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62 Shape Memory Materials (Robotics related products)




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This article is from the Robotics FAQ, by Kevin Dowling nivek@cs.cmu.edu with numerous contributions by others.

62 Shape Memory Materials (Robotics related products)


Nickel-titanium alloys were first discovered by the Naval Ordinance
Laboratory decades ago and the material was termed NiTinOL. These
materials have the intriguing property that they provide actuation
through cycling of current through the materials. It undergoes a
'phase change' exhibited as force and motion in the wire.
At room temperature Muscle Wires are easily stretched by a small
force. However, when conducting an electric current, the wire heats
and changes to a much harder form that returns to the "unstretched"
shape - the wire shortens in length with a usable amount of force.
Nitinol can be stretched by up to eight percent of their length and
will recover fully, but only for a few cycles. However when used in
the three to five percent range, Muscle Wires can run for millions
of cycles with very consistent and reliable performance.

            Table 1.  Flexinol Muscle Wire Properties
-----------------------------------------------------------------
               Wire    Linear  Typical  Deform. Recovery  Typical
Wire       Diameter    Resist. Current  Weight*  Weight*   Rate**
Name       (microns)  (ohm/m)     (mA) (grams)   (grams)  (LT/HT)
-----------------------------------------------------------------
 Flexinol 037     37       860       30       4       20    52/68
 Flexinol 050     50       510       50       8       35    46/67
 Flexinol 100    100       150      180      28      150    33/50
 Flexinol 150    150        50      400      62      330    20/30
 Flexinol 250    250        20    1,000     172      930     9/13
-----------------------------------------------------------------
   * Multiply by 0.0098 to get force in Newtons
  ** Cycles per minute, in still air, at 20 Centigrade
     LT = low temp 70 degrees C, HT high temp 90 degrees C

Research into shape memory alloys, polymer gels and micromechanism
devices is ongoing. Library browsing is a must to get recent
information on these areas.

"Mondotronics "
524 San Anselmo Ave.,
#107
San Anselmo, CA 94960
tel: 415.455.9330
tel: 800.374.5764
fax: 415.455.9333
net:
A number of muscle wire (nitinol) projects including a small walking
machine. Book and sample kit with 1m each of 50,100 and 150 um wire
- enough to build all 14 projects in book. [59]Mondo

"Memry Technologies "
57 Commerce Drive
Brookfield, CT 06804
tel: 203.740.7311
fax: 203.775.2359
Memry sell a Mitsubishi developed polyurethane based Shape Memory
Polymer. The material undergoes property changes in hardness,
flexibility, elastic modulus and vapor permeability under
temperature change. Medical applications is one focus for this
material.

"Milford Instruments "
United Kingdom
tel: (0977) 683665
fax: (0977) 681465.
Importers of the Parallax BASIC Stamps and Muscle Wires into the UK.

"TiNi Alloy Company "
1621 Neptune Drive
San Leandro, CA 94577
Sheets and wire of NiTinOL alloys.

10.2.3 Other Actuators (Robotics related products)

"Bridgestone Corporation "
3-2-25 Nishikubo,
Musashino City, Tokyo 180.
tel: 0422 54 5820
Rubbertuators: Rubber-based device that bends under applied
pneumatic pressure. For a rotation unit typical rotation angles are
360,120,90 degrees for linear unit the contraction rate cannot
exceed 20%.

 

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