Internal Friction Parameter in Shape Memory Alloys: Correlation Between Thermomechanical Conditions and Damping Properties in NiTi and NiTiCu at Different Temperatures

Among the different functional properties provided by shape memory alloys (SMA), the damping attracted increasing interest in the last decades. Particularly, the exploitation of pseudo-elastic properties to damp or prevent the oscillations of physical systems has received wide attention in civil engineering. In this context and in other practical applications, intrinsic damping properties at low strains are not yet well explored. To fill this gap, in this work, a systematic approach was taken to study the internal friction (IF) coefficient of several NiTi and NiTiCu SMA by tuning the microstructural condition through different thermal treatments. The changing of IF with respect to temperature in tensile, flexural and torsional configurations has been considered; tests have been accomplished at a solicitation strain in the order of 10-4 and at four frequencies (0.5, 1, 10 and 50 Hz). Results allow a broad overview of the intrinsic properties of the considered alloys with encouraging prospect for future applications. A reference scheme was reported in order to individuate the best SMA candidate in the light of the requirements in a wide range of possible applications, being a helpful guideline for the ideation and the design of novel devices.