Abstract

Magnetic shape memory effect exhibited by certain alloys at room temperature is known for almost 20 years. The most studied MSM alloys are Ni-Mn-Ga alloys which exhibit up to 12% magnetic field-induced strain (change in shape) depending on microstructure. A multibillion cycle operation without malfunction along with their “smart” properties make them very promising for application in electromagnetic (EM) actuators and sensors. However, considerable twinning stress of MSM crystals resulting in magneto-mechanical hysteresis decreases the efficiency and output force of MSM actuators. Whereas twinning stress of conventional MSM crystals has been significantly decreased over the years, novel crystals with Type II twin boundaries (TBs) possess even lower twinning stress. Unfortunately, the microstructure of MSM crystals with very low twinning stress tends to be unstable leading to their rapid crack growth. Whilst this phenomenon has been studied experimentally, the magnetic field distribution in anisotropic single twin-boundary MSM elements has not been considered yet. This paper analyses the magnetic field distribution in two-variant single twin-boundary MSM elements and discusses its effects on magnetic field-induced stress acting on the twin boundary.

Highlights

  • Very low twinning stress is obtained only when a single Type II twin boundaries (TBs) is present. This is distinctly different from the behaviour of Type I TBs which tend to form lamellar structures called fine twins [7, 9]

  • Magnetic field distribution in a single twin-boundary MSM element The analysis summarised in this paper is based on finite element (FE) analysis implemented using commercially available ANSYS Multiphysics software package

  • The magnetic field distribution in non-homogeneous two-variant MSM element is studied with FE analysis and its very non-uniform nature is discussed

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Summary

City Research Online

This is the accepted version of the paper. This version of the publication may differ from the final published version. URLs from City Research Online may be freely distributed and linked to. Reuse: Copies of full items can be used for personal research or study, educational, or not-for-profit purposes without prior permission or charge. Title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. 8th Joint European Magnetic Symposia (JEMS2016) IOP Conf. Study of magnetic field distribution in anisotropic single twinboundary magnetic shape memory (MSM) element in actuators

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