EXPLICIT FINITE ELEMENT MODEL FOR DETERMINING INFLUENCE OF CARTRIDGE CASE MATERIAL PROPERTIES ON SMALL CALIBER WEAPON FUNCTION

摘要

Ammunition-caused weapon stoppages can often be traced to issues with the cartridge case. Aside from dimensional specifications, case material properties have a significant impact on the cartridge case's ability to properly obturate and extract. For brass cartridge cases, material properties are typically characterized and controlled by case sidewall and head hardness measurements. This paper describes the development of an explicit-dynamic finite element model for Caliber .50 cartridge case pressurization, relaxation and extraction. Model results are validated against experimental measurements taken from fired cartridge cases possessing different case sidewall hardness profiles. The model predicts significant differences in weapon bolt load, residual case deformation, and extraction forces as a function of said profiles. Previously-identified weapon functioning issues resulting from inadequate cartridge case hardness profiles are explained and demonstrated analytically.