FEM IMPLEMENTATIONS OF MAGNETOSTRICTIVE-BASED APPLICATIONS

Abstract

Magnetostrictive transducers are used in a broad variety of applications that include linear pump drive mechanisms, active noise and vibration control systems and sonar systems. Optimization of their performance relies on accurate modeling of the static and dynamic behavior of magnetostrictive materials. The nonlinearity of some properties of magnetostrictive materials along with eddy current power losses occurring in both the magnetostrictive material and the magnetic circuit of the system makes this task particularly difficult.

This thesis presents continuum level, three dimensional, finite element analysis of magnetostrictive-based applications for different operating conditions. The Finite element models (FEMs) are based on boundary value problems which are first introduced in the "differential" form (Chapter 2) and then derived to a "weak" form (Chapter 3) suitable for the implementation on the commercial finite element software, FEMLAB 3.1©. Structural mechanics and electromagnetics BVPs are used to predict the behavior of, respectively, structurally-involved parts and the electromagnetic circuit of a magnetostrictive-based application. In order to capture the magnetostrictive material's behavior, static and dynamic three-dimensional multi-physics BVPs include magneto-mechanical coupling to model magnetostriction and the effect of the magnetic stress tensor, also known as Maxwell stress tensor, and electromagnetic coupling to model eddy current power losses (time-harmonic and dynamic case only). The dynamic formulation is inspired by the finite element formulation in the Galerkin form introduced by Perez-Aparicio and Sosa [1], but focuses on a weak form formulation of the problem suitable for implementation in the commercial finite element software FEMLAB 3.1©. Implementation methods of the introduced models are described in Chapter 4. Finally, examples of these models are presented and, for the coupled magneto-mechanical FEM, compared to experimental results.