Ratcheting behavior of pressurized elbow pipe with local wall thinning

Ratcheting deformation is studied on elbow pipe made of Z2CND18.12N stainless steel with local wall thinning subjected to constant internal pressure and reversed in-plane bending under load control. The local wall thinning is located at extrados and crown of elbow. It is shown that local wall thinning has a very pronounced effect on the ratcheting behavior of elbows, as compared to the ratcheting behavior of sound elbow specimen. Three-dimensional elastic-plastic analyses with ANSYS in which Chaboche and Chen–Jiao–Kim (CJK) kinematic hardening model are carried out to evaluate structural ratcheting behaviors. A reasonable agreement has been found between the experimental and the simulated results with CJK model for the ratcheting of the elbows. The ratcheting boundary is determined by evaluating variations in the plastic strain increment with CJK model. The effects of the depth and location of local wall thinning on the ratcheting response are discussed by CJK model. -- Highlights: ► Ratcheting deformation is studied on Z2CND18.12N elbow with local wall thinning. ► The local wall thinning causes a significant ratcheting strain rate during the initial cycles. ► Structural ratcheting strains of elbow are evaluated by 3D Elastic-plastic FEA. ► The ratcheting boundary of elbow with local wall thinning is determined