Studies in the transition from deflagration to detonation in granular explosives—III. Proposed mechanisms for transition and comparison with other proposals in the literature

Abstract

The experimental data and proposed mechanisms reported in the literature for studies in the transition from deflagration to detonation in porous explosives have been reviewed. Earlier proposed mechanisms identified the convective flame front as the driving force leading to formation of the precursor shock. More recent experimental results for 91/9 RDX/wax [1] show, however, that the driving force for shock formation originates near the point of ignition, behind the advancing convective flame front. Using the concept of an accelerating pressure buildup in the ignition region as the driving force for precursor shock formation (similar to cast explosive results) and pertinent literature permeability data, it is shown that most of the experimental results for porous systems (e.g., variation of predetonation column length with compaction and particle size) can be explained. Consequently, variations in deflagration transition mechanisms resulting from changing compaction have been proposed and discussed at length. The importance of energy per unit volume in the solid phase in producing the accelerated pressure buildup in the ignition region is illustrated with results from an RDX/wax series.