Analysis of displacement fields from a high-speed impact using shape descriptors

A composite bonnet liner subject to a high-velocity (70 m/s), low-energy (<300 J) impact by a 50-mm-diameter projectile has been investigated using computational simulation and by experiment. High-speed digital image correlation was employed to generate maps of displacement fields over the 1-m(2) bonnet at 0.2 ms increments for 0.1 s, that is, 500 datasets, and the results have been compared to those predicted by finite element analysis. Image decomposition was utilised to reduce the dimensionality of both datasets by representing them using adaptive geometric moment descriptors; these descriptors were used to perform quantitative comparisons of the datasets and to test the validity of the model based on all the available data. The model was found to be a good representation of the physical experiment during the first half of the impact event but a less good representation in the remainder of the test, probably because damping effects were not adequately incorporated into the simulation. The methodologies for data comparison and evaluation of model validity proposed and demonstrated in this study represent a significant advance in procedures for ensuring model fidelity and for creating model credibility in the simulation of dynamic engineering events.