Magnetostrictive Sensors and Actuators

We have noted that for smart structural applications magnetostrictive materials, like Terfenol-D, are as good as piezoelectric materials. The free-strain or the maximum strain under no-load condition in Terfenol-D is about 2000 μ-strain, which is comparable to free-strain of polycrystalline piezoelectric material; the band-width of the material is up to MHz level indicating it's superiority over SMA. Also, because of higher modulus of elasticity, the energy density of Terfenol-D is maximum among all the smart materials. Here, we will discuss how one can utilize these properties in developing actuators and sensors.

Many researchers have developed mini and micro-actuators using Terfenol-D. Consider for example, the mini-actuator developed by Anjannappa et al. A typical magnetostrictive mini-actuator is shown in Fig. 33.1.