Application of a Magnetic SMA Constitutive Model in the Analysis of Magnetomechanical Boundary Value Problems

摘要

A major complication in measuring material properties of ferromagnetic materials is the influence of the demagnetization effect. The resulting difference between the internal and applied magnetic field depends on the specimen geometry and the distribution of the magnetization inside the sample. This phenomenon also affects the interpretability of magnetic-field induced strain and magnetization data measured for magnetic shape memory alloys, which in turn makes the formulation of reliable constitutive models for these materials difficult. To solve this problem, the approximation of uniform magnetization is usually adopted, in which case a tabularized demagnetization factor can be used to correct the data. In this paper, the validity of this simplification is tested by explicitly solving the magnetostatic problem for relevant geometries, while taking the nonuniform magnetization of a magnetic shape memory alloy specimen into account. In addition to comparing the relation between the volume averaged internal and applied magnetic field, the local variation of the magnetic field and magnetization is analyzed.