Terfenol-D actuator behavior under pre- stress and step input current

Magnetostriction is the change in shape of materials under the influence of an external magnetic field as well as under pre- stress. The cause of magnetostriction change in length is the result of the rotation of small magnetic domains. This rotation and re-orientation causes internal strains in the material structure. The strains in the structure lead to the stretching (in the case of positive magnetostriction) of the material in the direction of the magnetic field. During this stretching process the cross-section is reduced in a way that the volume is kept nearly constant. The size of the volume change is so small that it can be neglected under normal operating conditions. Applying a stronger field and pre-stress leads to stronger and more definite re-orientation of more and more domains in the direction of magnetic field. When all the magnetic domains have become aligned with the magnetic field the saturation point has been achieved. (C) 2018 Elsevier Ltd. All rights reserved.