Direct magnetostriction and magnetoelastic wave amplitude lo measure a linear displacement

The change of the magnetization intensity induced by a tensile stress in magnetoelastic ribbons can be useful to evaluate a point displacement of an elastic body under deformation. The same measurement can be performed by means of the change in the amplitude of resonant magneteolastic waves, when a longitudinal stress is produced in the ribbons. A comparison between the two techniques is reported in this paper, with the aim to separate the sensitivity limits and the optimum method in different experimental conditions. It is shown how a large stress sensitivity of magnetization is related to a high stress sensitivity of the magnetoelastic waves amplitude but in a different range of applied stress. Generally, the first technique is most useful to investigate a large range of displacement(from 1 mu m up to 1 cm) with a good linearity but a decreasing precision if the displacement increases, while the second technique is the most sensitive and also precise (0.01 mu m) if little displacement ranges are to be investigated. (C) 2000 Elsevier Science S.A. All rights reserved.