Modeling and Simulation of Cook-Off scenarios of DEM-based three-dimensional propellant beds in cased ammunitions

In developing and optimizing solid propellants to maximize the performance and safety of barreled weapons, an understanding of the ammunition sensitivity to external mechanical and thermal stimuli to establish certain boundary conditions is essential in the design process to avoid cook-off scenarios. At high rates of fire, the weapon system, and particularly the barrel, is often highly heated by previous cycles of fire so that the ammunition of the following cycle is exposed to increased thermal influences. To handle these influences, numerical simulations can help in the development process to a better understanding. Current numerical approaches consider the propellant powder as a continuum inside the case. Due to the low thermal conductivity of the air-filled gaps between the individual propellant grains, the challenge here is to integrate these into numerical simulations. In this work, a simulation workflow is developed to realize the simulation of the boundary value-dependent heat transfer within a statistical propellant bed, which is generated by a discrete element method. Furthermore, possibilities for coupling with a chemical solver for the integration of Arrhenius-based source terms during cook-off scenarios are discussed. This can be used in future work for an optimized design of the ammunition case in terms of insensitive ammunition.