Shakedown Study of Pipes With External Corrosion Under Cyclic Bending and Internal Pressure

Pipelines and rigid risers are susceptible to corrosion. This is also a concern for pipes onshore and on process plants of floating platforms. Once detected the corrosion defect on pipes under cyclic loads, the analysis carried out to decide on keeping the pipe in operation or repair/replace should consider that the defect may experience cyclic plasticity caused by stress concentrations and thickness reductions. In this condition, ratcheting can cause rapid failure. This paper presents a study combining experiments and different analysis techniques to evaluate the occurrence of ratcheting in pipes subjected to cyclic bending and internal pressure. Experiments with different defect geometries were carried out. Numerical analysis using incremental plasticity and shakedown procedures are presented and compared with the experiments.