Ductile failure modelling of expanded aluminium tubes with embedded circular holes

A common technology used for well completion in the oil and gas industry is the solid expandable tubular technology, where a metal pipe is expanded radially towards the well bore. A challenge in this technology is to assess the mechanical integrity of the pipes during the expansion process. In this paper the ductile failure behavior of mechanically expanded aluminum tubes was studied experimentally and numerically. The expansion of the tubes was performed mechanically by using a conical mandrel with the objective to study the failure mode that governs the expansion process of this material. To localize the failure the tubes were drilled with circular holes. The fractured surfaces of failed expanded tubes were examined and revealed a flat ductile dimple rupture characteristic. A finite element model, which is based on continuum damage mechanics, is developed to mimic the experiments. The model also predicts ductile crack propagation and failure in the expanded tubes with embedded holes very well making it a suitable tool for studying the tubular expansion process and for optimizing the expansion tools used in this process.