Steady-State Crack Propagation in Pressurized Pipelines Without Backfill

Abstract

In a previous paper, a simplified dynamic-shell theory representation was formulated for steady-state motion in a pipeline without backfill. The present work extends this model by (1) incorporating a gas dynamics treatment to determine the axial variation in the pressure exerted by the gas on the pipe walls, and (2) incorporating a plastic yield hinge behind the crack tip. Solutions to the governing dynamic equations are obtained for these conditions and used to calculate the steady-state dynamic energy release rate as a function of crack speed. In the single full-scale experiment in which an independent estimate of the dynamic fracture energy is available for a pipe without backfill, the model predicts a steady-state speed of 780 fps. This can be compared with measured speeds which ranged from 725 to 830 fps in the test. Because the calculated steady-state dynamic energy release rate exhibits a maximum, it is suggested that this approach may offer a basis for crack arrest design of pipelines.