Steel plates subjected to localised blast loading: transient measurements using ultra‐high‐speed camera technology

In this paper, we chart a path to a method that enables us to extract temporal and spatially varying pressure loading effects on the transient response of steel plates under near‐field blast loading, employing ultra‐high‐speed cameras and DIC to measure the transient deformation field. The study addresses the challenges of obtaining full‐field, high‐fidelity DIC measurements in extreme blast environments by conducting small‐scale detonations in close proximity to steel target plates using two ultra‐high‐speed camera systems. A comprehensive error analysis of these systems is reported and challenges the historic norms of reported accuracy and repeatability in such testing, showing that errors as low as 0.01 mm can be achieved in transient measurements. Pressure measurements obtained via non‐contact DIC are compared with data from Hopkinson pressure bar measurements, providing cross‐validation of the methods. This research highlights the critical influence of several factors on the reliability of the results, including the chosen camera system, the geometry of the target plate and the errors introduced during DIC processing. The study demonstrates that, with careful attention to experimental design, short exposure times, thorough error evaluation for each camera system and consideration of the structural response, blast test results from DIC can be independent of the camera system used. Furthermore, the study finds that the design of the plate for obtaining accurate impulse distributions is more critical than the inherent camera system uncertainties. Within these limitations, the spatial distribution and temporal development of the impulse loading inferred from the DIC velocity data shows excellent correlation with direct measurements of impulse applied to a nominally rigid target by an identical explosive detonation. This offers a path to a method that could achieve the hitherto impossible task of extracting accurate data on the blast load applied in the extreme nearfield to deforming targets.