Some New Magneto-Mechanical Torsion Experiments

Abstract

The internal damping of ferromagnetic wires was measured as a function of either a superimposed static stress or an alternating magnetic field. Similar to a static magnetic field, a static stress affects the damping considerably. For example, the logarithmic decrement of a Fe‐40 percent Co wire in torsional vibration is reduced by a factor of 33 when a heavy weight is suspended on the wire. The effect of an alternating magnetic field on the damping was studied by varying the frequency of the field. It is found that the damping reaches a strong minimum at a field frequency of the order of magnitude of 20 cycles/sec. Magnetic hysteresis loss measurements were made which explain this phenomenon in terms of magneto‐mechanical hysteresis.