Single crystal anisotropy and coupled stability analysis for variant reorientation in Magnetic Shape Memory Alloys

Abstract

Magnetic Shape Memory Alloys (MSMAs) have been the subject of much research in recent years as potential high-actuation-energy multifunctional materials. In this work we analyze coupled magnetomechanical stability analysis of a variant reorientation mechanism for a single crystal based on a proposed 3-D magneto-mechanically coupled constitutive equations, derived in a consistent thermodynamic way. Discrete symmetry is considered to take into account single crystal anisotropy in the modeling. Analytical results are presented to demonstrate the influence of coupling and anisotropy in the stability of such a material system. Finally, a coupled Boundary Value Problem (BVP) using finite element analysis is performed by considering actual specimen geometry and boundary conditions that are used in the experiments. The numerical simulation reveals localization zones in the solutions due to the loss of ellipticity of the coupled magneto-mechanical problem.

Lie symmetry and conservation laws for magneto-static magnetic shape memory alloys system

“…The constant stress component σ xx = σ , and Λ xx = ε max are known from the experiments. The model parameters A , B , C , D and Y (in (2.3)) are computed from the known material constants (see [31]). The evolution of the volume fraction ξ ( H y ) during forward reorientation is the solution of the following nonlinear algebraic equation: italicΦfalse(Hy,ξfalse)=π−Y=σεmax+μ0normalΔMHy−A2false(1+ξn1−false(1−ξfalse)n2false)+B−Y=0. …”

Study of Non-Homogeneity of Magnetic Field Distribution in Single-Crystal Ni-Mn-Ga Magnetic Shape Memory Element in Actuators due to its Anisotropic Twinned Microstructure

“…When analyzed as part of a complete magnetic circuit, properties of the MSM element affect the total reluctance and, hence the total magnetic field produced by coils and/or permanent magnets. Demagnetization effects related to MSM element's shape also make the understanding of magnetic field distribution in the MSM region based on measurement results challenging [10]. There is a considerable difference between the magnetic field in the MSM element and the magnetic field that can be measured in the air gap.…”

“…There is a considerable difference between the magnetic field in the MSM element and the magnetic field that can be measured in the air gap. The significance of demagnetization and challenges associated with capturing related effects in analytical models have been mentioned numerously in publications e.g., [10]- [12]. However, effects related to geometry, non-homogeneity, anisotropy and non-linearity of magnetic characteristics can easily be taken into account in a FE model, a solution for which is obtained using numerical methods.…”

“…9, it can be concluded that MSM reluctance always decreases with strain. However, the opposite is true for air gap reluctance (10). Therefore, the overall change in the reluctance of magnetic circuit depends on the ratio of these two reluctances.…”

Influence analysis of phase transformation anisotropy of shape memory alloy wires embedded in sandwich plates with flexible cores by a third-order zigzag theory with dynamic three-dimensional elasticity corrections

“…The induced anisotropy not only leads to different material properties in tension and compression but also to distinct and asymmetric stress–strain and transformation curves in tension and compression. Experimental reports have confirmed the realistic asymmetry phenomenon of the stress–strain behaviors of the SMAs [29–35], especially at high strain rates [36]. Based on the inelastic strains due to the martensitic transformation, variant reorientations, and martensite to austenite transformations under thermomechanical loads observed in tension/compression experiments of CuAlNi single crystals, Sittner and Novak [37] developed a simple constant stress averaging approach to model the SMA polycrystal deformation behaviors.…”