1. Determining Micromechanical Strain Matthew Strasberg Cornell University

2. Biomedical Stents Nitinol Superelastic/Shape Memory Half billion Cycle lifetime Design Difficulties http://www.xebradigital.com/img/stent_image.jpg fractures

3. Continuum Mechanics Force FRACTURE

4. Four Micromechanical Processes in Nitinol Elastic Deformation Phase Transformation Twining Plastic Deformation

5. STRAIN

7. Usefulness At what localized strain do these processes occur? How can we determine the localized strain?

8. Geometry Bragg’s Law d

9. Strain

10. Tensor Transformation x y z   Q

11. Strain Calculation

12. Results

13. End Results Macro StrainMedical Use

14. Future Research How much information is needed to find strain? More Complicated Strain Cases Other Micromechanical Processes

15. Acknowledgements Erich Owens Apurva Mehta Sam Webb Stephanie and Adam SSRL SLAC, Department of Energy, SULI NDC