2. 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)
5. 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 ‘
6. • 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
7. Types:-
• Copper - aluminium - nickel
• Copper - zinc - aluminium
• Iron - manganese - silicon
(nitinol) – most useful
• Ni-Ti has that this
alloy exhibits above transformation temperature
8. ~ 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
10. • 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
11. ~ 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
12. 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%
14. • 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
15. Applications
• Active noise and vibration cancellation
• Sonar
• Fuel injection
• Medical
• Nozzle anti-clogging system (paper)
• Screening applications
• Metals casting industry
16. • Sonar transducers – very high power
transducers, long range transmissions
and communication applications
• Hydraulic valves – high speed valves
• Inchworm motors – in low frequency
sound transducers
17. • 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
18. Property PZT (Lead Zirconate Titanate) PVDF (PolyVinylidene Floride)
Curie temp
(degree Celsius) 212 100
Young's modulus
(N/m2 ) 59.51 310
Piezoelectric
constant 21210 2310
Maximum
electric field .41 4010
19. • 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
21. • 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
22. • 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
24. FACTORS CONSIDERED FOR ACTUATOR
MATERIALS
• Actuation voltage
• Speed of actuation
• Actuation force
• Stored energy
• Electrical resistivity
• Mechanical quality factors
• Resistance to fracture
• Young’s modulus
• Density
• Stress
• Resistivity
