Fatigue of superelastic NiTi wires under uniaxial loading.

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

Chicago

Congreso; ICOMAT 2017; 2017

Northwestern University

Fatigue is an important issue in applications based on the pseudoelastic behavior of NiTishape memory alloys where the stress induced transformation is inducedrepeatedly. There is a lack in the literature concerning the appropriate characterizationof 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 intrinsicfatigue properties of NiTi wires under uniaxial tensile loading conditions wasdeveloped. The proposed test methodology was applied to characterize thefatigue life under uniaxial tensile loading conditions of commercial ultrafinegrained (40-50 nm) superelastic Ni rich NiTi wires (50.9 at.% Ni). In addition, and for comparisonpurposes, strain controlled experiments were performed in wires in fullyaustenite and fully martensite states. The obtained results indicate adeleterious effect of the stress induced martensic transformation on thefatigue life of superelastic NiTi wires.