Ratcheting behaviour of elasto-plastic thin-walled pipes under internal pressure and subjected to cyclic axial loading

• The ratcheting behaviour of pressurized pipes under cyclic axial loading is analysed.
• A simple theoretical analysis allows explaining this kind of phenomenon.
• A condition on the backstress tensor indicates whether or not ratcheting will occur.
• A manipulation of variables allows uncoupling the analysis in the hoop direction.
• Elasto-plastic constitutive equations with kinematic and isotropic hardening are used.

The present paper is concerned with the analysis of the ratcheting behaviour of elasto-plastic thin-walled pipes under internal pressure and subjected to cyclic axial loading. Understanding the behaviour of this kind of structure at different load levels is of critical importance in a range of engineering applications such as in the design of structural components of power and chemical reactors. Depending on the kinematic hardening, the pipe may exhibit a ratcheting behaviour in the circumferential direction, which leads to a progressive accumulation of deformation. Many different constitutive theories have been proposed to model the kinematic hardening under such kind of loading history. The present paper presents a simple local criterion to indicate whether or not the pipe may exhibit a progressive accumulation of deformation. Such criterion is independent of the choice of the evolution law adopted for the backstress tensor. As an example, a semi-analytic approach using a mixed nonlinear kinematic/isotropic hardening model is proposed to be used in a preliminary analysis of this kind of structure.