Modeling, Manufacturing and Experimental Characterization of NiTi Based Belleville Springs

The properties of NiTi based Belleville springs have been analyzed by numerical simulations and experimental tests. In particular, the unique features of these components, mainly due to stress and/or thermally-induced phase transformation mechanisms, have been preliminary analyzed by finite element simulations, by means of a special constitutive model for NiTi alloys. Subsequently, Belleville washers have been manufactured from a commercial pseudoelastic NiTi alloy, by disk cutting and a successive shape setting by a thermo-mechanical treatment. Furthermore, the thermo-mechanical response of the washers, in terms of isothermal force-deflection curve and thermal cycles between phase transition temperatures, has been experimentally analyzed. The experimental observations confirm the numerical results, i.e. the springs show a significant effect of the temperature on the characteristic curve as well as a marked hysteretic behavior. Due to these properties NiTi Belleville washers can be used as smart elastic elements, i.e. with tunable stiffness and damping, as well as solid state actuators. Furthermore, the marked hysteretic behavior of the washers, in terms of force-deflection response, is particularly useful for the realization of vibration and/or seismic absorbers.