Stress Sensing Characteristics of Non-Contact Magnetoelastic Sensors Based on Substituted Cobalt Ferrite

摘要

We have investigated the stress sensing characteristics of magnetoelastic sensors based on magnetostrictive cobalt ferrite composites, which hold promise for non-contact stress sensing applications due to their high stress sensitivity and low cost. The sensors operate by the fact that applied stresses induce changes in magnetization, which can be detected by measuring the changes in surface magnetic field or permeability. In our previous studies the magnetic and magnetomechanical properties of cobalt ferrite have been improved by chemical substitution and magnetic annealing. In this work, we compared the stress sensing characteristics of the improved cobalt ferrite materials with respect to their sensitivity and linearity. Magnetomechanical tests were performed on selected cobalt ferrite samples bonded to aluminum alloy bars in either tensile or three point bending configurations. Results show that cobalt ferrite substituted with a small amount of manganese or chromium for iron exhibit higher stress sensitivities than the pure cobalt ferrite. This can be interpreted by the results of our recent studies showing that the magnetocrystalline anisotropy, which works against stress-induced changes in magnetization, is lower for the substituted cobalt ferrite.