Experimental Studies of Blast Wave Development and Target Loading from Near-Field Spherical PETN Explosive Charges

A detailed understanding the features associated with the development of blast waves in the near-field following a HE detonation, and the loading generated when these waves impinge upon a target is essential if analysts and designers are to be able to validate numerical modelling approaches to near-field blast problems, predict structural response and design efficient protective systems. However, there is relatively little in the published literature describing detailed experimental studies of this issue. This paper presents the results of an experimental test program which has been conducted in the UK to study near-field phenomena following the detonation of small (<200g) spherical PETN explosive charges. High speed video is used to capture the emerging structure of the detonation products and air shock, whilst the spatial and temporal distributions of reflected pressure are recorded using an array of up to 21 Hopkinson Pressure Bars set flush with an effectively rigid target. Reflected pressures are presented over a range of scaled distances from ~0.15-0.75m/kg1/3 and the results compared with predictions from Conwep. Localised features of the developing detonation product cloud and air-shock are observed which appear to match those seen in images from much larger explosions, suggesting that these are not strongly scale dependent. These features appear to have strong influence on the magnitude of the localised loading generated when they impinge on the instrumented target, resulting in very high localised variations of pressure and specific impulse both within the data set from a given test and between nominally identical tests. However, the total integrated impulse experienced by the target is relatively consistent from test-to-test.