Unified computer model for predicting thermochemical erosion in gun barrels

A gun-barrel thermochemical erosion modeling code is presented. This modeli ng code provides the necessary missing element needed for developing a gene ralized gun-barrel erosion modeling code that can provide analysis and desi gn information that is unattainable by experiment alone. At the current sta ge of code development, single-shot comparisons can be made of either the s ame gun wall material for different rounds or different gun wall materials for the same round. This complex computer analysis is based on rigorous sci entific thermochemical erosion considerations that have been validated in t he 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 communi ty mass addition boundary layer (TDK/MABL), gas-wall chemistry (TDK/ODE), a nd wall material ablation conduction erosion (MACE) codes. These five modul e 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 axia l position, predicted single shot thermochemical wall erosion showed that b oth interfacial and exposed surface gun steel eroded more than 1x10(6) time s faster than chromium. For chromium-plated gun steel, with its associated crack profile, it appears that interfacial gun steel degradation at the chr omium crack walls leaves unsupported chromium, which is subsequently remove d by the high speed gas flow.