磁歪振動子の大振幅励振時における内部損失の一測定法

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It seems that there has not been any practical and convenient method by which two kinds of internal loss, magnetic loss and mechanical loss, can be measured and estimated for magnetostrictive transducers excited in large amplitude. In this paper, a new method is proposed which is composed of an analogy of the usual open-short circuit test generally used for power transformer loss measurement. The proposed idea is discussed and examined on 28kHz rectangular ferrite transducers excited in large amplitude. As the method analogous to the open circuit test, the transducer undertest is clamped by the magnetostrictive force of another transducer with the same specification bonded on the acoustic radiation surface. The magnetic loss is immediately measured from electric input power measurements on the transducer at various alternating driving magnetic flux amplitudes (Fig. 2 and Fig. 8). As the method analogous to the short circuit test, the transducer under test is excited at B-type resonance frequency with no acoustic loading. The mechanical loss is immediately measured from electric input power measurements at various vibrational amplitudes of the radiation surface (Fig. 3 and Fig. 10). Leakage impedance must be taken into account in the present measuring method. As a countermeasure for this problem, leakage inductance is compensated by a mutual inductor circuit (Fig. 4). This method is examined by setting a simple searching coil (Fig. 5 and Fig. 6). Excitation winding resistance, which forms a real part of leakage impedance, is immediately known from loss measurement of an air core winding with the same size, and the loss is to be subtracted from the data. The whole internal loss which arises in a practically operating transducer is estimated by the summation of two kinds of internal loss measured by the present measuring method. This is examined by comparing the summation with the actual total loss measured by introducing a dummy load test based on a vibro-meter method (Fig. 13). The result shows a good agreement in the range of vibrational velocity of the radiation surface up to 7cm/sec rms (Fig. 14).
社団法人日本音響学会の論文
1976-05-01

磁歪振動子の大振幅励振時における内部損失の一測定法

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