Modeling for Non-Shock Initiation

A model is being developed to include non-shock energy contributions to explosive detonation. This model does not attempt to include all possible specific initiation mechanisms at the mesoscale, but instead looks at cumulative energy in the explosive through experimental calibration of a small number of coefficients. Both shock pressure and shear stress are accounted for in the summation. The model is designed to be robust, fast-running, and relatively simple to calibrate. The model is implemented into the CTH wave code as an extension to the existing History Variable Reactive Burn (HVRB) model currently used for shock initiation. The expression in the extended model uses the functional form of the Johnson-Cook strength model, as that relation contains terms for confinement, strain and strain rate, which contribute to the overall energy deposition. This form is not unique, other expressions will be examined that may be more comprehensive, but the current relation has provided reasonable results.