Elastoplastic analysis of defective pipelines under constant internal pressure and cyclicthermal loading

Shakedown and Ratcheting behavior of pipes under thermo-mechanical loading has an important role in their design. In this study, Plastic, Elastic shakedown and ratcheting limit of a pipelines with different type of defects subjected to constant internal pressure and a cyclic thermal gradient are analyzed. Different dimensions of these defects were also studied. Nonlinear Kinematic Hardening model of Armstrong- Frederick was used and material properties were considered temperature dependent. Shakedown and ratchet limit interaction diagrams (Bree's Diagram) of the defective pipeline identifying the regions of shakedown, reverse plasticity, ratcheting and plastic collapse mechanism are presented and parametric studies involving different types and dimensions of part-through slot in the defective pipeline are investigated. The maximum plastic strain range over the steady cycle with different cyclic loading combinations is evaluated for a low cycle fatigue assessment.

Keywords:

Shakedown , Ratcheting , Defective pipeline , nonlinear kinematic hardening model (NLKH)