Magnetostrictive Composite Bolt Fastening Characteristics and Internal Axial Force

Abstract

Herein, the fastening characteristics and internal axial force of magnetostrictive composite bolts using magnetic flux‐density change are experimentally and theoretically examined. Magnetostrictive composite bolts are fabricated using FeCo wire and epoxy resin by applying magnetic field and preload. The advantage of using a bolt made of magnetostrictive composite materials is that it has reduced weight and can be applied to prestress. Tightening tests are conducted, with and without external‐bias magnetic fields, to measure bolt strain and magnetic flux‐density change. Then, theoretical and finite element analyses are performed to calculate the strain, axial force, and magnetic flux‐density. Theoretical results are compared with experimental results to determine the relationship between tightening torque, internal axial force, and magnetic flux‐density change. It is found that the applied magnetic field and preload conditions during fabrication, as well as the bias magnetic field during the tightening tests, have a significant effect on the magnetic flux‐density change of magnetostrictive composite bolts. The results of this study help propose new possibilities for internet of things and structural health monitoring nodes.