Predicting the Magneto-Mechanical Behavior of MSMAs Subject to Complex Load Paths

The microstructure of magnetic shape memory alloys (MSMAs) is comprised of tetragonal martensite variants, each with their preferred internal magnetization orientation. In the presence of an external magnetic field, the martensite variants tend to reorient so that the preferred internal magnetization aligns with the external magnetic field. As a result, MSMAs exhibit the shape memory effect when there is a magnetic field in the vicinity of a material point. Furthermore, the tetragonal nature of the martensite variants allows for a compressive stress to cause variant reorientation. This paper studies the magneto-mechanical behavior of MSMAs under various load paths, including complex loading conditions where both the applied magnetic field and compressive stress vary simultaneously. Typically, MSMAs have been studied experimentally and modeled mathematically with either axial compressive stress or transverse magnetic field varying and the other remaining constant. For each load case, the mathematical models are calibrated with a set of experimental data that mimics those to be predicted. Model parameters have been found to be quite different when the calibration was performed with experimental results from different load cases. This work investigates if current models, namely the Kiefer and Lagoudasmodel or the Waldauer et al. model, are capable of predicting both of the typical loading configurations mentioned above with a single calibration. Furthermore, this work uses the Waldauer et al. model to simulate more complex loading, where an MSMA element is subject to simultaneously varying stress and field; this type of loading might occur if an actuator is being designed to displace a variable load over a controlled distance.