In this study, we numerically implemented the first iteration of a novel phase field based theoretical framework to predict the fracture mechanics of Ni2MnGa MSMAs. The proposed variational phase field fracture mechanics model uses an energy balance framework that accounts for the strain energy (elastic and reorientation), Zeeman and magnetic anisotropy energies, as well as the fracture surface energy. The model predictions are preliminarily validated against experimental data obtained during Vickers micro indentation, while a formal experimental program is developed for traditional tests on crack initiation and growth.
This study will report on the characterization of strain fields through DIC in Ni2MnGa alloys under combined tensile and magnetic loading. The DIC approach allows us to observe the evolution of the strain field over the entire sample, concurrent with the evolution of the twin microstructure of the sample, providing a more comprehensive insight on material behavior than traditional strain measurement techniques.
Preliminary results confirm that the strain field, during quasi-static tensile loading, is highly dependent on the nature of the sample microstructure (coarse or fine twin microstructure), and that pinning sites exist along the sample despite being a single crystal sample. The knowledge obtained from this study can be used to expand the realm of MSMA based applications, and to improve constitutive model predictions by accurately predicting the tensile response of the material.
This study aims to compare all MSMA power harvester studies reported to date and identify which design(s) yield highest power and efficiency. The study considers the location of the coil as the main differentiator of the reported designs and starts by generating open circuit voltage with a coil around the MSMA and a biaxial biased magnetic field. The experimental results obtained were compared with the results reported for other power harvesting systems, by normalizing the results with respect to experimental parameters like frequency, number of turns of the pickup coil, cross-sectional area of the pickup coil and sample size. Normalized experimental parameters were then used to calculate and compare the maximum electrical power output of the various power harvesting systems. Results suggest that the side coil setup produces a higher power as compared to the surrounding coil setup. This is primarily because, under the magneto-mechanical loading conditions specific to power harvesting, the maximum change in the MSMAs’ magnetization and correspondingly the largest change in magnetic flux density occurs across its thickness not along its length.
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