Author : Putti Abhilash and M. R. Chopade

The gun barrel is subjected to high dynamic loads along with very high temperature inputs for a very short period of time in the range of 30-40 milliseconds. Hence the time required for the heat dissipation is very small, which leads to the heat accumulation mostly at 2mm below the surface of the gun barrel. This creates high temperature gradients inside the gun barrel. The greater the rate of firing, the greater would be the heat accumulation on the surface. This rate of heat accumulation determines the various factors affecting the performance of the gun barrel like calculation of the cook-off temperature of the gun barrel, amount of wear, rate of deformation, fatigue life of the barrel etc. The paper uses thermochemical approach to calculate the heat transfer coefficient variation in the gun barrel. This data is then used for the calculation of the heat transfer rate in the barrel in further finite element simulations of the gun barrel. Using the pressure and velocity variations across the barrel axis along with the density variations and assuming variable burning rate of the propellant values of the Reynolds number is calculated. Then using the mean value of the Prandtl number of the products and Reynolds number,Nusselt number is calculated, from which heat transfer coefficient is obtained..

Keywords: Dynamic loads, high temperatures, cook-off temperature, wear, fatigue life, heat transfer coefficient.