Plastic Failure of Pipelines

摘要

The objective of this paper is to derive analytical solutions for the indentation, buckle propagation, and fracture of a plastically deforming pipeline. Rigid-plastic approximations are used to find the plastic deformation of a collapsed pipeline. Circumferential bending and longitudinal stretching are the only two dominant load resisting mechanisms considered in evaluating the rate of plastic work dissipation. The load-deformation response of the pipeline is characterized by a bending term which is independent of the deformation and a membrane term which increases linearly with pipeline deformation. It is shown that very long pipelines are susceptible to buckling, while longitudinal stretching resistance stabilizes plastic collapse in short pipelines. A closed-form solution for the steady-state buckle propagation pressure of an infinitely long pipeline is derived from this model. Analytical predictions of the propagation pressure are within 5 % of the experimental data. The plastic work due to longitudinal stretching accounts for 20-30 % of the propagation pressure, and the present model is an improvement of previous approximations which ignored longitudinal stretching. Finally, approximations of the maximum strains are made from the deformation field and a fracture criterion based on a critical rupture strain is used to predict fracture of a steel pipeline.