Evaluation of the axial force in an FeCo bolt using the inverse magnetostrictive effect

The use of the magnetic flux density change as a diagnostic parameter in screw tightening torque of bolts is discussed in this study. The proposed methodology uses the inverse magnetostrictive effect, considering that the magnetic flux density changes according to the internal stress of the bolt. In the experiments, we measured the strain and magnetic flux density of the magnetostrictive material FeCo bolt under tightening. Moreover, theoretical and three-dimensional finite element analyses were performed, and the axial force, torque factor, strain, and magnetic flux density were calculated. The experimental, analytical and theoretical results were compared, and the relationship between the bolt's internal axial force and the magnetic flux density was examined. Results show that the magnetic flux density in the FeCo bolt varies with changes in the magnitude of the bias magnetic field, and this study proposes the possibility of a new class of smart bolt. (c) 2020 Elsevier Ltd. All rights reserved.