Experimental assessment of near-field blast loading using digital image correlation

This paper presents an experimental study of a 400x400mm 1mm thick aluminium plate loaded by an explosive charge at three different stand-off distances (100, 150 and 300 mm). The back face of the plate is optically captured with high-speed video at a frame rate of 100,000fps and digital image correlation (DIC) post-processing is used to determine temporal displacement and velocity. This is recorded at approximately 2,200 data points across the plate surface, which results in a resolution of experimental data that is typically challenging to achieve, due to the near-instantaneous application of high magnitude loading. The velocity information is used to infer a specific impulse value for each individual data point and can therefore determine a spatial loading profile. The results show that closer stand-off distances result in an increased localisation and magnitude of loading. The spatial variation of specific impulse is shown to be significant enough that idealised Gaussian loading curves do not sufficiently represent the loading anomalies evident in near-field loading. The amount of data generated from each individual test allows a probabilistic approach that considers loading as a ‘banding’ rather than single idealised distribution for each stand-off. It is only with an appreciation of the spatial variability of loading magnitude and experimental data of this resolution that we can accurately simulate the real-world features of near-field blast loading.