Simulation of dynamic ductile failure in pipelines

A finite-element method computer simulation was constructed in order to assist in determining what material properties affect the resistance to dynamic ductile failure in pipelines. Such failure is caused by stable axial tearing that involves a substantial amount of plastic deformation, and is driven by the kinetic energy of the expanding gas. Various semi-empirical relationships exist in the literature to predict the toughness required for resistance to the propagation of a dynamic ductile failure, but these tend to be ineffective when applied to higher strength grades of steel. The present finite-element model is composed of two main sub-models. The gas decompression algorithm is based on analytical expressions and calculates the gas pressure throughout the pipe as the ductile fracture propagates. The material-response algorithm determines the behaviour of the material under the changing loading conditions. It simulates the material response, including rate-dependent yield as well as anisotropy of yield and work hardening. The model is validated by using comparisons with published data from the literature. This paper focuses on a description of the different components of the model and their interaction. In addition some observations from the various simulations are discussed.