TEMPERATURE DEPENDENCE OF A NiTi SHAPE MEMORY ALLOY'S SUPERELASTIC BEHAVIOR AT A HIGH STRAIN RATE

The temperature dependence of the dynamic compressive stress-strain behavior of a NiTi shape memory alloy (SMA) has been determined at a strain rate of 4.35 x 10(2) s(-1) with a split Hopkinson pressure bar (SHPB) modified for obtaining the dynamic stress-strain loops at constant strain rates. The environmental temperature was varied from 0 to 50 degrees C, where the SMA exhibits superelastic behavior through stress-induced martensite (SIM). Experimental results show that both the loading and unloading portions of the stress-strain loop are significantly temperature dependent. Shape memory effect below the austenite finish transition temperature, A(f), and superelastic behavior above A(f), are also observed at the high strain rate.