Shock Waves DOI 10.1007/s00193-017-0718-8 ORIGINAL ARTICLE Characterizing the energy output generated by a standard electric detonator using shadowgraph imaging V. Petr 1 · E. Lozano 1 Received: 27 September 2016 / Revised: 14 February 2017 / Accepted: 20 February 2017 © Springer-Verlag Berlin Heidelberg 2017 Abstract This paper overviews a complete method for the characterization of the explosive energy output from a stan- dard detonator. Measurements of the output of explosives are commonly based upon the detonation parameters of the chemical energy content of the explosive. These quantities provide a correct understanding of the energy stored in an explosive, but they do not provide a direct measure of the dif- ferent modes in which the energy is released. This optically based technique combines high-speed and ultra-high-speed imaging to characterize the casing fragmentation and the detonator-driven shock load. The procedure presented here could be used as an alternative to current indirect methods— such as the Trauzl lead block test—because of its simplicity, high data accuracy, and minimum demand for test repeti- tion. This technique was applied to experimentally measure air shock expansion versus time and calculating the blast wave energy from the detonation of the high explosive charge inside the detonator. Direct measurements of the shock front geometry provide insight into the physics of the initiation buildup. Because of their geometry, standard detonators show an initial ellipsoidal shock expansion that degenerates into a final spherical wave. This non-uniform shape creates variable blast parameters along the primary blast wave. Addition- ally, optical measurements are validated using piezoelectric Communicated by A. Higgins. B V. Petr vpetr@mines.edu E. Lozano jlozanos@mines.edu 1 Colorado School of Mines, 1600 Illinois Street, Golden, CO 80401, USA pressure transducers. The energy fraction spent in the accel- eration of the metal shell is experimentally measured and correlated with the Gurney model, as well as to several empir- ical formulations for blasts from fragmenting munitions. The fragment area distribution is also studied using digital particle imaging analysis and correlated with the Mott distribution. Understanding the fragmentation distribution plays a critical role when performing hazard evaluation from these types of devices. In general, this technique allows for characteriza- tion of the detonator within 6–8% error with no knowledge of the amount or type of explosive contained within the shell, making it also suitable for the study of unknown improvised explosive devices. Keywords High-speed imaging · Blast wave · Fragmentation · Energy distribution List of symbols a Fragment area a 0 Fragment area scale c 0 Local speed of sound C Charge mass of explosives C EB Equivalent bare mass of explosives d Distance camera-object M tot Total mass of casing M cyl Mass of casing cylindrical section M tip Mass of casing tip M Shock Mach number M s Scaled shock Mach number NTP Normal Temperature and Pressure n Weibull distribution parameter P Peak shock pressure P a Ambient pressure 123