Thermomechanical modeling of transient thermal damage in cannon bore materials

Modeling of cannon firing damage is extended to include time-varying gas temperature and convection coefficient data as inputs to finite difference calculations of near-bore temperature. Results are described for convective gas heating typical of cannon firing and for laser and combustor simulations of firing. Modeling is also extended to constant heat input conditions for comparison with laser simulation of firing. Slip-zone coating failure concepts of Evans and Hutchinson are adapted to predict shear stress on segments of thermally damaged material, including chromium and silicon carbide. Three measures of thermal damage are described: peak near-bore temperatures, which are highest for laser heating due to its relatively long 5 ms pulse duration; temperature difference between the heated surface and 0.1 mm below the surface, which is highest for cannon firing due to its peak convection during the initial 1 ms of the cannon firing pulse; and coating segment shear stress, which is relatively constant among the various types of cannon firing and simulated firing.