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Shape Memory AlloysSeth R. Hills

ECE5320 MechatronicsAssignment #1


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Outline Reference list

Links for more information

Major applications

Basic working principle illustrated

A typical sample configuration in application

Major specifications

Limitations

Selection Criteria

Cost information

Where to buy


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References:

http://www.cs.ualberta.ca/~database/MEMS/sma_mems/sma.html

http://smart.tamu.edu/

http://www.abc.net.au/science/news/stories/s832821.htm

Shape memory alloy micro-actuators for medical

applications; J. Peirs, D. Reynaerts, H. VanBrussel, K.U.Leuven - P.M.A. Celestijnenlaan300B, 3001 Heverlee
http://www.cs.ualberta.ca/~database/MEMS/sma_mems/sma.htmlhttp://www.cs.ualberta.ca/~database/MEMS/sma_mems/sma.htmlhttp://smart.tamu.edu/http://www.abc.net.au/science/news/stories/s832821.htmhttp://www.abc.net.au/science/news/stories/s832821.htmhttp://www.abc.net.au/science/news/stories/s832821.htmhttp://www.abc.net.au/science/news/stories/s832821.htmhttp://smart.tamu.edu/http://www.cs.ualberta.ca/~database/MEMS/sma_mems/sma.htmlhttp://www.cs.ualberta.ca/~database/MEMS/sma_mems/sma.html


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To explore further check out thesewebsites and articles:

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

http://www.fz-juelich.de/iwv/iwv1/index.php?index=65

http://www.nims.go.jp/Smart/eng/papers_e.html

http://www.fzk.de/stellent/groups/public/documents/p

ublished_pages/6__6_3__index_ia3f27b85c-2.php
http://www-civ.eng.cam.ac.uk/dsl/sma/smasite.htmlhttp://www.fz-juelich.de/iwv/iwv1/index.php?index=65http://www.fz-juelich.de/iwv/iwv1/index.php?index=65http://www.nims.go.jp/Smart/eng/papers_e.htmlhttp://www.fzk.de/stellent/groups/public/documents/published_pages/6__6_3__index_ia3f27b85c-2.phphttp://www.fzk.de/stellent/groups/public/documents/published_pages/6__6_3__index_ia3f27b85c-2.phphttp://www.fzk.de/stellent/groups/public/documents/published_pages/6__6_3__index_ia3f27b85c-2.phphttp://www.fzk.de/stellent/groups/public/documents/published_pages/6__6_3__index_ia3f27b85c-2.phphttp://www.fzk.de/stellent/groups/public/documents/published_pages/6__6_3__index_ia3f27b85c-2.phphttp://www.fzk.de/stellent/groups/public/documents/published_pages/6__6_3__index_ia3f27b85c-2.phphttp://www.nims.go.jp/Smart/eng/papers_e.htmlhttp://www.fz-juelich.de/iwv/iwv1/index.php?index=65http://www.fz-juelich.de/iwv/iwv1/index.php?index=65http://www.fz-juelich.de/iwv/iwv1/index.php?index=65http://www-civ.eng.cam.ac.uk/dsl/sma/smasite.htmlhttp://www-civ.eng.cam.ac.uk/dsl/sma/smasite.htmlhttp://www-civ.eng.cam.ac.uk/dsl/sma/smasite.html


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Nanomuscles Surgical instruments

Tissue Spreader

Stents (angioplasty)

Coronary Probe

Brain Spatula

Endoscopy: miniaturezoom device, bendingactuator

Force sensor

Smart skin (wingturbulence reduction)

Major applications:


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Definition of a Shape Memory Alloy

http://smart.tamu.edu/overview/smaintro/simple/definition.html

Shape Memory Alloys (SMAs) are a classof metal alloys that can recover apparent

permanent strains when they are heatedabove a certain temperature.


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Basic working principle

SMAs have two stable phases - the high-temperature phase, called austeniteand thelow-temperature phase, called martensite.

the martensite can be in one of two forms:twinnedand detwinned, as shown in Figure 1.

A phase transformation which occurs betweenthese two phases upon heating/cooling is thebasis for the unique properties of the SMAs.



8/22http://smart.tamu.edu/overview/smaintro/simple/definition.html


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The Effects of Cooling in theAbsence of an Applied Load

Upon cooling in the absence of applied load thematerial transforms from austenite into twinned

martensite. (no observable macroscopic shapechange occurs)

Upon heating the material in the martensiticphase, a reverse phase transformation takesplace and as a result the material transforms toaustenite.


Th ll I d d


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Thermally-Induced

Transformation with Applied

Mechanical Load If mechanical load is applied to the material in

the state of twinned martensite (at lowtemperature) it is possible to detwinthe

martensite. Upon releasing of the load, the material remainsdeformed. A subsequent heating of the materialto a temperature above the austenite finishtemperature (A0f*) will result in reverse phasetransformation (martensite to austenite) and willlead to complete shape recovery.

This process results in manifestation of theShape Memory Effect(SME).



11/22http://smart.tamu.edu/overview/smaintro/simple/definition.html

It is also possible toinduce a martensitic

transformation whichwould lead directly todetwinned martensite.If load is applied in theaustenitic phase and thematerial is cooled, thephase transformation

will result in detwinnedmartensite. --Very largestrains (5-8%) will beobserved. --


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Shape Recovery

Reheating the material will result incomplete shape recovery.

The transformation temperatures in this

case depend strongly on the magnitude ofthe applied load. Higher applied load values will lead to higher

transformation temperatures.

There is usually a linear relationship betweenthe applied load and the transformationtemperatures


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Example of Biomedical Application:

The Superelasticityof NiTinol appears

to be much morephysiologiccompared tostainless steel, forexample.

(http://www.memory-metalle.de/html/01_start/index_outer_frame.htm)


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Sample Application:

New metallic muscles that flex with little heat By evaporation and subsequent condensation in

a thin noble gas atmosphere, pure platinum is

converted into particles less than 5 nanometersin size.

These particles are then compacted into ananoporous body. The solid which is generated

is immersed into a conductive fluid (electrolyte)that fills the cavities. Via this electrolyte, an acidor a base, electric charges can be transported toall the nanoparticles of the solid.

http://www.abc.net.au/science/news/stories/s832821.htm


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Sample Configuration:

Application of an electric voltage causes theelectric charge of the electrolyte to change. As aresult, electric charges are also induced on the

surfaces of the nanoparticles. This changed charge

makes the atoms changetheir number of conduction

electrons and, hence, theirchemical identity

http://www.fzk.de/stellent/groups/public/documents


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Discussion of Application

An advantage to this new shape memory alloyis its efficiency. No other alloy or polymer can

compare to its strength and efficiency to

weight ratio. Nanomuscles weigh just one gram but can lift

140 grams, and are preferred to electric motorsas they are far cheaper to produce.


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Major Specifications

Pseudoelasticity

Displacement Range

Fatigue life Electromechanical ratio


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Limitations

Heat Dissipation Range of Motion

Stiffness/Flexibility

Relatively expensive to manufacture andmachine compared to other materials such assteel and aluminum.

Most SMA's have poor fatigue properties; this

means that while under the same loadingconditions (i.e. twisting, bending, compressing) asteel component may survive for more than onehundred times more cycles than an SMAelement.


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Selection Criteria

Range Sensitivity Repeatability Linearity and Accuracy Impedance Nonlinearities Static and Coulomb Friction Frequency Response


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Cost Information

Nanomuscles cost 50 cents eachcompared to US$300 for an equivalentelectric motor.


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Where to buy:

http://www.memory-metalle.de/html/01_start/index_outer_frame.htm

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