Failure analysis of extractor slipping in the cartridge case extraction process under different working conditions

A cartridge case extractor is a component which is used to extract cartridge cases out of a gun barrel. The extractor slipping from the cartridge case is a kind of motion failure caused by the coupled effects of friction and deformation. Certain working conditions have significant effects on this failure mode. In this study, a method for analyzing the failure behavior and condition of the extractor slipping is presented. The failure mode and theoretical model of the extractor slipping are firstly discussed. A finite element model is then established to simulate the cartridge case extraction process of a machine-gun. The effects of different working conditions, including ambient temperature, number of consecutive shots, and friction coefficient, on the cartridge case extraction process, are also analyzed. A concept of critical friction coefficient under a specific working condition is introduced in the extractor slipping condition analysis. The experimental results are also illustrated to verify the simulation results. Finally, the sensitive parameters of the extraction mechanism are analyzed and redesigned based on the established simulation model in order to reduce the failure rate of the cartridge extraction process.