New explorations of magnetoelastic force transducers wherein bending moments cause magnetic fields to arise

In previous work, a force transducer was described [1] wherein a force, F, applied in such manner as to impose a bending moment, B, on a circumferentially magnetized region of a tubular ferromagnetic member, caused a radial magnetic field, H_R, to arise in the space around the member. The polarity and intensity of H_R were found to vary closely with cosα where α is the position angle (measured from a normal stress, (σ = 0) location). This result was explained by a hypothetical model wherein a quiescently uniform circumferential magnetization, M, was caused to vary with α by the anisotropy associated with the unique stress distribution consequental to B. “Free poles” of density ρ = ∇M thus become the source of H_R. This hypothetical basis of operation of the described device was fully supported by experimental data [1] from tubes of 18% Ni maraging steel and Nickel 200, loaded in a 4 point bending apparatus. The novelty of the underlying phenomenon together with the potential range and utility of devices in which it might be employed, invites more critical exploration, results from which, are described here.