Magnetostrictive actuators are one of the most exciting new actuator technologies available today.  The recent material advances in the area of magnetostriction, mainly TERFENOL-D, have created new design options for mechanical and electrical engineers alike.  As the trend towards an electromechanical world continues more and more "smart materials" such as the rare-earth lanthanides, or giant magnetostrictive materials, will be of great benefit to design engineers.  Here at the University of South Carolina Department of Mechanical Engineering magnetostrictive actuators are being studied for their relevance to future mechatronic applications.    
 

Magnetostrictive materials are materials that exhibit a strain when exposed to a magnetic field.  In other words, magnetostrictive materials undergo a deformation when a magnetic field is present.  These materials are referred to as the Rare-Earth's.  Rare-Earth materials typically consist of the lanthanides group in the transition metals on the periodic table.

 

The difference between traditional magnetostrictive materials as opposed to giant magnetostrictive materials is the amount of strain per unit volume of the material.  Giant magnetostrictive materials are materials that undergo large amounts of strain (i.e., large deformations) for a given applied magnetic field.  One such material in the giant magnetostriction category is TERFENOL-D.  TERFENOL-D is a proprietary alloy consisting of terbium, dysprosium, and iron in varying compositions.

The use of materials such as TERFENOL-D will advance the development of electromechanical devices in mechanical engineering. Meaning, traditional mechanical devices will be replaced by electro-mechanical devices that benefit from magnetostrictive materials. This will usher in a new era in actuator and sensor technology.
 

Some of the recent developments surrounding magnetostrictive applications include solid state speakers, vibration “shake” tables, transducers, various types of sensors, and actuators.  Magnetostrictive devices show potential for replacing traditionally piezoelectric devices as well.  This last claim comes from the fact that magnetostriction is a material property that does not decay over time—experience less hysterisis  Furthermore, a magnetostrictive device is fairly robust as far as wear and tear are concerned.  Recent reports suggest that TERFENOL-D based actuators and sensors exposed to overheating will experience problems, however after the material is brought back to reasonable temperatures it will be functional once more.  This is in contrast to some traditional materials that are ruined after an overheating event.

 

Stay tuned for more information regarding the work being done with magnetostriction here at USC.   

Research