Improving global ferromagnetic characteristics of laminations by heterogeneous deformation

Abstract

In this paper, an experimental procedure is presented in order to handle magnetic measurements under uniaxial tensile stress reaching the plastic domain. The main advantage of the proposed procedure is that it does not require an additional magnetic core to close the magnetic flux path through the studied sample. The flux flows only in the sample and no parasitic airgaps are introduced, which avoids the use of H-coil to evaluate the magnetic field, often very sensitive and not easy to calibrate. A specimen of non-oriented (NO) FeSi (1.3%) sheet (M330-35A) is characterized under uniaxial tensile stress. In order to validate the proposed procedure, a comparison with the single sheet tester procedure is carried out. The results obtained by the two procedures are in a good agreement. Moreover, to illustrate the possibilities offered by the proposed procedure, we confirm some results met in the literature. We show that positive plastic strain leads to significant degradation of magnetic behavior. An applied tensile stress on a virgin (un-strained) sample leads to a magnetic behavior degradation. Whereas, on a pre-strained sample, an applied tensile stress results in reducing the deterioration caused by the plastic strain until a stress value called optimum. Above this threshold, the magnetic behavior re-deteriorates progressively.