Chapter 6 Flashcards
Advantages of SMA Actuators (5)
- Solid state actuator
- Bio-compatible
- Combined sensor and actuator
- means of activation by electricity, laser, and heat
- low voltage actuation
Disadvantages of SMA Actuators (5)
- Highly nonlinear
- Low bandwidth
- large actuation power
- low efficiency
- limited range of transformation temperature
Achieving Two-Way rotary motion with an SMA wire and Biasing spring
Upon heating of sma wire using electrical current the wire contracts and rotates a rotor. A torsional spring will be loaded. when heat is removed the torsional spring will return the rotor back to initial position.
Operating principle of Cryofit couplings
When the sleeve is in place,
it is heated, and this causes it to shrink in diameter,
swaging the tubes slightly, and forming a strong
union.These cryogenic couplings shrink and form a joint once they reach the operating temperature of the
application.
Explain SMA wire actuators
The SMA actuators are made
as wire, spring or ribbon shape. It is able to produce extreme forces from the viewpoint of volume to force ratio.
Operating principle of Shape Memory Saw-Tooth Bone Fixator
The SMA fixator is in martensite phase when stored in ice. After the fixator is implanted in a patient during the surgery. The temperature of the fixator will eventually rise to the patient’s body temperature, and during this process the fixator will transfer from martensite to
Austenite and return to the the closed configuration shape that it memorizes.
Principle of superelastic SMA for vibration Damping
To complete the cycle on a hysteresis loop, no heating is needed since the superelastic SMA will
return to its original shape (length) during the unloading process
Differenty types of SMA actuators (3)
Valves, robotic fish, controlability of flap movement of airplane,
Operating modes of SMA actuators and examples
-Deformation resistant manufactured with the intent that they may never be deformed beyond the limits that ordinary metals would tolerate (Cell phone antennas, Eyeglass frames, guide wires to guide catheters)
-Shape Restoring intent of returning to its original shape (Homer mammalok hook used for breast tumors, Atrial septal-defect occlusion system used for repairs of
occlusions, or holes, in the atrial wall of the heart)
SMA valves
The re-circulation flow is controlled by means of a piston, which is either in fully open or fully closed position depending on the temperature acting on a spring
Operational modes of superelastc actuators (e.g. stents)
Stents are used to support the inside
circumference of a tubular passage such as an esophagus, bile duct, or blood vessel.
Amplatzer septal occluder (Heart problems e.g. strokes coming from patiens with foramen ovale or holes in atria of the heart)
a device specifically designed to stop blood flow through all types of PFO
