Time of arrival as a diagnostic for far-field high explosive blast waves

Abstract

The ability to accurately determine blast loading parameters will enable more fundamental studies on the sources of blast parameter variability and their influence on the magnitude and form of the loading itself. This will ultimately lead to a better fundamental understanding of blast wave behaviour, and will result in more efficient and effective protective systems and enhanced resilience of critical infrastructure. This article presents a study on time of arrival as a diagnostic for far-field high explosive blasts, and makes use of the results from a large number of historic tests and newly performed experiments where the propagating shock front was filmed using a high-speed video (HSV) camera. A new method for optical shock tracking of far-field blast tests is developed and validated, and full-field arrival time results are compared against those determined from the historic data recorded using traditional pressure gauges. Arrival time variability is shown to be considerably lower than peak pressure and peak specific impulse, and is shown to decrease exponentially with increasing scaled distance. Further, the method presented in this article using HSV cameras to determine arrival time yields further reductions in variability. Finally, it is demonstrated that the method can be used to accurately determine far-field TNT equivalence of high explosives.

Experimental investigation of blast mitigation of pre-fractal obstacles

“…To decide if such reflections needed to be included within the impulse calculation, a custom script was written in MatLab to automatically process the signals. Typically, conventional methods involve the use of concepts such as first maximum in the cumulative impulse (Farrimond et al, 2022), or the use of a curve-fit to determine impulse (Rigby et al, 2014b). Due to the diverse nature of reflection patterns at each sensor location, the cumulative impulse signal can be influenced by these reflections.…”

Far-field positive phase blast parameter characterisation of RDX and PETN based explosives

“…The authors of this article have identified a consistent feature across all the reflected data collected, which has been discussed in detail as 'sensor ringing' (Rigby et al, 2014a;Farrimond et al, 2022). This, however, is not generally predicted in simplistic numerical models, as seen in Figure 11 which shows the experimentally recorded reflected pressure and specific impulse, compared against APOLLO simulations (with EOS parameters derived from Cheetah and EXPLO5 thermochemical codes, respectively) for 250 g PE10 hemisphere at 2 m stand-off.…”

“…Data was recorded using piezo-resistive pressure gauges in the historic tests and current tests and were processed using the automated techniques described in Farrimond et al (2022). Figure 3 shows the configuration of the far-field arena trials.…”

“…Chiquito et al (2019) and Bogosian et al (2019) both used similar methods of functional fitting curves to experimental data, and both presented results exhibiting enhanced consistency, reduced subjectivity and improved reliability of analysed blast data. Farrimond et al (2022) used two different data processing techniques to revisit the idea proposed by Stoner and Bleakney (1948) and Bogosian et al (2014) that variability levels differ with scaled distance. The results of both analytical techniques provided enough evidence to suggest that as the near-field is approached, Z < 3 m/kg 1/3 , a much greater spread in the arrival time data, and thus other blast parameters, is observed which agreed with findings presented by Simoens and Lefebvre (2015).…”

“…The pressure gauge data collected from these trials was processed using statistical curve fitting methods, initially proposed by Rigby et al (2014b) and further developed and validated for use by Farrimond et al (2022). The determination of the arrival time, t a , and positive phase duration, t d , were automatically assigned and then used in conjunction with the raw pressure-time data and equation ( 1), to output peak pressure, specific impulse and decay coefficients for a given test.…”