Failure criterion for steel pipe elbows under cyclic loading

• Thirty-eight sets of experiments were conducted on 3 inch pipe elbow specimens.
• The numerical simulation results are in good agreement with the test results.
• Park and Ang and Banon damage indices are used for failure estimation of the elbows.
• The low cycle fatigue curve of an elbow is derived.

Steel elbow components are considered to be critical parts in industrial piping system due to their probability of collapse or failure. Therefore, the structural behavior of elbows is considered with respect to failure criteria through experiments and corresponding numerical models. Thirty-eight sets of experiments were conducted on three inch pipe elbow specimens. The numerical simulation results of the specimens are in good agreement with the test results. Damage indices available in the literature are used for failure estimation of the elbows. We suggest that the damage calculated using the Park and Ang damage index, and the Banon damage index, based on only one failed specimen under any constant amplitude cyclic loading, can be defined as the failure point and used to predict the failure of the component under other loading amplitudes. Therefore, the low cycle fatigue curve of an elbow can be derived using these simulation results. We also found that the calculated damage of an elbow component under constant, non-constant, and fully or partial amplitude reversals is quite similar.