Influence of Microstructure on the Fatigue Performance of Nitinol: A Computational Analysis

Investigation into the influence of microstructure on Nitinol’s macroscopic response is a relatively new research topic. One important finding that is immerging from current studies [1-3], however, is the significance of grain orientation and their distribution (crystallographic texture) on macroscopic behavior by either inhibiting or promoting the stress-induced martensite (SIM) transformation. This study offers a micro-structural explanation for observed macroscopic behavior, in particular Nitinol’s unique fatigue behavior, through Finite Element modelling. ‘V-strut’ stent-like models, capable of accurately simulating Nitinol’s complex transformational behavior on a granular scale, are employed to determine the volume fraction of SIM present in material with varying crystallographic textures. Correlation is then made between the volume fraction of SIM present and the overall macroscopic response.

REFERENCES

[1] Lackmann J. et al., Materials Characterization 62 (2011): 298-303

[2] Barney M.M. et al., Journal of the Mechanical Behavior of Biomedical Materials 4 (2011): 1431-1439

[3] Robertson S.W. et al., Acta Materialia 55 (2007): 6198-6207