Prediction of fatigue life in cold expanded fastener holes subjected to bolt tightening in Al alloy 7075-T6 plate

• Combined cold expansion and bolt clamping improves fatigue life.
• Combined cold expansion and bolt clamping improves fatigue crack initiation life.
• Combined cold expansion and bolt clamping improves fatigue crack growth life.
• Combined cold expansion and bolt clamping reduces local amplitude and mean stresses.

In this paper, stress analysis of holed plates was implemented in order to estimate the fatigue life due to the combined effect of cold expansion and bolt tightening (clamping force). The fatigue life was divided into two phases of crack initiation life and fatigue crack growth life. The fatigue crack initiation and fatigue crack growth life estimations have been investigated numerically and the total estimated fatigue lives have been compared with the available experimental fatigue test results. To obtain the residual stress, pre-stress and strain distributions created by cold expansion and bolt clamping force, and also the stress and strain distributions under cyclic longitudinal loads, three-dimensional finite element models were employed using ANSYS software. The results obtained from the finite element analysis of cold expansion and bolt clamping were employed to predict the fatigue crack initiation life using Fatemi–Socie multiaxial fatigue criterion, and fatigue crack growth life using AFGROW computer code. The results show that there is a good agreement between the numerically predicted total fatigue life and experimental fatigue test results.