Teacher Summer Research Program

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Aerospace Engineering Shape Memory Alloys
Teacher Summer Research Program Texas AM
University June, 2007
Libana Zamudio-Sirman, Del Rio High School Dr. D.
Lagoudas and Dr. D. Davis, Faculty Advisors P.
Kumar, PhD. Candidate F. Phillips, REU student
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Shape Memory Alloy Research Team (SMART)

• Faculty, research staff and students
• Interest in developing experimentally verifiable
  constitutive models for Shape Memory Alloys
  (SMAs)
• Design capabilities of active or "smart"
  structures that utilize the shape memory effect
  for shape and actuation control applications

http//smart.tamu.edu
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Facilities and Support

• Use of state of the art thermomechanical
  facilities integrated with dynamics, control,
  flight simulation, and fluid mechanics lab
  facilities called an Intelligent Systems
  Laboratory (ILS) network
• Initiated by TAMU in 1992
• Supported by Army Research Office, Office of
  Naval Research, Air Force Office of Scientific
  Research and the State of Texas

http//smart.tamu.edu
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What is an SMA?

• Unique class of metal alloys that can recover
  apparent permanent strains when they are heated
  above a certain temperature
• Two stable phases
• high-temperature phase - austenite
• low-temperature phase - martensite

http//smart.tamu.edu
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Shape Memory Effect Stress Free Shape Recovery
STRESS
STRESS
Detwinned Martensite (unstressed - deformed)
Austenite (undeformed)
TEMPERATURE
TEMPERATURE
http//smart.tamu.edu
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Shape Memory Effect Shape Recovery Under Stress
STRESS
Detwinned Martensite
(stressed)
Austenite
M
M
A
A
f
s
s
f
TEMPERATURE
http//smart.tamu.edu
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The Pseudoelastic Effect
STRESS
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SMAs as Linear Actuators
http//smart.tamu.edu
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Using SMA and SMA technology in the Physics
Classroom

• Students will be introduced to the properties of
  SMAs and their uses
• After having completed Hookes Law and the
  elastic potential energy, they will be introduced
  to the properties of nonlinear springs, varying
  force constants, etc.
• Students will use the SMA springs (made by the AP
  Physics class for their experiments) and gather
  various data to calculate the spring constants
• Students will use different masses, different
  data collection devices to determine the
  constants and analyze sources of error. Students
  will measure and use the following

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Using SMA and SMA technology in the Physics
Classroom

• Students making the SMA springs will need to be
  prepared to work with sharp objects.
• They will need goggles and must wear close-toed
  shoes, long pants and no billowing sleeves
• If you have the proper furnace, it is recommended
  that you, the teacher place and remove the
  springs using high-heat tongs and heat resistant
  gloves, and only allow the students to handle the
  spring-bolts after sufficient cooling.

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Using SMA and SMA technology in the Physics
Classroom Timeline

• Background on SMAs- one 50-minute class period
• Preparing, training springs, and pre-lab
  assignment-one class period (if you are sending
  them to off-site to be cooked, then the pre-lab
  can be completed in class)
• Pre-lab consists of any sample calculations that
  you may want to review
• Lab- one class period\
• Post lab extension- teacher preference

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Making the SMA Spring

• Begin with pickled, low temperature Nitinol,
  0.025 diameter, round wire
• Wind the wire into the grooves of a 3/8 diameter
  bolt with a pitch of 16 turns/inch to a desired
  length
• The bolt should have small hex-bolt fasteners at
  the ends of the desired length.
• To train the Nitinol into a spring, place it in a
  furnace that has been pre-heated to 500oC for
  five minutes
• You may have to set the springs and have them
  trained somewhere else such as metal-working
  plant, knife maker, or by someone with an
  industrial kiln for annealing.
• After removing it from the furnace allow it to
  cool, then undo the ends and uncoil it from the
  bolt
• The wire will not look like a spring until it is
  heated up again via a low voltage or a lighter.
• If the spring has twists and/or kinks, simply
  undo them and heat that part slowly until it is
  uniform
• Always use tongs and heat resistant gloves when
  handling the hot spring and fire.

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From forced coiled SMA wire to permanent SMA
Spring
Cooled wire pulled off the bolt
Untrained coiled Nitinol wire
To make the spring coil run a current thru it or
simply heat it from one end to other slowly
removing the kinks bit by bit
Heating the coil in the furnace
Pictures by Libana Zamudio-Sirman, TAMU Bright
Building
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SMA Spring Lab

• Metric ruler to determine the length of the
  spring before it is loaded at room temperature
• Students will load the spring and measure its
  displacement
• Students will heat the spring via a battery and
  record the temperature at which the mass began
  rising at a smooth rate of acceleration
• Students will continue to heat the spring and
  record the temperature at which it begins to
  decelerate
• Students will repeat this process 5 times
• Students will use 5 different masses and repeat
  the steps
• Students will use the information to determine
  two spring constants, one for the Martensite
  phase and one for the Austenite phase.
• They will compare this constant to those
  calculated from Hookian Springs in the previous
  lab.
• Students will be using digital thermometers and
  thermocouples to record the temperatures

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Set up
Pictures by Libana Zamudio-Sirman, TAMU Bright
Building
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Pictures by Libana Zamudio-Sirman, TAMU Bright
Building
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SMA Lab Calculations

• All students will have already studied the law of
  conservation of mechanical energy, conservative
  and nonconservative forces and have determined
  sources of work lost to heat and deformation.
• The data calculated in the lab with the SMA
  spring will be used to determine the energy
  stored in this spring versus the energy stored in
  a normal spring of the same length, number of
  turns, and approximate mass density

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Calculations (continued)

• Students will plot the force versus displacement
  graph using Fmg for the force on the spring and
  the stretch of the spring as displacement
• The average slope of the graph will be the spring
  constant k, the spring
• Since the value k changes the students do not
  have a smooth graph and will have to use the
  graphing calculator to find a curve of best fit
• After inputting the data collected from the lab,
  students will use the calculation functions and
  take the first derivative of the function to find
  the slope of the line tangent to the curve at a
  specific point, this will be the k value
• The k value will be used for various calculations
  in the rest of the lab.

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Extras

• Lab-handout
• Purchasing information for Nitinol-handout
• The apparatus can be made from many materials,
  but it should be a frame that is at least 16
  tall and 8 wide with a solid base that can fit a
  metric ruler and possibly the battery. You will
  need L-brackets to secure the frame and ruler to
  the base. Several screws and washers (see
  pictures)

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Many Thanks to the following

• TAMU E3-Dr. Butler-Purry and Julianna Camacho
• Aerospace Engineering- Dr. Lagoudas and Dr. Davis
  and Gary Siedel
• TAMU Aerospace Materials Lab- Parikshith Kumar
  and Francis Phillips and the SMART Team