Investigation on Mechanical Resonance Induced by Magnetostriction in a Structure Based on Si-Fe Sheets

The noise generated by rotating machines and electrical transformers is harmful and its reduction has been the subject of several studies. Such systems are likely to come into resonance and become noisier. This resonance may come from mechanical or magnetic forces. The phenomenon of resonance is usually studied only if the frequency and the known spatial distribution of the excitation force are consistent with the natural frequency and the shape of the corresponding mode of the structure. We demonstrate in this paper that magnetostriction can induce resonance without, however, knowing its spatial distribution. A ferromagnetic frame made of a stack of non-oriented electrical steel (e.g., low-power transformers for railway applications) is used to confirm that mechanical resonance can be induced by magnetostrictive strain at a very low magnitude in in-plane and out-of-plane directions. Finite-element calculations are performed with laminated model and vibratory measurements are presented. A numerical model based on homogenization technique is also detailed. Then, experimental and computation results are analyzed and compared. Finally, results of resonance under magnetization when double the magnetizing frequency matches the resonance frequency of the ferromagnetic frame are described as well as the corresponding spectrum.