Development and experimental validation of an explosive combustion evolution model considering inertial constraint in casing motion

In this study, a model is developed to capture the combustion evolution of explosives under mechanical constraints, particularly focusing on the ignition process. The model separates the propellant reaction into two stages: the low-speed combustion stage and the crack propagation combustion stage. The casing response is categorized into three stages: the elastoplastic quasi-static stage, the complete yield stage, and the post-casing failure inertia-constrained stage. This classification allows for a detailed investigation of the casing deformation behavior. By coupling the explosive combustion network evolution with casing deformation dynamics, a combustion evolution model is established that incorporates the effects of inertial constraints during casing motion. Further, experimental setups are designed separately for axial and radial casing failures. A quasi-one-dimensional test system is created to examine the charge reaction evolution under axial failure-induced motion. By restricting the block to move exclusively along the axial direction, the axial velocity of the constrained block and the reaction-induced pressure evolution within the charge are measured, providing key parameters for the charge reaction model. These data are then used to calibrate the combustion model. Additionally, an experimental system is established to investigate explosive combustion evolution during radial casing failure, validating the applicability of the proposed model under inertia-constrained casing motion. The results demonstrate that the variations in casing velocity and internal pressure reflect the relationship between explosive energy release and the work done by the product gases. Incorporating inertial constraints into the model offers a more accurate depiction of explosive combustion evolution. This model also enables the determination of reaction degree and reaction rate trends, laying the foundation for quantifying combustion violence.