Characterisation of a gun recoil resistance model for use in internal ballistic modelling

Abstract

While ballistics focus on the behaviour of propellant and projectiles, gun mechanics covers the behaviour of all weapon components and mounts under launch conditions. Gun mechanics deals with the stress and strain of the associated system and components, as well as the dynamic behaviour involved. In the design of munitions, understanding the link between the munition and weapon system and the effect they have on each other is critical. Gun recoil is one of these links. Operational requirements often dictate weapon mass and dimensions, especially when it comes to larger calibre munitions. Fundamentally, this has significant effects on the momentum balance between the projectile and recoiling parts. It influences the ballistic performance of the system, specifically muzzle velocity through recoil. Accurate representations of weapon systems and the ability to model these systems are of critical importance to reduce development time and increase system accuracies. This research presents a procedure to identify and characterise a gun recoil resistance model based on a single degree of freedom, mass-spring arrangement. The purpose of such a procedure is to serve as a tool to the systems engineer to identify the recoil model that can be used to predict and determine the ballistic effects of gun recoil on munitions. A fourth-order Runge-Kutta integration is used to numerically predict the spring stiffness of the weapon system. The procedure iterates with a change in equivalent stiffness until convergence between simulated and measured recoil displacement is achieved, using the breech pressure of the weapon system, weapon mass and weapon displacement as inputs.