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

摘要

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.