Finite element modelling of magnetostrictive devices: investigations for the design of the magnetic circuit

Giant magnetostriction of materials such as Terfenol-D rods has potential applications for electromagnetic devices. However, many magnetic problems have yet to be solved. For instance, Terfenol-D has a low relative permeability of about 4 which is responsible for leakage flux and makes it difficult to correctly route both static and dynamic flux in the rods. Thus, to ensure homogeneous magnetic field along the rod, one has to compensate for the flux leakage at the rod ends. To that purpose an extensive computer modelling effort has been performed, on a basic actuator configuration. The Finite Element Method (FEM) has been used to analyse different magnetic circuit configurations. The leakage flux is quantified by the finite element computations. It leads to low magnetic coupling factor and, as a consequence, to low efficiency. Results for different configurations are compared and lead to an optimized design of the magnetic circuits including magnetostrictive rods