Effect of Magnetic Field on the Dynamic Behavior of Ferromagnetic Structures
磁场对铁磁结构动态特性的影响

In this paper,variation of the natural frequency of two types of ferromagnetic structures(i.e.,beam-plate and circular cylindrical shell) due to the applied magnetic field was investigated.The sweeping sine singles from Frequency Spectrum Analyzer actuated the specimen by piezoelectric ceramic.PVDF working as sensors sent the responding singles back to Frequency Spectrum Analyzer.According to the theory of resonance,the natural frequencies of the specimen can be obtained from the frequency responding curve.The same processing can be conducted to obtain the natural frequencies of each mode by changing the magnitude of the external applied magnetic field.The obtained results show that shift of the natural frequencies of beam-plate depends strongly on the direction of the applied field.When the magnetic field is along the length direction of the beam-plate the natural frequencies increase with increasing the magnitude of magnetic field,confirming available model predictions.However,when the magnetic field is in the thickness direction and increases gradually the natural frequency decreases first before it increases again.For the ferromagnetic cylindrical shell,the natural frequencies of the shell increase and finally reach a saturating state with increasing the magnitude of the magnetic field applied in the axial direction.