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.