FORCE TRANSDUCERS BASED ON THE STRESS DEPENDENCE OF COERCIVE FORCE

An alternative measurement regime for magnetoelastic force transducers, based on variations in coercive field, is described. H(c) is shown to be more directly related to the primary magnetic influence of stress, namely, the orientation of effective anisotropy, than conventionally used magnetization related parameters. The stress dependence of H(c) is shown to generally reflect opposing factors associated with rotational and wall displacement magnetization reversal processes. In materials wherein H(c) much less than K/M(s) wall motion dominates and if the product of lambda(s)/K and yield stress is high enough, large monotonic reductions of H(c) with positive (tensile) stress are shown to be possible. A more complex variation of H(c) with increasing compression is similarly expected. Experimental results from a transducer having an 18% Ni maraging steel core support these expectations.