ce520_lec_#4_sma

CE 520: Introduction to Smart Structures Technologies

Shape Memory Alloys

Hoon Sohn

Department of Civil and Environmental Engineering

Korea Advanced Institute of Science and Technology

Daejeon, Korea

(Lecture #4)

2Civil and Environmental Engineering Department CE520: Smart Structures Technologies

Shape Memory Effect – Video


History of Shape Memory Alloy

In 1932, Swedish physicist Arne Olander observed that a deformed AuCd alloy could returned to its original shape when heated

The first sustained research on SMA is attributed to William Buehler and his colleagues at Naval Ordnance Laboratory in 1961.

Copper-aluminum-nickel (CuAlNi), copper-zinc-aluminum (CuZnAl) and iron-manganeses-silicon (FeMnSi) also exhibit shape memory effects, but Nitinol remains the most widely used shape memory alloy.

SMA can recover upto 10% strains through temperature and stress induced transformations between high temperature austenite and low temperature martensite phases.


Shape Memory Alloys – Basics

Courtesy of DS Grummon, Michigan State University


Phase Transformation of SMA(Temperature Induced Phase Transformation)

Phase Transformation: The change from one alloy phase to another with a change in temperature, pressure, stress, chemistry, and/or time.

Alloy Phase: A particular arrangement of atoms (or crystal structure) in an alloy.

Austenite: The “stiff”, higher temperature phase present in a Nickel-Titanium (NiTi) alloy.

Martensite: The “soft”, lower temperature phase present in NiTi.

Hysteresis: The temperature difference between a phase transformation upon heating and cooling. In NiTi alloys, it is generally measured as the difference between Ap and Mp.

Ph

as

e


Terminology for SMA

Af Temperature:– The temperature at which a shape memory alloy finishes transforming to Austenite

upon heating.

Ap Temperature:– The temperature at which a shape memory alloy is about 50% transformed to

Austenite upon heating.

As Temperature:– The temperature at which a shape memory alloy starts transforming to Austenite

upon heating.

Mf Temperature:– The temperature at which a shape memory alloy finishes transforming to Martensite

upon cooling.

Mp Temperature:– The temperature at which a shape memory alloy is about 50% transformed to

Martensite upon cooling.

Ms Temperature:– The temperature at which a shape memory alloy starts transforming to Martensite

upon cooling.


Temperature/Stress Induced Phase Transformation


Schematic Illustration of SMA Effects

(a) Schematics of the mechanism of martensite deformation in SMAs and shape memory

effect.

(b) Superelasticity and stress-strain-temperature behavior of shape memory

Courtesy of Y. Liu, Nanyang Tech Univ., Singapore


Stress-strain Curve of SMA

Ms = -52 oC, Af = 30 oC

Stress-strain curves at different temperature

Photograph courtesy of H. Funakubo, Univ. of Tokyo


Shape Memory vs. Superelasticity

ε

σ

T

Loading

Unloading

Heating/recovery

Cooling

Shape memory effect Superelastic effectε

σ

Loading

Unloading

Shape Memory– The ability of certain alloys to return to a predetermined shape upon heating via a

phase transformation.

Superelasticity– if deformed slightly above the transformation temperature Af, a superelastic material

can recover all its deformation immediately after the unloading. The superelasticity

arises from the formation and reversion of stress-induced martensite.


Superelasticity vs. Quasiplasticity

Operating temperature determines whether the shape memory alloy material has shape memory effect or superelastic effect.

The transformation temperature can be adjusted by slight changes in alloy composition and through heat treatment.


Illustration of Phase Transformation

Courtesy of DS Grummon, Michigan State University


Shape Memory Alloys (SMA)

Materials that have the shape memory effect include– Nickel-titanium (most common SMA), also called Nitinol

– Copper-based alloys (less expensive than nitinol)

• Cu-Zn-Al

• Cu-Al-Ni

– Iron-based alloys

• Fe-Mn, Fe-Mn-Si, Fe-Pt, Fe-Ni, Fe-Ni-Co

Thermal treatment is required to introduce shape memory or superelastic effect in shape memory alloys– You will not be able to observe any shape memory effect if heat

treatment is not properly done


Nitinol (= NiTi + NOL)

Chart courtesy of Special Metals, Inc


Shape Memory Alloys (SMA)

Chart courtesy of Y. Liu, Nanyang Tech. Univ., Singapore

Merits of Nitinol as a Shape Memory Alloy

Corrosion resistance


Properties of Nitinol

Density, g/cu.cm (lb/cu.in.).............6.45 (0.233)

Resistivity, micro-ohms * cmAustenite.............................approx. 100Martensite............................approx. 70

Corrosion Resistance.....................Similar to 300 series

stainless steel ortitanium alloys

Young's Modulus, GPa, (1,000 ksi)Austenite.............................approx. 83 (12)Martensite............................approx. 28 to 41 (4 to

6)

Yield Strength, MPa (ksi)Austenite.............................195 to 690 (28 to 100)Martensite............................70 to 140 (10 to 20)

Ultimate Tensile Strength,MPa (ksi).............................895 (130)

Transformation Temperatures,deg.C (deg.F).........................-200 to 110 (-325 to

230)

Shape Memory Strain......................8.5% maximum

Photograph courtesy of Johnson Matthey,

Inc.


A list of Applications

Efficient pipe couplers, fasteners, connectors, and clamps

(Ex. Nitinol couplers have been used to join hydraulic

lines in F14 fighter planes since the late 60’s)

Biomedical applications: orthodontic wires, Nitinol hooks

to attach tendons to bone

Fire detector, sprinkler, gas shutoff, cell phone antenna


Applications: Inflatable SMA Antenna

Courtesy of J. Qiu, Tohoku Univ., Japan


Applications: Reusable Hysteretic Damping Device

0 10 20 30 40 50 60-0.02

-0.01

0

0.01

0.02

Dri

ft r

ati

o

(d) 3rd story

0 10 20 30 40 50 60-0.02

-0.01

0

0.01

0.02

Dri

ft r

ati

o

(e) 2nd story

0 10 20 30 40 50 60-0.02

-0.01

0

0.01

0.02

Time (sec)

Dri

ft r

ati

o

(f) 1st story

Uncontrolled

SMAWD-P

Uncontrolled

SMAWD-P

Uncontrolled

SMAWD-P


Applications: Reusable Hysteretic Damping Device

The core component of the reusable hysteretic damping device is superelastic nickel-titanium wire stands.

It has the following favorable characteristics for structural seismic response control: – Damage free under frequent and design basis earthquakes; – Reduced residual drift due to its self-centering capability – Reusable for many strong earthquakes because of the high fatigue life of NiTi

F

+

F

=

F

-1000

-500

0

500

1000

-0.015 -0.01 -0.005 0 0.005 0.01 0.015

Displacement (in)

F (

lb)

Illustration of the self-centering

mechanism of the device

Experimental hysteresis loop of the

proposed damping device


Cyclic Load Test Results of Hesteritic Damping Device

-1500

-1000

-500

0

500

1000

1500

-0.4 -0.2 0 0.2 0.4

Displacement (in)

Lo

ad

(lb

)


SMA for Seismic Hazard Mitigation

Reading: – Seismic design and retrofit using shape memory alloys, by R. Des Roches et al.,

Proc. China-U.S. Millennium Symp. of Earthquake Engineering, Beijing, China,

November 2000.

Courtesy of R. Des Roches, Georgia Tech.Steel Beam-Column Connections with Shape

Memory Alloy Rod as Energy Dissipation Elements


SMA for Seismic Hazard Mitigation

SMA Tendon for Bridge Restrainer

Courtesy of R. Des Roches, Georgia Tech.


SMA for Seismic Retrofit of Historical Structures

Reading: – Progress of application, research and development and design guidelines for

shape memory alloy devices for cultural heritage structures in Italy, by M.G.

Castellano et al., Smart Systems for Bridges, Structures, and Highways,

Newport Beach, March 5-7, 2001

Courtesy of MG Castellano et al., FIP & ENEA, Italy


Bone Repair with SMA

Photograph courtesy of J. Qiu, Tohoku Univ., Japan


Buckling Control

Courtesy of J. Qiu, Tohoku Univ., Japan


Smart Composites

Shape memory alloy (SMA) smart composites are fabricated by embedding SMA wires or plates in polymer matrix.

Such adaptive composites offer the potential to actively control the properties of the composite structures.

An SEM image of the cross section of fabricated TINi/CFRP smart composite is shown on the right.

Courtesy of Y. Xu, SSRC, Japan


New Types of SMA Materials

Magnetic Shape Memory (MSM) materials are a new class smart materials, capable of generating force and motion when exposed to a low magnetic field.

MSM materials combine the large and complex shape changes of SMA with the fast and precise response of magnetic control.

See for more details: www.adaptamat.com/technology/msm/

Photo courtesy of AdaptaMat, Finland


References

Review of Mechanics of Shape Memory Alloy Structures, by V. Birman, Appl. Mech. Rev., 50(11): 629-645, 1997.

Thermomechanical Aspects of NiTi, by J.A. Shaw and S. Kyriakides, J. Mech. Phys. Solids, 43(8): 1243-1281, 1995.

An overview of vibration and seismic applications of NiTi shape memory alloy, by S. Saadat et al., Smart Materials and Structures, 11: 218-229, 2002.

Progress of application, research and development and design guidelines for shape memory alloy devices for cultural heritage structures in Italy, by M.G. Castellano et al., Smart Systems for Bridges, Structures, and Highways, Newport Beach, March 5-7, 2001

Implementation and testing of passive control devices based on shape memory alloys, by M. Dolce et al., Earthquake Engrg. Struct. Dyn., 29(7): 945-968, 2000.


References (Cont’d)

Seismic design and retrofit using shape memory alloys, by R. Des Roches et al., Proc. China-U.S. Millennium Symp. of Earthquake Engineering: Earthquake Engineering Frontiers in the New Millennium, Beijing, China, November 2000.

Engineering Aspects of Shape Memory Alloys, by Duerig, et al., Butterworth Heinemann Publishers, London, 1990.

“Shape memory alloys,” by Hodgson, et al., Metals Handbook, vol.2, 10th Ed., ASM International, 2001.

“Thermomechanical aspects of NiTi,” by Shaw and Kyriakides, J. Mech. Phys. Solids, 43(8): 1243, 1995.

Johnson Matthey (specialized in manufacturing SMA products) – http://www.sma-inc.com

Shape Memory Alloy Data Base at Virginia Tech– http://www.cimss.vt.edu/shape_memory_database.html

Shape memory alloy (SMA) and other smart materials– http://www-civ.eng.cam.ac.uk/dsl/sma/smasite.html

http://www.sma-inc.com/

http://www.cimss.vt.edu/shape_memory_database.html

http://www-civ.eng.cam.ac.uk/dsl/sma/smasite.html

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