Unified computer model for predicting thermochemical erosion in gun barrels

A gun-barrel thermochemical erosion modeling code is presented. This modeling code provides the necessary missing element needed for developing a generalized gun-barrel erosion modeling code that can provide analysis and design information that is unattainable by experiment alone. At the current stage of code development, single-shot comparisons can be made of either the same gun wall material for different rounds or different gun wall materials for the same round. This complex computer analysis is based on rigorous scientific thermochemical erosion considerations that have been validated in the reentry nose tip and rocket nozzle community over the last 40 years. The 155 mm M203 Unicannon system example is used to illustrate the five module analyses for chromium and gun steel wall materials for the same round. The first two modules include the gun community interior ballistics (XNOVAKTC) and nonideal gas thermochemical equilibrium (BLAKE) codes. The last three modules, significantly modified for gun barrels, include the rocket community mass addition boundary layer (TDK/MABL), gas-wall chemistry (TDK/ODE), and wall material ablation conduction erosion (MACE) codes. These five module analyses provide recession, temperature, and heat-flux profiles for each material as a function of time and axial position. In addition, the output can be coupled to finite element cracking codes. At the peak heat load axial position, predicted single shot thermochemical wall erosion showed that both interfacial and exposed surface gun steel eroded more than 1x10(6) times faster than chromium. For chromium-plated gun steel, with its associated crack profile, it appears that interfacial gun steel degradation at the chromium crack walls leaves unsupported chromium, which is subsequently removed by the high speed gas flow.