Experimental study and characterization the thermomechanical coupling behavior of superelastic shape memory alloy bars subjected to rapid dynamic loads

Abstract

Currently, quasi-static tests are employed to capture the stress-strain relationship of superelastic shape memory alloys (SMA) in the seismic design of structures. However, SMA components experience rapid dynamic loads during earthquakes, which may result in stress-strain relationships that differ significantly from those obtained through quasi-static analysis. To address this challenge, a study was conducted using techniques such as differential scanning calorimetry (DSC) and cyclic uniaxial tensile tests with incremental amplitudes on a series of SMA bars subjected to various heat treatment procedures. The dynamics of phase transition were explored by analyzing the martensite fraction and temperature distribution of the specimens. It was found that the stress experienced by the SMA bars at higher loading rates exceeds that observed in quasi-static analyses. Moreover, the SMA bars may complete the martensite transition at lower strains than intended, potentially leading to premature fractures of SMA components in structures exposed to earthquakes.