Terfenol-D magnetostrictive linear motor

Halkyard, P

Abstract

Actuators and linear motors are a common way to provide single axis motion and force. Rack
and pinion, chain, belt, cable, screw, hydraulic and electric solenoid are a few of the many
types of actuators available. All have inherent strengths and weakness such as power
consumption, mechanical failure and usually a trade off with speed and resolution.
The thesis investigation is to develop a linear motion actuator based on the magnetic material,
Terfenol-D which alters its shape when subjected to a magnetic field. This phenomenon is
known as magnetostriction which can be defined as a changing of a material's physical
dimensions in response to its magnetization. Terfenol-D has the largest known
magnetostriction, 2000ppm at ambient temperatures [1], of all commercially available
materials. Because of these large strains it is given the term Giant Magnetostriction (GM).
In Terfenol-D the GM is dependent on the direction of the applied magnetic field with respect
to the direction in the crystal: the material elongates in the direction of the field and,
orthogonal to this, the material contracts within the principal of constant volume.
This property has been exploited by other researchers in the past resulting in Terfenol-D being
used as a short stroke conventional actuator in applications requiring large force at both high
and low frequencies, generating a range of applications including surgical instruments,
ultrasonic transducers and many others. It is this property of Terfenol-D that will be exploited
in this project in the development of the magnetostrictive linear motor.
Stepping motors based upon Giant Magnetostrictive (GM) materials are more complex
actuators than those based on a more conventional design. To get a long stroke, they use the
addition of several small steps, each produced by quasi static deformation of the GM
materials.
In this project the Kiesewetter Elastic Wave Motor using Terfenol-D, as referenced in the
abstract, was used as the starting point for the design of a new Terfenol-D based motor. In
particular, the project investigates different topologies of Terfenol-D in the design and
construction of a Magnetostrictive Linear Motor

Citation

Halkyard, P. Terfenol-D magnetostrictive linear motor. (Thesis). Salford : University of Salford

• Thesis Type: Thesis
• Deposit Date: Oct 3, 2012
• Award Date: Jan 1, 2011