Title page for ETD etd-10072005-094812
|Type of Document
||Dye, Tracy Earl
||An experimental investigation of the behavior of Nitinol
||Master of Science
|Rogers, Craig A.
|Leonard, Robert G.
|Robertshaw, Harry H.
- Shape memory effect
- Nickel-titanium alloys
- Smart materials.
|Date of Defense
Shape memory alloys (SMA) have the unique ability to recover large strains and
generate large recovery stresses via a repeatable martensitic transformation. Stressstrain
and shape memory effect characteristics are needed in order to develop SMA
force actuator design methods. Moreover, constitutive models able to quantitatively
predict these characteristics and thus be useful as engineering design tools are also
An experimental apparatus designed to characterize the mechanical behavior of SMA
was built and utilized. The apparatus is used specifically to gather stress-strain and
shape memory effect characteristics from nitinol wire whereby mechanical properties
associated with the material are determined. Phenomena such as the R-phase and
stress induced martensite serration are investigated. A one-dimensional constitutive
model is presented that quantitatively predicts stress-strain and shape memory effect
behavior and was developed with the intention of being an engineering design tool for SMA force actuators. Experimental stress-strain and shape memory effect
results are compared against that predicted by the model with the intention of verifying
the model. The model displays the ability to predict stress-strain behavior
that is in good quantitative agreement with experiment. The model also displays the
ability to predict hysteric shape memory effect behavior for free, controlled, and restrained
recovery cases of selected prestrains that is in good quantitative agreement
with experiment. The model is unable to predict shape memory effect behavior such
as the R-phase. Demonstrating the ability to experimentally investigate a constitutive
model will hopefully inspire further combined experimental and theoretical
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