Initial temperature effects on the shock initiation of high explosives

The initial temperature of a high explosive affects its shock initiation behavior. This may occur due to thermal expansion that induces microstructural changes, or because of direct effects on the chemical reaction rates. In this work, we explored the root cause using a physics-informed reactive flow model, the so-called Physically-Informed Scaled Uniform Reactive Flow model (πSURF). In previous work, we have used the model to gain insight into the role of porosity and pore size distribution in explosive performance. The model invokes the concept of the temperature- and size-dependent critical ‘hot-spot’, which in turn allows us to evaluate the fraction of the porosity ignited for a given shock strength. We can therefore also see the effect of initial temperature by estimating the change in the critical hot spot conditions at an elevated initial temperature. Here, we explore the model predictions for the explosive PBX 9501 at an initial temperature of 150 C in the form of the time- or distance-to-detonation and compare the results to experimental data. We found a favorable comparison. The model suggests the elevated temperature reduces the critical hot spot size, allowing a given shock strength to ignite a larger fraction of the porosity, relative to ambient temperature.