Modelling of the dynamics of a 40 mm gun and ammunition system during firing

This paper deals with the development of a finite element model of a 40 mm Case Telescoped Ammunition and its associated gun, able to describe the in-bore travel of the projectile during firing. This work is part of a PhD thesis, supervised by CTA International and the PRISME Institute, dedicated to the study of the parameters relevant to the accuracy of the Kinetic Energy Round. In order to conduct efficient parametric studies, they asked Nexter Munitions to take the lead for the finite element simulations of the in-bore travel, which is expected to be one of the most contributing phases of the firing event on the ammunition consistency. Nexter Munitions has set up a gun/ammunition model, applying the principles used for the same kind of work in 120 mm ([1] and [2]). The 40 mm study added some issues such as the progressive rifling of the gun, and the slipping obturator, which reduces the projectile spin rate. The model is compared to actual firing carried out by CTAI, through the strains measured on strain gages lying on the barrel and on an instrumented penetrator, ftted with an on-board data recorder. i The paper focuses on the correlation between the strain gages measurements and the simulation of the exact test configuration. It was necessary to run several configurations, with different contact logic and friction coefficients to match simulation and experiment.

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