Actuators and actuator materials

1. BY,
SHEBINA. A
ROLL NO:
15

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)

3. Actuator Material Classes

4. Actuator Materials
• Shape Memory Alloys
• Magnetostrictive Materials
• Piezoelectric & Electrostrictive Materials
• Electrorheological & Magnetorheological
Fluids

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

9. Applications…
• Automobile transmissions
• Shock Absorbers
• Small Pumps
• Window Openers
• Automotive
• Aerospace-
• Medical
• consumer

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%

13. • Young's modulus- 2.5-3.5x1010 N/m3
• Tensile strength- 28MPa
• Compressive strength- 300MPa
• Density- 9250kg/m3
• Strain- 0.6%

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

20. ~ APPLICATIONS
• Micro positioned
• Adaptive optics

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

23. Applications
• Tunable shock absorbers used in sports
equipment

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