Damping characteristics of a CuZnAlNi shape memory alloy

In this paper the mechanical behavior of copper-based SMA bars and their potential use for dissipating seismic energy is examined. In particular, results obtained from cyclic tests under tension–compression loading of martensitic CuZnAlNi shape memory alloy bars, with two different processing histories (hot rolled or extrusion), are reported as a function of strain amplitude, grain size and frequency. The stress–strain loops were asymmetric with respect to the central point and rather stable, especially for strains up to 2%. The effective module of elasticity diminishes significantly with strain. From hysteretic cycles, an equivalent damping of 12% was obtained for the larger strains imposed. The maximum tensile strain attained before fracture was 3.5%. Frequency, in the range of interest for seismic applications, had only a small influence on the damping values. For the conditions studied in this research, the bars produced from both processing histories presented similar mechanical properties. Fracture, when it occurred, was due to tensile action and it was rather brittle and intergranular.