Magnetostrictive Materials

By

ArunKumar.R

Introduction to Magnetostrictive materials

• Magnetostrictive Materials were discovered in the 1840s by James Prescott Joule, when he noticed that iron changed length in response to changes in magnetism and named the phenomenon the Joule Effect.

• Magnetostrictive materials can convert magnetic energy into kinetic energy, or the reverse, and are used to build actuators and sensors.

•  Magnetostrictive materials expand when exposed to a magnetic field, exhibiting the Joule Effect or Magnetostriction. •This occurs because magnetic domains in the material align with the magnetic field.• Similarly, when the material is strained its magnetic energy changes. This phenomenon is called magneto mechanical effect or Villari Effect.

  

Principle of Magnetostriction

• The origin of this effect is in the atomic or molecular level.

• This occurs because magnetic domains in the materials rotate to align with the magnetic field.

• In the presence of magnetic field the poles of the magnetic domain align themselves along the gradient of the flux lines of the field.

The following fig shows the magnetostriction without preload and magnetostriction with preload

Some kinds of magnetostrictive materials:

• cobalt

• iron

• nickel

• ferrite

• terbium Alloys (Terfenol-D)

• met glass

Preparation Methods

•Crystal Growth Techniques.

•Powder metallurgy.

•Preparation of laminated or fiber composites can be used to prepare the Magnetostrictive Materials economically.

New magnetostrictive materials• A new class of magnetostrictive materials has recently

been intensively investigated.  These materials have been termed Ferromagnetic Shape Memory Alloy Materials (FSMA).  They exhibit a twinning mechanism similar to that observed in traditional SMA materials such as NiTi and CuZn.  However, in a FSMA the shape change may be initiated using an applied magnetic field.

• Another material recently investigated is an iron/gallium alloy termed Galfenol.This alloy exhibits magnetostrictive effect at a volume fraction of 17%   gallium.

Composite Materials •   Polymer matrix composites, using a particulate

form of the magnetostrictive material, essentially eliminate eddy current losses to 100 kHz and beyond.  Furthermore, the polymer matrix used to bind the particulate produces a relatively tough material that can better accommodate tensile and shear loading states.

Applications

• Ultrasonic cleaners

• Ultrasonic pumps

• Sonar applications

• Active vibration and noise control systems

• Tuned vibration absorbers

• Torque sensors.

Thank you