Effect of cold expansion on the fatigue life of Al 2024-T3 in double shear lap joints: Experimental and numerical investigations

In this paper the effect of cold expansion on fatigue life improvement of aluminum alloy 2024-T3 plates used in double shear lap joints is investigated experimentally by conducting fatigue tests and numerically by implementing finite element simulations. In the experimental part, fatigue tests were carried out on the plates with cold expansion levels of 0%, 1.5% and 4.7% which were used in double shear lap joints. In the numerical study, three-dimensional finite element models were employed to predict stress distributions in the cold expanded plates used in the double shear lap joint. The results obtained from finite element simulation, have been employed to explain the trends which were observed in the experimentally attained S–N data and the fatigue crack initiation location. The experimental and numerical results showed that cold expansion improves fatigue life at low load levels and the life enhancement is more for the bigger cold expansion size. However, the fatigue life improvement is smaller in double shear lap joints compared to a single cold expanded plate.

► Cold expansion process on double shear lap joints leads to improved fatigue life.
► Cold expansion benefit for a double shear lap joint is lower than a single plate.
► Fatigue cracks are initiated from the pin entrance face at lower load in the joint.
► Fatigue cracks are initiated from the mid-plane at higher load in the joint.