The Effects of Propellant Grain Fracture on the Interior Ballistics of Guns
Memorandum rept. Mar 1988-Mar 1989
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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The two-phase flow interior ballistic code XNOVAKTC XKTC has been modified to include the effects of propellant grain fracture. An increase in propellant surface is related to the level of intergranular stress in the propellant bed, caused either by local bed compaction associated with the ignition wave or by grain impact against, most likely, the projectile base. The user specifies the increase in propellant surface to be associated with the level of intergranular stress. An increase in local gas production follows directly from the increase in burning surface interphase heat transfer and drag may similarly be linked to intergranular stress. This improved XKTC is used to illustrate the interior ballistic effects of grain fracture for two charges at two temperatures. Pressure waves in guns have long been linked to localized ignition and the distribution of ullage in the chamber propellant fracture resulting from associated increases in intergranular stress are shown in this study to provide a link to higher breech pressures as well.