Low-Cycle Fatigue Performance of the Sealing Plate Connection in Aluminum-Alloy Bolt-Sphere Joints

The low-cycle properties of aluminum-alloy bolt-sphere joints were investigated in this study through experimental research, finite element simulations, and theoretical analyses. To obtain the fatigue performance of the material, low-cycle fatigue tests of 6061-T6 aluminum alloy were first performed as the basis for component fatigue estimation. The low-cycle fatigue tests were then used to investigate the failure mode and fatigue life of the sealing plate connection specimens. The specimens failed at the junction of the sealing plate and the aluminum-alloy tube. The fatigue life is primarily determined by the precise size of the connection part. A finite-element model for a sealing plate connection was created to investigate stress and strain distribution. The results show a high-stress concentration at the bottom thread’s root. The maximum stress variation law is consistent with the low-cycle fatigue life variation law. Finally, a prediction for low-cycle fatigue life was attempted using the finite element result and the material’s fatigue performance based on the local strain approach. The prediction results were consistent with the test results.