Characteristics of the magnetoelastic effect in grade 400 NN nickel-zinc ferrite

Abstract

At the present time one uses ferromagnetic metals as the core material for magnetoelastic transducers. Large eddy-current losses limit operating frequency range, however. Ferrite is one of the materials with a high resistance and, therefore, a study of its magnetoelastic characteristics should be of both scientific and practical interest. The choice of grade 400 NN ferrite is explained in this report, and test results pertaining to two forms of magnetoelasticity in this material are shown, these forms having been selected on account of their easy technical application, namely: the amplitude of magnetic induction as a function of the compressive stress, and the amplitude of differential magnetic permeability as a function of the compressive stress. Curves of these two relations have been plotted for values of the magnetic field intensity. Both kinds of characteristics indicate a range of compressive stresses which is well suited for transducer operation. The effect of the magnetization mode on the magnetoelastic sensitivity is also analyzed here: this sensitivity is found to be several times higher than that of steels and, moreover, the position of the operating point not to be critical in the case of ferrite. In the report we also show a statistical evaluation of the test data, on the basis of which the dispersion of the magnetoelastic properties of grade 400 NN ferrite could be estimated. Finally, the effect of mechanical aging on the stability of its characteristics is indicated and the magnitude of its magnetoelastic hysteresis is quantitatively estimated.