Modeling dynamic ductile failure: extensions of the TEPLA model and application to dynamic fracture of expanding cylindrical shell

In this work, we present theoretical extensions to the TEPLA model for dynamic ductile failure of polycrystalline metals. The modified TEPLA model is equipped with a new robust solution strategy applicable under large deformation and general multiphysics conditions. We demonstrate the applicability of the new TEPLA model through simulations of dynamic expansion of aluminum 6061 using gas gun driven expanding cylinder experiments. In this experiment, a polycarbonate cylinder flyer is accelerated by a gas gun to impact another polycarbonate cylinder plug, which is located inside a metal cylinder of interest. The impact between the flyer plug and the inserted plug causes rapid expansion and fracture of the cylinder wall. Conventionally, the cylinders tested are free of defects. In this work, a surface defect was added to the cylinder wall to evaluate its effect on strain to failure. The existence of the surface defect on the cylinder wall helps localize the hoop stress and hoop strain at the defect location and weakens the dynamic strength of the cylinder. The radial expansion of the cylinder wall without surface defect is used as a baseline for comparison purposes. Using a dynamic ductile framework, we modeled this fracture process and study the role of the defect on lowering the hoop strain at failure or weakening of the dynamic strength of the cylinder wall.