Experimental Study of Preload Decay in Threaded Fasteners Application

The Nut and bolt assembly used in various mechanical applications are to be studied to find out decay happening due to vibrations applied to it. In this project I aim to study various combinations of threaded fasteners used in particular application such that decay due to vibrations could be explored. A significant advantage of a bolted joint over other joint types, such as welded and riveted joints, is that they are capable of being dismantled. This feature however, can cause problems if it unintentionally occurs as a result of operational conditions. Such unintentional loosening, frequently called vibrational loosening. It is important for the Designer to be aware of the bolt loosening mechanisms which can operate in order to design reliable joints. This research describes the dissertation work of studying the behavior of loosening mechanism considering the bolt preload decay. After review of literature it was concluded in this review that the most occurring root cause of loosening is side sliding of the nut or bolt head relative to the fastened joint, resulting in the relative motion occurring within the threads. If this does not occur or can be prevented, then the loosening of bolts can be reduced.