Finite element investigations of bolt clamping force and friction coefficient effect on the fatigue behavior of aluminum alloy 2024-T3 in double shear lap joint

In this paper, the effect of bolt clamping force on the fatigue life of bolted double shear lap joints was investigated numerically. To do so, finite element simulation results were used to illustrate the trends occurred in experimental fatigue tests showing the effect of bolt clamping on improving the fatigue life of double shear lap joints. The results show that clamping force decreases the resultant longitudinal stress at the hole edge thus the fatigue life increases compared to clearance fit specimens. In general, at higher tightening torque longer fatigue lives were achieved, however, below a certain load level the life improvement was discontinued because of fretting occurrence. Also lubricating the specimens reduces the advantages of the clamping force.

► Torque tightening creates compressive hoop pre-stress around the bolted hole.
► The created pre-stress is bigger in the top plane than middle plane of the main plate.
► Lubricating the mating surfaces diminished the advantages of torque tightening.
► Lubricating the mating surfaces reduces the fatigue life almost close to fatigue life of a non-tightened joint.