Shape Memory Alloys (SMA’s)

1
Shape Memory Alloys (SMAs)

• Daniel Frei
• Utah State University
• ECE 5320
• March 5, 2004

2
Outline

• References
• To Explore Further
• Application
• What is Shape Memory Alloy
• How does it work
• Major Specifications
• A Typical use The Smart Wing
• Another use Robotic Muscles

3
Outline (cont.)

• Advantages
• Limitations
• Who sells this?
• What materials are SMAs?
• Conclusion

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References

• http//www.cs.ualberta.ca/database/MEMS/sma_mems/
  sma.html
• http//smart.tamu.edu/
• http//www.reade.com/Products/General/shape_memory
  _alloys.html
• http//www-civ.eng.cam.ac.uk/dsl/sma/smasite.html
• http//www.fz-juelich.de/iwv/iwv1/index.php?index
  65
• http//www.sma-inc.com/html/_shape_memory_alloys_.
  html

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To Explore Further..

• http//smart.tamu.edu/
• http//www.cs.ualberta.ca/database/MEMS/sma_mems/
  sma.html
• http//www.designinsite.dk/htmsider/m1310.htm
• http//www.sma-inc.com/html/johnson_matthey_home_p
  age.html
• http//www.reade.com/Products/General/shape_memory
  _alloys.html
• http//www-civ.eng.cam.ac.uk/dsl/sma/smasite.html
• http//www.fz-juelich.de/iwv/iwv1/index.php?index
  65
• http//www.sma-inc.com/html/_shape_memory_alloys_.
  html
• http//www.mtm.kuleuven.ac.be/Research/ADAPT/index
  .html
• http//dpwww.epfl.ch/Gotthardt/groupegt.html

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Major Applications

• Coffeepots
• The space shuttle
• Thermostats
• Vascular Stents
• Hydraulic Fittings (for Airplanes)
• Used in the following
• Medical Tools
• Eyeglass Frames
• Bra Under wires
• Cellular Phone Antennae
• Orthodontic Arches

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What is Shape Memory Alloy?

• Shape memory alloys (SMA's) are metals, which
  exhibit two very unique properties,
  pseudo-elasticity, and the shape memory effect.
  Arne Olander first observed these unusual
  properties in 1938 (Oksuta and Wayman 1998), but
  not until the 1960's were any serious research
  advances made in the field of shape memory
  alloys. The most effective and widely used alloys
  include NiTi (Nickel - Titanium), CuZnAl, and
  CuAlNi.
• From http//www.cs.ualberta.ca/database/MEMS/sm
  a_mems/sma.html

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Meaning What ?????

• Shape Memory Alloys are Really Just a smart
  material that returns to its Normal shape and
  size after something like heat has manipulated
  it.
• Picture From http//smart.tamu.edu/

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How does this work???

• The two unique properties described above are
  made possible through a solid state phase change,
  that is a molecular rearrangement, which occurs
  in the shape memory alloy. Typically when one
  thinks of a phase change a solid to liquid or
  liquid to gas change is the first idea that comes
  to mind. A solid state phase change is similar in
  that a molecular rearrangement is occurring, but
  the molecules remain closely packed so that the
  substance remains a solid. In most shape memory
  alloys, a temperature change of only about 10C
  is necessary to initiate this phase change. The
  two phases, which occur in shape memory alloys,
  are Martensite, and Austenite. Martensite, is
  the relatively soft and easily deformed phase of
  shape memory alloys, which exists at lower
  temperatures. The molecular structure in this
  phase is twinned which is the configuration shown
  in the middle of Figure 2. Upon deformation this
  phase takes on the second form shown in Figure 2,
  on the right. Austenite, the stronger phase of
  shape memory alloys, occurs at higher
  temperatures. The shape of the Austenite
  structure is cubic, the structure shown on the
  left side of Figure 2. The un-deformed Martensite
  phase is the same size and shape as the cubic
  Austenite phase on a macroscopic scale, so that
  no change in size or shape is visible in shape
  memory alloys until the Martensite is deformed.
• http//www.cs.ualberta.ca/database/MEMS/sma_mems/
  sma.html

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In other words

• When the material is in the heated phase know as
  the Martensite it is easy to move and
  manipulate. Once it has cooled then it is in the
  Austenite phase and can retains the shape it is
  given. Size and metal characteristics do not
  change throw these processes.
• Pictures from http//www.cs.ualberta.ca/database
  /MEMS/sma_mems/flap.html

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Major specifications

• Must be a SMA
• Critical Tempature (50C-80C)
• Transformation Temperature Range (-250C
  to 200C depending on the material)
• Transformation Hysteresis (4C to 100C)

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A Typical use The Smart Wing
13
A Typical use The Smart Wing

• The smart is a new technology that uses Shape
  memory alloys to Change the Shape of the Wing of
  a Plane to make it more maneuverable. This is
  done by simply sending a electric current throw
  the part of the plane to heat it to the desired
  temperature. This changes the shape of the wing
  making the Plane more maneuverable. This was
  previously done with a heavy Hydraulic system,
  thus significantly reducing the weight of the
  plane. This is demonstrated to the right.
• Pictures from http//www.cs.ualberta.ca/database
  /MEMS/sma_mems/flap.html

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Another use Robotic Muscles
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Another use Robotic Muscles

• One of the biggest problems with robots
  simulating Human behavior is that they have
  difficulting with the simulation of our muscle
  and basic movements. Things like holding a pen
  or a pencil, feeling/touch, or just moving a
  finger are great challenges for Robotics.
• With Shape memory alloys work and simulate human
  muscle very well. When the heat of a wire
  changes the shape and move ability of the metal.
  This is similar to a muscle as a nerve send a
  pulse to the muscle the size doesnt change,
  however it does weaken or strengthen to
  accommodate the need of the movement.
• Pictures is from http//www.cs.ualberta.ca/datab
  ase/MEMS/sma_mems/muscle.html

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Advantages

• Bio-compatibility
• Diverse Fields of Application
• Good Mechanical Properties (strong, corrosion
  resistant)

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Limitations

• expensive to manufacture
• fatigue properties (twisting, bending,
  compressing)
• Extreme Heat and cold
• Must be a SMA
• YOUR IMAGINATION

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Who sells this

• http//www.sma-inc.com/html/johnson_matthey_home_p
  age.html
• http//www.memory-metalle.de/shape-memory-alloy.ht
  ml
• http//content.aip.org/APPLAB/v84/i1/31_1.html

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What materials are SMAs

• a.)Nickel-titanium alloys
• b) Copper-base alloys such as CuZnAl and CuAlNi
• c) Ag-Cd 44/49 at. C
• d) Au-Cd 46.5/50 at. Cd
• e) Cu-Al-Ni 14/14.5 wt. Al and 3/4.5 wt. Ni
• f) Cu-Sn approx. 15 at. Sn
• g) Cu-Zn 38.5/41.5 wt. Z
• h) Cu-Zn-X (X Si,Sn,Al) a few wt. of
• i)In-Ti 18/23 at. Ti
• j) Ni-Al 36/38 at. Al
• k) Ni-Ti 49/51 at. Ni
• l) Fe-Pt approx. 25 at. Pt
• m) Mn-Cu 5/35 at. Cu
• n) Fe-Mn-Si
• o) Pt alloys

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To Conclude..

• SMAs opens a door to a whole new world of
  Technolgy