Rate-dependent response of superelastic Cu-Al-Mn alloy rods to tensile cyclic loads

We report the results of tensile cyclic loading tests conducted to examine the dependence of constitutive relations for superelastic Cu-Al-Mn alloy rods on loading rates. Recently, Cu-Al-Mn alloy rods with diameters up to 8 mm have been developed by the authors, and it has been demonstrated that these rods have excellent superelastic strains of more than 8%, which is comparable to Ni-Ti alloys and far superior to other Cu-based alloys. No information is available, however, on the rate dependence of constitutive relations for Cu-Al-Mn alloys. In this study, we prepare two Cu-Al-Mn alloy rod specimens, whose lengths and diameters are 150 mm and 8 mm, respectively. Their stress-strain relations are examined under the loading frequencies of 0.001, 0.5, and 1 Hz with constant strain amplitude of 4.5%. It was found from the tests that the maximum stress increase in Cu-Al-Mn alloys due to higher loading rate was less than 5%. Thermo-mechanical analysis predicts that stress increase in Cu-Al-Mn alloys is about 1 4 of that in Ni-Ti alloys, which agrees reasonably well with the experimental observations. Such low stress increase is highly desirable in the design of seismic devices such as dampers and isolators.