Actuating a Magnetic Shape Memory Element Locally with a Set of Coils

Andrew Armstrong,Peter Müllner

doi:10.3390/met11040536

Abstract

The local actuation of a magnetic shape memory (MSM) element as used in an MSM micropump is considered. This paper presents the difference between an electromagnetic driver and a driver that uses a rotating permanent magnet. For the magnetic field energy of the permanent magnetic drive, the element takes in a significant stray field. In a particular case, energy reduction was 12.7 mJ. For an electromagnetic drive with an identical size of the MSM element, the total magnetic field energy created by the system was 2.28 mJ. Attempts to experimentally nucleate twins in an MSM element by energizing an electromagnetic drive failed even though the local magnetic field exceeded the magnetic switching field. The energy variation is an order of magnitude smaller for the electromagnetic drive, and it does not generate the necessary driving force. It was assumed in previous work that the so-called magnetic switching field presents a sufficient requirement to nucleate a twin and, thus, to locally actuate an MSM element. Here, we show that the total magnetic field energy available to the MSM element presents another requirement.

Highlights

Element Locally with a Set of Coils.Progress in modern technology depends upon novel materials with specific physical and functional properties
The simulation shows the fields induced in a single variant magnetic shape memory (MSM) element with the c-axis oriented horizontally.(a)
An MSM element was exposed to localized magnetic fields in two ways: (1) with a permanent magnet, (2) with sets of electrical coils and yokes

Summary

Introduction

Element Locally with a Set of Coils.Progress in modern technology depends upon novel materials with specific physical and functional properties. Some intermetallic alloys exhibit the shape memory effect, where the material experiences a shape change from an external stimulus such as temperature, magnetic field, and mechanical stress (e.g., [1,2,3]). Magnetic shape memory (MSM) alloys exhibit shape change resulting from magnetic field. Single crystal MSM alloy exhibits a large stroke and short actuation time with the ability to change its size and shape several million times. Upon the application of mechanical stress or a magnetic field, the twin domains reorient and enable high magnetic-field-induced strain. MSM alloys are considered for applications in microactuators, strain sensors [4], energy harvesters [5,6], and micropumps [7,8,9]

Results

Discussion

Conclusion