Ratchetting and ratchetting boundary study of pressurized straight low carbon steel pipe under reversed bending

With a quasi-three point bending apparatus, ratchetting and the ratchetting boundary were studied experimentally for a pressurized low carbon steel pipe under reversed bending. The ratchetting strain occurs mainly in the hoop direction. Multi-step bending revealed that the ratchetting rate increases with increasing loading level but reduces or even vanishes at a lower bending level imposed after a higher bending level. Ratchetting simulation was performed by elasto–plastic finite element analysis with ANSYS in which the Ohno–Wang model and some modified Ohno–Wang models were applied. By comparison with the experimental data, it is found that the Jiang–Sheitoglu model with a minor modification gives reasonable simulation. The ratchetting boundary was determined by the KTA/ASME, RCC-MR and C-TDF with the lightly modified Jiang–Sehitoglu model. By comparison with the experimental data range in this study, it is shown that the ratchetting boundary determined by the C-TDF method, with the lightly modified Jiang–Sehitoglu model, divides the shakedown region well.