C. Maletta, University of Calabria, Arcavacata Rende (CS), Italy; M. L. Young, Ruhr University, Bochum, Germany
Nickel-Titanium shape-memory alloys (SMAs) are prevalent in many engineering and medical applications due to their unique features, namely the shape memory and superelastic effects. As a consequence, much research has been carried out in order to better understand the mechanical and functional behavior of NiTi SMAs. However, few research programs have been devoted to the study of the fracture behavior of NiTi SMAs. This topic is of great interest since the stress-induced martensitic transformation occurs in the crack tip vicinity, which results from from highly localized stresses. Recently, the formation of martensite near the crack tip of NiTi alloys have been observed by synchrotron X-ray microdiffraction analysis [1], and some numerical studies have been carried out to better understand the effects of phase transformation on the crack tip stress distribution [2]. In this investigation, the extent of the transformed region, as well as its effects on the crack tip stress distribution, is analysed by an analytical model [3]. Predictions from this model are compared with results from synchrotron X-ray microdiffraction measurements. Finally, the effects of thermo-mechanical parameters on the crack tip stress distribution are examined.
References
[1] S. Gollerthan, M.L. Young, A. Baruj, J. Frenzel, W.W. Schmahl, G. Eggeler, 2009, ”Fracture mechanics and microstructure in NiTi shape memory alloys”, Acta Materialia, Vol. 57, pp. 1015-1025.
[2] G.Z. Wang, 2006, ”Effects of Notch Geometry on Stress-Strain Distribution, Martensite Transformation and Fracture Behavior in Shape Memory Alloy NiTi”, Materials Science and Engineering A, Vol. 434, pp. 269-279.
[3] C. Maletta, F. Furgiuele, ” Analytical modeling of stress-induced martensitic transformation in the crack tip region of nickel-titanium alloys”, Acta Materialia, doi:10.1016/j.actamat.2009.08.060
Summary: In this investigation, the extent of the transformed region, as well as its effects on the crack tip stress distribution, is analysed by an analytical model. Predictions from this model are compared with results from synchrotron X-ray microdiffraction measurements. Finally, the effects of thermo-mechanical parameters on the crack tip stress distribution are examined.
