A full 3D thermodynamic-based model for magnetic shape memory alloys

Abstract

Magnetic shape memory alloys (MSMAs) are interesting materials because they exhibit large recoverable strain (up to 10%) and fast response time (higher than 1 kHz). MSMAs are composed of martensitic variants with tetragonal unit cells and a magnetization vector that is approximately aligned with the short side of the unit cell in the absence of an external applied magnetic field. These variants reorient either to align the magnetization vector with an applied magnetic field or to align the short side of the unit cell with an applied compressive stress. This reorientation leads to a mechanical strain and an overall change in the material's magnetization, allowing MSMAs to be used as actuators, sensors, and power harvesters. This paper builds upon the work of Kiefer and Lagoudas as well as improvements proposed by LaMaster et al. to present a thermodynamic-based continuum model able to predict the response of an MSMA to any three-dimensional (3D) magneto-mechanical loading. The 3D nature of the model requires that the three variants, associated with the three axes of an MSMA single crystal, should all be allowed to evolve. In addition, this model includes evolution rules for the three magnetic domain volume fractions and the rotation of the direction of the magnetization vectors in each variant based on thermodynamic requirements.

Analysis and modification of a common energy harvesting system using magnetic shape memory alloys

“…In this relation, D ii is the magnetization factor along direction i . In general, equation (25) should be coupled with the previous relations, so that the terms related to demagnetization are seen in all final relations for the calculation of the internal variables, which has been done in other presented models (Chen et al, 2014; LaMaster et al, 2015). In this work, as the magnetic field is only along transversal direction (direction 2), magnetization values along directions 1 and 3 are always zero, so only the coefficient D 22 is needed.…”

“…In Figure 6, the influence of adding the demagnetization effect on the MSMA model is investigated. By applying a harmonic stress (shown in Figure 6) along x direction and 0.4 T bias magnetic field along y direction, the stress-strain curve and the relative magnetization-stress are plotted and compared with the experimental data (Heczko, 2005) and the 3D models (Chen et al, 2014; LaMaster et al, 2015). At first, the variants are along y direction, and by applying stress, reorientation occurs and the variants rotate toward x direction.…”

Modeling of magnetic shape memory alloy plates for pressure sensor application

“…The compliance is seen to change as a function of the variant volume fraction. The entire specimen compliance is set equal to the weighted linear average of the compliance of the variants as following (LaMaster et al, 2015)…”

بررسی تأثیر تنش جانبی بایاس‌کننده بر رفتار مکانیکی - مغناطیسی تک کریستال آلیاژ حافظه‌دار مغناطیسی

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