Multiphysics modeling of the initiating capability of detonators. I. The underwater test

Detonators are explosive devices used for the initiation of secondary explosives in commercial and military applications. They are characterized by their initiating capability, which is a critical factor for their safe and effective use but challenging to assess accurately. In this two-part study, we employ numerical simulations to investigate the blast wave generated by detonators and examine their initiating capability. The first part, presented here, follows the European underwater test of initiating capability, which evaluates detonators in isolation (direct method) and the second part considers detonators placed within a receiving explosive charge (indirect method). In the underwater test, the detonator is ignited inside a water tank and the initiating capability is assessed through pressure measurements in the far field. We employ a multiphysics methodology that allows the use of distinct mathematical models for each component such as two-phase reactive materials, elastic-plastic solids, and inert fluids. The computational implementation is validated against underwater experiments and is employed for the simulation of the blast wave generated by different types of detonators. The initial focus is on the general characteristics of the blast wave and subsequently on the differences between detonators of different shell material and thickness. Results show that the blast wave in the near field is asymmetric and varies significantly between detonators, but these features do not persist in the far field. The underwater test considers only the far field and is thus unable to capture the near field differences, which have a significant impact on the initiation of secondary explosives.