Ratcheting behavior of pressurized 90° elbow piping subjected to reversed in-plane bending with a combined hardening model

• Ratcheting behavior of austenitic stainless steel Z2CND18.12N elbow pipe is studied.
• Ratcheting strain is compared by with and without isotropic hardening rule.
• Ratcheting boundary is determined by FEA with and without isotropic hardening rule.

Ratcheting behavior of 90o-elbow pipe is experimentally investigated under constant inner pressure and force-controlled cyclic loading (abbr. cyclic reversed bending). The results indicate that the ratcheting strain occurs mainly in the circumferential direction. It is shown that the ratcheting strain per cycle increases with a reversed bending loading under the same inner pressure or inner pressure under the same reversed bending loading. In addition, the ratcheting behaviors of pressurized elbow pipe characterized by the Ohno-Wang (OW) II model with and without isotropic hardening rule are compared with experiments data. The predicted results show that the OW II model with isotropic hardening rule is slightly better than those without isotropic hardening rule. The ratcheting boundary of elbow pipe is determined by the Elasto-Plastic Finite Element Analysis and OW II model with and without isotropic hardening rule. It is observed that the determined ratcheting boundary of elbow pipe by OW II model with isotropic hardening rule is larger than that without isotropic hardening rule.