Loosening behaviour of threaded fasteners under cyclic shear displacement

Abstract This paper presents an experimental study on the loosening behaviour of threaded fasteners under cyclic shear displacement. The effects of the initial preload and the amplitude of the shear displacement on the loosening behaviour of the common zinc-coated bolts are investigated. Diamond-like carbon (DLC) coating is utilised to treat the surface of bolts for improving the wear resistance of threads. The thread damage is analysed after the tests. Results show that fatigue wear is the major wear mechanism on the first thread surface. The looseness of threaded fasteners is small under high initial preload and low amplitude of shear displacement. For DLC-coated bolts, the thread damage is slight, and DLC-coated bolts have a better anti-loosening property comparing with zinc-coated bolts.