Modeling the dynamical behavior of memristive {NiTi} alloy at constant stress for timevarying electric current input signals
Abstract
The dynamical electric behavior of a NiTi smart alloy thin filament when driven by time varying current pulses is studied by a structurebased phenomenological model that includes ratebased effects. The simulation model relates the alloy's electrical resistivity to the relative proportions of the three main structural phases namely Martensite, Austenite and Rphase, experimentally known to exist in NiTi alloy lattice structure. The relative proportions of the phases depend on temperature and applied stress. Temperature varies due to the selfheating of the filament by the Joule effect when a current pulse passes and also due to convective/radiative interchange with the ambient. The temperature variation with time causes structural phase transitions, which result in abrupt changes in the sample resistivity as the proportions of each lattice phase vary. The model is described by a system of four 1storder nonlinear differentialalgebraic equations yielding the temporal evolution of resistivity and output voltage across the filament for any given timevarying input current pulse. The model corresponds to a 4thorder extended memristor, described by four state variables, which are the proportions of each of the three NiTi lattice phases and temperature. Simulations are experimentally verified by comparing to measurements obtained for samples selfheated by triangular current input waveforms as well as for passively samples with no current input. Numerical results reproduce very well measurements of resistance vs. temperature at equilibrium as well as the full dynamics of experimentally observed IV characteristic curves and resistance vs. driving current for timevarying current input waveforms of a wide range of frequencies (0.0110~Hz).
 Publication:

arXiv eprints
 Pub Date:
 July 2021
 arXiv:
 arXiv:2107.11060
 Bibcode:
 2021arXiv210711060A
 Keywords:

 Condensed Matter  Materials Science
 EPrint:
 doi:10.13140/RG.2.2.29297.40805