Effect of interference fitting and/or bolt clamping on the fatigue behavior of Al alloy 2024-T3 double shear lap joints in different cyclic load ranges

• Results show that IF1.5-BC4 specimens have the longest fatigue lives.
• The shortest fatigue lives belong to CF and IF1.5 specimens at low load ranges.
• At high load levels the IF4.7-BC2 and IF1.5 specimens have the shortest fatigue lives.
• The crack initiation location depends on the load range in IF and IF-BC specimens.
• The FE results can predict the effect of techniques on the fatigue life of joints.

Two applied fatigue life improvement techniques of joints, interference fitting and bolt clamping, have been investigated comparing available experimental and finite element simulation results for Al-alloy 2024-T3 double shear lap joint specimens. Fatigue test results of interference fitted, bolt clamped and combined interference fitted-bolt clamped specimens were used to determine the effect of the different techniques on the fatigue life improvement in comparison with clearance fitted specimens. Also the fracture surfaces of the specimens were analyzed post-mortem to determine the fatigue crack initiation (and growth) locations. These locations were correlated to the applied cyclic load range. Results of the finite element analysis were used to help explain the trends observed in the experimentally obtained S-N data. Results showed that the fatigue life improvement not only changes for different techniques and magnitude of interference fit or tightening torque, but also depends on the applied cyclic load range.