Title page for ETD etd-10072005-094812


Type of Document Master's Thesis
Author Dye, Tracy Earl
URN etd-10072005-094812
Title An experimental investigation of the behavior of Nitinol
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Rogers, Craig A. Committee Chair
Leonard, Robert G. Committee Member
Robertshaw, Harry H. Committee Member
Keywords
  • Shape memory effect
  • Nickel-titanium alloys
  • Smart materials.
Date of Defense 1990-08-05
Availability unrestricted
Abstract
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 needed.

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 SMA research.

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