Uniaxial Magnetic Pulse Tension of TiNi Alloy with Experimental Strain Rate Evaluation

Background Magnetic pulse methods are known since the 80 s and have become widespread for revealing the patterns of fracture processes. The magnetic pulse method can be modified for uniaxial high strain rate tension and be used to investigate the mechanical and functional properties of materials. Objective The paper shows capabilities of the magnetic pulse method modified for uniaxial high strain rate tension, the scheme of experimental estimation of strain accumulation time and reveals the influence on the basic functional properties of the TiNi shape memory alloy. Method The special shaped TiNi alloy specimens were deformed in tension mode using the modified magnetic pulse method. The one-way shape memory effects were measured and compared with ones after quasi-static tension. We used COMSOL Multiphysics to evaluate possible heating of the specimens during tests. Results The technique resulted in a wide range of plastic strain rates from 2000s(-1) to 10000 s(-1), depending on the specimen's mass and residual strain. COMSOL Multiphysics simulation did not show the presence of induced currents or heating in the working parts of the specimens during the tests. The shape memory effect after magnetic pulse tension was lost compared to the shape memory effect after quasi-static deformation. Conclusions The method allows obtaining various strain rates at the same residual strains without changing in the loading system or dimensions of the working parts of the specimens. The shape memory effect depends on the time for pre-strain accumulation: the shorter the time, the less the shape memory effect upon subsequent heating.