Ratcheting study of pressurized elbows subjected to reversed in-plane bending

With a multi-axial test machine, ratcheting was studied experimentally for pressurized low carbon steel elbow's under reversed bending. The maximum ratcheting strain occurred mainly in the hoop direction at flanks. Hoop ratcheting strain was found at intrados for individual specimen. No ratcheting strain was found at the extrados for all tests. Ratcheting strain rate grew with increase of the bending loading level at the same internal pressure or with an increase of internal pressure at the same bending load. Ratcheting simulation was performed by EPFEA with ANSYS in which Ohno-Wang and Chen-Jiao-Kim kinematic hardening rules were applied by user programing. By comparing with the experimental data, it is found that predicted results by the Chen-Jiao-Kim model simulates reasonably. Ratcheting boundary was determined by C-TDF method with the Chen-Jiao-Kiin model.