Stimulating Vibration in Magnetoelastic Beams by the Circumferential Fields of Conducted Currents

Abstract

A means to cause continuous vibratory deflection of a flexurally stressed beam of ferromagnetic, non-zero magnetostriction material, by a longitudinally conducted time varying current is described. The deflection of a horizontal cantilever beam, caused by a weight attached at its free end, is due to a difference in strains between those regions under tensile stress and those under compressive stress, in which these strains have both mechanical and magnetoelastic components. The circumferential uniformity of the field from the current acts to reduce the magnetoelastic strain inequality, hence also a small portion of the beam's deflection. Alternating between current on and current off thus acts to raise and lower the weight. Cycling the applied current at a frequency that matches the prime mode frequency will produce vibratory deflection. Round wire beams, 20-85 mm long, ~1 mm diameter, of three different materials, with attached weights ranging from 60 to 600 mN were made to vibrate at their specific natural frequency (8-80 Hz) with peak strokes up to >10 mm by currents alternating between 0 and up to 9 A.