It may be noted that the Terfenol-D rods work very much similar to Piezo-stacks. Unlike piezo-actuators, the effect of thickness of a Magnetostrictive Mini Actuator (MMA) is not negligible. Hence, the induced (constrained) strain is related to the free-strain by the following relationship:

(33.1)

where b and t are, respectively, the width and thickness of the host beam, A_m and t_m are the cross-sectional area and thickness of the MMA. E -denotes the modulus of elasticity of the host-beam and E_m denotes the modulus of elasticity of the magnetostrictive material. The expression for the free-strain Λ , contains an additional term - the thermal effect due to current passing through the solenoid and hence Λ is expressed as

(33.2)

where G is the coil-constant,α^/ is the coefficient of equivalent thermal expansion, K and C₂ are two thermal constants which are obtained experimentally and i is the current passed through the magnetizing coil.