Superelastic Deformation Properties of TiNi Shape Memory Alloy

Abstract

The characteristics of energy storage and dissipation in TiNi shape memory alloys were investigated experimentally based on the superelastic properties under various thermomechanical loading conditions. The results obtained can be summarized as follows. (1) The recoverable strain energy increases in proportion to the rise in temperature, but the dissipated work per unit volume depends slightly on temperature. In the case of low strain rates, the recoverable strain energy and dissipated work do not depend on both the strain rate and the temperature-controlled condition. (2) In the case of high strain rates, while the recoverable strain energy decreases and the dissipated work increases in proportion to the rise in strain rate under the temperature-controlled condition, the recoverable strain energy increases and the dissipated work decreases under the temperatureuncontrolled condition.

Low-energy tensile-impact behavior of superelastic NiTi shape memory alloy wires

“…E r and W d change their tendencies because r As and r Af are higher at impact than at quasi-static range. Some authors have already observed this behavior for lower strain rate range, until 10 À1 s À1 (Pieczyska et al, 2007;Tobushi et al, 2005). It is worth to mention that, for complete SIM transformations without elastic deformation of martensitic phase, W d shows similar values below quasi-static limit and at impact strain rates, reaching through a maximum between them.…”

“…This feature is due to the fact that during unloading, temperature in the samples may be higher than the initial temperature of the test, if the strain rate is high enough and therefore transformation stresses will be also higher. At quasi-static range, some works have already confirmed that the temperature during unloading may be higher than that at the beginning (Pieczyska et al, 2007;Ogawa, 1988).…”

“…These results were obtained from the load-unload cycles with complete SIM transformation. There are some works that deal with dissipation energy of superelastic NiTi wires under constant controlled temperature (Lin et al, 1996;Tobushi et al, 1999), but only a few works deal with the natural response of these alloys without controlling the temperature (Pieczyska et al, 2007;Tobushi et al, 2005). These studies are limited to the maximum strain rate of 10 À1 s À1 .…”

Activity of stress-induced martensite transformation in TiNi shape memory alloy studied by infrared technique

“…Shape and size of the loop depend on the deformation parameters, among others on the test temperature, the strain rate and the strain range applied [1]. Furthermore, the higher the temperature the higher the stress level at which the martensite transformation occurs and develops [1][2][3][4][5][6][7][8].…”

“…Since the shape memory alloys are strongly temperature-dependent, the effects of thermomechanical couplings, i.e. interactions between the mechanical and the temperature fields in SMA subjected to stress-induced martensite transformation are of key value for their technical applications [1][2][3][4][5][6][7][8][9][10][11][12][13]. Nevertheless, due to some technical problems, investigations into measurements of the temperature variations accompanying the martensite transformation processes in shape memory alloys has been a recent development [1,2].…”