Teacher Summer Research Program Texas A&M University June, 2007

1. Aerospace Engineering Shape Memory Alloys Teacher Summer Research Program Texas A&M 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

2. 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

3. 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

4. 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

5. Detwinned Martensite (stressed - deformed) Detwinned Martensite (stressed - deformed) Twinned Martensite (unstressed) Mf Ms As Af Mf Ms As Af Shape Memory Effect: Stress Free Shape Recovery STRESS STRESS Detwinned Martensite (unstressed - deformed) Austenite (undeformed) TEMPERATURE TEMPERATURE http://smart.tamu.edu

6. 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

7. Detwinned Martensite (stressed) Austenite M M A A f f s s s s f f TEMPERATURE The Pseudoelastic Effect STRESS

8. SMAs as Linear Actuators http://smart.tamu.edu

9. Using SMA and SMA technology in the Physics Classroom • Students will be introduced to the properties of SMAs and their uses • After having completed Hooke’s 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:

10. 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.

11. 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

12. 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.

13. 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

14. 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 it’s 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

15. Set up Pictures by: Libana Zamudio-Sirman, TAMU Bright Building

16. Pictures by: Libana Zamudio-Sirman, TAMU Bright Building

17. 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

18. Calculations (continued) • Students will plot the force versus displacement graph using F=mg 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.

19. 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)

20. 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