Experimental Measurement of Pressure Loading from Near-Field Blast Events: Techniques, Findings and Future Challenges

The accurate characterisation of pressure loads imposed on structural members following the detonation of a high explosive is critical to our ability to design protective systems. This poses serious challenges for experimentalists, due to the high magnitude and short duration of loading. If the distance from the detonation to the target is relatively large, the loading is imparted through the interaction of a shock wave travelling away from the detonation through the surrounding medium, say air. Here, pressure magnitudes are typically in the range 103–106 Pa and are measurable using conventional, commercially available piezo-electric or piezo-resistive pressure transducers. A considerable effort has been expended on experimentally characterizing these “far-field” loads and consequently, we have a strong understanding of the mechanisms and magnitudes of loading. However, we are also interested in the loading when the target is very close to the detonation, for a range of protection applications, from aviation security to the design of personnel protection. Here, very different physical processes dominate. At these so-called “near-field” distances from a detonation (<~1 m/kgTNT1/3) the high temperature gaseous detonation products are still violently expanding, and loading on a target is generated by the impingement of both the shocked surrounding material and these products themselves. Blast pressures are often higher that the yield strength of structural materials and temperatures can reach several thousand Kelvin. Furthermore, loading can vary by an order of magnitude over very short distances and timescales. This paper will describe experimental work conducted at University of Sheffield on developing approaches to accurately measure and predict near-field blast loading and gain a better understanding of the underlying mechanisms of loading. The challenges inherent to this field of work will be discussed and an attempt made to identify some of the emerging themes for future research