Manufacturers rely on specialty bolts, nuts and threadlockers to keep fasteners tight and immune to vibration.
Vibration, expansion and contraction can create side-to-side thread movement, which leads to loosening and ultimately fastener failure (left). Fasteners that secure gaskets must be routinely retorqued to counter the compression set of the gasket over time. Otherwise, fasteners will experience relaxation, and their performance will degrade. Graphics courtesy Henkel Corp.
via Fasteners vs. Vibration | 2014-10-03 | Assembly Magazine.