Temperature dependent fracture properties of pseudoelastic SMAs: measurements and modeling

Tuesday, May 16, 2017
Sunset Pavilion (Paradise Point Resort )
Dr. Carmine Maletta , University of Calabria, Arcavacata Rende (CS), Italy
Dr. Emanuele Sgambitterra , University of Calabria, Arcavacata Rende (CS), Italy
Mr. Fabrizio Niccoli , University of Calabria, Arcavacata Rende (CS), Italy
Prof. Franco Furgiuele , University of Calabria, Arcavacata Rende (CS), Italy
Temperature dependent fracture properties of pseudoelastic NiTi-based Shape Memory Alloys (SMAs), were analyzed by both experimental measurements and theoretical modeling.

The Stress Intensity Factor (SIF) was estimated, at different values of the testing temperature within the pseudoelastic regime of the alloy, by Digital Image Correlation (DIC) measurements. In particular a fitting procedure was developed, which is based on the William’s expansion series, to calculate the effective SIF from the near crack tip displacement field obtained from DIC.

It was found that temperature plays a very important role on both SIF calculation and on critical fast fracture conditions. In addition, it was demonstrated that Linear Elastic Fracture Mechanics (LEFM) approaches fails in predicting fracture properties of SMAs because they completely neglect the effects of temperature. On the contrary, DIC results are in good agreement with the predictions of a recent theoretical model of the authors. Finally, results revealed that crack tip stress-induced transformations do not represent a toughening effect and this is a completely novel result within the SMA community.

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