Mechanical behaviour and friction evolution on bolted connections

Bolted connections are widely used to join mechanical and civil structures, which, usually, need to be adjusted or changed during their service life. Well-known mechanical applications are, for instance, the connections among the components assembled on front motorbike suspensions as well as the joints between the wheel hub and the wheel rim of vehicles or even bridge structures. Modern engineering materials used as bolts or substrates (for examples aluminium alloys, titanium alloys and composite materials), produce significant modifications to the mechanical behaviour of mated parts since the friction coefficients are subjected to a dramatic evolution both during and after the first tightening operation. This occurrence leads to a wrong estimation of the actual initial load applied to the screws and, as a consequence, to the connected parts. Furthermore an incorrect selection of bolts could be carried out due to the wrong estimation of actual stress field produced on bolt. In this paper the friction coefficient evolution and the mechanical behaviour of bolted joints have been deeply investigated in order to predict the stress field generated on the connected parts.