Geometry and strain in the transition region of a collapsing submarine pipe

Abstract

We investigate the phenomenon of buckle propagation in a thin-walled pipe caused by external pressure under steady-state conditions. We have made use of small-scale experiments on thin-walled steel and aluminium pipes, together with appropriate theoretical studies. In a previous paper [Buckle propagation in submarine pipelines. Int. J. Mech. Sci. 30, 217–228 (1988)] we described an investigation of the pressure required for steady-state propagation of the buckle in a given pipe. Here we describe some further aspects of the study, including a detailed experimental description of the geometry of the transition region and a preliminary assay of the surface strains experienced by the pipe when a buckle passes along it. The geometrical investigation confirms that the transition length is proportional to ( radius) 3 2 /( thickness) 1 2 , and the strain experiments show that the transition region involves three distinct zones of plastic straining in the surface, in addition to the plastic bending of the cross-sectional ‘hoops’ which was described previously.