Actuation and transduction by giant magnetostrictive alloys

Since the discovery and understanding of the magnetic properties of the rare earth elements, the transduction properties of magnetostrictive alloys has improved significantly over earlier nickel based alloys. Alongside the advances in permanent magnet technology, novel compounds containing terbium, dysprosium and iron are now available in commerical quantities. Given giant magnetostrictive strains (similar to 1200 ppm) coupled with a high transduction efficiency (> 50%) and a large load bearing capability, all of which can be realised in modest magnetic fields, these new materials are now being employed in a variety of applications. High frequency generation is still dominated by piezoelectrics, However, the new materials have an excellent low frequency response, operate at low voltages and can withstand stress cycling. Non-linear and hysteretic behaviour has been controlled by state of the art digital control techniques and algorithms touch an extent that active vibration cancellation has been successfully demonstrated. (C) 2000 Published by Elsevier Science Ltd. All rights reserved