stress
Resistivity