Determination of Critical Flaw Size in Gun Launched 40mm Grenade

The inspection and screening of flaws in high explosive filled gun fired projectiles are crucial to ensure safety for soldiers using these items. In bore failure of structural components are sure to produce lethal consequences, therefore it is of great importance to determine what the maximum permissible crack size is for a given component coming off of the production floor. The analytical process to determine critical flaw size occurs in two stages. First, ABAQUS Explicit finite element analysis code is used to conduct interior ballistic simulation of a 40mm shape charge projectile. The modeling scope includes interior gun tube geometry with drive band engraving and spin up effects. Pressure load inputs, which were derived from live fire test data, are used to drive the model. Secondly, the explicit model results are passed to NASGRO software for critical flaw size determination using linear-elastic fracture mechanics theory. The modeling information and approach to the problem will be presented in this paper as well as explicit model results and proposed inspection criteria.