Unified computer model for predicting thermochemical erosion in gun barrels

Abstract

The first known gun barrel thermochemical erosion modeling code is presented. This modeling code provides the necessary missmg 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 cunent 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 rigoroxis scientific thermochemical erosion considerations that have been validated in the reentry nosetip and rocket nozzle community over the last forty 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 standard gun community interior ballistics (XNOVAKTC) and nonideal gas thermochemical equilibrium (BLAKE) codes. The last three modules, significandy modified for gun barrels, include the standard 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 fiux profiles for each material as a function of time and axial position. In addition, this output can be coupled to FEA cracking codes. At the peak heat load axial position, predicted single-shot thermochemical wall erosion showed unaacked gtin steel eroded by a factor of one hundred million more than uncracked chromium. For chromium plated gun steel, with its associated aack profile, it appears that gun steel ablation at the chromium cracks leaves unsupported chromixmi, which is subsequently removed by the high-speed gas flow.

Thermal–chemical–mechanical gun bore erosion of an advanced artillery system part two: modeling and predictions

“…New insights provide additional details to our previous thermal-chemical-mechanical gun bore erosion characterizations, theories, mechanisms, models, and predictions for non-coated and coated cannons [5,10]. This erosion model was comprehensively extended for advanced direct fire refractory metal-coated gun bores with steel substrates in the latter reference.…”

“…In July 1995, we published our thermal-chemicalmechanical gun erosion model which included: CCET thermo-chemical gun model [5,6], XNOVAKTC interior ballistics gun model [5,7], MABL boundary layer gun model [5,8], MACE thermal gun model [5,9], and MACE erosion gun model [5,9]. This thermal-chemical-mechanical erosion 0043 model was comprehensively extended to include refractory metal-coated gun bores with steel substrates in a July 2000 publication [10].…”

Thermal–chemical–mechanical gun bore erosion of an advanced artillery system part one: theories and mechanisms

“…As we have seen in previous work [5,6], the high velocity reacting gases progressively wash and widen the interconnected canyons and form extending voids in the dead-end areas. At the midlife stage, the unsupported chromium plate breaks off where it is unsupported.…”

“…Thermochemicalrelated firing damage leading to erosion includes corrosion and scale damage very near the steel interface in the form of an oxidation layer and white layer. We have detailed all of these erosion mechanisms and components in previous work we conducted on other rifled artillery, smoothbore tank, and rifled medium caliber cannons [5,6]. The following discusses specific erosion mechanisms for this gun system although it has many similarities to our previously detailed artillery, tank, and medium caliber cannons.…”

“…We have previously said that degradation of the platelet-substrate interface plus mild thermo-mechanical forces and interfacial shearing forces are typical in gun systems [5,6]. Thermo-mechanical forces and interfacial shearing forces alone are not enough to take chromium platelets off the steel substrate.…”