Fatigue of superelastic NiTi wires under uniaxial loading

A. YAWNY; JAUREGUIZAHAR, S.; CHAPETTI, M.D.

Chicago

Conferencia; International Conference on Martensitic Transformation 2017; 2017

Northwestern University

Fatigue is an important issue in applications based on the pseudoelastic behavior of NiTi shape memory alloys where the stress induced transformation is induced repeatedly. There is a lack in the literature concerning the appropriate characterization of the intrinsic uniaxial fatigue life of commercial superelastic NiTi wires with ultrafine grain size. Therefore, in the present work an alternative method for accurate evaluation of the intrinsic fatigue properties of NiTi wires under uniaxial tensile loading conditions was developed. The proposed test methodology was applied to characterize the fatigue life under uniaxial tensile loading conditions of commercial ultrafine grained (40-50 nm) superelastic Ni rich NiTi wires (50.9 at.% Ni). In addition, and for comparison purposes, strain controlled experiments were performed in wires in fully austenite and fully martensite states. The obtained results indicate a deleterious effect of the stress induced martensic transformation on the fatigue life of superelastic NiTi wires.