Experimental and numerical comparison of cold expansion and interference fit methods in improving fatigue life of holed plate in double shear lap joints

In this paper experimental and numerical investigations have been carried out on comparison of cold expansion and interference fit techniques in improving fatigue life of holed plates made from Al 2024-T3 in double shear lap joints. Fatigue tests were conducted on the specimens to study the role of cold expansion and interference fit on fatigue life and failure mode. Also to explain the experimental results and to obtain the residual stress and pre-stress distributions in the specimens due to these two techniques, finite element simulations were employed. The experimental results revealed that the interference fitted specimens exhibit much longer fatigue life, compared to cold expanded specimens at lower amplitude cyclic load, but as the load increases the two techniques show almost the same fatigue life. The finite element simulations show that interference fit reduces the local stress amplitude around the fastener hole, whereas cold expansion reduces the local mean stress. The numerical simulations can clarify and explain the experimentally observed results.