Energy dissipation in shape memory alloy wires under cyclic bending

An analytical formula is developed to predict the energy dissipation in nickel-titanium (Ni-Ti) shape memory alloy (SMA) wires under cyclic bending. Such a formula is derived based on the classical beam theory together with an idealized material curve for SMAs. To demonstrate its accuracy, the formula is first applied to an elastoplastic wire. The results are in agreement with those obtained from finite dement analyses. This is attributed to the close proximity of the neutral plane to the centroidal axis of the cross-section during bending. Numerical results suggest that pre-straining the SMA wires in the form of an are is a feasible way to improve their damping capability. Besides, the amount of energy being dissipated is highly sensitive to the wire diameter, especially for the least pre-strained wires.