Bolts are basic fastening pieces

Bolts are basic fastening pieces, influencing the safety and reliability of a structural system (Liu et al., 2016). Thread fasteners, such as bolts, have a variety of advantageous applications allowing large machines to be made up of many components for ease in manufacturing as they can generate high clamping forces and retention (Bhattacharya, Sen and Das, 2010). Unfortunately, self-loosening has been determined as a primary failure mode in environments where vibrations occur (Liu et al., 2017). A popular study by Goodier and Sweeney (1945), analysed by many researchers, investigated the loosening mechanism of bolted joints initiated by dynamic loading and unloading, where the change in axial load results in a net effect of a small loosening rotation to the fastener (Dravid, Tripathi and Chouksey, 2014; Liu et al., 2017). However, Bhattacharya, Sen and Das (2010) argue that it’s only a partial explanation as Goodier and Sweeney (1945) did not obtain a complete self-loosening of threaded fasteners. Thus, there are other factors or a combination of mechanisms causing the loosening of bolt joints.