2023

Nemov Aleksandr; Saren Andrey; Matikainen Marko; Ullakko Kari; Mikkola Aki

Magnetic shape memory (MSM) alloys are among the most promising smart materials, capable of revolutionizing several multidisciplinary areas, such as soft robotics, digital hydraulics, and multiple biomedical applications. The characteristic aspect of the MSM effect is structure reorientation in a martensite of MSM alloy, associated with the movement of the twin boundary (TB), the interface between differently oriented martensite variants. Even though the MSM effect has been under investigation since its discovery in 1996, there is still plenty of controversy in theoretical predictions based on different assumptions. In our research, we investigated one of the fundamental aspects of the MSM effect – conditions for setting a (TB) in motion. The effect was analyzed for a two-variant specimen of five-layered modulated martensite of Ni-Mn-Ga with a single TB. Three-dimensional finite element analysis of magnetic field was employed, and energy-based criteria for setting the TB in motion was applied, using the results of magnetic field calculation. Results of the simulation study were compared with experimentally determined magnitude of the magnetic field required for initiating the TB movement in the considered specimen, and applicability of the used assumptions was assessed. Findings of the study clarify the role of three-dimensional non-homogeneous distribution of magnetic field across the TB, which is usually not accounted for in theoretical models of the MSM effect. Ways of further development of the approach for the simulation-based prediction of the switching field are proposed.