FEM simulations of incremental permeability signals of a multi-layer steel with consideration of the hysteretic behaviour of each layer

Shafts for power generation machines have to be inspected in regards to the mechanical-technological properties of the final product material. To save time and costs, the nondestructive 3MA technique, which is based on the measurement of electromagnetic properties of the inspected material, should be used for this purpose. Due to the machining process, the material shows a Multilayerstructure with different residual stress levels, each characterized by its own electromagnetic properties. To simulate signals of the so-called incremental permeability mode of 3MA, the individual electromagnetic properties had to be determined first. Subsequently, FEM methods have been developed, overcoming issues with respect to multiscale geometry and time, and the local hysteretic behavior identification at every point in the material under investigation. The developed computation strategy and the modeling assumptions are validated by a comparison of the numerical simulations with measurements and shows promising results.