Abstract
High strength and high thermal resistance magnesium (Mg) alloy bolt by using the wrought 9Al-Zn-2Ca alloy was developed for the purpose of fastening the Mg parts of the transportation industry. In the application to vehicles, both loosening and creep properties of the bolt are critical due to the vibration loading and thermal history subjected to the bolts. In this report, we focused on the loosening properties and relaxation of a fastening system using Mg alloy bolts in comparison with ordinal steel bolts. The experimental results revealed Mg bolt has higher resistance against bolt loosening than ordinal steels, which is also supported by theoretical review. Then the Mg bolt-Mg parts-Mg nut system was experimented to investigate the influence of thermal history on the axial force in the bolt. Finite element analysis was executed to explain the decrease of axial force in this fastening system. The result indicated Mg alloy bolt maintains the axial force at low initial clamping force more than steel bolts.
