Effect of cyclic stress on Terfenol-D

A rod of grain oriented Terfenol-D has been subjected to cyclic uniaxial stress of /spl plusmn/100 MPa about a mean preload of /spl sim/120 MPa applied along the <112> grain growth axis. The magnetostrictive strain and d-coefficient measured under uniaxial preload and quasi static magnetic fields are shown to increase after the initial 10/sup 6/ cycles of stress. The characterisation of the magnetomechanical behaviour from resonance analyses indicates a slight hardening of the material after /spl sim/6/spl times/10/sup 7/ cycles and that to regain optimum magnetomechanical coupling, the bias preload and DC bias fields require adjustment in keeping with the effects of the stress cycling. These initial results indicate that magnetostrictive devices constructed from Terfenol-D offer a significant advantage compared with ceramic (PZT) actuators when applied in load bearing situations.