Equivalent strain and stress models for the effect of mechanical loading on the permeability of ferromagnetic materials

An equivalent strain/stress approach is proposed for modeling permeability change in ferromagnetic materials due to mechanical loadings. The model can be used for transforming complex multiaxial mechanical loadings into equivalent uniaxial loadings parallel to the magnetic field, such that the permeability can be predicted only based on uniaxial measurements. Contrary to earlier approaches, the new definition of the equivalent strain/stress also accounts for shear strain/stress with respect to the magnetic field. The results are shown to match well measurements under multiaxial stresses.