CTH simulations of an expanding ring to study fragmentation

A high velocity impact will result in fragmentation which can be seen through EO/IR/RF signatures. Understanding fragmentation and how it relates to signatures is key to being able to characterize the impact. To study fragmentation in a computational context, an expanding ring was simulated using the shock physics hydrocode CTH. The simulations were set up to approximate the conditions of experiments performed by Zhang and Ravi-Chandar [On the dynamics of necking and fragmentation – I. Real-time and post-mortem observations in Al 6061-O. Int J Fract 2006;142:183–217]. The simulations resulted in random fragmentation patterns that are mesh size dependent. The simulations could not capture either the fragment sizes and distributions or the physics of the failure mechanism seen in experiments. The mechanics of failure represented in the simulations is extremely sensitive to the material model and how damage is treated in that model. However, the average fragment size in the simulations versus strain rate was found to be consistent with popular fragmentation models such as Grady–Kipp and Zhou–Molinari–Ramesh.