Tightening torque effect on fatigue performance of single-lap joints

The present work aims to investigate the fatigue performance, by detecting changes in the first-order natural frequency, of single-lap joint specimens subjected to dynamic loadings. A particular attention is given to the evaluation of the effect of tightening torque on fatigue crack initiation life and fatigue crack initiation position. The results show that the joint with the tightening torque of 10 Nm has the highest fatigue life among all investigated joints. The analyses further reveal that this is mainly attributed to the prolonged crack initiation life resulted from the suppressed crack initiation at the joint contacting surface due to the high fretting fatigue resistant produced by the appropriate level of tightening torque.