| The ratcheting effect greatly challenges the design of the components. With the assistance of the quasi-three point bending apparatus, ratcheting and the ratcheting boundary of pressurized straight Z2CND18.12N and Z2CN18.10 stainless steel pipes under bending loading and vertical displacement control were studied experimentally. The characteristics of progressive inelastic deformation in axial and hoop directions of the pipes were investigated. The experiment results show that the ratcheting strain occurs mainly in the hoop direction while there is less ratcheting strain in the axial direction. The characteristics of the bending ratcheting behavior under both control methods were achieved and compared. The cyclic bending loading and the internal pressure influence the ratcheting behavior of the pressurized straight pipe significantly under loading control and the ratcheting characteristics are also highly associated with the cyclic displacement and the internal pressure under displacement control. They all affect not only the saturation of the ratcheting strain but the ratcheting strain rate. A series of multi-step bending ratcheting experiments were conducted under both control modes. It is found that the bending history influences the ratcheting strain rate greatly. In addition, the ratcheting boundary is determined and compared based on KTA/ASME, RCC-MR and the experimental results. Finally, based on the results it is found that Z2CND18.12N pipes are better than Z2CN18.10 pipes on the resistance to the ratcheting deformation. |
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