1. Shape Memory Alloys Team:
High Torque Rotary Actuator/Motor
Team Members:
Uri Desai
Tim Guenthner
J.C. Reeves
Brad Taylor
Tyler Thurston
Gary Nickel NASA JSC Mentor
Dr. Jim Boyd Faculty Mentor
Reid Zevenbergen Graduate Mentor
JC will do the introduction of the team. 1

2. Outline Project Goal: Fall 2008 Fundamentals of Shape Memory Alloys
Design Concepts
Heat Transfer Analysis
Comparison and Recommendations
Future Tasks: Spring 2009
Questions
JC will quickly run through the outline of the presentation.

3. Project Goal: Fall 2008
Research and understand SMAs and their applications
Research current conventions: Electric motors
Develop concepts for a Rotary Actuator/Motor driven by SMAs
Evaluate concepts
Conduct initial analysis of chosen concepts
Select a baseline design
Motivation: Design a motor that will have a higher torque per unit volume and less weight than current motors.
JC will explain the goals of this semester and briefly expand on a few points.

4. What are Shape Memory Alloys?1 2 3 5 4
Deformed Martensite 2
Converting thermal
energy to mechanical
work.
Stress
Uri will discuss what SMAs are, what they do, and how they do it. 3 4 1
Self-Accommodated Martensite
Austenite 5
Temperature Mf Ms As Af

5. Applications of SMAs Aerospace: Medical Other
Airfoils, Boeing Chevrons, STARSYS
Medical
Stints, Instrumentation
Other
Eyeglasses frames, Locking mechanisms,
Underwires, etc.
Tim

6. Electric Motors Most applications for space utilize electric motors.
Electric motors are very dense and therefore there is a weight penalty
Electric motors operate better at higher speeds and lower torque: For low torque applications, a gear box must be added to the motor, which increases the weight.
Pittman motors have been used, in this case, as an example of electric motors with higher than average torque densities.
Highest torque density from Pittman motor studied:
6.83 oz in
Tim

7. Design Concept #1: Wire Rotary Actuator
Bias Spring
Rack and Pinion
Drive Shaft
SMA Wire
Tyler will describe how the mechanism works, including the advantages of the ratchet system.

8. Modeling Wire Behavior: Angular Displacement
Where:
Δθ = angle of rotation (rad)
εtrans = transition strain
L = length of SMA wire
Δx = change in length
R = respective radii
Tyler will then discuss how we obtained the final equation of output shaft rotation as a function of wire contraction.

9. Modeling Wire Behavior: Moments and Torque
Where:
F = respective forces
R = respective radii
k = spring constant
FSMA = SMA recovery force
Δx = change in length
η = efficiency of gear train
n = number of SMA wires
T = torque generated
Brad will continue by discussing the equations leading to the calculation of output torque.

10. Modeling Wire Behavior: SMA Analysis
Where:
εtrans = actuation strain
εelastic = elastic strain
σi = recovery stress
αA: coefficient of thermal expansion for austenite
T -T0: change in temperature
EM: Young’s Modulus for martensite
EA: Young’s Modulus for austenite
dSMA = diameter of SMA wire
n = number of SMA wires
Typical actuation stress values: 21,755-29,000 psi
Substituting above equation into previous moment equation
Brad continued

11. Results Pittman Motor: Model GM14X02 SMA Wire Application
Torque: 107 oz in
Torque Density: 6.83 oz/in2
SMA Wire Application
1 wire with diameter of 5mm or 10 wires with diameter of .02in (equivalent of 5mm)
Torque Density: Max: ° rotation Min: ° rotation
Brad

12. Transformation Temperature
SMA Wires
Company
Transformation Temperature
Sizing
Strain
Dynalloy
Flexinol:: Af: 70° - 100°C
Nitinol:: Af: 80° - 90°C
Flexinol:: 0.001”-0.02”
Nitinol:: 0.004”-0.01”
~4-5%
SMA, Inc.
Pseudoelastic
Af: -25°-125°C
Wire:: 0.012”-0.25”
Small Parts
Varying
Af: 70° - 90°C
Wire: 0.006”-0.1”
~3-5%
Uri will discuss viable option of obtaining SMA wires

13. Design Concept #2: Torque Tube Rotary Actuator
Torque Tubes
Casing
Drive Shaft
Bevel Gears
Uri will describe the setup of the torque tube mechanism

14. Mechanism Operation Torque Tubes Bevel gear attached to drive shaft
Uri will further explain, in detail, how the system functions.
Bevel gear attached to torque tube

15. Torque Tube Attachment Method
Casing
Uri will describe how we plan on overcoming the problem of attaching the torque tubes
Torque Tubes

16. Torque Tube Analysis Where: T = applied torque
J = polar moment of inertia
c = radius of beam
G = shear modulus
L = length of beam
φ = angle of twist
Analyzing a shape memory alloy torque tube:
Where:
γ = shear strain
γthermal= 0 (for isotropic material)
RM = median radius of tube RM

17. Torque Analysis γtrans Max Torque (oz-in) Torque (φ = 8°) 2% 10558.6
3069.4 3%
8348.7 4% 5% 6%
ηtrans=2%
This data based upon:
G = 152, psi
RM= 0.2 in
L = 2 in
J = in4

18. Heat Transfer: Overview
Drives SMA actuation
Cp varies between 0.32 and 0.6 during actuation
Material Properties (Nitinol)
Wire Properties
Torque Tube Properties
Density
Resistivity Cp
Activation
Relaxation
Austenite
6.45 g/cc
76 μΩcm
0.322 J/g°C
78 °C -
Martensite
82 μΩcm
42 °C
Trans.
0.6 J/g°C
68 °C
52 °C
Tim
Radius 1
Radius 2
Length
Voltage
Power
Conv. Coeff.
Tempa
0 cm
0.05 cm
10 cm
0.2 V
0.44 W
0.01 W/cc K
20 °C
Radius 1
Radius 2
Length
Exterior Heat
Conv. Coeff.
Tempa
0.3 cm
0.5 cm
5 cm
110 W – 70 W
0.1 W/cc K
20 °C

19. Heat Transfer: Wire Cycle Time: 8 Seconds Resistive Heating
4 seconds to heat
Forced Air Cooling
4 seconds to cool
Tim
Cycle Time: 8 Seconds

20. Heat Transfer: Torque Tube
Contact Conductive Heating
8 seconds to heat
Forced Air Cooling
10.5 seconds to cool
Tim
Cycle Time: 18.5 Seconds

21. Compare/Contrast and Future Recommendation
SMA Wire Design
SMA Torque Tube Design
Simple and feasible
Flexibility in altering torque versus output rotation: Gear Ratios
Less expensive to manufacture
Light weight
Modular design
Capable of extremely high torque output
Greater complexity
Difficult to implement multi- directional rotation
More expensive to manufacture
Tyler
Recommendation: The SMA Team recommends pursuing the SMA wire application due to its simplicity, feasibility and low cost. This design meets our objective of designing a rotary motor that has high torque per unit volume while maintaining a small weight.

22. Future Tasks: Spring 2009 Detailed analysis of SMA wire application
Detailed design of SMA wire application
Build working prototype
Test and compare results to theoretical
JC will explain the future tasks to be completed next semester.

23. Questions?
We will open the floor up for questions from the audience.