Modeling of the strain rate effect, creep and relaxation of a Ni-Tishape memory alloy under tension (compression) - torsional proportionalloading in the pseudoelastic range

Abstract

Several biaxial (tension (or compression)-torsion) proportional andnon-proportional loading experiments are performed by Jesse Lim and McDowell(in 1998) for thin-wall tubes of a Ni-Ti shape memory alloy (SMA). Inaddition to the mechanical behavior, temperature was measured withthermocouples during the experiments, as for Cu-Zn-Al SMA polycrystal(Vacher and Lexcellent in 1991), and their Ni-Ti exhibits an asymmetricalbehavior for tension-compression cycling.A model of pseudoelasticity in SMA performed by Raniecki and Lexcellent (in1998) allowed one to take into account the asymmetry observed intension-compression and the pure shear is extended in order to fit thesebiaxial proportional loadings.The change in temperature linked to the strain rate or during creep orrelaxation is evaluated by the integration of the heat equation.Correlation between the results obtained and the predicted results isfairly good.