Dimitris C.Lagoudas Shape Memory Alloy Research Team Aerospace Engineering Department Texas A&M University Intelligent Systems Laboratory An Introduction.

Dimitris C.Lagoudas

Shape Memory Alloy Research Team

Aerospace Engineering DepartmentTexas A&M University

Intelligent Systems Laboratory

An Introduction to An Introduction to Shape Memory Shape Memory AlloysAlloys

Texas A&M University Active Materials Laboratory

What are Shape Memory Alloys? What are Shape Memory Alloys?

•Shape Memory Alloys (SMAs) are metallic alloys that undergo a solid-to-solid phase transformation which can exhibit large recoverable strains. Example: Nitinol

Martensite•Low temperature phase•Monoclinic Crystal Structure

Austenite• High temperature phase•Cubic Crystal Structure

Twinned Martensite Detwinned Martensite

Texas A&M University Active Materials Laboratory

Thermally Induced Phase Transformation in Thermally Induced Phase Transformation in SMAsSMAs

Mf Ms As Af

AusteniteMartensite TEMPERATURE

Mf Ms As Af

AusteniteMartensite TEMPERATURE

(twinned)

(twinned)

Characteristic temperatures:Mf=Martensitic FinishMs=Martensitic StartAs=Austenitic StartAf=Austenitic Finish

Texas A&M University Active Materials Laboratory

Shape Memory Effect: Shape Memory Effect: Stress Free Shape RecoveryStress Free Shape Recovery

TEMPERATURE

ST

RE

SS

Mf Ms As Af

TEMPERATURE

ST

RE

SS

Mf Ms As Af

Twinned Martensite (unstressed)

Detwinned Martensite (stressed - deformed)

Detwinned Martensite (stressed - deformed)

Detwinned Martensite (unstressed - deformed)

Austenite (undeformed)

Texas A&M University Active Materials Laboratory

The Shape Memory EffectThe Shape Memory Effect

T

Cooling

Detwinning

Heating/Recovery

Texas A&M University Active Materials Laboratory

Shape Memory Effect: Shape Shape Memory Effect: Shape Recovery Under StressRecovery Under Stress

TEMPERATURE

STR

ESS

Mf Ms

Detwinned Martensite(stressed) Austenite

As Af

Texas A&M University Active Materials Laboratory

The Pseudoelastic EffectThe Pseudoelastic EffectS

TR

ES

S

TEMPERATURE

Mf Ms As Aff s s f

Austenite

Detwinned Martensite(stressed)

Texas A&M University Active Materials Laboratory

The Pseudoelastic EffectThe Pseudoelastic Effect

Mf

Ms

Af

As

Texas A&M University Active Materials Laboratory

SMA Demonstrations and ApplicationsSMA Demonstrations and Applications

Floral Arrangement SMA Actuated Butterfly: SMA Linear Actuator

Thermobile™ Demonstrator:SMA Properties/Thermodynamics

Texas A&M University Active Materials Laboratory

Where Are SMAs Used?Where Are SMAs Used?

Texas A&M University Active Materials Laboratory

SMAs in Bio-medical DevicesSMAs in Bio-medical Devices

Texas A&M University Active Materials Laboratory

SMA Space ApplicationsSMA Space Applications

Landis G.A., NASA Lewis Research Center, “Materials Adherence Experiment Results from Mars Pathfinder”, 26th Photovoltaic Specialists Conference, 1997

SMA RibbonBolt released

Texas A&M University Active Materials Laboratory

Links

Flexible tail

Joints

Model withoutskin

Model withskin

Rigid nose

SMAs as Linear ActuatorsSMAs as Linear Actuators

Texas A&M University Active Materials Laboratory

Miniaturized Walking RobotMiniaturized Walking Robot

The implementation of SMA wires coupled with a simple DC control system can be used to drive small objects without the addition of relatively heavy motors, gears, or drive mechanisms.

Texas A&M University Active Materials Laboratory

Biomimetic HydrofoilBiomimetic Hydrofoil