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The damping properties associated with hysteretic behavior of the pseudoelastic stress-strain (σ -ε) curves of NiTi shape memory alloy (SMA) wires were studied. Damping was characterized for wires of 2.46 and 0.5 mm diameter using samples of 120 mm in length. The effect of the frequency and size of the wire on the σ -ε curves were studied in the 3 × 10 −5 -3 Hz range, with 8% maximal strain. Damping associated parameters, such as hysteresis width, dissipated energy and specific damping capacity (SDC), defined as the ratio between the hysteretic energy and the maximum strain work over a complete pseudoelastic cycle, show maximum values at a specific frequency for each size diameter. These findings were explained in terms of the temperature effects associated to the heat of transformation. Results show that NiTi wire of 0.5 mm diameter has the highest SDC when cycling around 0.1 Hz while wire of 2.46 mm diameter has the highest SDC at 0.01 Hz. At 1 Hz, the SDC for 0.5 mm diameter wire is around twice that of 2.46 mm diameter wire.

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Shape Memory Alloys (SMAs) are good candidates for solid-state dampers appropriate for the oscillations of bridge stay cables because of their large recoverable strain, hysteresis and reasonable fatigue-life. This work experimentally analyzes the relevant properties of NiTi SMA and conducts facility measurements, frequency analyzes and simulations of the effects of SMA on stay cables. Appropriate phenomenological SMA models were developed and included in a Finite Element (FE) simulation environment. A complete damping solution for bridge stay cables was developed from these experimental analyzes. This paper detail the required properties for a NiTi SMA and analyzes their performance. For instance, the fatiguelife and several of the thermo-mechanical effects influencing the application of NiTi SMAs are outlined. The damping effect of the SMA was studied in two facilities. The first series of measurements was performed using cable 1 of the ELSA facility (JRC-EU, Ispra, Italy). The second was completed in two campaigns at IFSTTAR (Bouguenais, near Nantes in France). The numeric analyzes and simulated results were completely coherent with these experiments: the SMA dampers also drastically reduce the maximum oscillation amplitude induced by the simulated action. The frequency evolution of the damped cable was studied using direct calculations on the signals, the windowed Fourier transform and Morlet wavelets.

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